📙 The Future of Ecological Urban Living


1. Introduction

2. Basic principles and techniques

3. Interventions for the climate

4. Interventions against waste

5. Interventions for the water cycle

6. Interventions for other species

7. Material collection (TODO)

1. Introduction

What you will find here. This is a reference document collecting all kinds of unexplored ideas, little known and early stage solutions for ecological urban living in the near future. It is not your typical “green wellness” document recommending mindfulness and no plastic straws. Instead, this manual is intentionally extreme and radical, because that is the kind of response that we need in the current climate crisis and wider ecological crisis. This document is no ready-made instruction manual either, as the ideas are not yet ready for mainstream use. Instead, they are provided as inspiration for early adopters and urban living R&D labs. In our own organization, this is what The Reef aspires to be in the future; also, we are looking for other partners for this journey.

Structure. This document groups interventions into chapters by their primary goal or effect: for the climate, against waste, for biodiversity. Each sub-chapter treats a cluster of related interventions (“warm clothing”, “small heated spaces” etc.), where all these related ideas are treated in the form of a coherent text. Finally, tables and diagrams help to compare the relative impact and other properties of the interventions.

Content licence. This is an open source document under a Creative Commons Attribution 4.0 Unported licence (CC-BY 4.0), or at your option any later version.

Acknowledgements. This manual has been created with the funding and support of EIT Climate-KIC, a European climate action organization. EIT Climate-KIC is supported by the European Institute of Technology (EIT), a body of the European Union.

In addition, this manual as an open collaboration project received precious contributions from people in EIT Climate-KIC, the Edgeryders company and community, and from the Internet at large.

How to contribute. This manual is an open source project, and you are welcome to contribute yourself. However you obtained it, the most recent version is always a wiki on edgeryders.eu. After opening a (free) account on the edgeryders.eu platform, you can join the discussion thread below that wiki, adding your feedback, reports of problems with the document, or proposed additions. If you feel confident about your contribution, you can also directly contribute it by editing the wiki. The wiki uses Discourse flavoured Markdown for formatting, all of which is documented in our Discourse User Manual.

This is a wiki! Because this document is an open collaboration project with multiple editors, it is never really finished, just like Wikipedia for example. Expect to find some sections in draft state, TODO markers etc., because we keep working on and extending this document for our own purposes even after the end of the funded project where this document was started.

What is not included here. The following topics are outside the scope of this document and not treated here:

  • Well-known good practices. There is little need for yet another document about well-established and well-known practices of ecological urban living. We only deal with the future here, with what goes beyond the status quo. This includes little-known good practices, innovations and also refutations, in cases where an established practice is not a good idea for ecological living.

  • Long-distance traveling. Traveling within the city is considered part of urban living, but traveling beyond its limits is not. For long-distance traveling, we started the Green Travel Manual. And for measures to avoid business travel, see our Distributed Collaboration Manual.

  • Social and financial aspects. And motivation. This document is about technology only – to derive value from it, you need to come with both motivation and money to apply that tech. It will not help you to create the right incentives for ecological behavior in a group, or to persuade investors to invest in your ecological living project. It will also not prevent you from housing a capitalist enterprise or other status quo protecting organization in your ecological building. It will just tell you (right here and now): that would be completely self-defeating. Using ecological living techniques to hide the ecology-destroying nature of the status quo is called greenwashing.

  • Urban infrastructure. There is a lot that can be done for emission reduction with changes to the city’s infrastructure. This document is meant for building owners and inhabitants though, so it only covers what can be changed up to the scale of buildings. For innovations in urban infrastructure, we have another document called “An Autarky System for Cities”.

  • Rural living. For rural living, a very different set of green living techniques is possible. So we provide a companion document for that setting: “The Future of Ecological Rural Living”.

  • Industrial production. Urban households simply do not provide the space for industrial production, so we can’t include this part. We do however include criteria to select the most eco-beneficial industrial products where it is necessary to rely on them. Also, maintaining and repairing any artifact used inside the household and small-scale production and product modification fall into our definition of urban living.

  • Industrial logistics. This is a secondary problem following from centralized industrial production, and not a problem of urban living.

The role of demand reduction. [TODO, resource efficiency, efficiency at what?, SID, gradual/constant reduction timelines ]

The role of pre-market experimentation and innovation. [TODO]

Estimation of household benefits. We try (and sometimes fail) to put numbers on everything proposed in this document, so you can choose solutions based on evidence and not simply comfort or instinct. It is the ecological equivalent of effective altruism: using data and evidence to find the most effective ways of not harming our natural environment.

The benefits of everything included here is numerically estimated relative to a “business as usual” scenario of a typical household (1) in the same climate zone (2) in a so-called “highly developed” region, because these are the households with the worst ecological impacts. Solutions are then ranked by the benefits for a household in the same climate zone – because this is a household manual, and households should be able to always choose the next suitable solutions from the top of the list. Note that solutions are partially overlapping, so the sum of benefits can be higher than 100%; for example, a transition to communal living may involve some of the same changes as a transition to smaller heated spaces or collective purchasing. [TODO: In China as in the USA the top ten percent of urban + top five percent of sub-urban residents drive more then half of the CO2 emissions of the national carbon footprint. If Detroit, USA (pop. 2,7M) emits 25.5 t CO2 per person per year AND is ranked as unhappiest and most stressed of 150 US cities something is going badly wrong. What do people, households, and cities do better in places like Denmark, France, Colombia, or Costa Rica - which are much higher on the happiness index, while also relatively light on their footprints?

Global benefits. In addition, solutions are grouped together based on the estimated benefits when applied globally, into steps of reducing 50% of the remaining ecological impacts of human living activities.

Introduction to the urban environment. [TODO: tongue-in-cheek introduction that describes the urban environment in analogy to a jungle or desert: an ecosystem with opportunities and restrictions, to which the technology has to adapt, how much time we spend in the "built environment, what are the energy and material ins & outs]


2. Basic principles and techniques

2.1. Designing for mainstream adoption

To be relevant, there is no way around mainstream adoption of any future solutions for ecological urban living. The best way to design for mainstream adoption is to encapsulate complexity into either consumer products or commercial service offerings. In a way, in most European countries every consumer uses even nuclear power stations – mediated through the utility company. So basically every solution can be packaged or organized in a way that allows mainstream adoption. For most ideas discussed further below, this will be either a consumer product or a neighborhood-scale service offering.

2.2. Construction vs. usage

  • Consumption is 80% of the problem, construction 20%. The energy costs of constructing a house is 20% of its total lifetime energy costs, while the energy cost during its lifetime of usage is 80%. (TODO: source) When the building is well maintained and lives long, that ratio is skewed even more towards usage. This is why this document does not put much emphasis on construction but a lot on the activities of living, because that is where the greenhouse gas emissions etc. of urban living happen.

  • Innovation is hard. To make living greener, invest in human expertise instead. Innovation of products and materials often does not work at the start, and requires a lot of experimentation before it is ready for general use.

    For a small-scale setup like a communal living space, a more appropriate way to innovate green living could be “process innovation” for building maintenance. Basically, build up a system so that the community can maintain its own space: train different members as plumbers, electricians etc. and also get the relevant tools so that all problems can be fixed with little effort, extending the building’s utility, lifetime, and eco-friendliness. Investing in human expertise cannot go wrong, while investing in new materials and technologies may go wrong.

    A simple example: a concrete wall made from some new composite is not self-maintainable and may thus only last 50 years. There is no real need for such a wall though, as brick walls have been around for hundreds of years and we know how to maintain them for that amount of time. Innovation is also important, but one of the greatest values of a building is that we can keep it alive, and that is an important aspect of buildings being “green”.

  • The impact of human care on buildings. Buildings don’t last “100 years” like that, it can be 30 years or 300 years depending on the quality of their maintenance. So the cost of providing a function for a certain time is more determined by the care afterwards than by the initial investment. For example, Renzo Piano will rebuild the bridge that recently collapsed in Italy, with a version in steel that “will last 1000 years”, as he says. He did not mention with what maintenance. And bad maintenance was the main reason why the first bridge collapsed. So whatever you build, don’t care only for materials and high-tech, also care to put money into operation and maintenance. Because it is a new approach, this is innovative for the current time. Modern “sensor and IoT equipped” buildings can be a nightmare to maintain.

  • The cost of maintenance, and how to deal with them. Nothing is re-used for what it because that is a lot of manual work. And manual work is not time efficient, and we have not enough money in Europe to pay people for much of their time anymore. Just enough to pay them for operating machines – everything else is manufactured by machines or in China. The same limitations apply to unique construction of houses – instead, all new houses now look very similar, and the look results from the optimization to be built with machines, not with manual work. Again, the same limitations apply to building maintenance: in earlier centuries, a building was always maintained so it could live “forever”. Now, buildings have an expiry date and are then destroyed and replaced, because maintenance is “too expensive” manual work that cannot be automated away.

    In communal living, there is no general solution to that, but at least a partial one. Namely, comparing the cost of worktime and machine work is just a financial comparison that does not capture all the value. By working less outside of the community and more inside, people will have fun making their own things “inefficiently”, and in total may prefer that to working for money and buying industrially made items. That’s even more applicable when starting to make things not from scratch but from the waste of the surrounding society, such as all the stuff one can take out of buildings before they are being destroyed.

  • Bring careful observation back to modern architecture! The traditional architecture in different areas is very different, also within Europe. It developed over hundreds of years of incremental development. In the last 50 years, that changed a lot, so now most new houses all around Europe are built very similarly. Is that bad, and should we rather just trust the traditional, accumulated knowledge?

    Indeed, architecture always changes, and traditional knowledge gets lost. We don’t understand a lot of building features of traditional architecture and material use. It’s ok that processes change, the problem with the new processes is that they are not developed from careful observation of the objects and environment. For example, houses are optimized for efficient construction and not to last (because “cheap materials, expensive labor for construction and maintenance”). Similarly, commercial buildings like banks are remodeled every 7 years.

    New ways of ecological building can be informed from this process of “careful observation” of the past. That will allow to build with cheaper and more environmentally friendly materials in a way that achieves the same or better effects as with today’s “modern” materials. In addition, careful observation can inform how maintenance can extend the lifetime of modern buildings to a multiple of their planned lifetime.

2.3. How to approach converting a building

  • Starting from an old office building. The advantage here is that partition walls etc. can be easily removed and reconfigured.

  • Mobile conversion kit for temporary spaces. That’s a different approach to having an “own” space, and much simpler to realize: have a container with a kit to transform any abandoned building into a comfortable space within 7 days for 1-3 years of temporary use, with 2 days at the end to take all of that equipment out again. If this is about buildings that will be destroyed anyway, it will even be ok to remove walls and change the structure of the building when moving in. Utilizing abandoned buildings is also environmentally friendly because the continued maintenance extends the lifetime of these buildings.


2.4. How to approach architectural innovation

  • Exploring a proposal before it’s built. Architects to models a lot (actual physical models, not just 3D models). Others do a lot of discussions with potential users, to explore how they react to their design ideas.

  • Exploring construction innovations on a small scale. For construction innovations aimed at large-scale application, architecture studios (like that of Renzo Piano) combine architecture with research. That however cannot really be pulled off for a single community building. There are also software packages for thermal modeling, light modeling etc. – these are useful for spatial innovation, not for material innovation. Because non-standard materials are hard to model with these software packages. It may be possible (with the PEB thermal modeling software package for example) but even for professionals, using that software is hard and expensive. Ideally there would be open source software packages that encapsulated the complexity and allows non-professionals to take over design and modeling tasks formerly reserved for professionals. However, that seems not to exist (yet).

    A more appropriate technique for such a setup is to create a setting (both physical and by social organization) that is welcoming the construction innovations. This can include, for example: a building that is simple to re-configure; piping and wiring that allow to install new innovative machines and devices wherever people want; a large on-site workshop that allows to adapt the building and its equipment quickly.

