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.
Rübe1 schrieb:
Oh man, who came up with this? This is botched to the nth degree Could you please explain that in more detail?
The original wall had a U-value of 0.135 and included a 60mm (2.4 inches) wood fiber insulation board, which is the wall construction proposed by the carpentry company. However, this only meets the requirements for KfW55. Therefore, the energy consultant adjusted the wall so that the U-value reached 0.11 ("Wand_Thermofibre.pdf"), achieving KfW40 standards. However, this requires modifications to the studs, which will be complex and costly. That is why my idea is to simply double the thickness of the wood fiber insulation boards to 120mm (4.7 inches), which could also achieve a U-value of 0.11 without needing to change the studs.
My question now concerns the wall construction of these two variants. But when I read comments like "this is nonsense to the power of 10," that is not very constructive.
My question now concerns the wall construction of these two variants. But when I read comments like "this is nonsense to the power of 10," that is not very constructive.
Rübe1 schrieb:
Who came up with this? What exactly do you mean by that? I already mentioned who designed each wall construction. If you don’t clearly specify your question, it’s difficult to provide an answer. A “this” can mean anything.
World-e schrieb:
What exactly do you mean by that? I already explained who came up with which wall structure. If you don’t define your question clearly, it’s hard to answer. A “that” can mean anything.The question will relate to your #11, meaning your PDFs, the content! That’s where it was at least asked for the first time.
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