Hello,
we are building a new house and have an attic space with limited headroom. The plan is to use it partly as storage and partly as a play area for the children (there are windows).
The attic is unheated. The collar beams are insulated with PE foil (currently considering switching to a climate membrane shortly). OSB boards will be laid on the collar beams.
I requested a quote for insulating the sloped roof surfaces as well and am still waiting for it. I am also considering doing this myself.
After some research, I believe the correct approach would be as follows:
- Insulation between rafters using mineral wool, leaving about 4 cm (1.5 inches) of space towards the exterior vapor barrier
- Install a PE foil (or climate membrane) on the outside of the between-rafter insulation
- pay close attention to airtightness and fastening instructions
- use only adhesive or, if stapling, apply additional sealing tape underneath the staples
- allow about 10 cm (4 inches) overlap when joining two foil sheets
- seal transitions to gable walls / masonry and if necessary use a special sealant (with a similar appearance to silicone) for airtight closure
- Install counter battens perpendicular to the rafters
- firmly screwing them will compress the foil enough so that it remains airtight despite the holes from the screws
- alternatively, apply additional sealing tape at screw points between the rafters and counter battens
- Electrical installation only between the counter battens and only penetrate the drywall boards, never damage the PE foil
- Attach drywall to the counter battens
Regarding electrical installation in particular, is this approach proper as long as the PE layer is never punctured?
For the rest of the procedure, I plan to consult with the architect again to ensure I am not making any mistakes.
Thank you very much for your advice.
we are building a new house and have an attic space with limited headroom. The plan is to use it partly as storage and partly as a play area for the children (there are windows).
The attic is unheated. The collar beams are insulated with PE foil (currently considering switching to a climate membrane shortly). OSB boards will be laid on the collar beams.
I requested a quote for insulating the sloped roof surfaces as well and am still waiting for it. I am also considering doing this myself.
After some research, I believe the correct approach would be as follows:
- Insulation between rafters using mineral wool, leaving about 4 cm (1.5 inches) of space towards the exterior vapor barrier
- Install a PE foil (or climate membrane) on the outside of the between-rafter insulation
- pay close attention to airtightness and fastening instructions
- use only adhesive or, if stapling, apply additional sealing tape underneath the staples
- allow about 10 cm (4 inches) overlap when joining two foil sheets
- seal transitions to gable walls / masonry and if necessary use a special sealant (with a similar appearance to silicone) for airtight closure
- Install counter battens perpendicular to the rafters
- firmly screwing them will compress the foil enough so that it remains airtight despite the holes from the screws
- alternatively, apply additional sealing tape at screw points between the rafters and counter battens
- Electrical installation only between the counter battens and only penetrate the drywall boards, never damage the PE foil
- Attach drywall to the counter battens
Regarding electrical installation in particular, is this approach proper as long as the PE layer is never punctured?
For the rest of the procedure, I plan to consult with the architect again to ensure I am not making any mistakes.
Thank you very much for your advice.
What surprises me about this question and discussion is that the attic is not insulated but has thermal insulation glazing. Are you building a new house? What does your energy consultant say? In our case, the energy calculation for the KfW program was based on the building envelope, including the attic/roof space. The collar beams are insulated, but that wouldn’t even be necessary. Our entire roof is insulated right up to the last tile and is within the vapor barrier...
The pipes can definitely be installed in the attic (also in your case). What’s important is a proper, complete, and professional sealing around the vapor retarder/barrier area.
The pipes can definitely be installed in the attic (also in your case). What’s important is a proper, complete, and professional sealing around the vapor retarder/barrier area.
The attic is not intended as living space; otherwise, it would need heating, which would be more expensive, so it is not insulated.
The windows are triple-glazed simply because everything else is triple-glazed; it certainly doesn’t hurt, right?
I want to insulate the attic so it can be used occasionally. I used to have a LEGO play corner up there as a child and didn’t feel cold in winter because, despite being a new build at the time, it was insulated afterwards.
In summary, here are my key takeaways:
- 100% airtightness is not necessary, but close to it.
- For example, running a cable through the vapor barrier or small punctures from staples is less of an issue.
- The "balloon effect" (warm, over-pressurized air finding a hole in the vapor barrier where moisture then condenses) can be neglected for small holes.
- The vapor barrier must also be continuous and airtight at floor level (the horizontal plane of the attic floor), meaning it should be sealed with the lower vapor barrier to prevent moisture from traveling horizontally through the OSB boards to the outside, bypassing the upper vapor barrier layer.
- Insulation below the OSB boards (looking down from the attic), which is not protected by a vapor barrier, is not affected by moisture.
The windows are triple-glazed simply because everything else is triple-glazed; it certainly doesn’t hurt, right?
I want to insulate the attic so it can be used occasionally. I used to have a LEGO play corner up there as a child and didn’t feel cold in winter because, despite being a new build at the time, it was insulated afterwards.
In summary, here are my key takeaways:
- 100% airtightness is not necessary, but close to it.
- For example, running a cable through the vapor barrier or small punctures from staples is less of an issue.
- The "balloon effect" (warm, over-pressurized air finding a hole in the vapor barrier where moisture then condenses) can be neglected for small holes.
- The vapor barrier must also be continuous and airtight at floor level (the horizontal plane of the attic floor), meaning it should be sealed with the lower vapor barrier to prevent moisture from traveling horizontally through the OSB boards to the outside, bypassing the upper vapor barrier layer.
- Insulation below the OSB boards (looking down from the attic), which is not protected by a vapor barrier, is not affected by moisture.
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