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.
Strahleman schrieb:
Are you building with a heat pump? If so, do you achieve an annual performance factor (seasonal coefficient of performance) of 4.5 or higher? If yes, apply to BAFA together with a mechanical ventilation system with heat recovery (the two must be controlled together, e.g., via wireless communication), then you can get a 35% subsidy on the systems. This almost covers the cost of the mechanical ventilation system. I don’t know the annual performance factor of our heat pump, but we definitely get the 35% subsidy (without ventilation). Do you think we would also get 35% for the centralized ventilation system? That would certainly make it more interesting...
Strahleman schrieb:
Otherwise, what does the energy consultant say about building to KfW 55 standard without a mechanical ventilation system? Decentralized solutions always mean you bring the fan noise directly into the room, and the heat recovery will be zero or very close to zero. But especially if you like fresh air, I would consider investing in a mechanical ventilation system. I haven’t discussed the ventilation system yet with the energy consultant, only with the construction advisor so far. He says that with the general contractor, none of the buildings have ever started to develop mold, whether with ventilation or without. Although, I guess he might say something different if he wanted to sell me something...
Maybe it is simply because, as is often seen here, they don’t know how to design it properly and in a way that fits calculation software. What is better for a general contractor: a mechanical ventilation system that causes complaints, or one that is not installed at all and therefore causes no problems due to lack of planning?
Our completely independent energy consultant strongly recommended installing it, because an average household cannot ventilate as required in modern buildings.
Our completely independent energy consultant strongly recommended installing it, because an average household cannot ventilate as required in modern buildings.
S
Strahleman26 Jun 2020 01:12Abzug86 schrieb:
I don’t know the seasonal performance factor of our heat pump, but we will definitely receive the 35% subsidy (without ventilation). Do you think we would also get 35% on the central ventilation system? That would of course make it more interesting... Have the general contractor provide written confirmation that the heating installation meets the requirements for the BAFA subsidy, preferably with the approved BAFA application. Controlled mechanical ventilation has recently become eligible for funding when the heat pump is subsidized. However, the controlled ventilation and heat pump must be able to be managed together, for example via a common control unit like with Nibe, or through smart home systems (KNX, wireless, etc.). There are various information sheets from Nibe, Zehnder, Maico, and of course the official BAFA leaflet on this topic.
Abzug86 schrieb:
I haven’t talked to the energy consultant about the ventilation system yet, only the construction consultant so far. You should definitely discuss it with the energy consultant. Ours expressed concerns right from the start that we wouldn’t meet the KfW standard if we built without controlled mechanical ventilation. Our builder, on the other hand, said that controlled mechanical ventilation wasn’t necessary. It’s always different perspectives.
For us, building to KfW 70 standard without a controlled residential ventilation system is not even an option. The repayment subsidies on both sides are simply so attractive compared to the price that you really don’t have any other choice.
The price you mentioned is completely exaggerated.
What we also plan to do: we will most likely handle the heating and ventilation work ourselves and outsource it externally, as we don’t feel well supported by the construction companies in these cases. This way, you just go to a heating or HVAC specialist and ask for a quote, which will definitely save you quite a bit.
For us, there are recognized additional costs for KfW 55 ranging between 5,000 and 8,000 euros (additional insulation, etc.), depending on the provider. Otherwise, the house would barely differ by 1% compared to building it to KfW 70. The repayment subsidy is 18,000 euros, so you can calculate for yourself what you are actually paying.
On top of that, there is the BAFA subsidy for air-to-water heat pumps and controlled residential ventilation of 35%... So, as I said, mathematically, there really is no other option for us but to tackle this, whether you want to or not.
The price you mentioned is completely exaggerated.
What we also plan to do: we will most likely handle the heating and ventilation work ourselves and outsource it externally, as we don’t feel well supported by the construction companies in these cases. This way, you just go to a heating or HVAC specialist and ask for a quote, which will definitely save you quite a bit.
For us, there are recognized additional costs for KfW 55 ranging between 5,000 and 8,000 euros (additional insulation, etc.), depending on the provider. Otherwise, the house would barely differ by 1% compared to building it to KfW 70. The repayment subsidy is 18,000 euros, so you can calculate for yourself what you are actually paying.
On top of that, there is the BAFA subsidy for air-to-water heat pumps and controlled residential ventilation of 35%... So, as I said, mathematically, there really is no other option for us but to tackle this, whether you want to or not.
Abzug86 schrieb:
@exto1791
For us, the question isn't whether to build to KfW70 or KfW55 standard, but whether to have KfW55 with or without ventilation.Oh, sorry, I had something else in mind when I read through everything here.
I would still recommend choosing ventilation and possibly outsourcing the whole heating/ventilation system separately, as I mentioned before.
A cooling and air conditioning system will cost you about 12,000 euros.