New construction: Wood fiber insulation boards sensible as thermal protection

Hello everyone,

for our new building, according to the architects' plans, we have a standard roof construction with insulation between the rafters:
Underlay membrane (0.2W/mK) - 20cm mineral wool (0.035W/mK) - "PFTE foil" (0.23W/mK) [what is it actually intended for?] - plasterboard panels (0.25W/mK).

I inquired with two carpentry companies regarding an offer. Both optionally offered a 6cm wood fiber insulation board as insulation above the rafters (because both are "convinced of the system"). Apparently, this insulation partly serves as insulation for winter, but the main focus is on thermal protection in summer.
To keep it short and avoid lengthy explanations here: the material takes 12 hours to heat up completely and release the heat into the room (normal mineral wool lets the heat through completely after 6-7 hours). By the time the heat is released into the room, it is already night, and with normal ventilation and open windows, the heat can be dissipated and prevents heat from accumulating.
--> The entire attic (where we all sleep) should not heat up so much in summer.

Of course, this is not exactly cheap (the system is from the company Steico).

Does anyone here have experience with wood fiber insulation in new buildings and can share their experiences?
Especially in the sleeping areas under the roof, somewhat less heat in summer would make a big difference.

Best regards
André

No experience, but carpentries always offer this as standard. I also find it understandable that it brings some benefit and heat protection is very important to me. So much for the theory, I would also be interested in practical experience. Only probably very few have both systems for comparison.

The thing with the experiences is also my problem. It at least sounds logical. But since the insulation costs €6,000 according to the offer, I am hesitating. Although I am already prejudiced. As a child, I slept under the roof, every degree matters there. But nevertheless, I would be grateful for any experience shared.

Hi Crimson,

we have the panels as [Aufsparrendämmung].
The roof shape is [Pultdach], completely facing south, 17 degrees slope.
So the sun hits it hard from morning till evening in summer.
Of course, it still gets relatively warmer than the floors below, but that is at most a difference of 2-3 degrees Celsius and the room temperature never exceeded 25 degrees this summer.
The extra cost (for about 160m² of roof area about 4,000 gross) was a bit steep, that's true, but I would definitely choose it again if the attic space is used as living space.

They also have it and can confirm the 25 degrees. 35 degrees tilt and facing south without shade. Unless you have the windows open. But then the problem is getting the heat out of the house again.

The panels are also supposed to hold up very well in case of moisture (roof leaking).

I would do it the same way again, even though we have no comparison.

So you reinforce my opinion to put the panels on the roof. It is already advantageous when your own line of thought is confirmed by others. Thank you very much for the quick (and competent) responses.