  • On new facade materials (like PV panels). There is a house in Australia using PV panels as roof covering, somewhat tilted so that light can still get through to the inside. In architecture, there are multiple uses of wall finishing / cladding: weather protection, and allowing the building to breathe (humidity transfer to the outside to prevent humidity buildup, mould, dampness indoors etc.). Depending on weather condition, the outer layer is of different permeability, impacting how the building is breathing. In some parts of Portugal, tiles are used for example.

    So to start hacking together a new cladding system (such as from PV panels), a good tip is to start with experimentation. Nothing too big, nothing too drastic at the start. “Play with it.” Just to see how the material behaves, how it can be attached etc… It will be difficult to pull off such a hack, as the material was not designed for such a use, so may perform worse for it than industrial cladding systems. Or at least it will probably not perform better. For PV panels, a purely ornamental use (plus power generation of course) of PV panels, or a use as a sight protection / separation wall on a fence or similar, could be the first experiments, as not so much can go wrong.

2.5. Dealing with legacy laws and regulations

Routing around regulations. If you have no close neighbors, it is much simpler to ignore regulation because there is nobody who will complain to the authorities. Also, try to break only rules for the inside, not in relation to the outside environment. Then, the problem only arises when you want to sell the building – then an architect will have to check what has to be changed for that to be possible. So that will be the time to undo ones hacks and changes – and when keeping the house, it will never be a problem.

Combining houses in the city. Buying adjacent houses and making them into a single house by knocking down walls is prohibited in Brussels. But you could just do it, and put up the walls again when moving out :slight_smile:

Dealing with fire safety. In cities, public and communal spaces are tightly supervised by the fire brigade. They may mandate the type and material of walls, fire protection doors etc. to isolate buildings against each other so that there is a safety window for people in one part if another part catches on fire. For example, staircases in large buildings will have to be isolated from a kitchen space with a fire safety door.

Certification issues with material re-use. Any certified component of a building is not legal to be put to use again in a new building. The certification only applied when that equipment was installed the first time, but now the standards might be different and not cover these items anymore for getting a new building certified. For example, emergency lamps. All these items are now considered waste. It especially also applied to electronics components.

2.6. Take it to the neighborhood

By integrating social projects such as clothing exchange events and rescued food distribution, a communal household or other group can make the living in the whole local area more green, not just its own. It would be interesting to do the numbers for that, and it may turn out to be the most efficient way of emission reduction. From @Bernardo’s experience, a best practice to do these social service projects is to do those that also profit yourself, because then it’s not a net drain on the organizer: if you have kids, organize kids clothes exchange events; if you cycle, organize a cycle repair workshop; if you like dancing or working out, offer dance classes or open a gym in the communal space.

These can also be semi-commercial activities and still be a net benefit for the neighborhood. It provides a public good because of “zero marginal cost”: scaling the service up to more people beyond ones own and direct community’s needs does not really cost more, so can be provided as a service at a low price or even for free.

2.7. Household consumption accounting

The lifetime of a well-maintained building can be considered to approach infinity – the building is never used up in its entirety. Then, all ecological impacts of a household happen connected to the material and energy flows into and out of the house. Tracking these flows is quite a realistic task using energy meters, water meters, scales and barcode scanners. With barcode scanners, it is simple to record what purchased packaged items enter the house. With that setup in place, household level GHG accounting and optimization is also realistic.

Note that, to keep the accounting low-overhead, the unit of accounting is the household not the person. Nothing done in other households (living in a hotel, eating out etc.) is taken into account, as that is thought to belong to the accounting of other households. The disadvantage is of course that households are very different so that comparing results with other households is not simple – however, a rough estimate of (more comparable) per-capita greenhouse gas emissions can be made by adjusting for person days in the household and including long-distance traveling. And the main purpose is anyway to make progress over time in this one household, not to compare with others.

2.8. It’s all about resource efficiency

In spite of all ecological zeal, we’ll never propose that any human being has to leave Earth earlier than it will happen naturally to them. We’ll also not question the ultimate (non-material) life goals of anyone, whether they want an interesting, happy, beautiful or meaningful life.

With these constraints, there are only two things we can do to save our ecosystems. First: not making so many new people. Second: finding the most resource efficient way to have the life you are looking for. If you are looking for happiness in life, it is not enough to achieve this, but to achieve it with as little resource consumption as you possibly can.

3. Interventions for the climate

[TODO: Include a diagram of the benefits of each solution.]

3.1. Ecological household composition

TODO: Everything about “which people should live in this household to make it ecological” should go here, including:

  • communal living
  • family planning: the impacts of having children or not
  • sustainability and desirability of various household compositions
  • biographic milestones & decisions
  • time vs money graph

3.2. Small heated spaces [change to: Household Adaptations]


The idea is to develop alternatives to heating complete rooms or even the complete builing. Rather, one would just heat a small space inside a room. These small heated spaces can take many forms, and can embody feelings of comfort and hygge, providing comfort in the cold period of the year. Obviously, proper design is important to achieve this and make people love their small heated spaces. Examples of what these spaces could include:

  • a “bed cave”
  • an enclosed screen workspace inside a larger office
  • an enclosed kitchen corner
  • heated office chair
  • heated armchair, complete with a plushy cushion, blanket, warm shoes or footrest, into which one can completely disappear and that will then insulate the body
  • heated kitchen corner, with ceiling-high insulated glass walls as separation from the living area
  • a kitchen space configured to nudge consumption habits in the right direction: keep perishables in view, allow for easy snacking on nuts & other sustainable foods.
  • covers for pots and pans to control fumes / humidty, pressure cookers, pot insulation for cooking with residual heat, large thermos flasks
  • double insulated freezer / fridge
  • heated dining space, perhaps scalable to the amount of people taking part in a meal
  • heated bed, convertible between winter (cave style with heating) and summer (open style) modes
  • heated computer corner, with the computer (~20 W) and human body (~100 W) heating up the space
  • heated small bathroom, distinct from a larger bathroom with shower etc. that would only be heated on demand

Heating these spaces

The architecture and thermodynamics of such small indoor spaces is largely unexplored – for example, a comfortable “dining cave” might be heated by the presence of people (100 W each) and hot food. A glass-enclosed kitchen corner is pretty surely heating itself while in use.

Furthermore, air source heat pumps inside the small space that take their heat from the enclosing room are an efficient way to provide the heating, as their air source will be still at least 10 °C air, at which temperature heat pumps are pretty efficient. A cheap and DIY solution is to place a fridge into the small heated space, and to circulate air between the surrounding space and the inside of the fridge using two hoses and small fans. A fridge is a heat pump and will heat up the small space with its “waste heat”, extracted from the air circulating in it. This basically shovels the heat back that escaped from the small space into the surrounding room, which is how electric efficiencies of 250-350% are reached, compared to 100% for electric resistance heating. In addition, the electrical energy consumed by the fridge itself, heating up its motor etc., is also ultimately converted into heat that contributes to space heating, because the fridge is inside the small space.


Heating is currently one of the largest sources of greenhouse gas emissions, both inside buildings and as a fraction of global emissions [TODO; for initial numbers, see here].

Lowering the indoor temperature has major impacts on the heating energy use: for example, a detailed computer modeling study based on the UK housing stock estimates that lowering the thermostate setting from 19 °C to 18 °C will result in 13% savings of space heating energy (source). The same study shows an almost linear correlation: lowering the indoor temperature by 2 °C will lead to 25% savings of space heating energy. Also note that the amount of energy savings per degree change in room temperature varies considerably between buildings – to determine it experimentally for one building, see here.

Now the above idea of only heating the small heated spaces will probably result in an indoor temperature outside of these small spaces of about 13 °C during the heating season. It cannot be much lower, as 13 °C is close to a lower bound for air that is still comfortable and healthy even under prolonged exposure and with the body at rest. That’s a reduction of 6 °C compared to a usual 19 °C room temperature, and would lead to expected savings of 75% of heating energy, still assuming a linear relationship.

A 75% reduction in space heating energy is a huge amount, given that space heating takes up the largest amount of energy and on average still uses the largest amount of fossil fuels in a building. Compared with other energy-saving behavior adaptations, it saves more than 11 times as much energy than the next best one that is not related to space heating (namely “Install water efficient shower head and use twice every day”, see here).

Finally, there is an additional major energy saving related to the embodied energy of a building: manufacturing insulation material is energy intensive, and much less of it is needed when providing small heated spaces inside non-insulated larger spaces. Also, the insulation for small heated spaces can be made from salvaged materials as it does not have to withstand outdoor conditions for years. For example, paper, cardboard, crumpled plastic bags etc. are good insulation material and represent zero embodied energy when they are recovered from waste material.

3.3. Heated clothing

[TODO: Include a nice illustration of the heated clothing in use, with labeling of parts.]


Next to small heated spaces, heated clothing is the second major way of avoiding space heating – it is even more experimental and “extreme”, though. Heated clothes exist for outdoor activities, but nearly all of them use batteries (which is uneconomical for permanent use) or use catalytic fuel burners (which is inadequate for indoor use). Our initial ideas for R&D to solve these challenges include:

  1. Electrical quick connectors. Many activities in the home are stationery, including screen work, kitchen work and resting / sleeping. Electrically heated clothing that is connected to a (very safe!) SELV DC energy supply with a spiral cable and magnetic tear-away quick connector could be a comfortable option. The human body does not immediately feel cold when “turning off the heating”, but rather has enough stored heat for staying comfortable for 1-1.5 hours in cool (8-10°C) environments, given suitable clothing. This means that only an occasional connection to electricity is enough to keep warm with heated clothing.

  2. Heat buffering. Water is a harmless chemical with a very high heat capacity (4180 J/(kg*K)) and a suitable choice for a thermal mass “heat battery” to extend the usage time of heated clothing without any need for batteries. To create a heat buffer that lasts 3 hours with an output of 100 W (the same as the human body at rest and probably suitable for most use cases of heated clothing), one would need 300 Wh of stored energy in heat usable for body heating, here defined as heat >30 °C. That requires an amount of ~3.7 l of water at 100 °C (see). It seems possible to integrate these 3.7 kg of hot water into clothing comfortably, though that might also be the upper limit. Anyway, 3 hours of mobile operation is quite a comfortable solution already. The water would be re-heated whenever an electrical connection is available (see above) and could also be exchanged within 10-20 seconds with a quick connector hose attached to a reservoir. This is a much faster additional option compared to the 6-10 minutes that would be required for electrical re-heating with SELV electricity.

  3. Outdoor heater unit. For outdoor use away from the house, we would like a longer mobile use time, ideally a full day awake (16-20 hours). This becomes possible because outdoor use allows burning fuel. Ethanol produced from renewable resourced is a suitable, energy dense and safe fuel for this purpose. A mobile burner unit would be carried as a backpack or detachable handbag and would re-heat the 3.7 l of hot water whenever necessary. This is not strictly about ecological living, but a way to transform the human relation to outdoor space as a nice side effect: suddenly, it will be comfortable to have an outdoor dinner in winter, to cook outdoors etc… This in turn might prompt other lifestyle adjustments: why have a large living room when the outdoor area is now comfortable even in the midst of winter?

3.4. The resource-efficient kitchen

Today, the kitchen is the only remaining locus of production in an urban household. That’s why, apart from building heating and hot water generation, this is the place where most resource efficiency is lost and where most can be gained again.


  • putting lids on pots (predicted to save 120 kWh/a per household, see no. 22 in that document)

  • pressure cookers and humidity

  • upper body strength

  • kids and the kitchen

  • energy savings of communal cooking vs. cooking for 1-2 people

  • energy saving recipes, incl. cold meals

  • slow cooker as a kitchen appliance

3.5. Efficiencies of shabby chic

Build something old, not something new. Trying a conversion to make an old space look new is difficult, esp. on a budget. But trying to make an old space look old but great is much simpler and cheaper. It just needs old materials and good “shabby chic” taste.

