ᐅ Is insulation between rafters with a thermal conductivity of 0.032 sufficient, or is 0.035 adequate?
Created on: 28 Jan 2022 14:56
J
Jacy0505The question is already stated above; actually, our energy consultant should inform us promptly, but they are currently very busy.
Our construction company wants to order the insulation as soon as possible due to another announced price increase.
Therefore, the question to the group... For the Effizienzhaus 55 (efficiency house 55 standard), which cavity insulation should we use? The 035 (0.035 W/m·K) would be significantly cheaper, but the problem is whether it meets the requirements.
Thanks for your answers.
Our construction company wants to order the insulation as soon as possible due to another announced price increase.
Therefore, the question to the group... For the Effizienzhaus 55 (efficiency house 55 standard), which cavity insulation should we use? The 035 (0.035 W/m·K) would be significantly cheaper, but the problem is whether it meets the requirements.
Thanks for your answers.
H
Hausbau 5528 Jan 2022 15:01What thickness should the insulation be? If 240 mm (9.5 inches) with a thermal conductivity of 0.032 W/mK is planned, then 260 or 280 mm (10.2 or 11 inches) with 0.035 W/mK is also possible. Now you can assess the price accordingly.
We are building to KfW55 standard and using 20cm (8 inches) of 035 rock wool insulation. It is important that you achieve the required U-value, which in your case should apply to a cold roof. You might want to familiarize yourself with UBA KUSS and see how you can best meet your target U-value.
In terms of cost, I can say that I recently paid just under 1000€ for 100m² (1100 sq ft) of rock wool insulation at the hardware store with Biber; in my case, this is material only, so you would need to add in installation costs.
Do you have cross-section plans of the house? These should or might also indicate the thickness of the insulation.
In terms of cost, I can say that I recently paid just under 1000€ for 100m² (1100 sq ft) of rock wool insulation at the hardware store with Biber; in my case, this is material only, so you would need to add in installation costs.
Do you have cross-section plans of the house? These should or might also indicate the thickness of the insulation.
There are two calculation methods for KfW 55: either the entire house is calculated to meet the KfW 55 standard, which means, for example, that a poorer roof could be compensated by better exterior walls, and vice versa. Alternatively, each individual building component can be calculated to meet the KfW 55 value. While your question could be answered under the second method, it would be problematic if the energy consultant uses the first method and it later turns out that the roof would have needed to be better to compensate for, for example, poorer walls, foundation slab, or windows.
Long story short: this is something your energy consultant needs to answer.
Long story short: this is something your energy consultant needs to answer.
Hmm, he’s taking his time. But I guess we have no choice but to wait.
Another question that’s been on our minds... We have had approval for the KFW 55 grant since early November. Do you really think that is absolutely binding? Somehow, I’m still not fully confident. At the moment, we could still pull back. The price difference for building an energy-efficient house meeting the Effizienzhaus 55 standard is quite significant. Financially, it only makes sense for us with the promised funding. What do you think?
Another question that’s been on our minds... We have had approval for the KFW 55 grant since early November. Do you really think that is absolutely binding? Somehow, I’m still not fully confident. At the moment, we could still pull back. The price difference for building an energy-efficient house meeting the Effizienzhaus 55 standard is quite significant. Financially, it only makes sense for us with the promised funding. What do you think?
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