Hello everyone!
I have been reading and researching online and in this forum for a long time now, but unfortunately, I’m still not much wiser when it comes to mechanical ventilation with heat recovery.
My partner and I are planning a single-family house (160 m² (1,722 ft²)) with gas and solar energy, built to the KfW-70 standard. Now we are wondering whether we should install a ventilation system.
Friends of ours have a decentralized ventilation system in their new build and are very happy with it—they can’t imagine living without it anymore.
However, in various forums, people often say that for new builds, a centralized system is better. The whole ducting, with maintenance and the potential for germs, gives me a weird feeling... I would constantly wonder what’s actually in the air inside my home. Is that a misguided concern?
And is the decentralized ventilation really that much worse than the centralized system? You hear that a lot.
What kind of costs should we roughly expect for a ventilation system? Is it true that centralized and decentralized systems cost about the same?
Thank you very much for all your advice!
Goldbeere
I have been reading and researching online and in this forum for a long time now, but unfortunately, I’m still not much wiser when it comes to mechanical ventilation with heat recovery.
My partner and I are planning a single-family house (160 m² (1,722 ft²)) with gas and solar energy, built to the KfW-70 standard. Now we are wondering whether we should install a ventilation system.
Friends of ours have a decentralized ventilation system in their new build and are very happy with it—they can’t imagine living without it anymore.
However, in various forums, people often say that for new builds, a centralized system is better. The whole ducting, with maintenance and the potential for germs, gives me a weird feeling... I would constantly wonder what’s actually in the air inside my home. Is that a misguided concern?
And is the decentralized ventilation really that much worse than the centralized system? You hear that a lot.
What kind of costs should we roughly expect for a ventilation system? Is it true that centralized and decentralized systems cost about the same?
Thank you very much for all your advice!
Goldbeere
@ Building expert – you write:
. Single-family house built with ETICS (external thermal insulation composite system) → mold growth. Or then, when both partners work full-time jobs; especially during the period when the house is newly handed over, regulated ventilation is absolutely essential and should have the highest priority, regardless of the construction system.
Is this really independent of the construction system? We are planning a solid wood new build and have heard that the air tends to be too dry in such buildings, and air humidification might sometimes be considered.
A ventilation system is still being considered for ecological, comfort, and health reasons. Of course, such a significant investment must be carefully planned. A good indoor climate could also be achieved with clay plaster, but sufficient fresh air must be supplied regardless.
I would also be very interested in an answer here:
The background to my question: If you have planned a wood stove, that room usually cannot be connected to a central ventilation system.
Why is that?
. Single-family house built with ETICS (external thermal insulation composite system) → mold growth. Or then, when both partners work full-time jobs; especially during the period when the house is newly handed over, regulated ventilation is absolutely essential and should have the highest priority, regardless of the construction system.
Is this really independent of the construction system? We are planning a solid wood new build and have heard that the air tends to be too dry in such buildings, and air humidification might sometimes be considered.
A ventilation system is still being considered for ecological, comfort, and health reasons. Of course, such a significant investment must be carefully planned. A good indoor climate could also be achieved with clay plaster, but sufficient fresh air must be supplied regardless.
I would also be very interested in an answer here:
The background to my question: If you have planned a wood stove, that room usually cannot be connected to a central ventilation system.
Why is that?
B
Bauexperte15 Dec 2011 18:32Hello Carola,
Where ETICS is applied, I consider it a serious mistake to forgo ventilation (whether decentralized or centralized) in favor of, for example, a new kitchen.
The Energy Saving Ordinance 2009 – and the 2012 version likely even stricter by about 30% – essentially specifies how much heat loss a house is allowed to have. It is only logical that most providers try to implement this as cost-effectively as possible, and this is usually with ETICS. If you build with aerated concrete, brick, pumice stone, or sand-lime brick with mineral exterior plaster – all of which allow some moisture transport on their own – the problem of mold formation with proper ventilation is, to some extent, negligible (I will leave aside that sand-lime bricks and pumice stone typically also require ETICS). However, when you apply ETICS, moisture diffusion stops at the point where the ETICS meets the masonry, and the synthetic resin plaster (used to stabilize ETICS) contributes further. The moisture inside the house must go somewhere – plus, if I recall correctly, each person produces about 3.0 liters (0.8 gallons) of moisture per day through breathing.