TODO: This goes a lot into the direction of what Bernardo is saying about “building maintenance as architecture”. Just that we extend it beyond the building and to the interior as well. The idea is to “keep the old look and work well”, so that there is never ever a need for “renovation”. In fact, some old buildings with proper, nicely designed and thought-through (but not costly or carbon intensive) interior feel way more homely than modern, mass manufactured buildings with their white, minimalist aesthetics. How can a practice of communal living be built around this idea? How could that include household-size elements of a circular economy (basically “throwing nothing away”)? That also includes household-level production from raw materials that would usually be thrown away. It would extend to all areas of life, including a “shabby chic” clothing style. And it is not at all clear at the moment what that even means.

Inspirations from around the world. In traditional Japanese aesthetics, wabi-sabi, “the beauty of imperfection”, is about products made in a shabby chic style from the start. And the Japanese technique of kintsugi is about repairing broken ceramic vessels with gold, and can be seen as a celebration of breakage and repair as a part of the lifetime of objects.

3.6. Efficiencies of communal living


3.7. Cooking with biogas and hydrogen


3.8. Work / home integration


  • integrating the office or having a home office avoids commuter travel; see the Distributed Collaboration Manual for detailed tips on how to work with your colleagues in such a setup

  • Workplace / office integration. Offices are a very inefficient use of space: they are empty 16 or 24 hours a day, and still consume resources and represent embodied energy and emissions. Rather have your office in your home, for example a super-easy-to-clean room that is an office during the day and a party room in the evening. To be easy to clean, dangling furniture mounted to the ceiling could be a new approach.

3.9. Compact living spaces

TODO: Various good practices and architectural adaptations that allow living with more people in the same space without loss of comfort should go here, including:

  • good practices derived from student accommodation
  • innovative tiny house furniture
  • architectural innovations for better space utilization
  • sound and noise management in compact living spaces

Space-Saving Furniture. This is about “tiny house furniture innovations” so that 20 people can live in a house meant for 10. As a side effect, such furniture can also be used to solve the (urban) housing crisis that young people experience in cities. [TODO: Examples from YouTube etc.]

  • Communal living with or without apartmentalizing. If everyone has an own apartment and on top the communal spaces (party kitchen, courtyard, swimming pool etc.), it becomes more expensive per person, less space efficient and less resource efficient. It can work well in social terms, though. There may be a middle ground of providing individual rooms with private bathrooms each. Student housing in the UK is like that, but not quite. Also, youth hostels are like that, but not comfortable for the longer term.

  • Floors as sub-structuring. In the Cent-vingt-trois project in Brussels, floors emerged as a natural way to structure the space. Each floor had a certain dedication / specialty, for example children, receiving guests, or punk / anarchist aesthetics. The higher up the floor, the fewer random visitors it would get as there were no stairs – effectively allowing people to choose their level of privacy. People could move between floors, and that was the mechanism how the personalities of floors naturally emerged in the first place. This mechanism allowed people to live with people they like, and avoid people they don’t like – which always happens, and is a larger problem in smaller communities where there is less space.

Earplugs against noise. In compact living spaces, space is not an available tool to counter noise problems. For example, if your partner snores, just having separate sleeping rooms is not an option. But earplugs are a good solution for multiple of these issues. Consider always carrying a few reusable silicone earplugs in your jacket. Public transport for example is noisy: it needs to be designed for the hard of hearing. So if you have sensitive ears, plop in the plugs and arrive much more relaxed. Similarly, music earplugs work well to drown out annoying noises in public transport, or if you sleep close to someone who snores, or if there is a lot of traffic where you sleep. For sleep, even damaged earplugs where only one side works are fine (you can cut away the other side). Make sure you don’t damage the earplugs’ wire or the connected MP3 player or smartphone. That can be a challenge at night, so it may be justified to look for some well sealing, used wireless earplugs, even if their battery is weak.

3.10. Controlled ventilation


  • Add the ideas from the comment below and the article referenced there.

  • Include that the building should be tightened against draughts as much as possible.

  • An alternative approach to a fan for air exchange would be a pressure swing absorption system that enriches air with indoor CO2 and only purges that air, which might be 10% or less of the non-enriched air volume, leading to 90% energy saving related to ventilation. If the CO2 can be even more concentrated with this system, an expensive heat exchanger and blower might not be needed at all, as the energy lost by purging 100 times CO2 enriched air is insignificant.

3.11. Climate-friendly diet

TODO: The basics of how to change the composition of meals (not their mode of preparation) in order to be climate friendly. And what effect size this has.

3.12. Small interventions for energy efficiency

TODO: Complete the list of interventions below, and calculate the benefits of each change:

  • Room temperature of 14 °C. It may not be this exact temperature for everyone, but it turns out (from initial experiments by @matthias) that with suitable clothing, something around this temperature is perfectly comfortable even for seated work. It may be that the human body needs a few weeks to acclimatize. In addition, you probably need a solution for humidity management to prevent issues with condensation and mold.

  • Insulating curtains. TODO: There is an article in Low Tech Magazine about the benefits of insulating the inside of windows.

  • Anti-draught measures. TODO: The building should be tightened against draughts of cold air as much as possible. There are ways to measure how tight a building is by inducing slight overpressure with a large fan.

3.13. Free battery storage

In a renewables-powered future, there can never be enough storage for electricity. Here is a way how a small group of people can create a major amount of battery storage for basically free, and even derive financial benefit from it. The benefit comes from the fact that locally produced renewable electricity from free salvaged battery cells is three times cheaper than selling the electricity to the grid and buying it back when needing it later (Germany, 2019). It also is a pioneering effort for the time when grids will buy electricity from distributed storage like electric vehicles at higher prices than they buy renewable electricity at the time of production now.

Here is how to make this happen: In 2015, about 2.4 billion 18650 cells were produced, of which 1.8 billion were used in consumer devices etc. and 600 million by Tesla. These 1.8 billion are a stable yearly demand since 2010 (source). Given the typical lifetime of these cells of less than 5 years (300-500 cycles in consumer devices), this means they are replaced, not added. As these cells are not recycled, 1.8 billion cells are available every year for free. With a remaining average capacity of (say) 2 Wh (~20%) per cell, that means 3.6 billion Wh = 3600 MWh = 3.6 million kWh of storage capacity can be added every year. In 10 kWh units per household, this is enough for 360,000 “free” household-sized backup power plants per year.

These backup plants would be built as follows:

There would be a fireproof charging and discharging station where enough cells can be charged and discharged at a time to cover 80% of the households electricity needs. High demands (“cooking at night with electricity”) will be excluded and covered form the grid instead. By being fireproof and ejecting burning battery cells into a fireproof chamber, even “unsafe” undervoltage lithium-ion cells can be re-used safely.

In addition to the charging and discharging station, there would be large storage boxes where the batteries are stored in bulk. Each cell would be protected with a plastic casing so that the cell holders in the charging / discharging station can reach the terminals but so that the cells in loose bulk can never create a short circuit, because short-circuiting unprotected lithium-ion cells can lead to fires.

A mechatronic system would then be able to remove cells from the charging / discharging station and replace them with other cells. A proposal would be a large wall of battery cells, facing with their negative terminals to a cartesian robot that can extract and insert them one by one. The movement to insert a cell would consists of pushing it in, rotating it by 30° to lock a bayonet style lock, and releasing it, which results in spring pressure on the positive terminal securing the bayonet lock. The bayonet locking points would also serve as the negative terminal, which is possible by removing some of the plastic insulation from the cell’s metal container. Because the whole container is the cell’s negative terminal, with the exception of the one end serving as the positive terminal.

That way, electricity can be stored in pallet sized boxes. A 1 m³ pallet with loose bulk 18650 cells at 25% cell volume to total volume ratio and 2 Wh remaining capacity per cell could store roughly 30 kWh of electrical energy, enough for 4 complete days in an optimized communal household with 20 people.

There is no good reason to make an urban household off-grid, so there is no minimum required amount of battery storage. Every amount provides additional financial benefit, so the commune would simply collect and prepare as many battery cells as they can find.

Preparing the battery cells just means breaking open the batteries of notebooks, cordless powertools, electric bicycles and the like, harvesting the cells and placing them individually into protective plastic containers that also have a barcode on their side. The mechatronic system uses this barcode to automatically register the cell and then stores all relevant information about it: testing results, current carrying capacity, current charge state, performance degradation over time and finally that the cell died and has been removed from the system. This also allows to store cells with mixed charge states, mixed capacities and mixed current carrying capacity in the same container, as the charging / discharging station can identify and treat each cell individually.

A similar system can be created for the rather arbitrarily shaped lithium-polymer battery cells from smartphones, notebook computers etc… They would be placed into standard sized protective containers which then allow loose bulk storage and handling with an automated mechatronic system.

3.14. Thermal mass air conditioning

A simple and energy efficient way of keeping the inside of urban houses cool during the day is using water as a thermal mass for buffering the heat, dissipating it during the night again. Where this is not sufficient, heat pumps can be used as a supporting measure: 25 °C warm water as a heat sink still allows a heat pump to operate more efficiently than 40 °C outside air (see).

This system is the same technique as used for seasonal thermal energy storage, just applied to cooling. It needs a different reservoir (water or ground boreholes) though as the goal is different.

There is no need for seasonal storage here, though. Instead, the water will simply be cooled down during the night again, perhaps with enough buffer for up to warm nights where cooling is difficult. A highly efficient way of cooling is to let the water run down inclined rooftops in a circular pumped loop system, providing radiative cooling to the night sky, plus some evaporative cooling. This can be enhanced by covering the roof with polymers that have a high emissivity in the athmospheric IR radiation window. Luckily, such polymers area available commercially as film material from 3M, as used in this study. There is no need to apply a silver coating as done in that study, as the cooling will be only done during the night. However, applying that cooling provides a “supercool” roof during daytime, cooling to sub-ambient temperatures by itself even under direct sunlight.

3.15. Seasonal heat storage

Ground source or air source heat pumps are the state of the art for emission-free space heating. Here, “Test results [of the coefficient of performance] of the best systems are around 4.5. When measuring installed units over a whole season and accounting for the energy needed to pump water through the piping systems, seasonal COP’s are around 3.5 or less.” (source). This relates to the European standard test conditions of 0 °C source and 35 °C sink temperature.

In comparison, seasonal thermal energy storage with a combination of water tanks and boreholes already provides a seasonal coefficient of performance of 27, also accounting for all pumping energy (source, p. 5, using data for years 7-10 where the system was fully charged). So for every unit of electrical energy, BTES provides 770% as much heat as state-of-the-art ground source heat pumps! Even the theoretical maximum for heat pumps under the above standard test conditions is just a COP of 8.8 (source).

The Drake Landing Solar Community system of water tanks and boreholes used as an example here provided on average 96% of all space heating from solar energy (source, p. 5). As it works with just pumps and no heat pumps at all, this is a DIY friendly and simple system. Also, as it is the first system of its kind, so it certainly has plenty of room for cost savings and further optimization, all of which can be pioneered in urban ecological living projects. During the 10 year runtime since the start of that project they were already able to lower the pumping energy requirements considerably: “The main strategy to reduce power consumption has been to increase the set temperature differential through the glycol loop, which leads to lower flow rates and pump speed. […] With negligible impact on collector annual efficiency, the electricity savings are calculate[d] to be approximately 50% of the amount used with the original control strategy.” (source, p. 7). Their glycol loop needs 33.5% of their total pumping energy, so this equates to 16.75% total savings for pump electricity.

