ᐅ Upper floor ceiling – additional insulation? What makes sense?
Created on: 4 Apr 2017 09:46
R
rupapu
Hello everyone,
I bought a house built in 1991 and have been living in it for several months now.
The house has one and a half floors, and the ceiling of the upper floor (about 40 sqm (430 sq ft)) leading to the attic is currently only partially covered (right half of the house) with chipboards (approximately 24 mm (1 inch) thick). Between the rafters, there is Isover Rollisol-SB (WL-B1/040) insulation with a thickness of 120 mm (5 inches). Below this insulation, there is an aluminum vapor barrier (or vapor retarder?). This is not properly stapled to the rafters everywhere, and in those areas, there are black spots (mold?) on the chipboards.
I noticed this when I removed one of the boards to install insulation on the rest of the floor.
The goal is to make the entire attic walkable to store items like Christmas decorations, children's clothing, suitcases, etc.
My plan is to remove the insulation, install new foil (Isover Vario Duplex) from above to cover the rafters, reinstall the insulation without the aluminum "foil," and then put OSB boards or chipboards back on top.
Now I am wondering if I should double the thickness of the rafters from above and add extra insulation (for example, 120 mm (5 inches) Isover Integra ZKF 1-035) on top.
Does this make sense—adding the additional insulation—and is it worth it?
Is it even necessary to install a new vapor retarder everywhere?
The costs for everything are reasonable (several hundred euros), but the work itself is quite daunting :-(
I appreciate any advice, ideas, and recommendations.
Best regards,
Patrick
I bought a house built in 1991 and have been living in it for several months now.
The house has one and a half floors, and the ceiling of the upper floor (about 40 sqm (430 sq ft)) leading to the attic is currently only partially covered (right half of the house) with chipboards (approximately 24 mm (1 inch) thick). Between the rafters, there is Isover Rollisol-SB (WL-B1/040) insulation with a thickness of 120 mm (5 inches). Below this insulation, there is an aluminum vapor barrier (or vapor retarder?). This is not properly stapled to the rafters everywhere, and in those areas, there are black spots (mold?) on the chipboards.
I noticed this when I removed one of the boards to install insulation on the rest of the floor.
The goal is to make the entire attic walkable to store items like Christmas decorations, children's clothing, suitcases, etc.
My plan is to remove the insulation, install new foil (Isover Vario Duplex) from above to cover the rafters, reinstall the insulation without the aluminum "foil," and then put OSB boards or chipboards back on top.
Now I am wondering if I should double the thickness of the rafters from above and add extra insulation (for example, 120 mm (5 inches) Isover Integra ZKF 1-035) on top.
Does this make sense—adding the additional insulation—and is it worth it?
Is it even necessary to install a new vapor retarder everywhere?
The costs for everything are reasonable (several hundred euros), but the work itself is quite daunting :-(
I appreciate any advice, ideas, and recommendations.
Best regards,
Patrick
OSB panels are vapor permeable because their SD value is greater than 20, approximately 80 to 200.
From an SD value of 20, it is considered a vapor retarder. Since, with proper installation, no moisture is expected from below or only minimal amounts, this moisture will pass through the OSB panels to some extent, so to speak.
From an SD value of 20, it is considered a vapor retarder. Since, with proper installation, no moisture is expected from below or only minimal amounts, this moisture will pass through the OSB panels to some extent, so to speak.
Hello everyone,
I’ve received some replies, but none really addressed my questions properly :-(
What would be the correct setup? Is it enough to replace the membrane? Or would installing vapor-permeable boards be sufficient?
Is it worth adding more insulation? After all, I can no longer make changes to the sloped roof areas (such as adding insulation). And if the ceiling of the upper floor is better insulated than the sloped roof areas, I’m not sure if that actually makes sense. The sloped roof surface is about 20% larger than the upper floor ceiling.
I’ve received some replies, but none really addressed my questions properly :-(
What would be the correct setup? Is it enough to replace the membrane? Or would installing vapor-permeable boards be sufficient?
Is it worth adding more insulation? After all, I can no longer make changes to the sloped roof areas (such as adding insulation). And if the ceiling of the upper floor is better insulated than the sloped roof areas, I’m not sure if that actually makes sense. The sloped roof surface is about 20% larger than the upper floor ceiling.
My suggestion: keep the existing insulation and add an additional layer across the rafters. Then also add mineral wool insulation and cover with simple boards or something similar on top.
Currently, due to faulty aluminum foil, you don’t have a vapor barrier or vapor retarder. This doesn’t matter much in this case, because moisture can escape upwards through the gaps.
This also makes sense, as it can be done with relatively little effort and investment, in my opinion.
Currently, due to faulty aluminum foil, you don’t have a vapor barrier or vapor retarder. This doesn’t matter much in this case, because moisture can escape upwards through the gaps.
This also makes sense, as it can be done with relatively little effort and investment, in my opinion.
K
Knallkörper6 Apr 2017 11:32You should install a new and properly executed vapor barrier, preferably from below, so that the connections can be done correctly. Definitely avoid using OSB panels from above! As for adding extra layers of insulation, it probably isn’t cost-effective.
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