If you build a prefabricated house, you more or less live inside a plastic membrane because the system-related vapor barrier does not allow diffusion – but your bathroom/kitchen vapors and your breath still need to go somewhere.
This means that with prefabricated houses and solid houses with ETICS, measures must be taken to remove moisture, otherwise you will have an increased risk of mold at the coldest point of the external walls in each room!
I do not understand your statement that ventilation is an ecologically sensible system. It certainly increases comfort and is beneficial for health. Whether clay plaster really improves the indoor climate, I cannot say as I have not studied it sufficiently. However, I could imagine that entire clay walls would be more suitable for this.
I would be very interested in that as well.
Best regards
Carola schrieb:
@ Bauexperte - you wrote:
Single-family house built with ETICS (external thermal insulation composite system) => mold formation. Or, when both partners work full-time in a regular job; especially during the period when the house has just been handed over, regulated ventilation is absolutely essential, regardless of the building system.
Is it really independent of the building system? We are planning a solid wood new build and have heard that the air inside tends to be too dry and that using a humidifier is sometimes considered.
A ventilation system is still under consideration for ecological, comfort, and health reasons. Of course, such a large investment needs to be well thought out. Good indoor climate could also be achieved with clay plaster, but sufficient fresh air supply must be ensured regardless.
Where ETICS is applied, I consider it a serious mistake to forgo ventilation (whether decentralized or centralized) in favor of, for example, a new kitchen.
The Energy Saving Ordinance 2009 – and the 2012 version likely even stricter by about 30% – essentially specifies how much heat loss a house is allowed to have. It is only logical that most providers try to implement this as cost-effectively as possible, and this is usually with ETICS. If you build with aerated concrete, brick, pumice stone, or sand-lime brick with mineral exterior plaster – all of which allow some moisture transport on their own – the problem of mold formation with proper ventilation is, to some extent, negligible (I will leave aside that sand-lime bricks and pumice stone typically also require ETICS). However, when you apply ETICS, moisture diffusion stops at the point where the ETICS meets the masonry, and the synthetic resin plaster (used to stabilize ETICS) contributes further. The moisture inside the house must go somewhere – plus, if I recall correctly, each person produces about 3.0 liters (0.8 gallons) of moisture per day through breathing.
If you build a prefabricated house, you more or less live inside a plastic membrane because the system-related vapor barrier does not allow diffusion – but your bathroom/kitchen vapors and your breath still need to go somewhere.
This means that with prefabricated houses and solid houses with ETICS, measures must be taken to remove moisture, otherwise you will have an increased risk of mold at the coldest point of the external walls in each room!
I do not understand your statement that ventilation is an ecologically sensible system. It certainly increases comfort and is beneficial for health. Whether clay plaster really improves the indoor climate, I cannot say as I have not studied it sufficiently. However, I could imagine that entire clay walls would be more suitable for this.
Carola schrieb:
I would also be very interested in an answer to this:
Background of my question: If you plan a wood stove, usually that room cannot be connected to a central ventilation system. Why?
I would be very interested in that as well.