Another possible optimization concerns fully solar powered single-building systems. It seems simple to achieve 100% solar fraction continuously in a system that only serves one household. The reason that natural gas post-heating was sometimes needed in the Drake Landing project is that, depending on outside temperature, a heat fluid temperature of up to 55 °C was required, which might not be available from the BTES. However, the BTES certainly was able to provide 30 °C water, and that can be used for floor and wall heating systems in a single building that is close to a BTES in its cellar or backyard. It is just not economic to dimension all the Drake Landing district heating piping for 30 °C water to be enough even on the coldest days – adapting the fluid temperature rather than the pipe dimensions is more economic there, where much more pipework is involved.

Regarding the charge / discharge efficiency of borehole thermal energy storage:

Reported BTES round-trip efficiency [of 36-41%] is relatively low at Drake Landing due to high groundwater flow However, other studies have reported BTES efficiencies of 80–90%. Thus, proper site assessment regarding groundwater flow is important to promote higher efficiencies. Seibertz et al. determined that monitoring of cooling behavior from thermal gradients makes it possible to identify high ground-water flow zones using a decay time comparison. (source)

In zones of high ground water flow, BTES efficiency might be increased by underground dams, which can be as simple as burying a vertical layer of water impermeable clay around the borehole site, or simply one wall of that on the upstream side of the ground water flow. Alternatively, clay or silt could be injected in a ring of boreholes under high pressures to make the area more impermeable to groundwater flow. Or simply use all boreholes also for groundwater infiltration – after a few years and esp. with water rich in silt or clay, infiltration will no longer occur as the are around the borehole has been made water impermeable due to the silt and clay infiltration.

3.16. Seasonal heat storage with ASHP charging

:bulb: This is a major, unexplored innovation on top of the established seasonal thermal energy storage technology (presented here). It makes heating all winter with solar energy at least 46% cheaper than natural gas. So we explore this idea in detail in this dedicated section.

The concept: charging with photovoltaics and heat pumps. The idea is here to build a seasonal thermal energy storage system that is charged in summer with photovoltaics powered heat pumps and discharged in winter without heat pumps, by running warm water directly through radiators in the building.

  In contrast, all major seasonal energy storage plants (list, p. 11) feature one or both of the following systems: solar thermal collector panels to charge the heat storage in summer, and heat pumps to assist with extracting heat in winter. Plants that only use heat pumps are called “passive”, as they rely on the natural heat of the ground, slowly conducted from depth. In contrast, the Drake Landing Solar Community (DLSC) is one of the few large-scale systems using only solar thermal panels for charging and no heat pumps for extraction.

  The reason why the concept proposed here is so far unexplored is probably because both heat pumps and photovoltaic electricity only became cheap enough since about 2015 to be able to compete with solar thermal collectors the way shown here.

Cost comparison. The final decision for or against a new energy technology is, sadly, often purely financial: renewable energy would be much more widespread if it could compete with fossil fuel cost-wise. For heating, natural gas is the cheapest available fossil fuel option, and here the above concept provides a breakthrough 47% or more cost reduction compared to natural gas. The calculation below uses gas and electricity prices for Germany in 2019.

  • Ground-source heat pump: 0.091 EUR/kWh. This is the most efficient storage-less way to use a heat pump. The calculation is based on 0.32 EUR/kWh grid electricity prices and using a heat pump with a COP of 3.5, which accounts for water pumping energy etc. already: 0.32 EUR / (1 kWh * 3.5) = 0.091 EUR/kWh.

  • Natural gas: 0.063 EUR/kWh. This is simply the consumer price for natural gas in Germany in 2019 (source). Space heating costs will be somewhat higher as gas furnaces have an efficiency of 95-98% and some electricity is needed for pumping. This is neglected here.

  • Heat storage charged with PV + heat-pump: <0.034 EUR/kWh. The system converts 1 kWh locally produced photovoltaics electricity in summer to 3.5 kWh heat using a heat pump and stores it in the seasonal thermal energy storage. From that, 2.8 kWh is extracted again in winter, assuming a high but realistic 80% charge/discharge efficiency. The upper limit for the production cost of 1 kWh PV electricity is 0.0959 EUR, as that is the, supposedly profitable, fixed purchase price obtainable in Germany starting 2020-01-01 from selling PV electricity from plants sized 10-40 kWp (source). This yields a cost of heating of 0.0959 EUR / 2.8 kWh = 0.034 EUR/kWh, representing a cost reduction of 1 - (0.034 EUR/kWh / 0.063 EUR/kWh) = 46% compared to natural gas and of 63% compared to ground source heat pumps operated with grid electricity.

Additional cost saving options. Obviously, the calculations above do not account for the initial investments for heat pump and storage system. However, these costs will decrease as the technology matures, and also by extending the lifetime of the technology. There are also additional cost savings listed below that decrease cost further, so that the idea is probably financially competitive with natural gas given the current state of technology. A more detailed analysis is still needed.

  • Avoiding AC conversion. Additional cost reductions can be realized by running the heat pumps on direct solar DC electricity. To adapt to available energy supply, heat pumps would either run at variable speed similar to water pumps that are already available for this purpose, or multiple heat pumps would run in parallel to scale consumption with production. This avoids the investment in inverters and the 6-8% conversion losses of converting DC to AC electricity.

  • Using second-hand PV panels. Functional second-hand PV panels are available for about 40-50% of prices for comparable factory-new modules, and often even for free because PV modules are becoming a waste problem. The costs of electricity production can be reduced accordingly.

  • Zero-cost air conditioning. The cold air or water produced by the heat pumps can be used for air conditioning, in combination with small (~2000 l) tanks of cold water as thermal mass buffers. Since air conditioning needs are only present when there is sunlight, and a heat pump for charging a STES store is basically an oversized air conditioner, no additional energy for air conditioning will be needed. If energy needs for heating and air conditioning would be the same, this halves the energy needed for them.

  • Saving on pumping energy. Heat pumps need water pumps to charge the heat storage, but no water pumps to move energy from solar thermal collectors to a location close to the heat storage. Instead, electric transmission from PV panels us used, which has lower transmission losses compared to pumping against fluid friction.

  • Cheaper installation costs. Installing PV panels is simpler and thus cheaper than installing thermal solar collectors, which requires a lot of insulated pipework, more heavy-duty anchoring to the room structure etc…

Additional side benefits. The concept presented here has other benefits over thermal solar panels that do not have an immediate financial impact:

  • Electricity is more flexible. Electricity can be used for many more purposes compared to heat, making this solution more agile and flexible than thermal solar collectors. The system is basically a severely oversized PV plant, which will be able to cover the house’s electricity needs even throughout winter. It will also provide the energy for heating, but this is a less urgent need, buffered by several months of heat storage.

  • Suitable for all-electric energy grids. The PV-based system proposed here fits well into the “all-electric” strategy that many countries pursue for their transition to renewable energy. It can for example provide spare generation capacity for the grid, which the grid can use to deal with peak loads.

  • Avoiding grid transmission losses. Since all solar energy is consumed locally, this avoids the 5-8% conversion and distribution losses of the electric grid [TODO: source]. This is not true for the alternative of selling PV electricity in summer and purchasing grid electricity in winter to run a ground-source heat pump.

  • Avoiding peak loads on the grid. Compared to running heat pumps directly from grid electricity in winter, this system avoids peak loads on the grid on cold winter days when everyone would want to run their heat pumps. Likewise, due to all-local electricity production and the cold water tanks, the system also avoids any peak loads (any load, in fact) on the grid for air conditioning in summer.

  • Additional heat available without additional equipment. The Drake Landing Solar Community uses gas burners to post-heat water on cold winter days where the energy storage could not provide the necessary heat. A fossil-fuel free alternative is to run heat pumps with grid electricity in that case. With the system design proposed here, these heat pumps are already available, as they are used in summer to charge the heat storage. Also, some PV electricity is available even in winter, and by converting it with heat pumps to heat and storing it in hot-water tanks for short-term use, most of the additional heat requirements on winter days will not need grid electricity at all.

  • A seasonal storage for photovoltaic electricity. Compared to running ground-source heat pumps in winter, this system basically provides a very large, seasonal accumulator for solar electricity. It is stored in summer when it is available in excess and used in winter. Similarly, day-to-day volatility of solar PV production in winter is also equalized via heat pumps and short-term heat storage. This is a major part of solving the volatility issue of renewable energy, here be storing it as usable heat and not as electricity.

  • Alleviating the urban heat island effect. Thermal solar panels of ~34% module efficiency are basically black surfaces that convert all sunlight to heat and route 34% underground while 66% heats the air, contributing to the urban heat island effect. In contrast, PV modules with 21% module efficiency coupled with a COP 4.5 heat pump will, on the net, route 21% * 4.5 = 94.5% of the solar energy hitting the collector area underground. This way, it helps to alleviate the urban heat island effect, as this is equivalent to a cool roof with 94.5% reflectivity. When this technology is deployed on a large scale, this should become noticeable.

  • Much higher collector efficiency. Thermal solar collectors have a module efficiency of ~34% (the DLSC example) while modern monocrystalline PV modules achieve “only” 22.8% (source) – we assume 21% here for readily available modules. Heat pumps boost the PV module efficiency: to exceed a thermal solar efficiency of 34%, a heat pump would only need a coefficient of performance larger than 34% / 21% = 1.62. This is easily achievable. Using 25 °C indoor air as the source and 60 °C water as the output, the temperature difference is 35 °C, just as in the European standard test conditions for heat pumps. Under these conditions, heat pumps achieve a COP up to 4.5 (source), nearly tripling (!) the effective collector efficiency compared to thermal solar collectors (note :speech_balloon:).

    With a COP of 4.5, the PV / heat pump combination makes for an effective thermal module efficiency of 21% * 4.5 = 94.5%. Well irradiated outdoor space is often the limiting factor in cities, so being able to install 94.5% / 34% = 2.8 times more solar heating capacity than with thermal solar panels is a major improvement.

  • Better cold-weather performance. Due to their limited thermal insulation, flat-panel thermal solar collectors have a bad efficiency in cold weather. Evacuated tube collectors perform much better here, but are also much more expensive and need more surface area for the same nominal (summertime) heat output. Evacuated flat plate collectors combine the best of both worlds, but are also expensive and not yet readily available on the market.

    In contrast to that, photovoltaic modules have a higher efficiency in cold weather due to lower silicon temperatures. PV modules will easily be the most efficient collector in wintertime, as even evacuated flat panels will not achieve their 94.5% effective performance (as calculated above) in full sun. In overcast sky conditions, the advantage will be even higher because thermal collectors would not achieve the minimum temperature for space heating (30 °C) and thus have 0% effective performance, while PV panels with enough surface area can still power at least one heat pump. So to achieve a high direct solar contribution to heating in wintertime, this is clearly the best choice.

Water tanks as possible main storage. Water tanks are an established option for small seasonal thermal energy storage plants (see). They require less pumping energy to charge and discharge, providing an even higher COP. Also, they make the heat faster accessible, while ground based storage needs water tanks as buffers because heat cannot be extracted as fast. However, they require space, which will not always be available in city buildings; and beyond a certain capacity the total costs of a tank system become larger than that of borehole thermal energy storage.

  Now when applying the heat-saving techniques from this document first (heated clothing, small heated spaces etc.), a building’s heating requirements will already be 75%-90% lower. At that level, seasonal thermal energy storage with only water tanks could become the best option, both financially and space-wise.

Back-of-the-envelope calculation: water tank for a 20-person household. Seasonal thermal storage is more efficient the larger it is, as the lower surface-to-volume ratio prevents excessive heat loss. So let’s estimate the necessary size of a hot water tank for a 20 person household such as the future Reef:

  1. EU-28 heat needs per person. Space heating plus water heating in all households in EU-28 Europe in 2017 was 7 635 790 TJ + 1 762 499 TJ = 9.398289 EJ (source, via)

    Europe had ca. 511 million people in 2017 (source). This means 5109 kWh/(person * year) (calculation). Since this is an average for all of Europe, it will apply pretty well to the heat needs in a central European location.

