ᐅ Single-family house with KfW55 / mechanical ventilation with heat recovery or complying with Energy Saving Ordinance standard – experiences and opinions?
Created on: 31 Oct 2020 12:45
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Mertha257
Hello everyone,
First of all, I want to say that this forum has already provided me with many helpful suggestions and opinions. It’s really impressive to see the knowledge and engagement here!
In our case, the building permit / planning permission (with KfW 55 standard and controlled residential ventilation) was approved last week, and we have two remaining solid house providers to choose from, so we will decide shortly whom to go with for our construction project (typical single-family house, pitched roof, gas condensing boiler, interior and exterior walls made of sand-lime brick, about 190 sqm (2045 sq ft), construction costs around 460k plus additional costs).
We only have one open question left: so far, we were fully focused on KfW 55 with controlled residential ventilation — but now, shortly before finalizing, some doubts have arisen. The arguments we hear against KfW 55 and in favor of just following the energy saving ordinance (EnEV) are, for example:
- “Not worth it,” meaning the additional construction costs and KfW loan or repayment bonus are disproportionate for KfW 55; “better to build without KfW support in the current interest rate environment, it ends up the same.”
- “Noise from the controlled ventilation system,” meaning KfW 55 requires installing a ventilation system that could cause disturbing noise (we are subjectively very sensitive to noise). And the controlled ventilation is not necessary, “with reasonable airing behavior, it works without it, it’s cheaper and actually better for indoor air quality.”
- “The energy saving ordinance standard is sufficient with proper wall construction and decent windows; the slight additional energy savings aren’t worth the extra effort and potentially adding a noise source. Today’s homes built to the EnEV standard already have very low energy costs.”
- “You don’t need KfW 55 because you plan to live in the house permanently. If you wanted to sell again, KfW 55 would be more important.”
You might notice we are a bit unsure whether to stick to our KfW 55 plan or rather “downgrade” to the energy saving ordinance standard.
We would really appreciate your opinions, comments, advice, etc., as we want to finalize the deal with the general contractor this weekend.
Many thanks for your feedback and happy Halloween!
Mertha
First of all, I want to say that this forum has already provided me with many helpful suggestions and opinions. It’s really impressive to see the knowledge and engagement here!
In our case, the building permit / planning permission (with KfW 55 standard and controlled residential ventilation) was approved last week, and we have two remaining solid house providers to choose from, so we will decide shortly whom to go with for our construction project (typical single-family house, pitched roof, gas condensing boiler, interior and exterior walls made of sand-lime brick, about 190 sqm (2045 sq ft), construction costs around 460k plus additional costs).
We only have one open question left: so far, we were fully focused on KfW 55 with controlled residential ventilation — but now, shortly before finalizing, some doubts have arisen. The arguments we hear against KfW 55 and in favor of just following the energy saving ordinance (EnEV) are, for example:
- “Not worth it,” meaning the additional construction costs and KfW loan or repayment bonus are disproportionate for KfW 55; “better to build without KfW support in the current interest rate environment, it ends up the same.”
- “Noise from the controlled ventilation system,” meaning KfW 55 requires installing a ventilation system that could cause disturbing noise (we are subjectively very sensitive to noise). And the controlled ventilation is not necessary, “with reasonable airing behavior, it works without it, it’s cheaper and actually better for indoor air quality.”
- “The energy saving ordinance standard is sufficient with proper wall construction and decent windows; the slight additional energy savings aren’t worth the extra effort and potentially adding a noise source. Today’s homes built to the EnEV standard already have very low energy costs.”
- “You don’t need KfW 55 because you plan to live in the house permanently. If you wanted to sell again, KfW 55 would be more important.”
You might notice we are a bit unsure whether to stick to our KfW 55 plan or rather “downgrade” to the energy saving ordinance standard.
We would really appreciate your opinions, comments, advice, etc., as we want to finalize the deal with the general contractor this weekend.
Many thanks for your feedback and happy Halloween!
Mertha
M
Mertha2571 Nov 2020 10:33Mycraft schrieb:
Anyone who thinks or says that has simply never lived in a house or apartment with mechanical ventilation and doesn’t know what they’re talking about.
Simply put: central systems are all quiet. These are residential ventilation units, not commercial installations for restaurants or shopping centers. With decentralized or exhaust-only systems, the situation is naturally somewhat different. Thanks, Mycraft. I did some more reading online overnight, and it seems that there is still quite a bit that can be done to reduce noise levels with fans and silencers.
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Mertha2571 Nov 2020 10:35kati1337 schrieb:
Regarding noise levels: We have a central ventilation system (combined unit with heat pump) and I can’t say that I have ever noticed it outside the technical room.
If you stand in the utility room, you can hear the ventilation. But when you close the door to the hallway, you can barely hear anything.
And I have never heard the outlets or exhaust vents in the rooms. Not even at night in the bedroom when it’s quiet. But our system also reduces to level 1 at night. Even in the evening while taking a bath, you don’t hear anything in the bathroom, even though the exhaust is on. I have often held my hand in front to check if it’s running at all. Thanks, Kati1337! That’s good and reassuring to hear. Since we will be building with a gas boiler instead of a heat pump, your system unfortunately isn’t an option for us. But I will continue researching possible standalone mechanical ventilation with heat recovery systems that are as quiet as possible.
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Mertha2571 Nov 2020 10:37Yaso2.0 schrieb:
Compared to the subsidy, that's really not much..
For us, that would be an additional cost of 14,500 euros for upgrading from the Energy Saving Ordinance to KfW 55, plus another 6,000 euros for the central controlled residential ventilation system.
We will build according to the Energy Saving Ordinance, including a central controlled residential ventilation system.Hello Yaso2.0, thanks – may I ask which central controlled residential ventilation system you will choose (manufacturer/brand)?
Mertha257 schrieb:
Thank you, Kati1337! That’s good and reassuring to hear. Since we will be building with a gas boiler and not a heat pump, your seemingly very quiet system unfortunately isn’t an option for us, but I will continue to look for possible stand-alone controlled ventilation units that are as quiet as possible.Yes, there are definitely some options. To be completely honest: Yesterday, I noticed in the guest bathroom that I could hear the exhaust air. Probably because it’s such a small room and you are sitting almost directly under the exhaust vent. Nothing serious, but I wanted to mention it.
Mertha257 schrieb:
Hello Yaso2.0, thanks – may I ask which controlled residential ventilation system you will be using (manufacturer/brand)? We are getting a Vaillant recoVAIR.