ᐅ Insulated Brick vs. Sand-Lime Brick with Insulation

Hello,
we are currently planning our new building (4 residential units) and have finished the floor plans. Now we are slowly moving on to materials, fixtures, etc.

Our architect has designed the house using sand-lime bricks (his preferred building material) in relatively large blocks plus insulation (17.5cm + 13.5cm insulation as far as I remember). We have not set any special standards. The masonry should be relatively thin to make the rooms as large as possible since the floor area ratio is fully utilized and the room sizes are generally quite tight. A builder friend, on the other hand, swears by "thermally insulated bricks/blocks" without external insulation. The blocks would be more expensive, but faster to build, and external insulation would be omitted. Overall, this would be (considerably) cheaper. And from what I have seen, in most larger new buildings ("urban villas," etc.) they tend to use these large hollow bricks plus external insulation.

So now I’m unsure. I already asked the architect about this, but he didn’t really comment much. When you look at the manufacturers’ websites, of course they always praise their own products.

Best regards

imsi123 schrieb:

Bricks would be more expensive but quicker to install, and external insulation would not be necessary. So overall, that would be (significantly) cheaper.

Bricks are not cheaper than sand-lime bricks plus insulation. At energy-saving regulation standards, it’s roughly the same (in your case, around 30cm (12 inches) thick), but towards KfW standards it becomes increasingly more expensive.

I am critical of your option with 17.5cm (7 inches) sand-lime brick plus 13.5cm (5 inches) external thermal insulation composite system (ETICS) because:

1. 17.5cm (7 inches) exterior walls (brick portion) are really thin (there is hardly any brick left behind electrical outlets and cable channels). This is quite normal for sand-lime bricks but still "thin."

2. 13.5cm (5 inches) ETICS combined with the non-insulating sand-lime brick is also relatively thin (overall wall U-value including plaster, etc., is about 0.25 according to Ubakus), meaning the insulation is acceptable but not at the level of an energy-efficient house, depending on the heating system.

3. expensive and disadvantages of a hardly vapor-permeable, multi-layer wall construction

So somehow all the disadvantages are combined in one wall, without even considering the client’s requirement for the wall to be “as thin as possible overall.”

Considering that Town & Country still builds its standard houses with single-layer Ytong walls of 24cm (9.5 inches), that should be the thinnest variant that may comply with energy saving regulations depending on the heating system. However, for a four-unit building (how many floors?), it may no longer be structurally feasible and thermally not really ideal, but very, very inexpensive.

A 36cm (14 inches) Ytong wall would be somewhat thicker than the current 30cm (12 inches) but would still provide the same thermal insulation, would be a single-layer “breathable” wall, and cheaper than sand-lime brick plus ETICS.

@Mottenhausen
- 4-family house; basement, ground floor, first floor plus penthouse
- Energy-efficient house standard is not desired and was not a requirement.
- Heating currently planned (still without building services engineer): gas condensing boiler, solar thermal system, ventilation with heat recovery;
- Structural engineer quotes will be requested next week, then we will see what they recommend.
- May need to ask if the walls can be made thicker than specified.
Best regards