ᐅ New Single-Family House Construction (KFW70) / Aerated Concrete vs. Sand-Lime Brick / Which Material to Choose?

Use Poroton; aerated concrete offers even better performance but is more complex to work with since all joints must be sealed 100% airtight, especially the seams. Otherwise, you will have drafts in the cavities, which can cause unpleasant airflow near electrical outlets or drilled baseboards.

Hello everyone,

As mentioned earlier in the thread, we are building a KFW70 single-family house using solid construction with calcium silicate bricks and no basement.

The wall structure is as follows:
- Calcium silicate brick 15cm (6 inches)
- Mineral wool insulation with a thermal conductivity of 0.035 W/(m·K) 16cm (6.3 inches)
- Air gap
- Facing brick 11.5cm (4.5 inches)

(Interior walls: 11.5cm (4.5 inches) calcium silicate brick)

As a non-expert, I had assumed that an insulation strip would be laid on the foundation slab. However, the general contractor is installing an aerated concrete block (PPW 6-0.65) on a bitumen membrane, and afterwards continues with calcium silicate bricks.

From your perspective, is this acceptable? Or do these components not really fit together?

Thanks in advance for your comments and advice,
Lacos

Lacos schrieb:
....The general contractor is using an aerated concrete block (PPW 6-0.65) on top of a bitumen waterproofing membrane, then continuing with sand-lime bricks...

Why is he doing that? It is always more cost-effective to stay within the same "system" (modulus of elasticity). At the "base" of a load-bearing external wall, all the load from the masonry above is transferred. The compressive strength should be equal to or higher than that of the masonry above. I would not accept lower values.

Best regards.

I cannot say exactly why it was done this way. The initial explanation was the advantage of better insulation properties.

Lacos schrieb:
..... The first statement was about the advantage of better insulation properties.

I simply don’t have the time to adequately comment on every statement. However, the argument is largely meaningless. The main insulation effect of your wall assembly comes from the additional insulation, not from the structural shell! Here, KfW funding is intended or applied for. Usually, the windows and doors (WB) are broadly considered according to 4108 Annex 2 with 0.05 W/m²K (0.0088 Btu/(ft²·h·°F)). This means that all windows and doors must exactly comply with the standard. If there are deviations, proof of equivalence is required! Whether this plays a role here is unknown to me.

Best regards

The load-bearing walls of my house are made of sand-lime brick (20cm or 25cm in the basement) combined with a 14cm mineral wool insulation layer and the brick veneer I have chosen.

I think this should be fine. Every material has its advantages and disadvantages, after all.