Thermally Insulated Stone vs Calcium Silicate Brick with Insulation

Hello, we are currently planning our new building (4 residential units) and have finished the floor plans; now it's slowly about materials, fittings, etc. Our architect has planned the house using calcium silicate bricks (his preferred building material) in relatively large blocks plus insulation (17.5 + 13.5 insulation as far as I still remember). We have not set any special standards as a requirement. The masonry should only be relatively thin in order to design rooms as large as possible, since the floor area ratio is fully utilized and room sizes are relatively tight. A builder friend, on the other hand, swears by "thermally insulated stones/bricks" without external insulation. The stones would be more expensive but quicker to install, and external insulation would be omitted. So, all in all, that would be (considerably) cheaper. And it feels like with every larger new build ("city villas," etc.) one more often sees these large hollow bricks plus external insulation. So, I am now undecided. I had already addressed this with the architect, but he didn’t really say anything about it. If you look at the manufacturers' websites, of course, there is always only praise for their own product. Best regards

Bricks would be more expensive, but quicker to install, and external insulation would be omitted. So, overall it would be (significantly) cheaper.

Bricks are not cheaper than KS + insulation. At energy saving ordinance standard about the same (yours would be a 30), towards KfW it then becomes increasingly more expensive.

I see your variant of 17.5 cm KS + 13.5 cm ETICS critically because:

1. 17.5 cm exterior walls (brick content) are really thin (there is not much brick left behind the sockets and cable ducts) which is quite normal for KS, but still "thin"

2. 13.5 cm ETICS combined with the non-insulating KS are again relatively thin (total wall U-value including plaster etc. according to Ubakus around 0.25), i.e. the insulation is ok but also not at energy-efficient house level, depending on the heating type.

3. expensive and disadvantages of a hardly diffusion-open, multi-layer wall construction

So somehow all disadvantages combined in one wall, without even considering the client's requirement "overall as thin as possible."

Considering that Town & Country still builds its model houses with monolithic Ytong – 24 cm, this should be the narrowest variant, depending on heating, also compliant with the Energy Saving Ordinance. With 4 residential units (how many floors?), possibly no longer feasible statically and thermally not really great, but very, very cheap.

36 cm Ytong would be slightly thicker than the current 30 cm but would still have identical thermal insulation, would be monolithic "breathable," and cheaper than KS+ETICS.

-4we; basement, ground floor, 1st floor plus penthouse -Energy-efficient house standard is not desired and was not a requirement. -Heating is currently (still without building services planner) gas condensing boiler, solar thermal, ventilation with heat recovery; -Structural engineer quotes will be obtained next week and then we will see what he says. -May have to ask whether the walls may now be allowed to be thicker than specified.. best regards