ᐅ KfW 40 or better in solid construction without additional insulation possible?
Created on: 18 Nov 2019 08:44
S
Specki
Hello,
I was initially set on a timber frame construction for my future house. However, I am now reconsidering solid construction because it does have its advantages. Ideally, I would prefer this without additional external insulation, as that would be redundant and insulation typically does not last as long as the masonry itself. Poroton seems the most appealing option to me at first glance.
But is that even feasible? Are there bricks (or other solid building blocks) that on their own meet the KfW 40 standard, or possibly perform even better?
Does anyone have experience with this? Has anyone actually built something like this?
I’m open to discussion if you believe additional insulation makes sense. However, no “Styrofoam” will be used on the exterior walls; if anything, it will be an alternative material.
The comments I would rather avoid are those suggesting a lower energy standard would be sufficient. I will not build anything below KfW 40.
Thanks in advance for your input.
Best regards,
Specki
I was initially set on a timber frame construction for my future house. However, I am now reconsidering solid construction because it does have its advantages. Ideally, I would prefer this without additional external insulation, as that would be redundant and insulation typically does not last as long as the masonry itself. Poroton seems the most appealing option to me at first glance.
But is that even feasible? Are there bricks (or other solid building blocks) that on their own meet the KfW 40 standard, or possibly perform even better?
Does anyone have experience with this? Has anyone actually built something like this?
I’m open to discussion if you believe additional insulation makes sense. However, no “Styrofoam” will be used on the exterior walls; if anything, it will be an alternative material.
The comments I would rather avoid are those suggesting a lower energy standard would be sufficient. I will not build anything below KfW 40.
Thanks in advance for your input.
Best regards,
Specki
Let’s say you either need thicker insulation—which also eventually reaches its limits, especially with monolithic solid construction—or more efficient technology. Ideally, you have to accept one compromise, preferably the one that’s less expensive. And if you don’t want a thicker (or a completely different one that costs less for a given insulation performance at the desired additional delta) wall structure, then you can only optimize the technology.
This is about the primary energy demand relative to the reference building. One kWh of heat from oil or gas “costs” about 1.1 or 1.2 kWh primary energy, compared to solar energy with nearly zero primary energy. There is a lot of politics behind this factor. But theoretically, you could heat a relatively thin building envelope using a seasonal storage solar thermal system, and it would be acceptable.
However, at some point, this additional effort is no longer justifiable—except for true enthusiasts.
This is about the primary energy demand relative to the reference building. One kWh of heat from oil or gas “costs” about 1.1 or 1.2 kWh primary energy, compared to solar energy with nearly zero primary energy. There is a lot of politics behind this factor. But theoretically, you could heat a relatively thin building envelope using a seasonal storage solar thermal system, and it would be acceptable.
However, at some point, this additional effort is no longer justifiable—except for true enthusiasts.
@Specki
That wasn’t really the case. We had two timber frame builders compared for a KfW 40 house; one was more expensive, the other slightly cheaper. That surprised us as well. I don’t know if anything has changed since 2016/17.
The important thing is, if you want KfW 40 or a passive house, make sure to find a company for which this is standard.
For your information, it was different with KfW 55.
That wasn’t really the case. We had two timber frame builders compared for a KfW 40 house; one was more expensive, the other slightly cheaper. That surprised us as well. I don’t know if anything has changed since 2016/17.
The important thing is, if you want KfW 40 or a passive house, make sure to find a company for which this is standard.
For your information, it was different with KfW 55.
To add something to the original question:
We have walls made partly of 42.5cm (17 inches) bricks plus plaster and partly 30cm (12 inches) bricks plus mineral wool insulation and a ventilated wooden facade.
The area with the wooden facade was about 25% more expensive but also has 25% better insulation performance (If the same insulation value had been achieved, the cost difference would have been only marginal).
We have walls made partly of 42.5cm (17 inches) bricks plus plaster and partly 30cm (12 inches) bricks plus mineral wool insulation and a ventilated wooden facade.
The area with the wooden facade was about 25% more expensive but also has 25% better insulation performance (If the same insulation value had been achieved, the cost difference would have been only marginal).
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