  2. Stored heat needs per person. The example from DLSC shows that direct solar irradiation can be used to cover about half of household heat consumption over the course of a year, so the storage should be for about 60% of the year’s total heat requirements: 5109 kWh/(person * year) * 0.6 = 3065 kWh/(person * year)

  3. Tank volume per person. Water has a heat capacity of 4180 J/(kg*K) and the usable temperature difference is at most 65 K (30 °C floor heating water to 95 °C initial storage temperature). So to store 3065 kWh/person for the heating season, this would require 37.7 m³ of water per person (source).

  4. Applying efficiency. Assuming that 80% of heating needs can be saved with energy conservation measures including other techniques from this document, this is reduced to 37.7 m³ * 0.2 = 7.54 m³ to store 3065 kWh/person * 0.2 = 613 kWh/person.

  5. Storage sizing for 20 people. For a 20-person community household, this results in a total required storage volume of 7.54 m³ * 20 = 151 m³ to store 613 kWh * 20 = 12 260 kWh.

  6. Tank measures. An interesting architectural option is a used stainless steel storage tank from the chemical industry placed centrally in a building. Structurally it would rest on the ground and be insulated all around to prevent excessive heat losses. Heat leaks in summer would be offset by the heat pumps providing cooling, and in winter they would contribute to space heating, improving the charge / discharge efficiency. In a four-storey building with an undivided upper storey and 2.30 m “economical” storey height, 6 m tank height plus insulation should fit into three storeys (confirmed below, as 40 cm insulation is needed). Assuming a simple cylindrical form, a 151 m³ tank of 6 m height will then be 5.66 m in diameter (source).

  7. Insulation thickness. 20% seems a good guess for base load heating that never has to be turned down during the heating season. In other words, 20% natural heat loss through the insulation during the heating season is acceptable, which amounts to 12 260 kWh * 0.2 = 2452 kWh. We have a 6 month = 180 day heating season and 157 m² tank surface. This allows an average heat flow of 2452 kWh / (180 d * 24 h/d * 157 m²) = 3.62 W/m². With a (95 °C + 30 °C) / 2 = 62.5 °C average tank temperature, the temperature difference to a 14.5 °C indoor temperature is 62.5 °C - 14.5 °C = 48 °C. Styrofoam insulation has a thermal resistance of 0.03 W/(m*K). To limit heat flow to 3.62 W/m², it would have to be 40 cm strong (formula, calculation).

  8. Lost floor area. A tank of 5.66 m + 2 * 40 cm = 6.46 m diameter means that a floor area of pi * (6.46 m / 2)² = 32.8 m² is lost per storey, or 3 * 32.8 m² = 98.3 m² over the tanks three-storey height. Assuming a “compact but reasonable” 25 m² per person (between a 13 m³ legal minimum and the current 42.5 m² EU-28 average), a 20 people household would have 500 m² net, or 500 m² + 98.3 m² = ~600m² gross floor area including the water tank. So 16.4% of floor area is lost to the water tank, which is considerable but doable.

  9. Necessary PV area. To collect the tank’s total 12 260 kWh stored usable heat with a system efficiency (incl. charging pumps) of 21% * COP 3.5 = 73.5% in 6 months non-heating season in May to October in Munich (where 65.4% of the total PV production occurs, of a total of 947 kWh / kWpsource), the required collector area is just about 27 m² (calculation).

3.17. Ecologically responsible childcare

Unsupervised child play. In a communal space that is somehow enclosed (not like a gated community, but a bit …), unsupervised play is simple, even in today’s age and in cities. Children can become quite self-sufficient – @alberto mentioned how in such a neighborhood in Milano, the children made all the adults keep their doors unlocked so the kids could go in and out of the houses of their friends to get water, go to the toilet, meet their friends etc… It made the environment more social for everyone, and is more efficient regarding adult attention. It’s not directly “green”, but frees up precious time for other activities, including for those that take more time but less other resources and are thus part of “green living”. It also lowers the need to move children around in a car between activities.

Provision for children activities at home. “Do you really need your children be driven to karate and back? Make them a football place in the courtyard instead.” And similar approaches. It uses less energy for transport, and it frees up adult time for other aspects of a greener lifestyle, which is often more time-consuming.

3.18. Cool and supercool roofs and walls

Surfaces that both reflect incoming sunlight and also cool by emitting IR radiation, preferably in the atmospheric window, keep relatively cool under direct sunlight and can even cool to subambient temperatures (see: overview of recent research). One of the most promising materials for mass production is just a commercial dual-polymer film material coated with silver sputtering on its back (source).

Applying existing paints and materials and also the new materials in architecture can provide better energy efficiency and comfort in summer:

Cool roofing limits total cooling loads in summer, reduces the severity of the urban heat island (UHI) problem in towns and cities, and helps eliminate peak power demand problems from operation of many air conditioners. Added feedback benefits from cool roofs […] include ventilation with cooler air and higher performance of adjacent chillers when in cooler air. (source)

3.19. Ecological construction indoors

It will be difficult to apply cob and other natural, upcycled or otherwise low-footprint building materials on the structural parts of buildings due to legal regulations and durability in outdoor conditions. However, all kinds of separation walls, thermal mass and sound insulation elements on the inside can be built from cob and other natural materials that “can be sourced in the backyard”. This is esp. useful when the stories of a building only have structural outside walls and just pillars inside, and when the ceilings are durable enough to carry the additional weight of indoor cob walls.

Example techniques:

  • Indoor cob plastering. This can easily be applied in urban living situations, both with respect to looks and practical considerations. See for example how it is used in this refurbishing project. Cob can usually be made from local soil on-site, as most soils contain a certain amount of clay that can be extracted.

  • Wattle and daub. Can be used for indoor separation walls of varying thickness.

  • Papercrete. Papercrete is a light and well-insulating material that can be locally made into blocks or poured into whole walls with just trash paper and concrete as its ingredients.

Literature: (all works are available online in open access fashion)

3.20. Heating with compost

Composting produces low-grade heat, but in both household and industrial composting, this heat is not used for anything. It can however be used to heat a whole house, as shown below. For a good overview of all published material about compost heat extraction, see: “Heat Recovery from composting: A Comprehensive Review of System Design, Recovery Rate, and Utilization”.

The compost produced from kitchen scraps of urban inhabitants will not be enough to provide all the heat required for space heating, but collecting organic trash for free around the neighborhood is easily possible. Heat extraction from composting is similar to partially burning the biomass. Usually, the amount of heat recoverable depends heavily on the scale on the system:

On an energy-per-weight basis, energy recovery rates were 1159 kJ/kg DM [dry mass] (s = 602 kJ/kg DM) for lab-scale systems, 4302 kJ/kg DM (s = 2003 kJ/kg) for pilot-scale systems, and 7084 kJ/kg DM (s = 3272 kJ/kg DM) for commercial-scale systems. (source, p. 11)

This is due to much lower surface-to-volume ratios in large-scale systems, avoiding heat loss to the environment. In the system below, all heat loss to the environment contributes to space heating because the compost heat is placed inside the house, so we can assume the 7084 kJ/kg dry mass heating value of compost. In a highly energy efficient community of 20 people, a total of 12 260 kWh is required for space heating. This would be contained in 12 260 kWh / 7084 kJ/kg = 6230 kg of compostable biomass on a dry mass basis, resulting in 6-10 m³ of humus produced per year (TODO: better numbers). The compost vessel size should be large enough to store as much finished humus as can be loaded on a typical tipper truck or trailer for transportation to farms.

There are several advantages over burning biomass: (1) no need for drying the biomass before burning; (2) all biomass can be composted, whereas biomass burners are always specialized for one sort of fuel only; (3) there is no particulate air pollution in contrast to burning wood, and this is an important point in cities; (4) the end product is humus, a valuable agricultural input, and its accumulation in soil is a way of carbon sequestration. In contrast, the complete burning of biomass is at best carbon neutral.

In addition, there are advantages over the current practice of municipal collection of organic trash and centralized composting: (1) the heat is used for space heating instead of being lost; (2) the humus end product is significantly lighter and more compact than the initial biomass (incl. branches, leaves etc.), which should make its transportation to farms about 3 times more energy efficient (a guesstimate, so far); (3) the neighborhood-scale collection can be done manually because the weight, volume and distances are small, and this decarbonizes this part of the collection logistics.

An initial proposal for a system would be to place a 2-2.5 m diameter stainless steel tank vertically into the center of the house, containing the composting biomass. The tank can for example be obtained second hand as a 20 ft tank container. The biomass would be filled in at the top and extracted after 2-3 years at the bottom. Different from all systems outside of buildings, here 100% of the composting heat will eventually be used for space heating as it seeps through the walls into the building. The tank would be insulated enough to prevent excessive heat loss or heating up the surrounding rooms too much, and if necessary a heat exchange loop of copper tube might be routed between the tank and insulation and route captured heat into a hot-water tank for distribution to other parts of the building. Some other equipment will also be necessary: forced ventilation with compressed air from below; a heat exchanger in the hot steamy compost fumes; and an extraction screw, ideally pouring the compost right on a truck parked aside the building.

3.21. Flexible electricity demand

Even before this is used as a feature in the national grid, you can “help the grid” by consuming electricity only when renewable energy production is high and demand is low. If everyone does this, it avoids the need for most energy storage, currently the biggest challenge of integrating renewable energy into the grid.

Examples include:

  • Cook with electricity when renewables production is high, otherwise cook with biogas and hydrogen. This also applies to the water kettle – instead of an electric kettle, develop and use a dedicated gas-powered water kettle.

  • Use a circuit that starts the washing machine and dishwasher when a delay, triggered when renewables production is high.

  • Have enough clean clothing so that using the washing machine only becomes necessary every 2-4 weeks. That should be enough buffer to catch times of high renewables production. You basically store energy in clean clothes.

  • Use fridges and deep freezers with cold storage and an extreme amount of insulation. Such devices are already made for campervans. They store energy non-electrically in cold and can stay off for 12 hours or more while renewables production is low.

3.22. Workshop, parts and a handyperson

A building with 15 or more inhabitants that intends to emphasize ecological living can afford to employ one handyperson for building management, usage optimization, repairs and custom manufacturing.

That person will come with a complementary skillset of broad handicrafts and tech knowledge, a workshop and parts store that together enable a multitude of ecological living techniques that are not possible in smaller households:

  • When there is a person who is paid to monitor and optimize a building’s energy and resource efficiency, the incentives stack up correctly for this task to be done. That alone might already pay that person’s full-time salary. In normal households it’s the opposite: inhabitants are careless with resources because that allows them to have more time or energy to earn the money to pay for that carelessness “and some more”.

  • Inhabitants can drop off household appliances and electronic devices to be repaired, or even better do the repairs together with the handyperson. As there will be a store for all kinds of parts and tools to adapt parts and even manufacture custom parts, repair and maintenance jobs become much cheaper. For example, with 10 broken bicycles you can keep your own bicycle running for free, forever.

  • Furniture can be repaired and even custom built from parts of old furniture, trashed furniture, homegrown bamboo etc. and other material found in an extensive “parts library” near the workshop. There is no need to ever buy new furniture.

  • Inhabitants can design small helpful devices together with the handyperson, and manufacture them with in-house tools incl. a 3D printer. These devices will be very specific for the local context and can enable idiosyncratic energy savings and resource efficiencies that are impossible with purchased products. TODO: Examples from Thingiverse.

  • Inhabitants have a patient mentor to learn new tech skills themselves incl. bicycle maintenance, computer repairs an other useful skills for their personal future. This can be extended into neighborhood-scale handicrafts events and courses, which over time will enable a lot of people to provide items from home-based repair, remanufacturing and production, rather than from purchasing anything new.

