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!
R
Rowley65124 Oct 2013 13:00It’s definitely not possible to make a general statement like: today, you don’t need to build a house without a mechanical ventilation system with heat recovery. It always depends on the individual circumstances (as has already been mentioned here—such as the standard like KfW 70, 55..., wall construction, size, number of occupants, even down to "showering habits," and so on).
The fact is that houses have always been built using hollow clay bricks without any problems with moisture or mold. And apart from better windows, not much has changed with this type of house.
Of course, the situation is different if you build a KfW 55 house or better, or add a thick layer of insulation along with a vapor barrier to your exterior walls. In that case, I think a mechanical ventilation system with heat recovery would definitely be advisable...
That’s my take on this topic as an amateur.
The fact is that houses have always been built using hollow clay bricks without any problems with moisture or mold. And apart from better windows, not much has changed with this type of house.
Of course, the situation is different if you build a KfW 55 house or better, or add a thick layer of insulation along with a vapor barrier to your exterior walls. In that case, I think a mechanical ventilation system with heat recovery would definitely be advisable...
That’s my take on this topic as an amateur.
D
DerBjoern24 Oct 2013 13:09Houses built to the energy saving regulation standard are also airtight. This is not only the case by definition for KfW houses. Brick walls are also airtight and waterproof. The interior plaster already acts as a barrier here. The majority of moisture removal takes place through ventilation. If this is not the case, it indicates a construction defect...
R
Rowley65124 Oct 2013 13:18I never said that brick walls are "airy." Otherwise, there would be drafts in the living room! Of course, they are airtight but still vapor permeable. Most of the moisture is removed through ventilation, and only a small amount actually diffuses through the wall. However, this is better than nothing, or better than a thickly insulated exterior with a vapor barrier.
By the way, proper ventilation is only half the battle against moisture. The other important factor, especially during the first few years, is to heat the house properly, including the less frequently used rooms.
By the way, proper ventilation is only half the battle against moisture. The other important factor, especially during the first few years, is to heat the house properly, including the less frequently used rooms.
D
DerBjoern24 Oct 2013 13:22There is no noticeable diffusion through. Whether there is additional insulation or not, what passes through is negligible. It would be silly if the wallpaper peeled off the walls after just a few days of rainy weather.
But you are right about heating. That is also quite important...
But you are right about heating. That is also quite important...
Dear forum members,
After reading many claims, concerns, and uncertainties regarding the topic of "controlled ventilation," especially related to mold formation, I would like to briefly share my practical experience:
I live in a well-insulated and sealed prefab house (not yet KfW 70 standard), a timber frame construction with a vapor barrier film beneath the drywall lining (as is common in prefab construction). The house is evenly heated with a low-temperature underfloor heating system, with the sleeping area slightly cooler.
The wall and window elements are so well and equally insulated that there are no cold surfaces anywhere in the house where moisture could condense and settle. No wall moisture means no mold!
Four people live in the house. In winter, we regularly ventilate by quick airing as needed, especially during cooking (using the exhaust hood) and after meals to remove odors from the house.
In summer, the humidity level naturally settles around 50% relative humidity (as measured by a calibrated hygrometer). During the heating season, humidity inside the house drops significantly. For general comfort and to protect some antique furniture, we are therefore forced to add humidity during the heating season. Using a cold evaporation humidifier, we add 3–4 liters (0.8–1.1 gallons) of water daily, which allows us to maintain the desired 50% humidity.
I cannot understand the frequently stated necessity of a controlled ventilation system for moisture removal at all. In my opinion, with a uniformly well-insulated and airtight building envelope, this investment and its associated ongoing costs can be avoided.
After reading many claims, concerns, and uncertainties regarding the topic of "controlled ventilation," especially related to mold formation, I would like to briefly share my practical experience:
I live in a well-insulated and sealed prefab house (not yet KfW 70 standard), a timber frame construction with a vapor barrier film beneath the drywall lining (as is common in prefab construction). The house is evenly heated with a low-temperature underfloor heating system, with the sleeping area slightly cooler.
The wall and window elements are so well and equally insulated that there are no cold surfaces anywhere in the house where moisture could condense and settle. No wall moisture means no mold!
Four people live in the house. In winter, we regularly ventilate by quick airing as needed, especially during cooking (using the exhaust hood) and after meals to remove odors from the house.
In summer, the humidity level naturally settles around 50% relative humidity (as measured by a calibrated hygrometer). During the heating season, humidity inside the house drops significantly. For general comfort and to protect some antique furniture, we are therefore forced to add humidity during the heating season. Using a cold evaporation humidifier, we add 3–4 liters (0.8–1.1 gallons) of water daily, which allows us to maintain the desired 50% humidity.
I cannot understand the frequently stated necessity of a controlled ventilation system for moisture removal at all. In my opinion, with a uniformly well-insulated and airtight building envelope, this investment and its associated ongoing costs can be avoided.
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