Hello, we plan to start building our own home this year.
I already have two active discussion threads on this forum about it.
https://www.hausbau-forum.de/threads/Hausbau-kfw70-ca-150m-welche-Heizung-Gas-lwwp.12261/
https://www.hausbau-forum.de/threads/wir-wollen-bauen-ist-das-was-uns-angeboten-wird-so-i-o.12269/
We just got back from discussing the offer with the supplier.
I tried to talk about heating and ventilation; he shared his experiences, opinions, and advice.
This didn’t quite match what I had read so far, so now I’m uncertain and confused again.
We requested a 150m² (1,615 sq ft) solid house built to KFW 70 standard.
This is achieved through insulation and a gas-solar heating system. More details are in my other threads.
When I asked about a mechanical ventilation system with heat recovery, he said it’s not needed, that regular airing is sufficient.
He also said his son built a KFW 70 house with gas-solar three years ago and that he would never do that again. Better to build without KFW 70, save the money for the energy certificate inspection and the solar system (about 5,000), keep the insulation as is, and move on. Apparently, it’s not financially worthwhile.
Regarding the wall construction, another supplier told me the following:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: Yes, of course, we don’t list that separately because it’s required by DIN (German industrial standards).
Today, with our current supplier:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: No, that’s a cavity insulation. That might have been necessary in the past, but with today’s insulation materials, it’s no longer needed.
So what is correct? Is an air gap between the insulation and masonry required by DIN, or does it depend on which insulation material is used?
I already have two active discussion threads on this forum about it.
https://www.hausbau-forum.de/threads/Hausbau-kfw70-ca-150m-welche-Heizung-Gas-lwwp.12261/
https://www.hausbau-forum.de/threads/wir-wollen-bauen-ist-das-was-uns-angeboten-wird-so-i-o.12269/
We just got back from discussing the offer with the supplier.
I tried to talk about heating and ventilation; he shared his experiences, opinions, and advice.
This didn’t quite match what I had read so far, so now I’m uncertain and confused again.
We requested a 150m² (1,615 sq ft) solid house built to KFW 70 standard.
This is achieved through insulation and a gas-solar heating system. More details are in my other threads.
When I asked about a mechanical ventilation system with heat recovery, he said it’s not needed, that regular airing is sufficient.
He also said his son built a KFW 70 house with gas-solar three years ago and that he would never do that again. Better to build without KFW 70, save the money for the energy certificate inspection and the solar system (about 5,000), keep the insulation as is, and move on. Apparently, it’s not financially worthwhile.
Regarding the wall construction, another supplier told me the following:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: Yes, of course, we don’t list that separately because it’s required by DIN (German industrial standards).
Today, with our current supplier:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: No, that’s a cavity insulation. That might have been necessary in the past, but with today’s insulation materials, it’s no longer needed.
So what is correct? Is an air gap between the insulation and masonry required by DIN, or does it depend on which insulation material is used?
From... to, depending on the size of the house. When in doubt, go with what is being offered to you. Ours (decentralized), calculated for a small house, is probably around €5,500 (about 6,000 USD); for us, €5,000 (about 5,500 USD) for materials plus installation and wiring—so I would estimate around €7,500 (about 8,200 USD). A centralized system is likely more in the range of €8,000 to €12,000 (about 8,700 to 13,100 USD).
A controlled ventilation system is not mandatory for a single-family house, and you can definitely achieve KfW 70 standards through other means. But would manually ventilating—that is, airing out the house quickly to let warm air out and allow cold air in during winter—be a viable alternative?
And why not aim for KfW 70? In two years' time, it will be the standard. A house built to that standard will have a better position in the sales market, even after 20 years.
And why not aim for KfW 70? In two years' time, it will be the standard. A house built to that standard will have a better position in the sales market, even after 20 years.
S
Sebastian7918 Apr 2015 10:21ypg schrieb:
And why not KfW70? In the year after next, it will be the standard. The house will perform better on the resale market, even after 20 years.I hear that quite often, but I don’t find the argument convincing. What about the houses built 7 years ago to KfW70 or 60 standards or similar? Today, they wouldn’t even meet the current energy saving regulations.
And in 20 years, no one knows what crazy ideas the government/EU will come up with (the insulation craze will probably come to a natural end). By then, no one will care that the house was built under an energy saving regulation from 20 years ago.
What do you think?
I’m building to KfW standards more by chance – we didn’t specifically plan for it, we are not over-insulating, yet we still achieve KfW56 and include the €50,000 grant at favorable conditions.
After subsidies, we’re paying about €5,800 (around $6,300) total for all the materials for our central ventilation system Helios 500 with an enthalpy exchanger, including planning – installation will be done by us. And this is already a fairly high-quality and large ventilation system.
The initial quote from the plumber for a much smaller and lower-quality system was nearly €12,000 (about $13,000)…
S
Sebastian7918 Apr 2015 10:34Because you can’t insulate indefinitely – have you ever seen an insulation curve? It levels off significantly at the end – the savings compared to the investment won’t pay off within 20 years.
For example, we insulate our sand-lime brick walls with only 14 cm (5.5 inches) – I understand that with anchors, a bit more than 20 cm (8 inches) is currently possible. However, this means the house has to be “bigger,” the materials are much more expensive, and the effect – well, try calculating it with a U-value calculator. The difference between thermal conductivity grades WLG 035 and WLG 024 isn’t as large as you might initially think.
Next, in my opinion, the ecological impact of a construction project will become more important – then, builders of solid houses will face challenges, and timber (frame) houses will be promoted and encouraged.
For example, we insulate our sand-lime brick walls with only 14 cm (5.5 inches) – I understand that with anchors, a bit more than 20 cm (8 inches) is currently possible. However, this means the house has to be “bigger,” the materials are much more expensive, and the effect – well, try calculating it with a U-value calculator. The difference between thermal conductivity grades WLG 035 and WLG 024 isn’t as large as you might initially think.
Next, in my opinion, the ecological impact of a construction project will become more important – then, builders of solid houses will face challenges, and timber (frame) houses will be promoted and encouraged.
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