Heads up to those of @reef-full that were not at today’s plenary, and in particular @RichardB, @mariaAM, @Hannah, @Jeroen and @joannes: we consented to a proposal on the setup of an energy community. One of the components of this proposal was that we agree to not go for geothermal at this stage. The decision needs to be made, because installing geothermal heat pumps implies that we need to allocate 20 m2 in the basement. When we apply for the permit, we need to include a full plan of the basement, so the decision needs to be made now.
What I mean by "letting go of geothermal at this stage is:
Geothermal is off the table for the first 10-15 years. We can reconsider once the air-source heat pumps come up for replacement.
The decision on the plans of the basement could, in principle, be modified later by introducing a rectificatif to the building permit application – so, the decision is in principle reversible.
As an add-on to the proposal, we agreed to ask the architects to make the building “geothermal ready” (unless it is horribly expensive). We believe it is as simple as having a pipe in the basement that we could, in the future, use to connect the basement (where the heat pump would be) to the deep hole in the ground that we could drill in the future.
You can still object in the next 48 hours. Also, I would like to get an idea of where you stand on this because it is the households with a strong commitment to sustainability and some financial means that, in the terms of the proposal, can bankroll the energy community. Could you have
Hello Alberto, the proposal is fine by me (us), well done by everyone involved!
We support the idea to found an energy community, whether and to what extend we’ll be able to contribute to solar panels and batteries will depend on the final pricing of the Reef, as such I think once we have an Entrepreneur Général, we’ll know more.
As I unfortunately couldn’t be present at today’s plenary, I still wanted to take the opportunity to explain one reason as to why I’m a lesser fan of the air heat pump solution, and that is because I perceive they aggravate the cross-subsidisation from bigger to smaller units: We had discussed in the past that smaller units add proportionally more to construction costs than larger units due them requiring proportionally more ressources , and here we’re dealing with a cost position that is almost entirely made up of costs per unit (sth like 10k?), but then divided by our distribution key, where as a result larger units contribute more due to the larger space they occupy. When we consented to our valuation key, your argument against the inclusion of a size factor was that the finition will absorp some of these cost effects. I wonder then whether we shouldn’t discuss to move heat pumps from casco to finition?
The way I read your post I understand you are implying that you are not a fan of air-source heat pumps because they aggravate the cross-subsidisation from bigger to smaller units. Do I understand that correctly?
If yes, can you please explain to me how that would be different for geothermal heat pumps? This is not fully clear to me.
Yes your understanding is correct and in this context the geothermal solution, albeit being more expensive in absolute terms, has a positive side to it as it’s cost structure is to a larger extend of a fixed kind and to a lesser extend in variation of the number of households. Now my intention is not to re-open the discussion on what kind of heat pumps we should install or on the components of our valuation key - I‘m more cautious on the feedback we got on the pricing of the bigger units from interested parties. Also, I reckon the cahier de charges will at some point allow to follow up how much a unit actually costs to build, a large difference with our price tag can then lead to issues with mortgages as banks are not likely to base the estimated value of a unit on our model but more on the cahier de charges.
Thank you for the proposal @Alberto! We are ok to let go on geothermal heat pumps. I think my major concern was that I have always seen geothermal heat pumps as the even more sustainable option than the air-source heat pumps. And I got the idea that we were choosing for air-source heat pumps out of mere economical reasons. It made me think of offsetting CO2 emissions (although probably the comparison doesn’t go well): you book an airplane, you pay for CO2 offsetting as this is economically more interesting, although the better option would have been to pay more for a train and contribute drastically less to CO2 emissions . As we are not opposing to the proposal, maybe this is something we can discuss further another time at the occasion of a plenary meeting or a FM dinner. We are in any case fan of the energy community. Thanks for the work you have put in, interesting stuff!
Aha, got it. No, in my understanding both AS and GT heat pumps use electricity from the grid. How green that is depends on the energy mix of the grid itself. GT is more efficient, but not vastly so, only about 30%. So moving from AS to GT is not like moving from the plane to the train: you are still on the plane, but you moved from economy+ to economy class.
On the other hand, a serious solar array means we can produce locally 2-3,000 kWh per year per unit. This is energy that is green for sure, because it comes from our own roof and not from the grid. Again, we are moving to economy class – still on the plane, but we are doing it a greatly reduced cost.
Where we are moving to the train from the plane is with good insulation. Instead of 15,000 kWh per year per unit (and it’s methane!) we reduce our heating-induced consumption to something like 2-3,000 (and it’s electricity).
Just as a short update: we talked to the architects and Walk yesterday, and it seems that it will be possible to make the building “geothermal ready” for when we’ll need to replace our aerothermic heat pumps in 15 years. What I understand from it, is that it means that they will pay attention to leaving space for drilling (in the future) when placing the rainwater tanks, and also making sure there are entry points for the pipes at the bottom of the buildings. All this should be feasible, and will be taken into account.
Progressive insight… which makes me now unfortunately really regret the choice for aerothermic heat pumps. The 30+ heat days came very early this summer. As you all know by now, I am a really big fan of the floor cooling we have in our apartment. I learned yesterday that floor cooling with aerothermic heat pumps is not at all sustainable: 1. only with geothermal heat pumps, you can have a passive cooling of your house, as it just uses the constant temperature of 10 degrees from the earth plus a little bit of energy to make the heat pump running; aerothermic heat pumps need way more energy to keep your floor cool as they need to convert the hot air. They need more energy than solar panels can provide on hot days (and there are also very warm cloudy days, when solar panels will be of very little use); 2. aerothermic heat pumps use a refrigerant gas (just like airconditioners) for cooling, which is also not at all sustainable compared to the passive cooling from geothermal heat pumps. This article on the Flemish government’s website explains it better than I do: Koelen met een warmtepomp | Vlaanderen.be (in Dutch).
