Hello everyone,
We are currently starting to deal with the technical aspects of our single-family home.
I haven’t found a thread discussing whether a ventilation system generally makes sense or not. So here is a general discussion thread on the topic:
At first, we looked into various timber frame construction providers, which made us quite sensitive in this area. Naturally, a ventilation system is quite important due to the tighter building envelope, which I can completely understand. However, everything is also marketed accordingly...
Since we have now decided to go with a regional solid construction company, completely different questions arise:
I currently have a detailed offer from a solid construction company:
- $10,000 additional cost for thermal insulation measures
- $13,000 additional cost for a central ventilation system or $9,000 additional cost for a decentralized ventilation system
--> So the repayment subsidy of $18,000 is of little use to me; on the contrary, I am even paying extra for this (of course, I get a “better” house in return).
Key Data:
- Single-family home city villa, 150m² (1,615 ft²) with basement
- Air-to-water heat pump
- Building material: brick
The questions I am now asking myself:
1. Is a ventilation system even necessary to achieve KfW 55 standard?
2. If yes, would it maybe make more sense to go for KfW 70 and forget about the subsidy?
3. Is a ventilation system really that great? There are many reports about noise, high maintenance, etc.
4. If yes, in our building project would a decentralized or central system be better? I have read a lot of positive things about decentralized systems, so central ones might not be an option? Is that correct or not?
5. Is it even possible to reach KfW 55 standard otherwise? Do you really have to ventilate every 2 hours? Are there any experiences?
6. Is the additional $10,000 cost for KfW 55 without a ventilation system justified? Are the prices for the ventilation systems justified?
I know this is an endless debate and there are clearly two opinions here. However, we find it really difficult to make a decision. Maybe a few discussions and information here will help us make up our minds.
We are currently starting to deal with the technical aspects of our single-family home.
I haven’t found a thread discussing whether a ventilation system generally makes sense or not. So here is a general discussion thread on the topic:
At first, we looked into various timber frame construction providers, which made us quite sensitive in this area. Naturally, a ventilation system is quite important due to the tighter building envelope, which I can completely understand. However, everything is also marketed accordingly...
Since we have now decided to go with a regional solid construction company, completely different questions arise:
I currently have a detailed offer from a solid construction company:
- $10,000 additional cost for thermal insulation measures
- $13,000 additional cost for a central ventilation system or $9,000 additional cost for a decentralized ventilation system
--> So the repayment subsidy of $18,000 is of little use to me; on the contrary, I am even paying extra for this (of course, I get a “better” house in return).
Key Data:
- Single-family home city villa, 150m² (1,615 ft²) with basement
- Air-to-water heat pump
- Building material: brick
The questions I am now asking myself:
1. Is a ventilation system even necessary to achieve KfW 55 standard?
2. If yes, would it maybe make more sense to go for KfW 70 and forget about the subsidy?
3. Is a ventilation system really that great? There are many reports about noise, high maintenance, etc.
4. If yes, in our building project would a decentralized or central system be better? I have read a lot of positive things about decentralized systems, so central ones might not be an option? Is that correct or not?
5. Is it even possible to reach KfW 55 standard otherwise? Do you really have to ventilate every 2 hours? Are there any experiences?
6. Is the additional $10,000 cost for KfW 55 without a ventilation system justified? Are the prices for the ventilation systems justified?
I know this is an endless debate and there are clearly two opinions here. However, we find it really difficult to make a decision. Maybe a few discussions and information here will help us make up our minds.
Tego12 schrieb:
For this, I have a humidifier placed in an exhaust room, which humidifies the air and the system then distributes it throughout the house via the enthalpy heat exchanger. But that only really works with an enthalpy heat exchanger, right? Otherwise, there is typically no point in a controlled residential ventilation system where air exchange between exhaust and supply air actually takes place, correct?
Nummer12 schrieb:
I had a similar conversation with a general contractor. That whole argument fell apart the moment I read the contract – the same GC who claimed "works great without controlled residential ventilation" clearly excluded all damages caused by moisture and required the homeowner to ventilate multiple times a day. That’s not consistent at all. I once visited an occupied KfW55 house without controlled residential ventilation where the air hadn’t been aired out beforehand – my first impression was that the indoor air was quite stuffy. Same here. GCs prefer installing decentralized ventilation, and in every house we visited with this GC, the devices were turned off and the air was really stuffy. So, decentralized or no ventilation was immediately ruled out for us.
I recently had two more discussions with two different general contractors, making it a total of three conversations with general contractors. The contractors nearby build almost everything in the surrounding new development areas and all have a very good reputation.