  • Inhabitants are welcome to drop off any unused item in the parts library and tell what should be done with it (lending, gift etc.). The handyperson will catalogue and sort it in accordingly, and somebody else from the household or neighborhood will use it again at the next opportunity. This makes reuse so comfortable that people will actually do it, esp. since it provides the immediate benefit of physically getting rid of “useless stuff” that will then reside in the parts library.

  • The handyperson will collect certain types of wastes from the neighborhood and city and can do hacks and remanufacturing with them that are impossible in industry because they cannot be automated or because of safety concerns for consumer products. Examples include: harvesting solar cells from broken photovoltaics modules and building new modules from them; harvesting lithium-ion cells from broken accumulators and creating “free” battery storage for the house from these.

If the household cannot afford paying a normal wage for this as a job, then the job could also be the equivalent of a live-in nanny job for a handicraftsperson: instead of caring for people, that person cares for things, in exchange for a place to stay, food, health insurance and a moderate amount of money. That person might come from abroad, just as live-in nannies often do.

4. Interventions against waste

Circularity is a property of ecologies, where “ecology” means a long-term sustainable system of all species incl. humans. This means that avoiding permanent waste lends itself as a suitable goal for sustainable living, even though it contributes to other goals as well. For example, longer product lifetimes avoid manufacturing, which saves the GHG emissions from transportation and industrial processing.

This section includes everything that avoids products becoming waste: in an ideal setting, products are either avoided, repaired, reused or recycled, as much as possible within the home. It also includes everything that avoids or cleans up pollution, and everything that avoids the external transport and processing of unavoidable waste, such as organic waste. Wastewater is rather treated in the section about the water cycle.

4.1. Radically avoiding material consumption

A household’s energy consumption can be switched to be green fast and easily: just switch to a provider of renewable electricity, ditch the car, and use heat pumps for space heating. This is very different for all material consumption, as the industrial processes happened in the past, far away and in a complex network of suppliers, making it impossible to guarantee that any physical product was produced “sustainably”.

For this reason, material consumption should be avoided as radically as possible. Another reason is resource depletion, because in any not-fully-circular economy, material consumption permanently increases resource entropy, making resources permanently unavailable for future generations.

The ways to avoid material consumption are nicely summed up in the 4R principle (“Reduce, Reuse, Recycle and Recover”), however it needs some unpacking. For example, it entails the following not-too-obvious changes:

  • Fashionable and new / clean looks is not a criterion to decide if a resource (clothing, car, furniture) is still good to use or should be discarded.

  • Sharing resources is a way to reduce their number, such as tool sharing in a neighborhood tool library.

  • Good operation, protection and maintenance is a way to reduce the need for material products, because they will break less often and will be sufficient even when not performing like a newest-generation product.

  • Buying used items reduces the demand for new items.

  • Sometimes, you can replace material consumption with energy consumption. For example, downloading a film instead of buying a DVD.

4.2. Plastic free living


  • Have a (communally researched) list of local purchase options etc. for no-plastic-packaging food etc…
  • Share your grocery shopping – that is needed to be able to get items plastic free, as plastic-free shops might be further away, or sell in larger quantities.

4.3. Against food waste

Food waste is 15% of GHG emissions.

Avoiding food waste is a communal activity. That’s a major aspect of greener living that is possible in community, and less possible in small households. Because with more people, larger amounts of rescued food can be utilized, with a large commercial kitchen food can also be preserved easily etc… On top, rescued food can be shared in the neighborhood, which makes urban living greener even for others.

Food preservation workshop:

  • solar dehydrator
  • canning and pressure canning equipment
  • large collection of canning glasses
  • fermenting equipment

5. Interventions for the water cycle

This includes everything that conserves and recycles freshwater, prevents and cleans up water pollution, helps with groundwater infiltration and evaporation. The latter is a major (and neglected) component of the water cycle and provides immediate local benefits through cooling. There are more aspects how the environment contributes to the water cycle (cloud seeding etc.) but it seems that it would need a much larger area than cities to influence them.


5.1. Rainwater capture and infiltration

Relevant literature:

  • To Catch the Rain. About rainwater harvesting. The book is open content but you need to enter your email address to get it .

  • Prospects for Managed Underground Storage of Recoverable Water. 2008. 350 pages. Very interesting discussion of how to store excess water in groundwater, by infiltration with basins, trenches and wells. Quite high-level and not containing instructions directly, but instructions can be derived from this after study.

5.2. Water evaporation

Runoff water and even lightly contaminated greywater is usually not suitable for groundwater infiltration, and infiltration of pure rainwater also makes no sense if your city has extensive systems in place to drain groundwater away as fast as possible.

In these cases, evaporating that water is another meaningful way to use. Water vapor carries away a lot of sensible heat, so if applied in a whole neighorhood, evaporating large amounts of collected water during the summer will probably reduce outdoor temperatures. (TODO: Add numbers of a guesstimate for this.) Just take care to not install any dark surfaces in order to support water evaporation – if the intention is cooling, this is self-defeating as it only contributes to the urban heat island effect.

As a side benefit, evaporating the resulting greywater allows you to legally use collected rainwater for free, that is, without having to pay wastewater fees for it. When applied on a large scale and in tandem with careful water conservation, wastewater grading and filtration at the point of consumption, it should even be possible to avoid 90-95% of wastewater making it to the sewage system at all. This is not a major challenge in European cities, but in developing cities it may be a way to deal with the overchallenged or non-existing sewage system. A public sewage system might not be needed at all, as the remaining wastewater can be collected with pumping vehicles.

TODO: Practical ways to evaporate water, including a garden, a garden with a closed bottom, sprinkling the roof, sprinkling the asphalt of public streets, and flat-plate evaporators where the resulting solids can be scraped and disposed in the end.

6. Interventions for other species

This includes everything that supports the well-being of non-human species of the biosphere, from animals to plants to molds and bacteria. Unlike the other sections, this is rather about inspiring examples and less about numbers, because the ecological benefits are really hard to quantify, and because the impacts of urban households will necessarily always stay small because they cover such a small area only.

TODO: Elaborate on the following ideas / notes:

  • voting with your money against habitat destruction: Buycott
  • habitat for birds, based on the UK study that found birds multiplied a lot because people feed them over the winter
  • habitat for insects, based on the U.S. example of a guy providing the protected space for this one endangered butterfly species

7. Material collection (TODO)

Literature tips from Autarky Library

Foam pads for comfort and warmth

Until public transport starts offering extra cushions for the knees of very tall people, or the backs of somewhat delicate riders - just bring your own. It does not have to be an overpriced outdoor pillow. A folded piece of down-cycled yoga mat, or sleeping pad will do fine. Store it directly against your back in a rucksack for improved carrying comfort, or better protect a notebook’s bottom edge, with minimal weight or volume issues.

Now you can also work far more comfortably at that coffee place or in the park and pick your favorite place without getting cold too quick.

As another side effect, this kind of clothing system might find its first entry into the market as outdoor clothing for professionals working in cold weather regularly.

Sharing and services related interventions

Sharing stickers, sharing insurance,

“Ebay-agents”, “Bike repair agents”, “Upcycling agents”, “trusted neighborhood mail/shopping agent”

Small fans

With low power and low noise. Sleep, work, drying clothes indoors.

Resource efficient hygiene

  • showers
  • hygiene standards and communal living

Mobility related interventions

  • For cycling, automatic door closers adjusted for bikes and kids

  • Shared bike locks (Bluetooth codes) - share with friends, social cohesion

  • E-bikes and commutes (event week / month + incentives to curb apparent extremism), e-scooters charging and energy awareness
    Better practices and less prejudice concerning remote work

Mobile tech life extenders

Many notebooks and mobile phones break because they are mishandled / dropped. Simple interventions allow …

Choosing ecologically beneficial work

This should include numbers about the climate impacts (and other ecological impacts, where possible) of different types of jobs. Office jobs where you don’t do anything of effect at all may be quite beneficial under these measures. Ecosystem restoration work is even better, of course.

Heat recovery from wastewater

Heat from all wastewater should be extracted using passive cooling and, in a second stage, an electrical heat pump, before finally discharging the wastewater. There will be an optimum temperature for discharging the wastewater, namely the temperature where heat can be just as efficiently extracted with the heat pump from outdoor air or (better) the ground. Ground temperature is ca. 12 °C year-round, so that would be the temperature to discharge wastewater at. Or probably a bit lower (9-10 °C) as heat extracting from water at surface level does not need as much pumping energy as extracting it from a 30-80 m deep borehole. The average wastewater temperature can be determined based on hot and cold water volumes in a household, and from that the recoverable energy can be determined.

GHG offsetting

It may turn out that emission offsetting by donating to the various schemes created for this purpose is, for the time being, the most effective intervention for the climate that affluent urban residents can make. This will change once the low-hanging fruits of carbon offsetting are gone and demand for it rises, at which point the price (EUR / t CO2e) will rise and some local solutions to avoid emissions become more cost effective. But for the time being, earning more money and donating it for emission reduction could be best for everyone who can earn more money. [TODO: Calculate if that’s the case, and up to what carbon price.]

TODO: Include instructions, or links to instructions, for cost-efficient carbon offsetting. For example, in Germany donations to some of these projects can be registered as tax-deductible donations up to a limit of 20% of ones annual income, reducing income tax accordingly.

Climate-friendly investing

Next to offsetting, this may turn out to be the second most effective intervention for urban residents, if they have money to invest. TODO: Do the numbers.

Intra-city hospitality networks

These networks would allow to stay over at or near a place one visited in a different part of the city. Unlike AirBnB and similar, this system would work without monetary compensation – instead, it is in exchange for hosting other people at ones own place.

Benefits include:

  • Not having to use GHG-inefficient transport modes, which are often the only ones available late at night: cabs and night buses.

  • Time savings when one has to visit the same place or a place in the same part of the city again the next day.

  • Extending the capacity of a communal home for guests by temporarily moving out for a few days.

Climate-friendly hospitality

Hosting friends etc. coming to the city is probably most climate-friendly in a guest space or guest room inside ones own house. TODO: Calculate a comparison of an own guestroom with both a hotel and different types of AirBnB offers.

Insulated indoor clothing

When they can choose, people prefer a warm room and thin clothing over a cooler room and warm clothing. This seems to be because warm clothing is often heavy, uncomfortable and movement inhibiting.

It does not have to be like this. Heated clothing is the most extreme solution to this challenge, but before going that way, a new style of indoor clothing can go a long way. Even with just one light down jacket and a shawl, comfortable desk work is permanently possible down to 14.5 °C (data point by @matthias). With highly optimized non-heated clothing, it should be comfortable down to 10 °C, perhaps even to 8 °C.

A few design hints from personal experiments include:

  • The clothing should be very light and very compressible, because that makes it not inhibit any movements. Down clothing with very light ripstop fabric is so far the best choice, both for jackets and trousers.

  • A shawl is a surprisingly effective piece of clothing.

  • Footwear deserves special attention as the feet are usually the first part of the body to start feeling cold, both because the feet have low blood circulation esp. at rest, and because air close to the floor is usually the coldest air in the room. There are some aerogel insulated outdoor shoes produced commercially. An aerogel insulated indoor shoe could become a well-loved type of clothing, and lends itself to DIY production.

As a side benefit, it may be that resistance against respiratory infections is higher for people who are acclimatized to inhaling cool air because they live in cool rooms all the time. This is just anecdotal evidence for now (by @matthias) but there might be studies or other data to confirm it.

Automated building control system

It seems that a lot (!) of energy efficiency and resource efficiency can be gained when controlling indoor temperature, humidity and electricity consumption with an integrated electronic system, running open source software that can be easily adjusted by the building inhabitants and that is intelligent enough to optimize internally for how to achieve its goals. Example functions would include:

  • Deciding when it is better to purge excess humidity by heating and ventilation in intervals, and when it is better to use chemical absorbent that can be regenerated with heat in the summer again.

