ᐅ OSB panels in the pitched roof

Created on: 12 Aug 2017 22:47
M
Marchonisch
We want to insulate the entire roof with 20 cm (8 inches) of mineral wool.

We plan to build the attic floor using OSB boards.

While reading and researching online, I have come across several points that made me think more carefully...

Is there a risk of mold forming beneath the OSB boards?

My understanding is that if the insulation between the rafters is properly sealed with a vapor retarder, the attic floor project should not be a problem.

We are also considering insulating the ceiling (the upper floor ceiling under the roof).

Does that make sense?
KlaRa13 Aug 2017 20:17
Marchonisch schrieb:
But we are planning to insulate the rafters beneath the roof tiles. However, not the attic for living space.

Is that a problem?

No, that is not a problem; in fact, it is generally the better solution overall!
M
Marchonisch
13 Aug 2017 20:30
Why is this the better solution?

I thought the best solution regarding energy efficiency is to insulate both the roof and the attic?
KlaRa13 Aug 2017 20:45
Hello "Marchonisch",

here is a metaphorical response to your last comment:
If you’re worried, you could wear suspenders together with a belt. Then your pants definitely won’t slip down!
Usually, based on experience, a belt alone is enough.

More efficient in terms of lower heating costs is definitely insulation under the top floor ceiling. Otherwise, you end up heating the attic unnecessarily.
But in the end, it’s your choice; both insulation methods are acceptable and both are used in practice!
M
Marchonisch
13 Aug 2017 21:32
And the OSB boards can be installed regardless of whether the roof or attic is insulated. Or, of course, if I insulate both?
KlaRa14 Aug 2017 08:32
KlaRa schrieb:
Otherwise, there is no reasonable explanation why wood-based panels should not be installed in a dry room (meaning: no rain enters and there is no condensation on the surface of the wood-based panels).

This question has already been answered.
Under non-climate-controlled conditions, wood-based panels may warp slightly, but if they are nailed to battens or glued in tongue-and-groove joints and used only as a subfloor in a rarely used attic (not a living space), this is insignificant.
N
Nordlys
14 Aug 2017 09:00
KlaRa
I’m not an expert.
But my builder, who is a carpenter by trade, said that for our cold attic – the ceiling between the floors is insulated, not the roof – he prefers to use spruce tongue-and-groove boards nailed board by board as a covering instead of OSB. This way, the mineral wool insulation underneath is not sealed off so tightly. He also said it wouldn’t be more expensive.
Karsten