We are planning a new build as an energy-efficient house according to the Energy Saving Ordinance, KfW70 standard. The developer claims that with very good insulation, solar thermal systems, and a condensing boiler, etc., this can be achieved without mechanical ventilation. A new build is sealed quite tightly as verified by a blower door test. The developer says we do not need to worry about moisture problems.
We are also used to regular manual ventilation from living in our old house... However, there the cold, fogged-up window was a reliable indicator...
The additional costs for a ventilation system would be significant...
What do the experts here think? Is it better not to forgo such a system, or does it not matter? I do not want to suffocate at night or discover mold after two years...
We are also used to regular manual ventilation from living in our old house... However, there the cold, fogged-up window was a reliable indicator...
The additional costs for a ventilation system would be significant...
What do the experts here think? Is it better not to forgo such a system, or does it not matter? I do not want to suffocate at night or discover mold after two years...
Gartenbau schrieb:
... diffusion, especially through thick walls, is a slow process, which in my humble opinion is not suitable for continuously removing large amounts of moisture...That is exactly the question. It should certainly be possible to calculate this. With a diffusion-open construction method and regular ventilation, I can well imagine that it works without a mechanical ventilation system. With diffusion-tight construction, as already described, I would not take that risk.
PenK schrieb:
What issue do you have with answers from other forum members? None, as long as I roughly agree with them. Otherwise, I give my opinion, since this is a discussion forum.
Best regards,
NB: Netiquette should actually be a matter of course!
Hello,
what an emotional thread.
Let me summarize (for myself).
For a "standard" KFW70 house, such a system is not necessary.
- However, it does offer a significant increase in comfort, especially with heat recovery.
Don’t take it the wrong way, but for this—by my standards—insufficient justification for such an investment, I would also prefer to spend the money on something else in a new build.
Call me old-fashioned, but I would rather continue to ventilate as I always have, listen to outside sounds with the window open, and not feel like I’m living in complete isolation.
what an emotional thread.
Let me summarize (for myself).
For a "standard" KFW70 house, such a system is not necessary.
- However, it does offer a significant increase in comfort, especially with heat recovery.
Don’t take it the wrong way, but for this—by my standards—insufficient justification for such an investment, I would also prefer to spend the money on something else in a new build.
Call me old-fashioned, but I would rather continue to ventilate as I always have, listen to outside sounds with the window open, and not feel like I’m living in complete isolation.
Sorry for butting in,
... but especially after the statement ...
it ultimately seems to be just about convincing oneself to overlook the clearly recognized potential problems...
My personal opinion:
If someone today cannot afford a controlled residential ventilation system costing around €9,000, they should probably continue renting.
(There are truly far too many forced foreclosures...!)
Anyone who believes that their previous ventilation habits are sufficient for the mentioned property should get comprehensive advice beforehand.
Anyone building with a developer should know what they are getting into.
One point that has been somewhat overlooked in the previous discussion is the airtightness issue of the heat-exchanging building envelope.
Anyone who thinks they are buying a sufficiently airtight house just because an air exchange rate is documented below the Energy Saving Ordinance limit (in the case of “window ventilation,” that means 3 complete, mostly unintended air changes per hour) should be aware that permanent airtightness (essentially for the entire life of the house) must be assumed here...
Making a building only “fit” for the blower-door test (or handover/acceptance) can basically be done by any painter!
Anyone who believes that, in practice, the detailed planning of the airtightness layer required according to DIN 4108-7, along with proper professional installation under all necessary conditions and its monitoring (including documentation), actually takes place, should keep dreaming... or ask the developer the right questions!
The developer also calculates costs.
Why should they recommend a ventilation system?
The profit they would make from it surely does not justify the effort required to meet the then mandatory 1.5 air changes per hour (which also must perhaps be proven by a truly independent tester).
They are likely to ignore their liability issues here because court proceedings take time... and ultimately do not concern them much.
(By the way, my test certificates always state independently of the measured values: "... The measurement result does not exclude hidden defects." ... Wonder why?)
Determining the financial impact of such defects is probably far more difficult than the aforementioned cost-effectiveness comparisons... unless one immediately factors in demolition costs.
... but especially after the statement ...
Gartenbau schrieb:
In any case, such a system initially requires an investment of around €10,000, which is simply not affordable financially...
it ultimately seems to be just about convincing oneself to overlook the clearly recognized potential problems...
My personal opinion:
If someone today cannot afford a controlled residential ventilation system costing around €9,000, they should probably continue renting.
(There are truly far too many forced foreclosures...!)
Anyone who believes that their previous ventilation habits are sufficient for the mentioned property should get comprehensive advice beforehand.
Anyone building with a developer should know what they are getting into.
One point that has been somewhat overlooked in the previous discussion is the airtightness issue of the heat-exchanging building envelope.
Anyone who thinks they are buying a sufficiently airtight house just because an air exchange rate is documented below the Energy Saving Ordinance limit (in the case of “window ventilation,” that means 3 complete, mostly unintended air changes per hour) should be aware that permanent airtightness (essentially for the entire life of the house) must be assumed here...
Making a building only “fit” for the blower-door test (or handover/acceptance) can basically be done by any painter!
Anyone who believes that, in practice, the detailed planning of the airtightness layer required according to DIN 4108-7, along with proper professional installation under all necessary conditions and its monitoring (including documentation), actually takes place, should keep dreaming... or ask the developer the right questions!
The developer also calculates costs.
Why should they recommend a ventilation system?
The profit they would make from it surely does not justify the effort required to meet the then mandatory 1.5 air changes per hour (which also must perhaps be proven by a truly independent tester).
They are likely to ignore their liability issues here because court proceedings take time... and ultimately do not concern them much.
(By the way, my test certificates always state independently of the measured values: "... The measurement result does not exclude hidden defects." ... Wonder why?)
Determining the financial impact of such defects is probably far more difficult than the aforementioned cost-effectiveness comparisons... unless one immediately factors in demolition costs.
R
ralph123459 Aug 2010 10:59I can read all sorts of things in the long post, especially a lot of polemics. But not your opinion on why the ventilation system would be indispensable. A shame...
Gartenbau schrieb:
But not your opinion on why the ventilation system would be indispensable. What a pity...Strictly speaking, it is not indispensable, as there is no legal requirement to install it. If that is enough for you, then your "savings" of 9,000 € (approximately $9,900) are fine, right?
Well, that must make your developer happy too!
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