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?
U
Username_wahl19 Apr 2015 15:42We are building a timber frame house. The insulation will be cellulose. According to the architect/energy consultant, we will easily meet KfW55 standards, and it will be quite "eco-friendly" thanks to the use of renewable raw materials.
A traditional masonry house builder we consulted already rolled their eyes when we mentioned KfW70. With wooden houses, achieving good insulation might actually be easier.
A traditional masonry house builder we consulted already rolled their eyes when we mentioned KfW70. With wooden houses, achieving good insulation might actually be easier.
But always keep in mind: good insulation does not necessarily mean just a high insulation value. Especially in timber construction, the quality can vary significantly! Two cardboard panels with 20cm (8 inches) of glass wool in between may have a great insulation value, but I wouldn’t want to live in that. In timber construction, the necessary mass should also be considered. This is what makes high-quality timber construction quite costly.
L
LittleWulf21 Apr 2015 10:38After our meeting with the financial advisor yesterday, it currently looks like we do not want to build a KFW70 house after all.
The financial benefit is too small. However, I will still go with the planned insulation, the underfloor heating with tighter pipe spacing designed for 35°C (95°F), and a ventilation system.
Solar thermal energy can always be added later if needed, and we can still have the KFW70 certification confirmed by an expert at that point. Because, as far as I understand, solar thermal is only useful for that purpose. Although our financial advisor looked surprised when I mentioned "around 30 years until it pays off." He said he had heard it pays off after 10 years. I need to double-check which system we were offered. If it really does pay off after 10 years, we might consider including solar thermal after all, but without the KFW70 expert certification. Because if we do not take out the loan (with a 10-year fixed interest rate, and the remainder tied for 20 years), then why get the written confirmation that it is KFW70?
What do you think?
The financial benefit is too small. However, I will still go with the planned insulation, the underfloor heating with tighter pipe spacing designed for 35°C (95°F), and a ventilation system.
Solar thermal energy can always be added later if needed, and we can still have the KFW70 certification confirmed by an expert at that point. Because, as far as I understand, solar thermal is only useful for that purpose. Although our financial advisor looked surprised when I mentioned "around 30 years until it pays off." He said he had heard it pays off after 10 years. I need to double-check which system we were offered. If it really does pay off after 10 years, we might consider including solar thermal after all, but without the KFW70 expert certification. Because if we do not take out the loan (with a 10-year fixed interest rate, and the remainder tied for 20 years), then why get the written confirmation that it is KFW70?
What do you think?
S
Sebastian7921 Apr 2015 10:45Yes, that would also be nonsensical.
He is probably referring to photovoltaic systems, which usually pay off after 10-14 years (depending on size, orientation, and usage).
He is probably referring to photovoltaic systems, which usually pay off after 10-14 years (depending on size, orientation, and usage).
D
Doc.Schnaggls21 Apr 2015 12:25Hello,
we only had the solar thermal system prepared, meaning the necessary pipes and empty conduits were installed from the utility room in the basement up to the attic.
Since we are already heating and producing hot water with an air-to-water heat pump, we consider our photovoltaic system on the roof to be more important and practical than a solar thermal panel.
What kind of heating system have you planned?
Best regards,
Dirk
we only had the solar thermal system prepared, meaning the necessary pipes and empty conduits were installed from the utility room in the basement up to the attic.
Since we are already heating and producing hot water with an air-to-water heat pump, we consider our photovoltaic system on the roof to be more important and practical than a solar thermal panel.
What kind of heating system have you planned?
Best regards,
Dirk
L
LittleWulf21 Apr 2015 12:53A gas heating system.
And the consultant also said that, according to his recollection, he was thinking of a system larger than 7–9m² (75–97 ft²), but we only have 5.02m² (54 ft²).
And the consultant also said that, according to his recollection, he was thinking of a system larger than 7–9m² (75–97 ft²), but we only have 5.02m² (54 ft²).
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