ᐅ Materials for Exterior and Interior Walls (KfW 55 Standard)
Created on: 13 Aug 2021 14:16
B
Baumeister86
Dear all,
After initial discussions with local general contractors and reviewing construction specifications, some questions arose regarding the wall materials (assembly).
We would like to build to the KfW 55 standard, as it doesn’t seem to deviate much from the usual practice. Additionally, we want good sound insulation (unfortunately, the air traffic from BER airport can still be heard in eastern Berlin, even though planes will not fly directly over us). Therefore, I am a bit overwhelmed by the many exterior wall options.
Monolithic construction seems advantageous to me, as masonry should last much longer than external thermal insulation composite systems (ETICS) and require less maintenance. Are there any reliable experiences with ETICS? Also, I’m a bit unsure about calcium silicate brick (best sound insulation, but I don’t want sand falling down every time I drill). How is the maintenance of facade render handled? I cannot recall my parents having that done in almost 30 years (house built in the late 1970s).
Porous concrete with a wall thickness of 36.5 cm (14 inches) should meet KfW requirements (U-value <0.2), while clay blocks require additional filling with perlite. However, from what I have researched, sound insulation of clay blocks is better than porous concrete, at least on paper. How does this compare in practice?
Lightweight expanded clay aggregate blocks were also offered to us (however, as a pre-assembled system wall). You would need a lot of ETICS on this to meet the KfW standard—how is the sound insulation in this case?
Most importantly, what are the costs of these options (calcium silicate brick + ETICS vs. porous concrete vs. insulated clay blocks) for, say, a city villa with a 10 x 10 m (33 x 33 ft) footprint? Most general contractors work only with one option or the other (and I have not yet found any insulated clay blocks).
To avoid noise transmission inside the house, regular clay block walls seem reasonable (12 cm or 24 cm [5 or 10 inches] if load-bearing). Calcium silicate bricks seem somewhat heavy (and the sand issue)?
Thank you very much for your opinions.
Stephan
P.S.: Are we really looking at 2100–2500 €/m² (195–230 $/ft²) for a “normal standard” house now in Brandenburg? Or did we consult the wrong general contractors?
After initial discussions with local general contractors and reviewing construction specifications, some questions arose regarding the wall materials (assembly).
We would like to build to the KfW 55 standard, as it doesn’t seem to deviate much from the usual practice. Additionally, we want good sound insulation (unfortunately, the air traffic from BER airport can still be heard in eastern Berlin, even though planes will not fly directly over us). Therefore, I am a bit overwhelmed by the many exterior wall options.
Monolithic construction seems advantageous to me, as masonry should last much longer than external thermal insulation composite systems (ETICS) and require less maintenance. Are there any reliable experiences with ETICS? Also, I’m a bit unsure about calcium silicate brick (best sound insulation, but I don’t want sand falling down every time I drill). How is the maintenance of facade render handled? I cannot recall my parents having that done in almost 30 years (house built in the late 1970s).
Porous concrete with a wall thickness of 36.5 cm (14 inches) should meet KfW requirements (U-value <0.2), while clay blocks require additional filling with perlite. However, from what I have researched, sound insulation of clay blocks is better than porous concrete, at least on paper. How does this compare in practice?
Lightweight expanded clay aggregate blocks were also offered to us (however, as a pre-assembled system wall). You would need a lot of ETICS on this to meet the KfW standard—how is the sound insulation in this case?
Most importantly, what are the costs of these options (calcium silicate brick + ETICS vs. porous concrete vs. insulated clay blocks) for, say, a city villa with a 10 x 10 m (33 x 33 ft) footprint? Most general contractors work only with one option or the other (and I have not yet found any insulated clay blocks).
To avoid noise transmission inside the house, regular clay block walls seem reasonable (12 cm or 24 cm [5 or 10 inches] if load-bearing). Calcium silicate bricks seem somewhat heavy (and the sand issue)?
Thank you very much for your opinions.
