ᐅ Materials for Exterior and Interior Walls (KfW 55 Standard)
Created on: 13 Aug 2021 14:16
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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?
Berlinho schrieb:
So, is the conclusion basically a matter of personal preference between filled Poroton blocks or sand-lime bricks plus external thermal insulation composite system (ETICS)? Both meet the KFW55 standard and both insulate so well that the windows end up being the weakest link in the chain.
- Are they also similar in price?
- How about durability, in terms of "leaving something for the grandchildren" (if there ever will be any)?
- Bonus question: What minimum thickness should interior walls in sand-lime brick have to provide good sound insulation to adjacent rooms?
For many, "taste" is not a strict principle when choosing between monolithic construction or ETICS; many homeowners take a pragmatic view. Personally (without claiming absolute truth), I prefer monolithic construction, and from a professional standpoint, I generally advise placing more importance on the builder and the relationship between the homeowner and builder than on who offers the absolute best single wall system. EXCEPTIONALLY, ANY top-quality product can be turned into a disaster by shoddy workmanship. EVERY block – no matter if it “sings best” or “dances best” – has its specific handling requirements, and it’s possible to cause construction defects with ANY block if its particularities are not instinctively well understood. The same applies to individual properties: sound insulation issues are much more often caused by design and workmanship errors at junctions with other building components, where the gap between poor and excellent work is many times wider than the spectrum covered by lab values for the materials.
Also, when it comes to price, you never have completely free choice: each builder usually has two preferred types of blocks they work with regularly and chooses between them mostly based on current personal purchase price; you can form an opinion about this—say, based on test magazines—about which you would prefer. But for a third block type, the builder will pass on the supplier’s retail price since volume discounts won’t apply.
Proportional relationships between material thickness and properties are unfortunately wishful thinking in reality, no matter what calculations might suggest. Complex systems NEVER behave linearly.
Look your builder in the eyes and ask yourself two things:
1. Do you trust their character, and
2. Do you trust their abilities?
Until then, don’t read too many test reports, because what you really need is something like a “dealer’s instinct” as @Nordlys calls it.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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Baumeister8614 Aug 2021 11:27Berlinho schrieb:
Good evening,
I have the same question as the original poster. Thanks @Baumeister86, perfect timing to ask this here!
So, is the conclusion simply a matter of "preference" between filled Poroton or sand-lime brick plus external thermal insulation composite system (ETICS)?
Both meet the KfW 55 standard and both insulate so well that, in the end, the windows are the weakest link in the chain.
- Are they also similar in price?
- How about durability, in the sense of "leaving something behind for the grandchildren" (if there ever are any)?
- Bonus question: What thickness should interior walls made of sand-lime brick have at a minimum to provide good sound insulation to the adjacent room?
I imagine it’s very difficult to test this during a model home tour and hope for real experience reports here, even though they will naturally be subjective.
Sorry for sneaking in here like this. If this breaks any forum rules, please just give me a quick heads-up.
Good luck Good questions, nice to know I’m not the only one with these thoughts. Looking forward to any tips we get.
Berlinho schrieb:
Good evening,
I have the same question as the original poster. Thanks @Baumeister86, perfect timing to ask this here!
So, is the conclusion basically a matter of personal preference whether to use filled Poroton blocks or sand-lime bricks plus external thermal insulation composite system (ETICS)?
Both meet the KFW55 standard and insulate so well that, in the end, the windows are the weakest link in the chain. What do you mean by filled Poroton? We are getting Poroton t09d without filling, and it still meets KFW55. We intentionally did not want ETICS.
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Baumeister8614 Aug 2021 11:45Acof1978 schrieb:
What do you mean by filled Poroton? We are getting Poroton t09d without filling and it still meets KfW 55. We deliberately did not want external thermal insulation composite system (ETICS). You are building with 42cm (16.5 inches) masonry, right?
The standard "Poroton plan brick T9-36.5cm (14.4 inches)" only achieves a U-value of 0.23 W/m²K (≤0.2 is required for KfW). Although the question is whether 6cm (2.4 inches) less on the left and right sides makes that much of a difference. True. It is probably cheaper than the additional insulated Poroton?!
Baumeister86 schrieb:
You’re building with 42cm (16.5 inches) masonry units, right?
The standard "Poroton-Planziegel-T9-36.5cm" only achieves a U-value of 0.23 (=<0.2 is required for KfW). Although the question is whether 6cm (2.4 inches) less on each side makes that much difference. True. It’s probably cheaper than the additionally insulated Poroton?! See below. 36.5 cm (14.4 inches). They always meet KfW 55. The windows are, for example, for passive houses.
Acof1978 schrieb:
What do you mean by filled Poroton? We are getting Poroton T09d without any filling, and it still meets KfW 55 standard. We deliberately chose not to use external thermal insulation composite system (ETICS). By filled, I meant in terms of sound insulation. I was told that Poroton has poorer sound insulation compared to sand-lime bricks and that filling it improves this. I’m using the subjunctive here deliberately because this is "dangerous half-knowledge" and "hearsay" 😀
@11ant
Thank you very much for the feedback. That makes complete sense. The best material is useless if it’s poorly assembled.
That leaves question number two – is there a clear “winner” here?
Or should the deliberate omission of an answer be understood as follows: durability, insulation, and soundproofing are so similar for both materials that the choice of brick or block should not determine the choice of builder, meaning one should not feel limited in contractor selection just because one prefers sand-lime brick over clay brick or vice versa?
Thanks again for the input. I’m already taking away the lesson not to be too rigid, especially when you don’t really have much expertise yourself!
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