ᐅ Is it feasible to build an Energy-Efficient House 40 using calcium silicate blocks and wood fiber insulation?
Created on: 29 Jan 2023 10:36
A
Araknis
Hello,
I am currently struggling with the Ubakus calculator and trying to figure out if it is even possible to reach the EH40 standard using a construction method with calcium silicate bricks and wood fiber insulation boards. I found values online for the walls of EH40 houses around 0.22 W/(m²·K). By the way, we absolutely do not want a timber-frame house.
According to Ubakus, this could be achieved with 200 mm (8 inches) of Quadro calcium silicate bricks with a thermal conductivity class of 2 and 160 mm (6 inches) of wood fiber boards, for example Steicoflex 036, resulting in a U-value of 0.218. Mathematically, it’s a close call. When I just search for calcium silicate bricks combined with external thermal insulation composite systems (ETICS / external wall insulation), I often come across wall assemblies with 175 mm (7 inches) of calcium silicate bricks and sometimes 300 mm (12 inches) of expanded polystyrene (EPS). For the interior plaster, I have set 10 mm (0.4 inches) of lime plaster, and for exterior plaster, 10 mm (0.4 inches) of silicone resin render.
At the moment, I can’t really tell if achieving EH40 with calcium silicate bricks and wood fiber insulation is feasible. Could someone shed some light on this?
I am currently struggling with the Ubakus calculator and trying to figure out if it is even possible to reach the EH40 standard using a construction method with calcium silicate bricks and wood fiber insulation boards. I found values online for the walls of EH40 houses around 0.22 W/(m²·K). By the way, we absolutely do not want a timber-frame house.
According to Ubakus, this could be achieved with 200 mm (8 inches) of Quadro calcium silicate bricks with a thermal conductivity class of 2 and 160 mm (6 inches) of wood fiber boards, for example Steicoflex 036, resulting in a U-value of 0.218. Mathematically, it’s a close call. When I just search for calcium silicate bricks combined with external thermal insulation composite systems (ETICS / external wall insulation), I often come across wall assemblies with 175 mm (7 inches) of calcium silicate bricks and sometimes 300 mm (12 inches) of expanded polystyrene (EPS). For the interior plaster, I have set 10 mm (0.4 inches) of lime plaster, and for exterior plaster, 10 mm (0.4 inches) of silicone resin render.
At the moment, I can’t really tell if achieving EH40 with calcium silicate bricks and wood fiber insulation is feasible. Could someone shed some light on this?
Of course, that’s possible. You just need somewhat thicker insulation compared to EPS (032).
The sand-lime brick is usually 17.5cm (7 inches) thick with a compressive strength of 1.8–2.0 MPa. However, this mainly concerns structural stability, as the brick itself provides little to no thermal insulation (same applies to the plaster).
Fixed U-values for individual components are not very meaningful and can only serve as a rough guideline. Nonetheless, a U-value of 0.22 for the masonry seems unusually high for a KFW 40 standard building.
The sand-lime brick is usually 17.5cm (7 inches) thick with a compressive strength of 1.8–2.0 MPa. However, this mainly concerns structural stability, as the brick itself provides little to no thermal insulation (same applies to the plaster).
Fixed U-values for individual components are not very meaningful and can only serve as a rough guideline. Nonetheless, a U-value of 0.22 for the masonry seems unusually high for a KFW 40 standard building.
Araknis schrieb:
I have also come across values of 0.2 and 0.15. So far, I haven’t encountered an official KfW document providing a concrete figure. Or maybe I’m looking in the wrong place... Because it doesn’t exist. The entire building envelope is considered.
This includes not only masonry surfaces depending on the orientation, but also roofs, parts of the building in contact with the ground, glazing, and so on. The overall structure must comply, not just individual components.
Masonry obviously plays a significant role because of its share in the building envelope, so it’s tempting to say that 0.15 is a much more realistic target value than the previously assumed 0.22 for a KfW 40 single-family house.
Ultimately, your approach should be: Hello energy consultant, this is my building design. How thick do the different insulation materials need to be to just meet KfW 40 standards? Plus any additional preferences (cost-effectiveness; as thin exterior walls as possible; or other considerations).
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