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.
Another point: If your general contractor installs mechanical ventilation with heat recovery in less than 10% of their projects, I would probably be somewhat skeptical about how well it is implemented. For companies that have been installing mechanical ventilation with heat recovery as a standard for a long time, I have slightly more confidence that the overall system is well-developed.
exto1791 schrieb:
Why shouldn’t I build a KfW 55 house??? Again... I get a repayment subsidy of 18,000 with an additional cost of about 5,000. WHY should I build a KfW 70 house????It’s not just that you are skeptical about the ventilation system, you are also not exactly convinced by heat pumps.
So I wonder how you plan to achieve the EnerPHit 55 (Effizienzhaus 55) standard.
My personal recommendation for you would be a conventional gas condensing boiler with solar thermal support, window rebate ventilation, and underfloor heating (which is already designed to be heat pump compatible, meaning low flow temperature).
Whether it’s possible to build an EnerPHit 55 with that setup, I don’t know. I would suggest asking your general contractor about this.
I would also be interested to know what exactly is included in your “KfW 55” package costing 4,000 to 7,000, and what kind of building systems technology is involved.
Regarding the repayment subsidy and the financial gain you are aiming for, I would personally forgo it. Although 13,000 is a significant amount, over the lifetime of the house or the loan term it becomes less relevant; for me, it wouldn’t be worth compromising my own convictions.
For the sake of formality, I want to emphasize that my recommendation to you does not reflect my personal beliefs about new builds in the current era in any way.
Fortunately, values can be measured and figures can be verified. I don’t need a contractor including in their contract that regular ventilation prevents mold.
Whether it’s the CO2 level in the room or the heat loss caused by ventilation, it’s clear that the difference between KfW55 and KfW70 standards isn’t huge. But just compare the heating costs of houses from the 1970s or 1980s—usually not all rooms are heated, or heating is done with a fireplace.
Our house has 4-5 rooms per floor. If I had to walk through the house every time to ventilate them, oh dear... Of course, I would prefer to build it airtight.
Whether it’s the CO2 level in the room or the heat loss caused by ventilation, it’s clear that the difference between KfW55 and KfW70 standards isn’t huge. But just compare the heating costs of houses from the 1970s or 1980s—usually not all rooms are heated, or heating is done with a fireplace.
Our house has 4-5 rooms per floor. If I had to walk through the house every time to ventilate them, oh dear... Of course, I would prefer to build it airtight.
I don’t know any general contractor who likes to install central ventilation systems. There is too much potential for errors during the structural work phase, and it reduces their overall profit margin. However, rental apartment buildings are nowadays almost always equipped with such systems because landlords want to avoid problems with mold.
There is no simpler decision in construction than whether to install controlled residential ventilation or not. There are clear decision parameters for this. It is not a matter of belief; as my predecessor said, it can all be measured.
There is no simpler decision in construction than whether to install controlled residential ventilation or not. There are clear decision parameters for this. It is not a matter of belief; as my predecessor said, it can all be measured.
A controlled residential ventilation system is like many things. If you never had it, you don’t miss it and can’t really understand the benefits. But once you have enjoyed continuously fresh air, you don’t want to be without it anymore (at least I don’t know anyone with a controlled residential ventilation system who would ever want to go back...).
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