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
M
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
kati1337 schrieb:
We had to pay an additional 1750€ for the energy consultant (50% of the total invoice), and around 2500€ for perimeter insulation.Compared to the subsidy, that really isn’t much..
For us, upgrading from the Energy Saving Ordinance to KfW 55 standard would cost an additional 14,500 euros, and the central mechanical ventilation system would add another 6,000 euros.
We will build according to the Energy Saving Ordinance including a central mechanical ventilation system.
Mertha257 schrieb:
- "Not worth it," meaning the additional construction costs/KfW loan or repayment grant are disproportionate at KfW 55; "better to build without KfW support in these interest rate times, ends up the same without KfW."KfW 55... it’s not that expensive after all, Mertha257 schrieb:
Noise generation of the controlled residential ventilation system, meaning KfW 55 brings a ventilation system into the house that can cause disturbing noise in some cases (we are subjectively very sensitive to noise). And the controlled residential ventilation is not necessary, "with reasonable ventilation behavior it works without it as well, is cheaper, and anyway results in better indoor air quality."With good house design, the utility room is not audible. With proper controlled residential ventilation settings, the ventilation system is not audible.
Mertha257 schrieb:
The energy saving ordinance is more than sufficient in terms of energy and efficiency standards with reasonable wall construction and proper windows; "the little extra energy savings are not worth the additional effort and bringing another noise source into the house." "Today’s houses built to the energy saving ordinance standard already have very low energy costs."In my opinion, that is correct. Still, controlled residential ventilation should be considered separately and certainly does not harm a house built according to the energy saving ordinance, as it provides comfort in ventilation. Mertha257 schrieb:
You don’t need KfW 55 because you intend to live in the house yourself until old age. If you wanted to sell it again, KfW 55 would be more important."Who can really predict what you will need to do in ten years? I would view controlled residential ventilation independently: it is a convenience. Manual ventilation requires effort and time.
KfW 55 is fine, as is KfW 70. Price-wise, it’s not a decisive factor right now...
Specki schrieb:
I would approach it the other way around. Wouldn’t it possibly make more sense to upgrade from KfW 55 to KfW 40+?… while KfW 40 is somewhat excessive if you don’t see the point or have the money for the extra cost. It’s not necessary.ypg schrieb:
... while KfW 40 is a bit exaggerated if you don’t see the point or don’t have the money for the additional cost. It’s not necessary.I see it differently. If you already have KfW 55 and a mechanical ventilation with heat recovery is installed anyway, you only need a bit more insulation to reach KfW 40. That’s just a few centimeters.
I would definitely install a photovoltaic system on the roof. Electricity prices are rising, and eventually, an electric car will be in the picture. If I go for KfW 40+, I get the battery storage for free through subsidies.
Over the lifetime of the house and insulation, the additional costs (minus the subsidies) will definitely pay off. If you ever sell the house, KfW 40 is also a higher-quality standard than KfW 55, since the trend is moving increasingly in that direction.
So, KfW 40+ means a bit more initial investment, but it’s worth it. That’s how I see it, and that’s why I recommend it.
Specki schrieb:
I see it differently. If you already have KFW55 and a controlled ventilation system, it doesn’t take much more insulation to reach KFW40. Just a few centimeters.
I would definitely install a photovoltaic system on the roof. Electricity prices are rising, and electric cars will eventually become common. If I upgrade to KFW40+, I get the battery storage covered by the subsidy.
Over the lifetime of the house/insulation, you will save the additional costs (after subsidies) anyway. If you sell later, KFW40 is also more valuable than KFW55, since the trend is moving further in that direction.
So KFW40+ initially requires a bigger investment, but it’s worth it. That’s how I see it, and that’s why I recommend it. Then you’re exactly the kind of person who understands the point and can afford it.
M
Mertha2571 Nov 2020 10:31nordanney schrieb:
Define your noise concern. Is it about the noise coming from the ventilation outlets, or the noise from the ventilation unit itself (which should normally be installed in the basement/attic/utility room with proper soundproofing)?
The ventilation unit is always "noisy"; that’s inherent to the technology. The noise from the ventilation outlets is extremely quiet. From my experience, you only hear the airflow when the house is completely silent. Otherwise, not. Hello Nordanney, basically both are our concern since our bedroom is directly above the utility room. However, we would try to ensure proper decoupling of the mechanical ventilation system and also increase the concrete slab thickness from 18/20cm to 22cm (7/8 inches to 8.7 inches). Regarding the ventilation outlets, we have also heard from acquaintances and noticed ourselves that noticeable noise can sometimes come from them. Maybe there is a solution with different, preferably low-friction fans or sound attenuators?
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