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

The keyword fire risk would also be an argument against a non-heated storage floor, and the likelihood of cracking increases with every change of material, for example also with calcium silicate block interior walls in a brick house. This partly reminds me of this discussion: https://www.hausbau-forum.de/threads/holzhaus-innenwaende-aus-stein.35568/

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11ant schrieb:

The keyword fire risk would then also be an argument against the unconditioned storage loft, and the likelihood of cracks increases with every material change, for example also with calcium silicate interior walls in a brick house. This partly reminds me of this discussion: https://www.hausbau-forum.de/threads/holzhaus-innenwaende-aus-stein.35568/

A wooden structure is generally less expensive than a concrete ceiling.

However, we are getting the concrete ceiling at the same price – so basically, I don’t have any disadvantage from that, right?

exto1791 schrieb:

However, we get the concrete ceiling at the same price – so basically, I have no disadvantage from that, right?

On the contrary: for your general contractor, it is probably more practical to apply a mixed calculation for both options rather than calculating each variant in detail every time. The fact that you also need load-bearing walls on the upper floor is generally not a disadvantage – unless they are arranged in an especially unfavorable way “incongruent” to those on the ground floor, which might then require additional beams or reinforcement. Homeowners tend to agonize over every little detail, but contractors “have” to think in cubic meter scales; otherwise, their business doesn’t add up. More steel or concrete is cheaper than spending extra labor hours on calculations to five decimal places, which only Excel-obsessed homeowners (and the big-name providers of solid construction licenses) can afford. For a local contractor, it’s not a cause for concern if they simply charge the same price for both options as a simplification. In their workflow, it’s basically just like choosing a different color.

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Insulation on the concrete ceiling instead of full rafter insulation – here is the response from my main contractor on this topic:

To be honest, I’m not very enthusiastic about it.
The attic space then becomes a cold zone. This limits its use as storage space.
If slightly warmer air enters the attic through the ceiling opening in winter and meets the cold air at the underside of the roof, condensation will occur at that spot.

What do you think? Is he right?

I don't recall if he addressed this in his main thread, but @Nordlys insulated his attic afterwards.

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He is right. It is exactly what he said that prompted us to insulate the floor afterwards with rigid insulation and Climafilm. Now it is fine. A conditioned room, frost-free in winter, reasonably cool in summer.