Summer heat protection and winter insulation - experiences?

Hello everyone,

we are planning the new construction of our house using timber frame construction.

At the moment, I am dealing with the insulation of the roof regarding summer heat protection and winter insulation. I am looking for ways to optimize or find the ideal compromise.

The planned structure is currently as follows:

- Clay roof tiles
- Counter and supporting battens
- Diffusion-open underlay membrane
- Roof truss
- Thermal and sound insulation between rafters and collar beams within the thermal envelope (240mm, WLG 035)
- Vapor diffusion retarder
- Substructure (battens)
- Gypsum board (GKF 12.5 mm)

The attic will not be insulated, expansion within the thermal envelope.

I wonder whether increasing the WLG of the mineral wool from 035 to 032 would have any effect with regard to improving summer heat protection. Or should the mineral wool thickness be increased from 240mm to, for example, 280mm? Or perhaps a different insulating material should be chosen?

What do you think or have you had any experience with this?

Thank you very much

Regards

Sky

24cm WLG 035 has U = 0.142 W/m²K
24cm WLG 032 has U = 0.130 W/m²K
28cm WLG 035 has U = 0.122 W/m²K

When it comes to thermal insulation (winter), timber frame construction is already far ahead. I wouldn’t obsess over optimizing it.
But honestly, improving heat protection in timber frame construction... if that is a priority, build with solid materials. Due to the lack of mass in timber frame, this is a major disadvantage.
In summer, heat does not creep through the wall, but through solar gains from glazed areas and open windows/doors.

Additional money would probably be better invested in external shading, possibly automated according to the sun’s position, ventilation systems (off/low during the day when hot, to get rid of warm air at night), or air conditioning.

In the wall structure we have wood fiber boards and a ventilation system is also installed.

Now it's about the roof. What is cheaper? Upgrading from 035 to 032 or upgrading from 240 to 280 mm?

In terms of summer heat protection, is it more beneficial to change the WLG or the thickness?

For 28 insulation, you also need 28 beams... I think that is then significantly more expensive than switching to 032. However, I would personally only do this if the additional cost compared to 035 is not too high. It probably won't be worth it.

Now it's about the roof. What is cheaper? Upgrading from 035 to 032 or upgrading from 240 to 280 mm?

Is it more beneficial for summer heat protection to change the WLG or the thickness?

The WLG 032 insulation is probably cheaper than adding 4 cm, which affects the beam thickness.

However, both have virtually no impact on summer heat protection, as mentioned above.

Alternatively, supplement the counter-battens with wood fiber. Overlay battens would be too expensive. Or use OSB instead of drywall. That should also help a bit.