ᐅ Sloped Ceilings, Double-Layer OSB and Gypsum Board for Thermal Insulation
Created on: 13 Jun 2020 14:22
H
hauspeter
I want to improve the summer thermal insulation during the roof conversion and therefore plan to install double layers of OSB and gypsum board. A vapor retarder, Isover KM UV with a variable Sd value, was used.
Now I am concerned that the vapor retarder might not function as intended due to the diffusion-tight OSB panels, meaning it might not remain vapor-permeable in the summer as expected. Above this, there is 240 035 glass wool and a vapor-permeable underlay membrane installed.
I see the following alternatives:
1. OSB and gypsum board as planned
2. Double-layer gypsum board
3. Single-layer gypsum board as usual.
Now I am concerned that the vapor retarder might not function as intended due to the diffusion-tight OSB panels, meaning it might not remain vapor-permeable in the summer as expected. Above this, there is 240 035 glass wool and a vapor-permeable underlay membrane installed.
I see the following alternatives:
1. OSB and gypsum board as planned
2. Double-layer gypsum board
3. Single-layer gypsum board as usual.
Vicky Pedia14 Jun 2020 20:32Joedreck schrieb:
OSB is indeed a vapor barrier. However, I don’t see this as a problem. OSB has mass, and mass helps with heat protection.
I haven’t installed wood fiberboard yet, but it could be a possible solution. The issue lies in the adhesive used in the panel. If there is any dew point condensation, it will inevitably lead to mold. But why insist on using wood-based panels? Gypsum board is perfectly fine!
H
hauspeter14 Jun 2020 23:50Joedreck schrieb:
That’s why the underlay is vapor-permeable Yes, that’s the case.
Vicky Pedia schrieb:
But why insist on wood panels? Drywall is good! We missed the chance for exterior insulation between the rafters, but I still want to do something against the heat. 240mm (9.5 inches) wood fiber insulation boards cost about 30 EUR/m² (3 times more than glass wool). An additional layer of OSB or drywall, on the other hand, is a minor extra cost.