New single-family house (KFW70)/aerated concrete vs. sand-lime brick/what to use?

Hello everyone,

a quick question regarding the wall construction. The following has been agreed upon so far, is it okay from your point of view (KFW70):

0. Plaster layer inside
1. Sand-lime brick: 17.5 cm
2. Insulation at least: 14.0 cm
3. Air layer
4. Facing brick: 11.5 cm

The wall is supposed to be 46 cm thick in total. What do you think? Is the insulation enough for a KFW70 single-family house? Or is it only sufficient for KFW70 because it is "calculated favorably" with a ground source heat pump?

Best regards, Lacos

Hello,

.... What do you think about it?...

According to my experiences and findings, you couldn’t have chosen a better wall structure. I think you are basically in good hands on the construction side!

.... Is the insulation sufficient for a KFW70 single-family house? Or is it only sufficient for KFW70 because it is "cooked up" with a geothermal heat pump?...

It can’t really be answered in general terms, but the probability is very high! Possibly even significantly better! For example, if the building is close to KFW 55, one should possibly rethink it! Sometimes it’s small things!
Especially with the insulation layer, the WLS value is important, not just the thickness!
Here’s a tip: Check the delivery note and document the respective stickers => compare with the proof! For the cladding shell, make sure that no mortar residues “clog” the air layer! Cover rising masonry consistently against precipitation (inner and outer shell)!

The Energy Saving Ordinance or the KfW efficiency standards always depend on two parameters that must be complied with!

HT´ - indicates the overall thermal quality of the building envelope (transmission heat losses)
qp´´ - takes into account, in addition to HT´, the energy efficiency of the system technology!

“Cooking up” figures always occurs when the schedule prescribed by proofs is not adhered to by subsequent planning/dimensioning/execution, e.g. of the system! This is not uncommon but almost routine! Often, the system side is not planned at all, planned incorrectly, or estimated/assumed incorrectly.
In my opinion, not a suitable basis for a long-term investment decision.
You can see the effects in the image above.

If actual energy demand and supply do not harmonize, the actual energy efficiency looks rather gloomy, especially with very sensitive heat generators such as heat pumps!

Best regards

Thank you very, very much for the confirmation
There are still some things to clarify (e.g. max. supply temperature of the underfloor heating <=35 degrees) etc., but that already sounds very good. Thanks again!

....(e.g. max. supply temperature of the underfloor heating <=35 degrees) etc.,...

This refers to the overall system conditions! Room by room, completely different necessities/needs can be present! => Room heating loads!

v.g.

We plan to construct the shell very similarly. Can you say how much more expensive it is than a shell with facing bricks using 25 cm masonry bricks, insulation, and facing bricks (with approximately the same insulation values)?

Hello everyone,

the following wall structure has now been chosen:
- Gypsum plaster: 15mm
- Sand-lime brick: 150 mm
- Mineral fiber WLG 35: 160 mm
- Air layer (static): 20 mm
- Facing brick 1800: 115 mm
= Total wall thickness 46 cm // U-value should be between 0.18 - 0.19.

Is this a wall structure that would be favored or still optimizable?

Regards and thanks,
Lacos