ᐅ Materials for Exterior and Interior Walls (KfW 55 Standard)

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?

Baumeister86 schrieb:

Is a "standard quality" house now really priced at 2100-2500€/sqm in Brandenburg?

If you don’t want an off-the-shelf standard house or a fixed price list, but rather a house shaped by your own ideas, you should calculate accordingly.
Our general contractor built with insulated 42cm (16.5 inch) Poroton blocks and 11cm (4.3 inch) sand-lime brick interior walls.
Since Tegel airport closed, you still have our planes overhead 😎

Baumeister86 schrieb:

But I don't want sand trickling down all the time while drilling, do I?!

Why do you think sand would trickle when drilling into calcium silicate brick?

Keep my stone mantra in mind and build with the contractor you feel most comfortable with, and then use a type of brick they often work with.

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Nida35a schrieb:

If you don’t want a standard house off the shelf or from a price list, but a house shaped by your own ideas, this is how you should calculate it.
Our general contractor built with 42cm (16.5 inches) filled Poroton blocks, interior walls with 11cm (4.3 inches) calcium silicate bricks.
Since Tegel closed, you still have our planes flying overhead 😎

@Nida35a I just checked their website. It says the building material is Liaplan (expanded clay). Is that correct, or did you specifically ask for Poroton?

Yeah.. be glad. Where we currently live, we can wave at the planes. I definitely need to change that a bit again, even though it’s nice being close to the lakes ;-).

Baumeister86 schrieb:

but I don’t want sand constantly falling down when drilling, right?!)

Drilling dust will always fall, no matter what type of stone or wood is used.

Baumeister86 schrieb:

How does renewing the exterior plaster work?

It’s usually not necessary… I had a plastered house from 1978… small settlement cracks or cracks in the paint can be repaired differently. The plaster will probably outlast you.

Baumeister86 schrieb:

With a wall thickness of 36.5cm (14 inches), aerated concrete should meet the requirements for the KfW standard (U-value <0.2), while clay blocks will need additional filling with perlite.

Sound insulation aside: usually, the noise mainly comes through the windows.

Baumeister86 schrieb:

P.S.: Is a “standard” house nowadays really around 2100-2500 €/m² (195-230 $/ft²) also in Brandenburg? Or did we just have the wrong general contractors?

It seems about right to me. But ask @Acof1978, who is also planning to build in Brandenburg and knows the prices.

Baumeister86 schrieb:

P.S.: Are we really at a "standard" house price of 2100–2500 €/m² (195–233 USD/ft²) now, even in Brandenburg? Or did we have the wrong general contractors?

That sounds about right. We are paying (old price) around 2,800 €/m² (260 USD/ft²), but that includes:
- KfW 55 energy standard
- Ground-source heat pump, controlled mechanical ventilation
- Photovoltaic system of 13.29 kWp
- Raised ceiling heights (3 m (10 ft) raw height)
- Rainwater cistern (10 m² (108 ft²))
- Bungalow, 140–150 m² (1,500–1,615 ft²)
- Fireplace
- Electric roller shutters including central control
- Double-sided coated windows. Color: Winchester.

If you need recommendations for construction companies, just let me know.