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
We also built with a mechanical ventilation system with heat recovery (I never want to do without it again) and followed the KFW55 standard due to the new financing conditions. The full 120,000 euros at the KFW interest rate plus an 18,000-euro repayment grant were worth the additional effort to us. We also had to pay an extra 1,750 euros for an energy consultant (50% of the total invoice) and around 2,500 euros for perimeter insulation.
Good luck,
Kati
Good luck,
Kati
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pagoni202031 Oct 2020 14:46OWLer schrieb:
I’m a bit surprised that you see KFW55 as automatically linked to mechanical ventilation with heat recovery?I feel the same way. Initially, I didn’t want a mechanical ventilation system, but now I know we will have one. Here, central mechanical ventilation with heat recovery is mostly recommended, but we will still consider what exactly suits us; definitely a mechanical ventilation system with heat recovery.This decision is based entirely on our personal feelings and habits, and not at all dependent on any funding agency. We are not yet sure if we will apply for such funding. First, the house will be planned exactly how it fits our needs and what makes us comfortable within the possibilities. For KFW, for example, I would never want to completely "wrap" our house in a thermal insulation system, whereas something like wooden cladding might be an option. Both the system and the appearance must appeal to me, regardless of KFW and grants.
All other doubts you hear are absolutely justified... or maybe not... There is a pro and contra for every decision, and the last advice I would give you is to base your choice on other people’s opinions or casual talk, but also not on KFW requirements. It has to be the right fit for YOU alone, which is often overlooked in my opinion.
For me, the important question is: Do I see it as an improvement in comfort if the indoor air is exchanged automatically? For me—as someone who was originally against it—the answer is yes. But I won’t let comfort be dictated by calculations. Take your time with this uncertainty and, for example, check out one of the companies like Zehnder, listen to them, and discuss YOUR concerns there. Everyone perceives things differently!
Mertha257 schrieb:
Should I stay with the KfW 55 plan or rather "downgrade" to the Energy Saving Ordinance standard?Why should that decision be a “downgrade” as long as you implement all the comfort features you want?OWLer schrieb:
I am building with mechanical ventilation and would not do it without it. Regardless of KFW or the Energy Saving Ordinance.YepOWLer schrieb:
For just under $20,000 there is a lot of technology.......but only the technology I would have chosen anyway without KFW.Generally, I am a fan of innovation and technology, but not of what I see as often exaggerated, expensive automation or equipment without noticeable comfort improvements. For example, we have installed a “standard underfloor heating” system, and during the day I often feel the temperature/climate is just not how I want it. That never happened in my old house (radiators, no underfloor heating, no mechanical ventilation).
No need to apologize for the repeated topic—the search function here is really poor. I hope your possible mechanical ventilation system works better; otherwise, you might be better off without it.
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nordanney31 Oct 2020 15:26Mertha257 schrieb:
Are there any experiences with particularly quiet mechanical ventilation models from current product lines?Please clarify your noise concern. Are you referring to the noise coming from the ventilation grilles or the noise produced by the ventilation unit itself (which is usually installed in the basement, attic, or a technical room and should be insulated)? The ventilation unit is always somewhat "noisy"; this is inherent to the technology. The noise from the ventilation grilles is extremely low. From my experience, you only notice the airflow when the house is completely silent; otherwise, it is not audible.
Mertha257 schrieb:
And you don’t need mechanical ventilation with heat recovery; "it works fine with reasonable ventilation behavior without it, is cheaper and actually provides a better indoor climate." Anyone who thinks or says that has simply never lived in a house or apartment with forced ventilation and doesn’t really know what they are talking about.
Mertha257 schrieb:
Are there any experiences with particularly quiet mechanical ventilation with heat recovery models from current product generations? Simply put: central systems are all quiet. After all, they are residential ventilation units—not commercial systems for restaurants or shopping centers. With decentralized and purely exhaust systems, the situation is of course somewhat different.
Mycraft schrieb:
Anyone who thinks or says that simply has never lived in a house or apartment with mechanical ventilation and doesn’t know what they’re talking about.
I agree with that. I was hopeful but skeptical about the indoor air quality before. But I would never want to live without it again.
There is simply fresh air everywhere all the time. You can’t imagine it unless you’ve experienced it yourself.
In the morning, I walk from the bathroom back to the bedroom expecting the “stale night air before airing out,” and every morning I’m still surprised that this stale air just doesn’t exist anymore.
Regarding noise levels: We have a central ventilation system (combined unit with heat pump), and I can’t say that I have noticed it outside of the utility room.
When you stand in the utility room, you can hear the ventilation. If you close the door to the hallway, you don’t hear anything anymore.
I have never heard the outlets / exhaust vents in the rooms. Even at night in the bedroom when it’s quiet, there is no noise. But our system also lowers to level 1 there. In the evening, while taking a bath, you don’t hear anything in the bathroom even though the exhaust is running. I have often put my hand near it to check if it’s actually working.
When you stand in the utility room, you can hear the ventilation. If you close the door to the hallway, you don’t hear anything anymore.
I have never heard the outlets / exhaust vents in the rooms. Even at night in the bedroom when it’s quiet, there is no noise. But our system also lowers to level 1 there. In the evening, while taking a bath, you don’t hear anything in the bathroom even though the exhaust is running. I have often put my hand near it to check if it’s actually working.
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