ᐅ Is edge insulation of the floor slab necessary?

Hello everyone,

We are about to start building our single-family house without a basement. The exterior wall will be constructed using insulating concrete blocks (Liaplan Ultra 8) with a wall thickness of 36.5 cm (14.4 inches) and a U-value of 0.20, without any additional external insulation.

The floor slab setup is planned as follows:
25 cm (9.8 inches) concrete
0.5 cm (0.2 inches) exposed bitumen roofing membrane
12 cm (4.7 inches) additional polystyrene XPS insulation (0.035 W/mK)
6 cm (2.4 inches) cement screed
1.5 cm (0.6 inches) tiles

No edge insulation of the floor slab (perimeter insulation) is planned. According to the builder, this is not necessary because of the insulation on the floor slab.
Is this statement basically correct, or will there be a thermal bridge between the floor slab and exterior wall, leading to higher heating costs?

Thank you very much in advance for your help!!

Regards
Frank123

Hello,

Frank123 schrieb:
....Edge insulation of the floor slab (perimeter insulation) is not planned. According to the general contractor, this is not necessary because of the insulation on the floor slab.

Besides the fact that this is not a general contractor but a main contractor/general contractor, a look at the Energy Saving Ordinance/KfW certificate is helpful here. It is very likely that a general thermal bridge correction factor of 0.05 was used. This means that this detail must precisely comply with DIN 4108-2, be equivalent, or better. If there are deviations, proof of equivalence is required!
Note: The accompanying external construction supervisor should pay special attention to the execution of thermal bridges!

Best regards

Thank you for the quick response.

If I have used the wrong terminology here, please excuse me – I am just a layperson.

€uro schrieb:

...a look at the Energy Saving Ordinance/KfW verification is helpful here. Most likely, a standard WB surcharge of 0.05 has been applied.

Your assumption is correct! Does this now mean that the planned insulation – if properly installed – is acceptable, or should the design be revised?

Frank123 schrieb:
...If I have used the wrong terminology here, I apologize – I am just an amateur.

That’s not a problem, as in 99.9% of cases it is accurate. There are particularly significant legal differences between BT and GU/GÜ, which one should ideally be clear about in advance when planning to build or buy.

Frank123 schrieb:
...Your assumption is correct! Does this mean that the proposed insulation – if properly installed – is acceptable, or should the plan be modified?

I cannot reliably answer this question as I do not have detailed knowledge on the matter. If the thermal envelope (WB) is actually implemented as demonstrated in the detailed verification, there should be no cause for concern regarding the demand requirement (heating operation). To what extent this actual demand, and how high it is, can be effectively met should be answered by the system’s designer.