  • TODO

There is also value in having a peer-to-peer relationship between this technological system and the inhabitants, collaborating to achieve high targets of resource efficiency. This is different from the usual scenario where humans treat “their” technology as a slave. For example:

  • The house control system might realize that it would have to start burning heating fuel soon as the heat buffers run low, and in turn might ask humans to use prepared room separation measures to close off some spaces as unheated space during the passing of a cold front.

  • The house control system might realize that room temperature in a certain room is abnormally high, and send a human to investigate.

Cargo bicycles and electric cargo bicycles


Neighborhood CSP

The above sections contain several uses for direct solar radiation already, including for borehole thermal energy storage. Together, it means that all available direct solar radiation is valuable and should be harvested. This requires solar tracking mirrors.

With the right design, solar tracking mirrors these can be much cheaper per surface area than photovoltaics panels or thermal solar collectors, allowing economic installation in locations where photovoltaics or thermal solar is not economical, esp. the vertical walls of buildings. This means that CSP and photovoltaics do not compete for the same space. Solar tracking mirrors can also be installed on top of photovoltaics panels or integrated with them into the same modules (of ca. 15 cm thickness). Then, the mirrors would be aligned to produce minimal shadows whenever PV production is more important. And that will only be the case some of the time: CSP has a higher efficiency than PV collectors and at times of direct solar radiation the grid and all storage might simply be saturated with solar electricity. During diffuse light conditions, the system will be in PV production mode of course.

A quick outline of the design would be like this: imagine self-contained modules of the size of typical PV panels and about 150 mm thick, which can be installed both vertically on walls and as pivoted window shades, and inclined or horizontally on roofs. They would contain arrays of 140 mm mirrors, protective glazing, a mechatronic system to control the mirror alignment, a wireless interface to receive instructions for mirror alignment (for example Bluetooth LE) and small PV panels to power this mechatronic system. These modules would be installed on all surfaces in the neighborhood that receive a reasonable amount of direct solar radiation during the year and have at least one sink in line of sight. One computer would receive “light requests” from sinks, “light offers” from mirror modules, and would calculate mirror alignment commands to direct mirrors to sinks. As the mirror modules are self-contained and encapsulated into a closed space, they do not require attention or external energy after their installation.

Sinks for direct solar radiation would include:

  • water tanks made from black metal and insulated behind vacuum by encapsulating them inside an evacuated glass vessel

  • black metal receptors on elevated positions, with a heat exchanger to heat water that is then cycled to heat water tanks inside the house (from where the heat may later go into borehole thermal energy storage)

  • large black metal pots, similar to water tanks but meant for higher temperatures, allowing to regenerate calcium chloride drying agent at 170 °C etc.

  • windows, to heat a room or provide natural lighting with moderate amounts of concentrated sunlight

  • solar kilns, drying large amounts of biomass fuel

  • air heaters, then using the hot air to dry large amounts of food items (directly exposing food to solar radiation should rather be avoided as it degrades the food)

  • wastewater evaporators

Communal childcare spaces

Safe spaces for children to make parenting and childcare less time consuming. This also allows for community members to care for groups of children, relieving other community members to do other work.

Should be integrated with the normal living area as much as possible. For example, for small children: if the building has a large inner courtyard with child-safe toys, plants etc., that’s is a good choice. Plus, in winter, an indoors room for the same task.

In terms of saving emissions: it avoids the need for kindergarden buildings, heating that building, and transport to and from that building.

Office / party space

An office and co-working space during the day that can be quickly converted into a party space at night.

The coworking space would include good office equipment (incl. printers, a film plotter etc.). Also, a self-service coffee machine and coffee would be provided. Then, by flipping some furniture around, the space will transform into a multi-use space for parties, yoga sessions and the like.

Mobile Personal Shelves

This is the replacement of the more normal “one room per person” concept which is totally a waste of space.

People don’t get own rooms in the commune, but own shelves. The shelves would have wheels and look like sack barrows with boxes on them, so they can be moved around in the house easily, including up and down stairs. This way, people can move between rooms in a few minutes, or store their shelf when leaving the house for a few days, both enabling full utilization of the available space.

In addition to the rolling shelf, there would be a communal storage room for other items, where everyone would have one or more lockable shelf compartments. They would be able to keep these even while not living in the house, for long-term storage. Even the mobile personal shelf itself can be locked in there.

Mobile Spare Beds

Proposal: 10-20 folding cots made from bamboo, with attached bednets and rain covers, to sleep on the rooftop when needed. They can of course also be placed inside rooms.

Private Bathrooms

Giving every member their own bathroom with toilet, urinal, wash basin and shower is one of the simplest ways to prevent transmission of (gastrointestinal) diseases in the commune. Everyone would also clean their own bathroom, of course.

On the other side, this move also decreases the need for bathroom hygiene, as one cannot infect oneself with own germs – one will either be infected already, or immune already against these germs. This way, the time, water and detergents needed for cleaning are all reduced, and likewise the potential social friction over cleaning the bathroom.

Neighborhood services

  • Local business database. Should include all shops / businesses in the city and the surrounding villages, and also all the products they have, as long as they are interesting for potential purchasing. Businesses further away would also be included if they sell something that is rare / precious enough to be purchased from further afield.

    By providing others access to this information online, it basically creates a local online shopping platform.

    The commune would of course prefer to buy local products in order to create and support the local economy. And that is how it would use this business database: instead of purchasing something from a big city or from abroad, commune members would first evaluate if they can get alternative products from the local area. This will be true for many agricultural items, spices, herbs etc., and also for furniture, basketry work, blacksmith work etc…

  • Map with points of interest. This should esp. be integrated with the local business database, but will also have other POIs besides that.

    See: “Creating a “Points of Interest” map with open source tools”, https://edgeryders.eu/t/9067

    Should include features to contribute back to OpenStreetMap.

  • Resource reservation system. Technically, this is one of multiple applications using the database records dealing with “things”. See my analysis of suitable open source software: https://edgeryders.eu/t/6629 . This includes two Python based open source applications that can be used as a basis. If the commune integrates a guesthouse, this system has to be usable for commercial guestroom booking. Then, it must allow payment in money (via Stripe) and PayCoupons.

  • Webshop. * For outsiders to be able to see and buy the commune’s products and services. Technically, this is one of multiple applications using the database records dealing with “things”.

Building material remanufacturing


  • Glass wool and rockwool. reusing glass wool sheet material as blow-in glass wool

  • Polystyrene. Polystyrene foam from old buildings, packaging etc. is typically simply burned, but it can easily be glued into new blocks in a DIY manner.

Various ideas

Diet: By supplying the body with external heat (from heated clothing, to make it efficient) it can be put on a hypocaloric diet and still be thermally comfortable. Since food contains a lot of embodied emissions, this allows to save about 25% of them, or up to 40% when starting from the average daily calory intake which includes about 400 kcal in excess of what is necessary to keep ones weight (U.S. data).

It is also possible to be comfortable in cold rooms mostly due to a hypercaloric diet: stay in cold rooms for some weeks, then start eating a carb-rich hypercaloric diet and you’ll feel comfortable with light clothes in 13 °C rooms, possibly below. The body will produce more heat from the available excess food, and this will be very noticeable and last 24 hours a day.

In total: if you can choose, choose heating with heated clothing, then food, then space heating.
avoiding all food waste: half of all produced food is currently wasted, so it’s possible to half the worldwide emissions from food by just reducing food production by half and avoiding all waste; alternatively, half of the population can eliminate their emissions from food completely by eating what would otherwise be wasted
The major emission sources globally (considering all GHG gases by warming potential) are, in 2010 data:

  • energy (heat and electricity production): 47%
  • agriculture and land use changes: 21.4%
  • transportation: 11.2%
  • residential and commercial buildings (mostly construction due to concrete usage): 7.6%

For urban ecological living, it is essential to care about heat, electricity, diet and transportation, in that order. Everything else is kind of negligible.

Source: https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions#emissions-by-sector
VAWT grids are said to be more efficient by 1000%. Could be added to urban rooftops.
looking for a parking place
traffic jam avoidance
statistics about person km per country, split by urban and rural
advanced LED lighting
distributing rooms in the house according to temperature preference: people. who like it warmer in their room will get rooms close to the center of the building, without outside walls, so that the waste heat from their rooms will heat the rooms of others who have rooms bordering outside walls. Also, the kitchen and living room would be in the center.
errand aggregator: an efficient system that avoids traveling in the city by making people help each other out with their errands
Personal consumption tracking and rationing: in a communal living setup, water taps, electrical sockets and perhaps even light switches would detect who operates them, aggregate the usage in digital form, inform about excess usage, and perhaps even deny service when somebody is much in excess.

However, when harvesting rainwater locally and generating electricity mostly from photovoltaics, this only makes sense for the electrical stove, oven and water kettle in the kitchen.
modern dorms: It makes no sense to build, heat and clean complete rooms just for sleeping 8 hours a day. Instead, a different style of dorms could be great. Each person or couple would get their own “pod”, with a curtain etc… There would be mixed dorms for singles and perhaps even dorms for couples. Dorms would not be very large, but fit 6 people into a room that would usually sleep 2. This way, people can cluster in groups that like each other and are compatible (regarding snoring etc.). In exchange, dorm sleepers get access to a luxurious room that they can book by the hour without costs (for making love, when being sick etc.). Dorms would use pods in two layers and sound and light sucking material and shapes everywhere (against snoring etc.). Both the dorms and the pods theselves would also be heavily insulated so that ideally, dorms will heat themselves from the body heat of people inside.
large compact buildings: when you can choose, choose a building that is as close to cube or sphere shape as possible and is wall to wall with other buildings, because this reduces the heating costs
supply-based electricity consumption: Even without the national grid supporting this, one can already start locally to equalize supply and demand in renewable energy. Just look at a website (which already exists for many countries) that provides information about the current wind and PV output power, or otherwise use wind and solar conditions as a proxy. Also calculate a prognosis for this based on weather prognosis data. Then have an automated mechanism that starts planned tasks (such as dishwasher, washing machine etc.) when supply in renewables is high and demand is low.

In a communal living setup, this could be incentivized by charging differently: running the washing machine “right now” might cost the person three times as much as running it “within the next 12 hours whenever there is a good opportunity”.
hang-drying clothes
Large communal washing machine, plus a smaller “vertical vibrating type” washing machine for delicate items. It remains to be seen how much such a setup would be more economical. People would have name tags on their clothes and drop them in two or three buckets depending on how they should be washed.
hot-fill dishwasher and washing machine

Ventilating when the room is empty. To get rid of humidity behind indoor insulation elements, the room would detect when it is not occupied and then stir the air with fans to move the humidity into humidity absorbing material (calcium chloride).
slow cooker as a kitchen appliance
glass cube office: like cubicles, but completely made from glass, mostly for having small heated spaces but also for sound proofing, while still allowing contact with your co-workers
heat pumps to replace the kitchen stove (at least when no more efficient means of cooking is available, such as local hydrogen or biogas production); this requires a heat pup output temperature of at least 150 °C
high temperature heat storage for cooking
heat pump water heaters with tanks; they can be fed from a seasonal thermal energy storage; there is no need for tank temperatures over 60 °C for legionella safety, washing machine or dishwasher temperature

Overview: https://www.phcppros.com/articles/9447-the-case-for-heat-pump-water-heaters
heat pump water kettle: replacing the ordinary water kettle in the kitchen with a heat pump generating 75-80 °C water and then resistive heating to heat it the last 20 °C to boiling; or if possible using a heat pump for the whole heating; or just connect the water kettle to the hot water piping with very short piping to the house’s central heat pump water heater

also add buttons to tell the system how much water to make, and avoid a minimum setting; that alone will reduce energy needs by about 40%


Hey @matthias I’m up for adding to this document if you’d like. If you don’t mind we could do a quick zoom call to just align on scope, etc. a little bit.

