ᐅ KfW 55 – Ventilation System: Yes or No? – Experiences

Created on: 19 May 2020 13:29
E
exto1791
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.
tomtom7931 Jul 2020 19:11
The blinds are fully open on the north side, with only slits open on the south and west sides. It is dark, but cool.
Tarnari31 Jul 2020 19:25
tomtom79 schrieb:

Blinds are fully open on the north side, while only slits are open on the south and west sides. It is dark, but cool.
It would be interesting to see how this works with external venetian blinds. We will have a mix of blinds and venetian blinds. On the south side venetian blinds, also on the west side of the ground floor, otherwise mostly blinds.
Tolentino31 Jul 2020 19:33
Shades or roller shutters?
tomtom7931 Jul 2020 19:54
I meant roller shutters; internal shading doesn’t provide much benefit.
L
Lumpi_LE
31 Jul 2020 20:06
Venetian blinds provide the same heat protection as roller shutters, but they do not make the room as dark.
Tarnari31 Jul 2020 20:15
I also meant roller shutters; I usually just say roller blinds.