Stephan
P.S.: Are we really looking at 2100–2500 €/m² (195–230 $/ft²) for a “normal standard” house now in Brandenburg? Or did we consult the wrong general contractors?
motorradsilke schrieb:
With a small local builder. Bungalow, heat pump, chimney for the fireplace, electric shutters, no mechanical ventilation system, no photovoltaic system, no KNX. We will install the fireplace ourselves.We are also going with a small construction company (about 20 houses per year). Your price is good 🙂
We built with 17.5cm (7 inches) sand-lime brick plus 14cm (5.5 inches) external thermal insulation composite system (ETICS) — in your case it would be thicker due to KfW55 standards. Interior walls are 11.5cm (4.5 inches) sand-lime brick.
I am very satisfied with the exterior walls; acoustically, there are no issues. However, if I were to build again, I would also make the interior walls 17.5cm (7 inches) thick, especially for the bedrooms. The bricks used inside have a different bulk density compared to the exterior bricks and do not insulate quite as well at the same thickness.
The exterior bricks are rated with a compressive strength class of 2.0, while the interior bricks have a strength class of 1.6.
I am very satisfied with the exterior walls; acoustically, there are no issues. However, if I were to build again, I would also make the interior walls 17.5cm (7 inches) thick, especially for the bedrooms. The bricks used inside have a different bulk density compared to the exterior bricks and do not insulate quite as well at the same thickness.
The exterior bricks are rated with a compressive strength class of 2.0, while the interior bricks have a strength class of 1.6.
Basti2709 schrieb:
We built with 17.5cm (7 inches) sand-lime bricks plus 14cm (5.5 inches) external thermal insulation composite system (ETICS) — you might need more thickness due to KfW55 standards. Interior walls are 11.5cm (4.5 inches) sand-lime bricks.
I am very satisfied with the exterior walls; acoustically, there are no issues. However, if I were to build again, I would make the interior walls 17.5cm (7 inches) thick as well, especially for the bedrooms. The interior bricks have a different bulk density than the exterior bricks and don’t insulate quite as well at the same thickness.
The bricks used outside have a compressive strength class of 2.0, while the interior ones are rated 1.6. All right :-) We are building with 36.5cm (14.5 inches) Poroton blocks without ETICS. Interior walls are 17.5cm (7 inches), except for the drywall partitions, which we will decide on later to allow easier modifications in the future (after several years).
In my opinion, even 36.5 can work with KfW55 if the entire building envelope is considered and not just built according to a reference value. At the end of the day, it all comes down to cost and where effort is invested. Fundamentally, a better wall never hurts 😉
From an energy efficiency perspective, the most technically sensible solution is actually external insulation composite systems (EICS); thermal mass on the inside, insulation on the outside. Depending on the design, there are other systems beyond the classic "we glue polystyrene insulation on," including ventilated façades, etc., which are usually not found in the typical single-family home range or even in standard construction specifications.
As already mentioned, there are significant differences in sound insulation performance among windows, which often perform noticeably worse than the walls themselves.
From an energy efficiency perspective, the most technically sensible solution is actually external insulation composite systems (EICS); thermal mass on the inside, insulation on the outside. Depending on the design, there are other systems beyond the classic "we glue polystyrene insulation on," including ventilated façades, etc., which are usually not found in the typical single-family home range or even in standard construction specifications.
As already mentioned, there are significant differences in sound insulation performance among windows, which often perform noticeably worse than the walls themselves.
Basti2709 schrieb:
The bricks on the inside have a different bulk density than the bricks in the exterior wall and do not insulate quite as well at the same thickness. The insulating capacity of sand-lime bricks is basically negligible anyway, as they have almost none. I think somewhat lighter bricks were used on the inside for structural reasons. Our sand-lime brick walls are 15 cm (6 inches) thick both inside and outside and all have a bulk density of 2.0.
Basti2709 schrieb:
On the outside, the bricks are specified with a strength class of 2.0, and on the inside with 1.6. Be careful—bulk density is different from brick strength. The latter for sand-lime bricks is usually around 12 (or 20), so it is in a completely different range than bulk density.
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