ᐅ Insulation of the Basement Slab Using Thermo-Brick

Hello,

there are countless discussions online about whether to insulate above or below the slab. However, I haven’t found any in connection with a basement built from a 42.5cm (17 inch) thermal block.

We are building a basement with blocks (Bisotherm 42.5cm / 17 inch) instead of concrete because it saves us about €25,000 and only part of the building is in contact with the ground. Unfortunately, the question of whether to insulate above or below the slab has come up again.

Some companies and acquaintances say that insulating below the slab is essential to avoid possible thermal bridges. Others are convinced that insulating on the slab is better because it’s cheaper and the thermal envelope is already created by the insulation on the slab and the thermal block. Actually, the energy certificate wouldn’t change in either case.

It’s true that insulating on the slab is cheaper, but I’m not sure about the rest since everyone seems to have a different opinion.

So, should we save those few thousand euros or not?

Best regards

The way houses are built today, it ultimately doesn’t matter where the ventilation takes place. The issue of thermal bridges is basically valid but negligible.

009_frank schrieb:

Some companies and acquaintances say that it is absolutely necessary to insulate beneath the slab to avoid potential thermal bridges. Others are convinced that insulating on top of the slab is better because it’s cheaper and the thermal envelope is already established by the insulation on the slab and the thermal block.

I would insulate above the slab, but the argument concerning thermal bridges is valid.

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

11ant schrieb:

I would insulate above the slab, but the argument about thermal bridging is valid.

Would you insulate from above mainly for cost reasons, or are there other reasons?

nordanney schrieb:

The way houses are built nowadays, it ultimately doesn’t matter where you vote. The issue of thermal bridging is basically correct, but negligible.

In what way negligible? Do you mean that thermal bridges cannot occur if everything is done correctly?

009_frank schrieb:

In what way negligible? Do you mean that thermal bridges cannot occur if everything is done correctly?

No, with insulation above the floor slab, all walls have thermal bridges downward – but not to the extent that it would be visibly noticeable on the heating bill.

009_frank schrieb:

Would you insulate from above for cost reasons, or are there other reasons?

I have doubts about the long-term safety of insulation foams buried under the house (and its load). I trust my reasoning and my engineering intuition more than trying to be a perfect example of insulation dogma.

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/