For me this is more than a luxury thing. Our summers will get hotter, heat waves more common, and as I intend (hope) to grow old in The Reef, I find it a pity that I didn’t experience the floor cooling when we made this choice, and that I also wasn’t informed that floor cooling with aerothermic heat pumps is just way less sustainable. I feel really bummed that we will have to wait 15-20 years before we can make the choice for geothermal heat pumps.
Thanks a lot for bringing this up. It’s not for nothing that there was a group that insisted on exploring all possible ways to go for geothermal heat pumps, and cooling options was definitely one of the reasons that stood out.
When we were having the final discussions on this with the technical experts, we specifically brought up the issue of cooling. I don’t have enough scientific background to understand all the details of it, but the answer we got is that regardless of the type of heatpump you choose, the cooling potential is limited to 2°C, because otherwise there is a risk of condensation. (I’m hoping that somebody else can explain this better)
For the PEB all units will need to get the “no risk of overheating” green light. This will include sun protection. So in theory this should be covered.
In theory it’s also possible to re-open the discussion about the heat pumps (I would need to check), because it’s not part of the permit. You do need a special environmental permit for geothermal heatpumps though, so it’s also not something that can wait much longer.
At the same time, I would encourage you to go through the documentation of our decisions once again. The way I understand it, these were the main arguments:
It is technically possible that only some households would get a geothermal heat pump (provided there is a minimum amount). The extra cost would be 10-15k per unit. Given that 7 units are unsold, we would also need to make that decision on their behalf.
There is a bit of a solidarity element in this, in that the money that people would invest in a geothermal heat pump, cannot be invested in the energy community, which would make it possible for the entire group to get lower electricity prices.
For this reason, I would personally let it rest (based on the entire decision history we went through), but you are free of course to continue the research.
And finally a personal note: I’m gonna live on the bloody third floor and my health issues get worse when temperatures are high, so my heart is really with the geothermal heat pumps. I am counting on the sun protection and keeping windows closed, and I am considering making my unit airco-ready, depending on what the architects will advise.
To add another variable, I am personally wary of floor heating/cooling because they are hard to maintain. Anything breaks, you are in for a big expenditure and lot of hassle. I will be looking a chunky radiators that a technician can access with a screwdriver.
Interesting, I have a totally different idea/ experience on this: with floor heating, you have a system that is easily hassle-free for 30 years. Radiators bring more (short-length) pipes that come with wear and leaks. But this is up to individual households, right?
Doesn’t really take away my disappointment about the geothermal heat pumps and the fact that we didn’t choose the more sustainable alternative.
I know this is what the architects said, but I am convinced it is just not correct: from 2 personal experiences, in our apartment we are able to keep it a nice 23 degrees when outside temperatures are 30 (like this week), and the same goes for my brother’s house (different orientation, different environment, same effect), and we are both not troubled by condensation issues; also a very good friend of mine (whom I spoke yesterday, hence all the new insights…) who is an engineer specialised in heating techniques contradicts this.
I feel you, but it reads again like a real real pity to me. Keeping windows closed (and I guess you mean covered) is just sad during summer (but ok, that’s a personal feeling). Installing air condition is an even worse option in terms of sustainability (and I say this without a personal judgement of anyone’s choice for air condition). All this when geothermal heat pumps were within our reach…
For me, the sustainability of our project as written in The Reef’s Blueprint is a top priority. I feel that we have lost a big opportunity, partly because we were more concerned with our own short term cost efficiency (lower electricity prices in the energy community) that didn’t fully take into account the costs for the planet. I think my feeling of disappointment particularly comes from the fact that the choice was made at a time when I was very stressed and not feeling well for other reasons than The Reef, and there was no capacity with me nor Jeroen to get better informed on this. If only I had the chance to have that conversation with my friend earlier… Anyways, writing posts here from the feeling of disappointment is probably not the best idea, I’ll try to let the feeling pass by before I start looking into it again.
I share your disappointment, and I’d be happy to meet up for a chat if that helps.
It’s true that sustainability is a top priority, and at the same time we have also been very clear from the beginning that we aspire to be “as sustainable as possible”, because there are important budget constraints.
Having been at the forefront of this geothermal heat pumps battle, I feel like we have done everything that we could to keep this in, but that the argument of solidarity is an equally important one.
Our key principle of “participation means power” still holds of course. So if after some reflection you find the energy to dig deeper into this, that will be possible and welcome (provided the architects agree).
Finding this an interesting topic close to my heart, i have been trying to look up some things, particularly geothermal heatpumps in combination with cohousings.
I came accross two cohousings: BioTope (Gent) and Boldershof (Oostende), both have opted for individual geothermal pumps. The most interesting project i find is Biotope, as they were energy ambassadors till Arpil 2024 (focus on circular economy, sustainability,…) and in this role wrote several fiches meant for other projects/architects/… I contacted them to see whether we can receive these documents.
I also saw they opened their doors during the ecobouwers openday last year, but not sure they will participate this year (Open days sustainable houses in Brussels and Flanders) as the ambassador role ended last year. I wouldn’t mind trying to visit them in or outside the context of these open days… I see they organise tours for max 30 people, but at a price of 250 euro.
Having said that, I also agree with Lee, that the architects will need to agree with this, and the fact that this might have a negative impact on the energy community / solidarity aspect (which would make me sad). But maybe one shouldn’t exclude the other…
Some extra info about these projects (in Dutch):
BioTope:
. As we are not opposing to the proposal, maybe this is something we can discuss further another time at the occasion of a plenary meeting or a FM dinner. We are in any case fan of the energy community. Thanks for the work you have put in, interesting stuff!
I’m very interested to read into these fiches as well.