ᐅ Wooden ceiling will be replaced with drywall. Should additional insulation be added?
Created on: 15 Jan 2022 13:42
A
Arcus19Hello,
this project involves a semi-detached house that was built around the turn of the millennium (1999-2001). The affected apartment has been rented out until now but will soon be occupied by me.
In the attic, there is approximately 100 sqm (1,076 sq ft) of wooden ceiling, which will be replaced. The new ceiling will consist of drywall (gypsum board) and plaster.
I am wondering whether I should also add insulation below the rafters.
So far, there is only insulation between the rafters—glass wool, about 20 cm (8 inches) thick. Below that is a vapor barrier/vapor retarder (blue and white striped foil), followed by the wooden ceiling.
I have done some research and it seems that the thickness of insulation below the vapor barrier can be about 20% of the thickness of the insulation above it.
Therefore, I was considering 3.5 cm (1.4 inches) Gutex wood fiber insulation boards.
I also expect better soundproofing, since the newly built bypass road was surfaced with noisy asphalt, and traffic noise has increased significantly and can sometimes be heard inside the rooms. Additionally, the extra thermal insulation against cold and heat is a benefit. The rooms there are used as offices for home working.
I haven’t seen much comparable experience in this forum. Are there any experiences with this approach? Also regarding potential moisture issues that might develop.
Thank you in advance.
this project involves a semi-detached house that was built around the turn of the millennium (1999-2001). The affected apartment has been rented out until now but will soon be occupied by me.
In the attic, there is approximately 100 sqm (1,076 sq ft) of wooden ceiling, which will be replaced. The new ceiling will consist of drywall (gypsum board) and plaster.
I am wondering whether I should also add insulation below the rafters.
So far, there is only insulation between the rafters—glass wool, about 20 cm (8 inches) thick. Below that is a vapor barrier/vapor retarder (blue and white striped foil), followed by the wooden ceiling.
I have done some research and it seems that the thickness of insulation below the vapor barrier can be about 20% of the thickness of the insulation above it.
Therefore, I was considering 3.5 cm (1.4 inches) Gutex wood fiber insulation boards.
I also expect better soundproofing, since the newly built bypass road was surfaced with noisy asphalt, and traffic noise has increased significantly and can sometimes be heard inside the rooms. Additionally, the extra thermal insulation against cold and heat is a benefit. The rooms there are used as offices for home working.
I haven’t seen much comparable experience in this forum. Are there any experiences with this approach? Also regarding potential moisture issues that might develop.
Thank you in advance.
We have Gutex wood fiber insulation boards on the roof and the exterior wall, but not on the inside. They are supposed to be effective for summer heat protection due to their relatively high mass, and also useful for sound insulation.
The main issue I see in your case is that the construction from inside to outside is no longer as usual. The dew point will not shift significantly because of this, but the vapor retarder prevents moisture from passing from the inside to the outside. This means the moisture will remain in the Gutex boards or be released back into the room. Whether this is good in the long term? I believe a building physicist or, alternatively, a qualified energy consultant can advise you on that.
The main issue I see in your case is that the construction from inside to outside is no longer as usual. The dew point will not shift significantly because of this, but the vapor retarder prevents moisture from passing from the inside to the outside. This means the moisture will remain in the Gutex boards or be released back into the room. Whether this is good in the long term? I believe a building physicist or, alternatively, a qualified energy consultant can advise you on that.
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