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?
EveundGerd21 Apr 2015 22:47As far as I remember, the house construction must be supervised by an assessor who certifies that the building meets KfW 70 standards. This cannot be done afterwards, especially not after a longer period of time. Otherwise, there would be many homeowners wanting to obtain the certification retrospectively.
KfW only specifies that you must meet a certain insulation standard (HT) and a specific primary energy demand (kWh/m²a). I don’t think you receive a label for that, just the energy sticker to attach or something like that ^^ It’s more of a selling point for the "now" or the next few years. Eventually, you will have to state something like "KfW 55 according to the Energy Saving Ordinance 2009" or similar.
We are facing the same question about whether to build according to kfw 70 standards or just follow the Energy Saving Ordinance.
The price premium for additional insulation and solar thermal systems is almost €8,000 (about $8,000)!
The fixed interest rate period of only 10 years makes me somewhat hesitant. On top of that, there’s the 300-liter (about 80-gallon) tank in the small 9 m² (about 97 sq ft) utility room!
Is it really worth it just considering a potential resale value?
Because for €8,000 (about $8,000), I can already get a lot of gas...
The price premium for additional insulation and solar thermal systems is almost €8,000 (about $8,000)!
The fixed interest rate period of only 10 years makes me somewhat hesitant. On top of that, there’s the 300-liter (about 80-gallon) tank in the small 9 m² (about 97 sq ft) utility room!
Is it really worth it just considering a potential resale value?
Because for €8,000 (about $8,000), I can already get a lot of gas...
EveundGerd21 Apr 2015 23:00BeHaElJa schrieb:
At some point, you have to say something like "KFW 55 according to the 2009 Energy Saving Ordinance" or similar.Why should that cost 8,000 euros – why do you need a 300-liter (80-gallon) tank?! Just so you can use the solar thermal system? A 300-liter (80-gallon) tank is not that big. Solar thermal is rarely economically worthwhile because you simply use too little hot water.
What do you gain from KfW 70? About 2,000 euros (over 10 years) in interest subsidies and, of course, the additional savings in energy consumption – whether you can save 6,000 euros here is uncertain... but it probably won’t be a huge loss either.
If you artificially add measures that don’t really fit the house concept, I would question that – especially with such unusual heating concepts. A bit more insulation never hurts.
What’s the issue with your KfW 70? The heat transfer coefficient (U-value, so the insulation) or the primary energy demand?
What do you gain from KfW 70? About 2,000 euros (over 10 years) in interest subsidies and, of course, the additional savings in energy consumption – whether you can save 6,000 euros here is uncertain... but it probably won’t be a huge loss either.
If you artificially add measures that don’t really fit the house concept, I would question that – especially with such unusual heating concepts. A bit more insulation never hurts.
What’s the issue with your KfW 70? The heat transfer coefficient (U-value, so the insulation) or the primary energy demand?
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