ᐅ Full-rafter insulation for roofs or insulation on concrete slabs

Hello everyone,

We are planning to build the ceiling on the upper floor as a concrete slab instead of a wooden structure – now the question is about the insulation for the upper floor/roof.

According to the energy-saving regulations, the roof no longer requires insulation; it is sufficient to insulate the concrete slab. The attic space will not be used as living space (city villa – 2 full floors) but only as utility space.

Since full rafter insulation is naturally much more expensive, the question arises whether insulation on the concrete slab is sufficient?

Just to make sensible use of the space in the attic, I would insulate the roof rather than the concrete ceiling.

https://www.hausbau-forum.de/threads/dach-Dämmung-auf-geschossdecke-oder-unter-dem-dach.36573/

KingJulien schrieb:

https://www.hausbau-forum.de/threads/dach-Dämmung-auf-geschossdecke-oder-unter-dem-dach.36573/

I hadn’t seen that, thanks! The thread can be closed then

exto1791 schrieb:

We are planning the ceiling on the upper floor as a concrete slab instead of a wooden structure – now the question is about insulation on the upper floor/roof. [...] The attic space, in our case (townhouse – 2 full floors), is not intended as living space but only as storage area.

Oh, if only the original poster would get into the habit of linking their main threads about house planning when asking specific questions. I don’t have time right now to dig deep into your thread history – so I can’t really understand the point of placing a concrete slab on the upper floor if there is just storage space above. You probably won’t be storing coal there, after all.

exto1791 schrieb:

Since full rafter insulation is naturally much more expensive, the question is whether insulation on the concrete ceiling alone is sufficient?

Yes, I agree fully when it comes to insulating the ceiling instead of the roof – considering the consequences of a semi-conditioned storage room – but I can’t follow the reasoning behind using concrete here.

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11ant schrieb:

Oh, if only the original poster would get into the habit of linking their main house planning threads when asking specific questions. I don’t have time right now to dig through your thread history in detail – so I can’t really understand the point of placing a concrete slab on the upper floor if there will only be storage rooms above. You probably wouldn’t store coal up there anyway.

Yes, I fully agree with the idea of a ceiling instead of a roof—considering the consequences of a non-conditioned storage space—but I can’t follow the reasoning behind using concrete.

The advantages are thermal and sound insulation, no fire risk, and prevention of cracks between drywall and masonry.