ᐅ Is it feasible to achieve a KfW 70 energy efficiency standard using exterior masonry with 17.5 cm autoclaved aerated concrete (AAC) blocks, 16 cm mineral wool insulation, and a brick veneer?
Created on: 16 Feb 2015 18:17
D
derstefanm
Hello everyone,
I couldn’t find any useful information online, so I have a question.
Is it possible to meet the KfW standard with a new build wall construction consisting of 17.5 cm (7 inches) sand-lime brick / 16 cm (6 inches) glass wool / 4 cm (1.5 inches) air gap and facing brick? I know that for KfW 70 not only the wall structure matters but also the energy source, windows, etc. However, in principle, would this be feasible? I am looking for an alternative to Poroton, and sand-lime brick seems like a good option, especially considering sound insulation and fastening possibilities.
Thanks for your answers.
Best regards,
Stefan
I couldn’t find any useful information online, so I have a question.
Is it possible to meet the KfW standard with a new build wall construction consisting of 17.5 cm (7 inches) sand-lime brick / 16 cm (6 inches) glass wool / 4 cm (1.5 inches) air gap and facing brick? I know that for KfW 70 not only the wall structure matters but also the energy source, windows, etc. However, in principle, would this be feasible? I am looking for an alternative to Poroton, and sand-lime brick seems like a good option, especially considering sound insulation and fastening possibilities.
Thanks for your answers.
Best regards,
Stefan
Hello everyone,
we built with 17.5cm (7 inches) sand-lime bricks, 14cm (5.5 inches) mineral wool insulation with a thermal conductivity of 0.032 W/mK, and 11.5cm (4.5 inches) facing brick. Our entire building meets KfW 70 standards. Although, to be honest, I didn’t really care about following any KfW guidelines since we didn’t use any KfW funding.
Our main goal was to minimize energy consumption from fossil fuels (gas), and I think we succeeded quite well.
I can only say that a setup with 16cm (6.3 inches) mineral wool plus at least 3cm (1.2 inches) ventilation gap in the cavity can cause problems. At least that’s what our architect and a civil engineer friend told us. The gap is too wide for the standard wall ties that are normally embedded during masonry. You need special ties, which are more expensive, and the benefit of 2cm (0.8 inches) thicker insulation is rather minor.
Otherwise, we are very satisfied with the build. Our first heating season is now behind us, and the gas consumption is about 400m³ (14,130 cubic feet) since last October plus 2 cubic meters (70.6 cubic feet) of wood, which we burned in the water-based tiled stove.
Best regards
Fragi
we built with 17.5cm (7 inches) sand-lime bricks, 14cm (5.5 inches) mineral wool insulation with a thermal conductivity of 0.032 W/mK, and 11.5cm (4.5 inches) facing brick. Our entire building meets KfW 70 standards. Although, to be honest, I didn’t really care about following any KfW guidelines since we didn’t use any KfW funding.
Our main goal was to minimize energy consumption from fossil fuels (gas), and I think we succeeded quite well.
I can only say that a setup with 16cm (6.3 inches) mineral wool plus at least 3cm (1.2 inches) ventilation gap in the cavity can cause problems. At least that’s what our architect and a civil engineer friend told us. The gap is too wide for the standard wall ties that are normally embedded during masonry. You need special ties, which are more expensive, and the benefit of 2cm (0.8 inches) thicker insulation is rather minor.
Otherwise, we are very satisfied with the build. Our first heating season is now behind us, and the gas consumption is about 400m³ (14,130 cubic feet) since last October plus 2 cubic meters (70.6 cubic feet) of wood, which we burned in the water-based tiled stove.
Best regards
Fragi
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