ᐅ Which type of stone is best for exterior walls?

Created on: 28 Dec 2014 17:38
T
thomas_neo
Hello everyone,

We are currently planning our single-family home in the Stuttgart area. Apart from the exterior wall, most details are already decided. The house will be built in a quiet residential area with underfloor heating and gas.

I have received three options:

1. 17.5 cm (7 inches) brick + external thermal insulation composite system (ETICS) (standard wall) with no extra cost.
2. Ytong 36.5 cm (14 inches) block – if I may call it that – with a thermal transmittance of 0.23 W/m²K – additional cost: €8,900.
3. Poroton with 0.19 W/m²K – additional cost: €12,200.

I don’t really want to insulate my house with expanded polystyrene (EPS). I’m not a fan of that. Now I’m hesitating between options 2 and 3. What would you recommend?

Thank you very much.
Z
Zeltli
3 Jan 2015 20:35
Why did you choose the T8? Was it because of price/performance? What energy standard does your house meet?
T
thomas_neo
4 Jan 2015 23:02
In our opinion, this type of brick offered the best value per performance and achieves an even better U-value than Ytong. KFW70 standard. We are not yet sure if KFW55 is also achievable. This remains to be seen.
K1300S5 Jan 2015 14:58
The information about Ytong or aerated concrete blocks is not entirely accurate. There are aerated concrete blocks with a lambda value of 0.08 – even some with 0.07. See for example here:

Ytong Planblock – the Classic
The Ytong Planblock is suitable for all load-bearing and stabilizing walls. The low dimensional tolerance and tongue-and-groove profiling allow for fast installation using thin-bed mortar with a joint thickness of 1mm (0.04 inches). The result is a high-quality, homogeneous masonry with excellent thermal insulation. Due to their light weight, aerated concrete plan blocks are also suitable for interior walls constructed afterward as well as for renovation and refurbishment projects.

Top energy performance with Ytong λ=0.08 W/(mK)!
For those wanting to build monolithically at the highest level today, the high thermal insulation system solutions from Ytong are indispensable. The patented Ytong Planblock PP2-0.35 features an excellent thermal conductivity value of 0.08 W/(mK) for solid building materials while maintaining very good load-bearing capacity. With this, single-layer wall constructions 36.5cm (14 inches) thick already meet the energy standards of a KfW Efficiency House 55. Moreover, the Planblock already complies with the energy-saving requirements set to be mandatory from 2020 onward.

Aside from that, there is of course also a Wienerberger brick with 0.07 W/(mK) – so I would first request offers for these four options and then decide which one truly offers the best value for price and performance. In our case, the price difference between 0.08 and 0.07 was practically negligible.

Good luck

K1300S
Lassemann6 Jan 2015 21:37
Hello everyone,

I hope I’m not bothering you by posting a question here in this thread, which fits the topic well but actually concerns our building project (not Thomas’s).

We are currently planning a plastered building with a monolithic aerated concrete structure with the following characteristics according to the specifications:

  • 42cm (16.5 inches) thick, PP2, thermal conductivity class (WLG) 0.35
  • 1) Could someone please explain what PP2 means?
    2) I looked up WLG and more or less understood it. But is 0.35 a good or rather a poor value? What value would you recommend aiming for?

    Thank you very much!

K1300S7 Jan 2015 08:33
PP2 stands for aerated concrete plan block strength class 2. It refers to the compressive strength class of the block—basically, how much weight it can bear without being crushed.

However, the 0.35 value in connection with the thermal conductivity rating (WLG) seems odd to me, since pure insulation materials (like mineral wool) typically have a value around 0.035 (W/m·K) — which would be WLG 035 (without the decimal). On the other hand, this is an unattainable value for aerated concrete. Current standards suggest it should be at least around 0.06 (W/m²K).

That said, this wouldn’t be the first construction specification I’ve come across that contains outright nonsense.
B
Bauexperte
7 Jan 2015 10:14
Good morning,
K1300S schrieb:

... However, this value is unattainable for aerated concrete. According to current data, it should be at least 0.06 (W/m²K).
How do you arrive at that?

I increasingly notice in this thread that the users involved are focusing solely on the type of block to be used. This is a misconception! No matter how good a block is, it cannot compensate for the location of the plot, the predominant seasonal weather conditions, optimistically calculated window values, or borderline roof insulation ... and so on.

Whether a house can be occupied energy-efficiently depends on its overall design, including the location of the plot. Some calculation deficits can be offset by a suitable block; but certainly not everything...

Regards, Bauexperte

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