Perfect, very happy about that! Re. a Zoom call, I’m completely swamped until tomorrow afternoon. But you can already “add stuff” (your ideas on the topic), fitting it roughly into the structure that I started for this document. I’ll not be editing here until tomorrow, so just go ahead :slight_smile:

We’ll figure out the rest of our collaboration in the call then.

Great - tomorrow afternoon should work fine if it doesn’t get too late.

Here are the questions that we discussed with @bernardo today. I will integrate his answers into the manual above in the next days. For now, enjoy the questions.

Regarding construction and building conversion

  • Management and budgeting of construction projects. Basically, what is the standard practice to estimate the cost of renovation and conversion of a building. Before going into details (calculating materials needed etc.), hopefully there are good rules of thumb based on building type, size, age and the intended type of conversion? Where do we find these numbers?

Regarding compact living

  • If you had to create a space-saving furniture system for tiny houses, how would you approach this? The challenge is that all the tiny houses are different and space restricted, so the same furniture will not fit everywhere …

  • What are good approaches for splitting a warehouse style space into small living spaces so that the conversion takes up little embodied energy? And ideally, one could still switch flexibly between usage as a large space and usage as smaller spaces.

  • Lighting and ventilation solutions for windowless rooms? Which can happen as a result of space sub-divisions.

  • Modern dorms. If you had the task of designing a modern dorm that is comfortable for ≥6 adults, including couples, how would it look like?

  • Flexible room use. We want to set up a communal living scheme where people do not have fixed rooms but rather get a room only for the time when they are in the space, and based on their current needs. What would be good architectural interventions and interior ideas to make moving between rooms comfortable even if people had to do it every other day?

Regarding minimally invasive conversion

  • Minimal conversion techniques. Which ideas did you practice already or think about regarding minimal, ecologically friendly adaptation of spaces that you occupy? For example, the exposed brick wall idea in the communal kitchen of Bosch Tanneurs. Anything resulting in “shabby chic” optics and that uses salvaged materials (or no materials at all) is highly appreciated.

  • Decorative salvaged materials. What old, salvageable materials can be re-used in a decorative manner to modify rooms in such a way that they look “old, shabby chic and used but authentic, warm and nice”? This relates to floor covering, wall covering and indoor insulation.

Regarding energy efficiency

  • Nice window-less kitchen and living room. Heating-wise it is efficient to have the warmest rooms (kitchen and living room and bathroom, but not toilet) in the center of the building. How to make them nice and livable even though they will have very few or no direct windows to the outside?

  • What to focus on re. household energy efficiency? So far we focus on heating, and partially cooking, as the areas where interventions can yield the most energy savings. Any area we are missing?

  • Office space with small heated spaces. For heating efficiency in the office, we are looking for designs that split a large office into smaller heated spaces while still being a nice place to work, with frequent and good contact to colleagues. A row of small meeting rooms will not do it. If you had to do this, starting from a large footprint office (15×15×3 m), how would it look like?

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@matthias — I ran across this last year and thought it would match some of the goals to achieve re ventilation. In this case, the site explains how to do ventilation on demand, using a suitable process variable CO2 — the intent is to ensure just enough fresh air gets into the space to ensure everybody doesn’t get too drowsy. This is more of a thing in climates up north where opening a window is ill advised this time of the year :snowman_with_snow:


The author of the site went this route since they found the controls on their heat recovery ventilator to be crude, by only using humidity; and by continuously running at lower fan speed. These days the cost of CO2 and humidity detectors are at the point an automated solution could help optimize the air in a living or working space, and be controllable enough based on load.

I suspect I am not the only one that has considered dozing off in a stuffy conference room. :laughing:


Aww, that’s a great idea for a control algorithm to save air heating energy, thanks a lot for adding it here! It already gave me the inspiration for some more ideas:

  • I should use this system in the truck where I live. Also I should test CO2 levels after 8 hours of being in there with the windows closed. Right now I keep the window open a bit at night, even in winter, fearing that I might suffocate in that close tight plastic box otherwise :smile:

  • To keep air quality alright in small heated spaces located in larger unheated rooms, automatically adjusted ventilation openings controlled by CO2 level might be all it needs. No fan or heat exchanger needed.

1 Like

@matthias — regarding:

  • Management and budgeting of construction projects. Basically, what is the standard practice to estimate the cost of renovation and conversion of a building. Before going into details (calculating materials needed etc.), hopefully there are good rules of thumb based on building type, size, age and the intended type of conversion? Where do we find these numbers?

As an initiative, I reached out to local engineer who specializes in restoring and renovating older historic buildings. He got back to me in a few moments (!) but mentions it is a bit more nuanced, since it really is site specific.

Currently there is no industry wide rule of thumb for costs based purely upon building type, size and age. There are a few different costing approaches for getting rough order of magnitude (ROM) cost estimates. The type of conservation and the required intensity is going to be a factor.

Typically a starting point is a professional review of the site, and they will make a ROM estimate based partly upon the rules of thumb they reference and partly upon their own experience. I have often heard references to the dollars per square foot based upon building condition and end goals – but they do vary between professionals.

Not sure that helps much, but this is an example of the challenge for conservation of old buildings. There are just enough exceptions to every rule it can be dangerous making rules. The greater unknowns tend to be the factor that scare stakeholders from following best practices, because they worry about what can go wrong – taking solutions that cost more (both economically and ecologically).

The last sentence (emphasis mine…) here is a bit of an eye opener; since I suspect through experience that he has lived through this, where unlikely consequences drive the redesign to be bigger in scope than is actually needed; it’s not rightsized. Unfortunately, I’ve lived through this also, wayyyy too many times. I would suggest that this point should be made as a risk in this document…


Some intermediate results from today, calculated to make The Reef a 20-person household with solarpunk :sun_with_face: heating:

Let’s put a 5.66 m diameter and 6 m high water tank into the center of the building, insulate it with 40 cm styrofoam and connect it with heat pumps powered by 27 m² of solar panels during the summer – then we have a zero-emission space and water heating system for the inhabitant’s heat requirements during all winter in central Europe. What’s more, operation costs are 46% lower than burning natural gas (!), which means there will be no economic reason for burning fossil fuels for heat anymore.

This assumes that compact living, heated clothing, small heated spaces and other ideas from the document above lower heat requirements to 20% of current average values already – which is actually easy. The detailed calculations are in section “3.16. Seasonal heat storage with ASHP charging”. Since this sounds a bit too good to be true, @trythis is invited to poke holes into the idea :wink:


Avoiding AC conversion. Additional cost reductions can be realized by running the heat pumps on direct solar DC electricity. To adapt to available energy supply, heat pumps would either run at variable speed similar to water pumps that are already available for this purpose, or multiple heat pumps would run in parallel to scale consumption with production. This avoids the investment in inverters and the 6-8% conversion losses of converting DC to AC electricity

You may want to take inspiration from a scuttlebutt denizen who worked on the opposite problem; refrigeration. (@)joeyh did a batteryless offgrid fridge for keeping his food. Programmed in haskell, because.

Additionally, even DC powered items may require switching elements and loss for variable speed operation. In the case of AC inverters, most have a ‘dc-link’ stage prior to the H-Bridge; most will permit direct DC in connection on these terminals with proviso for proper overcurrent protection.

Many multi motor applications I have seen are set up in a one variable speed, many single speed topology; where the matching of the demand and the supply are compensated by the inverter; and the single speed starters are dispatched by a plc.

I’m a huge fan of this method for solving for heating demand; https://de.wikipedia.org/wiki/Heizlast . I ran the numbers on my “cabane” and found the heating demand is around 100W/ºC. Another rule of thumb I have seen is the 70l of storage per kw of biofuel heating capacity:

A well-insulated water tank will keep water hot for a few days until the water storage temperature drops. The size of the hot water storage can vary from 50-70 L/kW (4.0-5.5 U.S. gal/1,000 BTUh) of boiler input power depending on winter weather for small manual biomass boilers. Since it requires approximately 1 kilojoule (1 BTU) of heat to raise the temperature of 454 g (1 lb) of water by 0.55°C (1°F), a 2,250-L (600-U.S. gal) hot water storage tank operating with a design temperature difference of 22°C (40°F) will store 60 kWh (200,000 BTU). That volume of water storage can hold enough heat to meet the January average domestic heat load of a 205 m2 (2,200 ft2) home with good insulation located near Ottawa, Ontario, for 7 hr. Loading the biomass boiler twice a day will meet the peak daily demand if using a properly sized water storage tank. – http://www.omafra.gov.on.ca/english/engineer/facts/14-009.htm#7

I will admit I haven’t checked your numbers out, and just providing this as another datapoint :smile:


@matthias — Another datapoint from lowtechmagazine providing some of the rational for communal living.º

A 2002 investigation of firewood consumption in traditional houses in Nepal measures the annual firewood consumption per household to be between 6 and 33 m3, which corresponds to between 35 and 165 Gigajoule (GJ) of energy. [14-16] This seems quite a lot in comparison to the total energy use in contemporary households, which is around 75 GJ per year in Germany and around 105 GJ in Canada.
However, the average Nepalese household participating in the research consisted of 5 to 12 people, while households in modern societies have shrunk to little more than two people. In the Nepalese households under study, energy use was between 2 and 33 GJ per capita, while another, more recent research paper on firewood consumption for heating, cooking and lighting in Nepal calculates a per capita use of roughly 2.5 to 10 GJ of energy per person per year. [17-18] In comparison, total household energy consumption per capita is around 30 to 40 GJ in countries like the Netherlands, Germany and Canada.

º I subscribe to lowtechmagazine via rss; and get new articles when they come out :smile:


Oh, hello to a fellow Low Tech Magazine subscriber :blush: I just finished reading that same article!

These numbers from Nepal are all the more surprising given the kind of draft-rich, uninsulated mud-and-stone houses that comprise the “average Nepalese household” in 2002. It basically means this (picture I took in 2015 in Rasuwa district … it’s a natural cut-away presentation created by the earthquake, so it’s easy to see how the walls and inner structure were made):

But what they lack in insulation, they make up in compact living. One could even say that heating is 80% just a psychological problem: if you enjoy being close with the people around you, you can cope with 80% less heated space.

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The mass of 27 cubic meters of water is around 27 tons. As long as you are at ground level (or below) this could be manageable.
But if you plan to go any higher the structural support requirements will be massive - e.g. really thick concrete walls (really bad CO2 footprint).
Other points to consider:

  • In terms of hygiene it is often better to keep a smaller volume hotter (70°C ?) and mix it down with cooler water. That is if you want to use the water besides thermal mass.
  • If for some reason you have a particularly bad year, how do you best avoid coordinated failure? I would hope outright freezing (leading to destroyed container) can be avoided.
  • 27 tons on site are a huge risk, esp. once the things age. Catastrophic failure might be rare, but even gradual leakage would be a major headache.
  • In seismically active areas one would have to look very, very closely at the implications.
  • 27 (plus insulation) cubic meters will take up a significant footprint per person, even more so if the container is round, and worse, has to sit in the center where it gets in the way of everything.
    This makes me wonder if you would not better turn it into a somewhat thinner column that may be easier to mass produce (extrusion), reinforce it with a fiber sleeve (recycled glass or pitch based carbon), and partially bury it?
  • May require added ground fortification, problematic for retrofits, not suitable on every terrain type.
  • Sensors for leak detection would be needed, but tech has made a good bit of progress on that front in recent years (incl. smart fabrics).
  • Multi-party homes would be interested in having the worst insulation on their parts of the tank, resulting in a race to the bottom dynamic.

A couple of pro-points:

  • Water is a concern in many places, so having quite a bit of it on hand is generally good, and potentially a virtuous circle. Germany is still “littered” with public wells, back from the WW3 planning days - this would be even more relevant for most places.
  • Heat is often a underappreciated energy storage solution. Provided it does not raise too many other costs or complications it is often the most long term sustainable of “batteries”.
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