ᐅ KfW 55 standard with a timber house – U-values: wall 0.18 W/m²K – roof 0.16 W/m²K
Created on: 24 May 2015 10:20
-
-Markus-
Hello,
While looking for a building partner, my wife and I found a local carpentry company that makes a very good impression on us and with whom we can well imagine collaborating.
What we like is the ecological construction method. In addition, the provider offers the installation level that I absolutely require, which other modular home manufacturers usually do not, or only include in the more expensive passive house walls.
The price also seems reasonable—especially since the above-mentioned ecological construction method reduces our land cost through a funding program.
My goal is to have a KfW 55 house—not (only) because of the funding, but also for permanently low operating costs. Again noted here: achieving the KfW 55 standard would make the land significantly cheaper.
The U-values upon inquiry are:
- Exterior wall: 0.187
- Roof: 0.166
In addition to geothermal energy, a controlled residential ventilation system is planned.
Are these U-values still considered standard today? I think the roof is quite good, but the exterior wall is only average compared to other providers.
Thanks and best regards
-Markus-
While looking for a building partner, my wife and I found a local carpentry company that makes a very good impression on us and with whom we can well imagine collaborating.
What we like is the ecological construction method. In addition, the provider offers the installation level that I absolutely require, which other modular home manufacturers usually do not, or only include in the more expensive passive house walls.
The price also seems reasonable—especially since the above-mentioned ecological construction method reduces our land cost through a funding program.
My goal is to have a KfW 55 house—not (only) because of the funding, but also for permanently low operating costs. Again noted here: achieving the KfW 55 standard would make the land significantly cheaper.
The U-values upon inquiry are:
- Exterior wall: 0.187
- Roof: 0.166
In addition to geothermal energy, a controlled residential ventilation system is planned.
Are these U-values still considered standard today? I think the roof is quite good, but the exterior wall is only average compared to other providers.
Thanks and best regards
-Markus-
Just for comparison of the values – solid construction with sand-lime bricks, faced:
For the exterior wall, we have a U-value of 0.176 W/m²K
Pitched roof: 0.162
Ground slab: 0.31
We only applied for KfW70, but we are annoyed because if you don’t meet the requirements, it just falls back from KfW55 to 70 – an upgrade “upwards,” that is from KfW70 to KfW55, apparently is not possible...
One more tip: If you are planning geothermal energy, definitely spend a few hours here in the forum – also search for the term “trench collector.” It saved us nearly €10,000.
For the exterior wall, we have a U-value of 0.176 W/m²K
Pitched roof: 0.162
Ground slab: 0.31
We only applied for KfW70, but we are annoyed because if you don’t meet the requirements, it just falls back from KfW55 to 70 – an upgrade “upwards,” that is from KfW70 to KfW55, apparently is not possible...
One more tip: If you are planning geothermal energy, definitely spend a few hours here in the forum – also search for the term “trench collector.” It saved us nearly €10,000.
The more I read, the more confused I become:
I have now seen an annual primary energy demand of about 73 kWh/m²a, as well as a transmission heat loss of 0.4.
I believe the transmission heat loss is just at the limit of the 2014 Energy Saving Ordinance, and the 73 kWh/m²a also seems a bit high to me.
@Frank: Would you have been able to achieve KfW55 standard?
Regards,
Markus
I have now seen an annual primary energy demand of about 73 kWh/m²a, as well as a transmission heat loss of 0.4.
I believe the transmission heat loss is just at the limit of the 2014 Energy Saving Ordinance, and the 73 kWh/m²a also seems a bit high to me.
@Frank: Would you have been able to achieve KfW55 standard?
Regards,
Markus
We will probably achieve KFW55 with the following values:
Windows: Uw = 0.75 ~
Roof and roof slopes: 0.155
Exterior wall: 0.186
Floor slab: 0.166
Front door: 1.2
All this with a ground-source heat pump, controlled mechanical ventilation, and without a circulation pump (I’ve learned that this is probably a factor as well ^^)
Without the geometry of the house, these values are only approximate. The proportions of windows, walls, and roof are also crucial.
The overall thermal transmittance (HT) we have is 0.246 (which means achieving KFW55 is actually quite tight for us)
Q-value of 31.26 kWh/m²a (this fits quite well with KFW55)
Windows: Uw = 0.75 ~
Roof and roof slopes: 0.155
Exterior wall: 0.186
Floor slab: 0.166
Front door: 1.2
All this with a ground-source heat pump, controlled mechanical ventilation, and without a circulation pump (I’ve learned that this is probably a factor as well ^^)
Without the geometry of the house, these values are only approximate. The proportions of windows, walls, and roof are also crucial.
The overall thermal transmittance (HT) we have is 0.246 (which means achieving KFW55 is actually quite tight for us)
Q-value of 31.26 kWh/m²a (this fits quite well with KFW55)
I believe so – the certificate shows just under 40 kWh/m²a (just under 4 kWh/ft²a) and about 0.3 for the heat loss coefficient, but we made some additional changes to the insulation all around, removed the circulation pump, focused on heat recovery in the controlled ventilation system, etc.
It’s worth spending a few hours on u-wert.net before starting construction – their heating demand calculator is also very useful.
It’s worth spending a few hours on u-wert.net before starting construction – their heating demand calculator is also very useful.
Are additional elements included in HT and Q besides the components themselves, or can the values from the structural engineer’s/building physicist’s table be used?
If the adjustments you mentioned are still made, could the whole situation look completely different?
Best regards
-Markus-
If the adjustments you mentioned are still made, could the whole situation look completely different?
Best regards
-Markus-
Similar topics