All of them, without exception, said that KfW 55 standard or better without a mechanical ventilation system is not a problem. You just need to ventilate normally, and that works fine. They also all mentioned that it depends on the building material, and if you use bricks, there are no issues due to their breathability. Moisture release is therefore not a problem, and so far, none of them have ever had any problems with mold. KfW 70 is quite similar to KfW 55, they said. In principle, they would all build to KfW 70 as well, but due to the subsidies, it doesn’t make much sense.
If a ventilation system is installed, they all recommend a decentralized system. Regarding central ventilation, everyone mentioned the same issue: the ducts look extremely dirty, and no one really wants to take a closer look inside. What might build up over a few years is still unclear.
All of them, without exception, said that KfW 55 standard or better without a mechanical ventilation system is not a problem. You just need to ventilate normally, and that works fine. They also all mentioned that it depends on the building material, and if you use bricks, there are no issues due to their breathability. Moisture release is therefore not a problem, and so far, none of them have ever had any problems with mold. KfW 70 is quite similar to KfW 55, they said. In principle, they would all build to KfW 70 as well, but due to the subsidies, it doesn’t make much sense.
If a ventilation system is installed, they all recommend a decentralized system. Regarding central ventilation, everyone mentioned the same issue: the ducts look extremely dirty, and no one really wants to take a closer look inside. What might build up over a few years is still unclear.
Well, then "everyone, really everyone" must have no idea...
Breathable bricks—oh, someone else has been talking about walls that breathe?
Decentralized ventilation—now that’s really exciting.
The pipes look terrible? a) How would they know that? b) Nothing happens to them after a few years—unless, of course, you don’t install filters. By the way, these things can also be cleaned.
No one can ventilate properly unless they are at home all day, don’t sleep through the night, and have a fetish for opening windows.
The affordable alternative is trickle vents combined with centralized exhaust. At least those ensure some air exchange.
Breathable bricks—oh, someone else has been talking about walls that breathe?
Decentralized ventilation—now that’s really exciting.
The pipes look terrible? a) How would they know that? b) Nothing happens to them after a few years—unless, of course, you don’t install filters. By the way, these things can also be cleaned.
No one can ventilate properly unless they are at home all day, don’t sleep through the night, and have a fetish for opening windows.
The affordable alternative is trickle vents combined with centralized exhaust. At least those ensure some air exchange.
These seem to be general contractors who build in the same way they always have, so the usual talk about ventilation systems fits the picture well. For me, all three would be out of the question; at most, I would let them handle the gas and sanitary technology. Under no circumstances, however, would I entrust them with a heat pump or (decentralized) ventilation system.
This is really incredible...
Is it possible for me to find a specialist who can install the ventilation system? Can this be installed simultaneously with the house construction, or can it (a central system) also be added later on? Or do I have to coordinate this specifically with my general contractor (GC)?
I might consider finding someone myself who does a clean job and keep the GC out of it...
Honestly, I don’t think I’ll find any GC who “willingly” installs these ventilation systems.
It’s probably because this KfW 55 standard is very, very new, and the GCs haven’t really given it much thought yet.
I’m just having a hard time with this: They probably build around 120 houses a year, all KfW 70, and apparently no one had any issues or “missed” this ventilation system. I don’t think a KfW 55 house differs that much from a KfW 70 house.
Over the weekend I’m going to visit my cousin, who built a KfW 70 house without a ventilation system. The blower door test showed that it’s very close to a KfW 55 house. So I can find out firsthand what the situation really is.
Is it possible for me to find a specialist who can install the ventilation system? Can this be installed simultaneously with the house construction, or can it (a central system) also be added later on? Or do I have to coordinate this specifically with my general contractor (GC)?
I might consider finding someone myself who does a clean job and keep the GC out of it...
Honestly, I don’t think I’ll find any GC who “willingly” installs these ventilation systems.
It’s probably because this KfW 55 standard is very, very new, and the GCs haven’t really given it much thought yet.
I’m just having a hard time with this: They probably build around 120 houses a year, all KfW 70, and apparently no one had any issues or “missed” this ventilation system. I don’t think a KfW 55 house differs that much from a KfW 70 house.
Over the weekend I’m going to visit my cousin, who built a KfW 70 house without a ventilation system. The blower door test showed that it’s very close to a KfW 55 house. So I can find out firsthand what the situation really is.
Lumpi_LE schrieb:
Well, then "everyone, really everyone" has no idea...
Breathable bricks – oh, another one talking about breathable walls?
Decentralized ventilation – that really sounds promising.
The pipes look terrible? a) How would they know that? b) Nothing happens over a few years – unless you don’t install filters. By the way, you can also clean those things.
No one can ventilate properly unless they are home all day, don’t sleep through the night, and have a fetish for opening windows.
The affordable alternative is trickle vents combined with central exhaust. At least they provide some air exchange.So, is the building material not crucial for the indoor climate, or can a certain material not prevent mold?
Similar topics