ᐅ Energy Efficiency Certificate KfW55 – Target KfW40 – Question: Steps & Costs
Created on: 19 Apr 2016 13:26
W
world-e
Hello everyone,
I have a question regarding structural engineering and energy efficiency:
We are currently planning a timber frame house with a basement. A ventilation system is also planned but has not been included in this energy performance calculation. According to the energy certificate, it is currently a KfW55 house. Please see the attached excerpts in the PDF. If more information is needed, please ask.
When I asked the energy consultant what would be necessary to achieve KfW40, he said the basement insulation would need to be 16cm instead of 12cm thick. This would result in the timber frame wall needing to be thicker as well (also for structural reasons). When I asked if the wood fiber insulation on the exterior wall could simply be made thicker (120mm instead of 60mm) to reach a U-value close to 0.11, he replied that this is not possible because the timber studs must rest about two-thirds on the foundation slab or basement ceiling. This would again require a thicker stud. Overall, the additional costs would be around €30,000–40,000, which would never pay off. I was not given any further explanation as to why the costs are this high.
My questions are:
1.) What do you think about these additional costs — can they be realistic?
2.) The wood fiber insulation boards don’t necessarily have to end flush with the outer edge of the concrete, right? They can protrude, correct? If the wood fiber board is thicker, it would just stick out a bit (6cm) without requiring any changes to the timber framing. And if the wood fiber insulation extends outward, wouldn’t the basement insulation be able to be thicker as well?
3.) What other options might I have to achieve KfW40 in a cost-effective way?
I hope you can help me understand this better. Many thanks.
I have a question regarding structural engineering and energy efficiency:
We are currently planning a timber frame house with a basement. A ventilation system is also planned but has not been included in this energy performance calculation. According to the energy certificate, it is currently a KfW55 house. Please see the attached excerpts in the PDF. If more information is needed, please ask.
When I asked the energy consultant what would be necessary to achieve KfW40, he said the basement insulation would need to be 16cm instead of 12cm thick. This would result in the timber frame wall needing to be thicker as well (also for structural reasons). When I asked if the wood fiber insulation on the exterior wall could simply be made thicker (120mm instead of 60mm) to reach a U-value close to 0.11, he replied that this is not possible because the timber studs must rest about two-thirds on the foundation slab or basement ceiling. This would again require a thicker stud. Overall, the additional costs would be around €30,000–40,000, which would never pay off. I was not given any further explanation as to why the costs are this high.
My questions are:
1.) What do you think about these additional costs — can they be realistic?
2.) The wood fiber insulation boards don’t necessarily have to end flush with the outer edge of the concrete, right? They can protrude, correct? If the wood fiber board is thicker, it would just stick out a bit (6cm) without requiring any changes to the timber framing. And if the wood fiber insulation extends outward, wouldn’t the basement insulation be able to be thicker as well?
3.) What other options might I have to achieve KfW40 in a cost-effective way?
I hope you can help me understand this better. Many thanks.
I created the PDFs from u-wert.net. However, these are meant to only show the wall construction according to the energy performance certificate. That’s why I asked for constructive feedback on the design. Unconstructive comments like "this is rubbish" don’t help anyone here and can be spared.
B
Bauexperte25 Apr 2016 10:33World-e schrieb:
Unconstructive comments like "this is rubbish" don’t help anyone here and can be left out. At first, I was also tempted to ask for a different tone; this is neither a green nor a blue forum.
On the other hand, your own communication style is not exactly helpful; you need every piece of necessary information practically “pulled out of you.” You ask all over the place in many forums; you do not contribute yourself or share your knowledge in any way. So you are only acting as a sponge.
Rübe must have noticed this too; therefore, his reaction to you is still quite moderate.
Regards, Bauexperte
Building expert, forget about green, that's just marketing now. In the blue section (where the green ones used to be), there were clear indications of problem areas. Here's one more: First lesson—axial spacing, for example. Then, using a 12mm (0.5 inch) OSB panel as a shear wall is already risky. Some say you can’t achieve airtightness with anything less than an 18mm (0.7 inch) panel. If you came up with this yourself as a private person, well, you can’t be expected to know better. But if this is coming from your "professionals," then that would be serious.