Hello everyone,
maybe someone here can give us a good tip, as we are quite uncertain about a ventilation system.
We are planning to build a house (solid construction) according to KfW 70 standards, with underfloor heating, a fireplace, and a solar system. That much is already decided.
We received an offer from Company A for a ventilation system with heat recovery, and the salesperson recommended it to us.
At Company B, the ventilation system is significantly more expensive, and the salesperson told us that since the house is so well insulated, moisture would not be an issue... where would it come from? The rest could be regulated by normal airing anyway.
(I also think he realized that his ventilation system would have blown our budget and now I worry that he advised us against it just for that reason!)
My husband and I are laypersons, but my instinct tells me that the better the house is insulated, the more problems I would have getting rid of moisture and stale air inside the house, right?
After all, a blower door test does show that there is very little air circulation.
Am I completely wrong?
We are a bit torn now, since such a system is not exactly cheap! But is it necessary, or just a nice extra?
Thank you very much for your help!
maybe someone here can give us a good tip, as we are quite uncertain about a ventilation system.
We are planning to build a house (solid construction) according to KfW 70 standards, with underfloor heating, a fireplace, and a solar system. That much is already decided.
We received an offer from Company A for a ventilation system with heat recovery, and the salesperson recommended it to us.
At Company B, the ventilation system is significantly more expensive, and the salesperson told us that since the house is so well insulated, moisture would not be an issue... where would it come from? The rest could be regulated by normal airing anyway.
(I also think he realized that his ventilation system would have blown our budget and now I worry that he advised us against it just for that reason!)
My husband and I are laypersons, but my instinct tells me that the better the house is insulated, the more problems I would have getting rid of moisture and stale air inside the house, right?
After all, a blower door test does show that there is very little air circulation.
Am I completely wrong?
We are a bit torn now, since such a system is not exactly cheap! But is it necessary, or just a nice extra?
Thank you very much for your help!
Peppy1981 schrieb:
... and the final heat calculation only takes place after the contract is signed. I don’t really understand what is meant by a "heat calculation." Presumably, they mean the standardized heating load. However, that is a power value, not energy!Peppy1981 schrieb:
..."But a KfW 70 is always included!" according to the seller. Then it should be no problem at all to include "KfW 70" in the contract! In the end, only what is contractually agreed upon counts—not any pre-contractual sales talk from a general contractor (GC)/general builder (GB)! Not to forget, the legal responsibility towards third parties lies solely with the client, not with the contractor acting on their behalf! The GC/GB should be aware of this.Peppy1981 schrieb:
...Is that common practice? Can you get KfW 70 without ventilation when using geothermal energy? KfW 70 can generally be achieved without mechanical ventilation with heat recovery. However, whether it is possible in this case can only be determined through detailed calculations.If the project is "cutting it close" or "optimistically calculated," problems could arise. As always, nothing is certain!
"Geothermal energy" is not a random factor and certainly does not guarantee low operating costs. The source must be correctly sized according to demand; otherwise, one must expect modest annual performance factors despite initially high investment costs. Likewise, heating surfaces and hydraulics must be properly designed.
Completely trusting a GC/GB seller blindly is not advisable. You can protect yourself by consulting an independent, external advisor/planner. If the GC/GB has significant issues with this, you quickly find out what kind of partner you are dealing with.
Best regards
We were given the following ventilation concept for a KFW70 house:
Trickle vents (RegelAir) installed in all windows
Exhaust fans with humidity sensors in the bathrooms and utility room
A preliminary energy calculation showed that sufficient air exchange is possible with this ventilation concept. According to these calculations, there are numerical values indicating how many square meters of air exchange/supply take place.
Which information is relevant in this context? I would like to take a closer look at this calculation!
I understand that you still need to ventilate manually with such a ventilation concept. But could it possibly be sufficient if, for example, you don’t manage to ventilate the house in the morning?
Trickle vents (RegelAir) installed in all windows
Exhaust fans with humidity sensors in the bathrooms and utility room
A preliminary energy calculation showed that sufficient air exchange is possible with this ventilation concept. According to these calculations, there are numerical values indicating how many square meters of air exchange/supply take place.
Which information is relevant in this context? I would like to take a closer look at this calculation!
I understand that you still need to ventilate manually with such a ventilation concept. But could it possibly be sufficient if, for example, you don’t manage to ventilate the house in the morning?
@Peppy1981
We are likely going to have an air-to-water heat pump installed with ventilation.
In your initial post you definitely mention solar. Our heating specialist told us—because we also wanted solar—that he would be happy to combine solar with a heat pump since he makes a good profit from it, but he does not actually recommend this combination. He explained that at the temperatures where solar panels are effective, the heat pump works at a similar capacity. So, solar would basically be working "against the pump," and you don't really gain anything from combining the two.
We are likely going to have an air-to-water heat pump installed with ventilation.
In your initial post you definitely mention solar. Our heating specialist told us—because we also wanted solar—that he would be happy to combine solar with a heat pump since he makes a good profit from it, but he does not actually recommend this combination. He explained that at the temperatures where solar panels are effective, the heat pump works at a similar capacity. So, solar would basically be working "against the pump," and you don't really gain anything from combining the two.
jenga schrieb:
...- that he is happy to combine solar with a heat pump because he profits well from it, but he does not recommend this combination to us because the heat pump at the temperatures where solar systems are beneficial basically does the same work as solar. Keep this guide; it won’t be to your disadvantage! The actual benefit of solar thermal systems is often greatly overestimated, initially regardless of whether it is for domestic hot water only or also with central heating. However, solar thermal systems have become almost standard for every general contractor/main contractor. The actual benefit, despite additional investment, is typically not contractually guaranteed. Anyone who suspects something shady here is not wrong. The regulatory conditions of the Energy Saving Ordinance contribute their part to this misleading situation. Best regards
K
kleineelfe23 Oct 2013 00:25cuhnie schrieb:
We were proposed the following ventilation concept for a KFW70 house:
Window rebate vents (RegelAir) in all windows
Exhaust fans with humidity sensors in the bathrooms and laundry room
A preliminary energy calculation showed that sufficient air exchange is achievable with this ventilation concept. According to these calculations, there are specific values indicating how many square meters of air exchange / supply occur.
Which details are important here? I would like to take a closer look at this calculation!
I understand that even with such a ventilation concept, manual airing is still necessary. But could it possibly be enough if, for example, you sometimes miss airing the house in the morning?Does anyone have any advice?
We are currently facing a similar problem.
Yesterday we performed a blower door test on the shell structure with a result of 1.2. Basically good, but we have actually decided against a mechanical ventilation system (not primarily because of costs, but rather due to lack of time for installation, cleaning, noise from the ducts, and door gaps).
We are building a KFW 70 house with a timber frame structure, equipped with an air-source heat pump and no solar energy usage (solar thermal is pointless, photovoltaics are currently unattractive due to insufficiently developed storage solutions but might be retrofitted in the future), along with a pellet stove (whether water-heated remains undecided; we are also advised against it).
However, we don’t know how to realistically manage "just opening windows for ventilation three times a day." Besides the temperature drop during winter, we simply don’t have the time. We are both working and don’t want to become slaves to ventilation.
Are there no reasonable, less extensive alternatives?
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