Best regards
Goldbeere schrieb:
...Yes, we are planning to install a room-air-independent wood stove in the living room. If I understand correctly, the stove is supposed to get its combustion air through the chimney. I would reconsider this! Goldbeere schrieb:
...By the way, my partner is not yet convinced about the cost-benefit ratio of a mechanical ventilation with heat recovery system. He would rather invest the money “more sensibly” and continue ventilating manually as before. I tend more towards a mechanical ventilation system but without heat recovery – that would exceed our budget. I would reconsider this as well! Either a mechanical ventilation system with heat recovery or none at all! Goldbeere schrieb:
...If a mechanical ventilation system cannot be planned in the living room – wouldn’t a decentralized solution be more practical? How else can the living room be ventilated (besides manually)? If the living room is the traditional supply air zone of a mechanical ventilation system and also the room where a certified, approved, room-air-independent stove or masonry heater is installed, there should be no problem due to over- or equalized pressure! Best regards
Bauexperte schrieb:
...Where an external thermal insulation composite system (ETICS) is applied, I consider it a serious mistake to forego ventilation (whether decentralized or centralized) and instead, for example, prioritize a new kitchen. Bauexperte schrieb:
... , the synthetic resin render (to stabilize the ETICS) contributes to the issue. The moisture inside the house has to go somewhere – in addition, if I remember correctly, every person produces about 3.0 liters (0.8 gallons) of moisture per day through breathing. Yes, the moisture has to go somewhere! Bauexperte schrieb:
...If you build a prefabricated house, you are essentially living inside a plastic wrap, since the system-related vapor barrier does not allow diffusion – but your bathroom/kitchen vapors and your breath still need to escape somewhere. That's right, moisture-regulating and moisture-buffering interior plasters are often missing in prefabricated houses!We are familiar with this problem as well. Our house dates back to the 1950s and was insulated this year, with new airtight windows installed. Now I constantly have condensation on the windows, which I can no longer dry out with the morning airing. Even when the heating is barely on, the windows fog up, and so far it hasn’t even been very cold outside. I’m curious to see how it will be in winter.
This is also one of the reasons why I want to build something new.
This is also one of the reasons why I want to build something new.
B
Bauexperte23 Dec 2011 00:12Hello,
Rather rare...
To prevent moisture condensation in multilayer assemblies, the thermal resistance should increase from inside to outside (thermal insulation layer on the exterior), and the vapor resistance should decrease. These conditions are met, for example, in the wall build-up: interior plaster, sand-lime bricks, solid bricks, mineral wool, air cavity, facade panel (wall with ventilated cladding). If the wall remains damp—which is especially important to consider in new constructions—then water behind a waterproof or water-repellent outer layer, as can be the case with an insulated facade system, cannot easily escape by diffusion, leading to long-term damage to the masonry.[1]
[Source 1] Kur, Friedrich; Wohngifte, Handbook for Healthy Building and Furnishings
Thanks to planners at the green desk in Brussels, this is a relic from good old times; meanwhile, at least small ventilation flaps for windows are offered again—which is better than nothing.
It’s not that simple; usually inhabitants are home in the evenings and nights, and not all humidity is removed by twice daily ventilation—including moisture from the morning shower.
In new buildings, moisture inevitably accumulates, even though today many bricks are glued—less than before, but the screed still introduces plenty of water into the house, and an ETICS does not make the situation any easier. That’s a fact.
Best regards
S.D. schrieb:
However, there are also quite a few people who find controlled residential ventilation rather unpleasant.
Rather rare...
S.D. schrieb:
And I also don’t think that a building with ETICS (external thermal insulation composite system) “breathes” worse than one without, since a wall actually does not “breathe” at all.
To prevent moisture condensation in multilayer assemblies, the thermal resistance should increase from inside to outside (thermal insulation layer on the exterior), and the vapor resistance should decrease. These conditions are met, for example, in the wall build-up: interior plaster, sand-lime bricks, solid bricks, mineral wool, air cavity, facade panel (wall with ventilated cladding). If the wall remains damp—which is especially important to consider in new constructions—then water behind a waterproof or water-repellent outer layer, as can be the case with an insulated facade system, cannot easily escape by diffusion, leading to long-term damage to the masonry.[1]
[Source 1] Kur, Friedrich; Wohngifte, Handbook for Healthy Building and Furnishings
S.D. schrieb:
Places where indoor humidity could escape before a renovation are usually around windows and doors.
Thanks to planners at the green desk in Brussels, this is a relic from good old times; meanwhile, at least small ventilation flaps for windows are offered again—which is better than nothing.
S.D. schrieb:
Furthermore, I do not consider it a problem if an unoccupied apartment (both spouses working) is not ventilated during the day, as humidity mainly comes from the occupants who are not at home. As long as the place is not full of plants and aquariums, I see no risk of mold.
It’s not that simple; usually inhabitants are home in the evenings and nights, and not all humidity is removed by twice daily ventilation—including moisture from the morning shower.
In new buildings, moisture inevitably accumulates, even though today many bricks are glued—less than before, but the screed still introduces plenty of water into the house, and an ETICS does not make the situation any easier. That’s a fact.
Best regards
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