ᐅ Combination of different thermal conductivity classes (stone wool)
Created on: 19 Jun 2018 13:03
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martin50939M
martin5093919 Jun 2018 13:03Hello everyone,
We are about to build a single-family house in the Rhein-Sieg district. Since we need to install a steel beam above one window, a sand-lime brick will be used in that area instead of the usual 36.5cm (14.4 inches) aerated concrete blocks. Our site manager wants to use a 24cm (9.4 inches) sand-lime brick with 12cm (4.7 inches) insulation (rock wool with a thermal conductivity of 0.035 W/mK), which will also insulate the ceiling above the ground floor.
I would be much happier with a 30cm (11.8 inches) sand-lime brick combined with 6cm (2.4 inches) insulation. Our suggestion was to use 6cm (2.4 inches) of rock wool with a thermal conductivity of 0.032 W/mK. However, our site manager said that combining insulation materials with thermal conductivities of 0.032 and 0.035 W/mK is not advisable because it could create thermal bridges.
Cutting a 30cm (11.8 inches) sand-lime brick down to 28cm (11 inches) is not an option. The necessary equipment is not available to our shell builder.
Best regards from Cologne
We are about to build a single-family house in the Rhein-Sieg district. Since we need to install a steel beam above one window, a sand-lime brick will be used in that area instead of the usual 36.5cm (14.4 inches) aerated concrete blocks. Our site manager wants to use a 24cm (9.4 inches) sand-lime brick with 12cm (4.7 inches) insulation (rock wool with a thermal conductivity of 0.035 W/mK), which will also insulate the ceiling above the ground floor.
I would be much happier with a 30cm (11.8 inches) sand-lime brick combined with 6cm (2.4 inches) insulation. Our suggestion was to use 6cm (2.4 inches) of rock wool with a thermal conductivity of 0.032 W/mK. However, our site manager said that combining insulation materials with thermal conductivities of 0.032 and 0.035 W/mK is not advisable because it could create thermal bridges.
Cutting a 30cm (11.8 inches) sand-lime brick down to 28cm (11 inches) is not an option. The necessary equipment is not available to our shell builder.
Best regards from Cologne
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nordanney19 Jun 2018 13:14Why are you happier with a 30cm (12 inch) masonry unit? What issue do you see?
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martin5093919 Jun 2018 13:21Below is a 36.5cm (14.4 inches) wall.
On top of that, a 24cm (9.4 inches) wall plus insulation.
Ceiling of the ground floor.
Then walls again with a thickness of 36.5cm (14.4 inches).
Personally, I find the overhang simply too large. I know the structural engineer has deemed it safe, but I don't feel comfortable with it. That’s why I would have preferred a different solution.
On top of that, a 24cm (9.4 inches) wall plus insulation.
Ceiling of the ground floor.
Then walls again with a thickness of 36.5cm (14.4 inches).
Personally, I find the overhang simply too large. I know the structural engineer has deemed it safe, but I don't feel comfortable with it. That’s why I would have preferred a different solution.
That is purely a matter of perception and not based on facts. Sand-lime brick has significantly better load-bearing properties than aerated concrete. A load-bearing exterior wall made of sand-lime brick is usually 175mm (7 inches) thick...
The "mix" of thermal insulation values is nonsense. But whether you can even get WLG 032 (thermal conductivity 0.032 W/mK) mineral wool for that component is something I would question first. To avoid thermal bridges, I would rather consider rigid foam boards like PUR/PIR. A thickness of 6cm (2.4 inches) would be by no means sufficient. Damage caused by thermal bridges is much more realistic than structural overthinking.
The "mix" of thermal insulation values is nonsense. But whether you can even get WLG 032 (thermal conductivity 0.032 W/mK) mineral wool for that component is something I would question first. To avoid thermal bridges, I would rather consider rigid foam boards like PUR/PIR. A thickness of 6cm (2.4 inches) would be by no means sufficient. Damage caused by thermal bridges is much more realistic than structural overthinking.
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Hausbauer119 Jun 2018 22:27The load-bearing properties of sand-lime brick are clearly superior to those of aerated concrete. A 24cm (10 inch) sand-lime brick likely has even better load-bearing capacity than a 36.5cm (14 inch) aerated concrete block. So, I wouldn’t worry about that.
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