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.
That sounds quite confusing, and a lot doesn’t seem to add up...
1. Problem: The windows in the unheated attic certainly aren’t thermal insulation windows, are they?
2. The vapor retarder on the upper floor must seamlessly continue into the attic. If you have already insulated and clad the upper floor, you would need to tear all that open again.
Furthermore, why do you want to leave a 4 cm (1.5 inches) gap there? Your concerns about sealing, screwing, and stapling are not quite correct in this context. How was the plastering done at the top? That inevitably causes leaks... and so on.
1. Problem: The windows in the unheated attic certainly aren’t thermal insulation windows, are they?
2. The vapor retarder on the upper floor must seamlessly continue into the attic. If you have already insulated and clad the upper floor, you would need to tear all that open again.
Furthermore, why do you want to leave a 4 cm (1.5 inches) gap there? Your concerns about sealing, screwing, and stapling are not quite correct in this context. How was the plastering done at the top? That inevitably causes leaks... and so on.
Hello, thank you for your answers.
Unfortunately, you did not address the question about the electrical installation.
Nevertheless, your concerns are of course interesting.
Yes, they’re standard, just like in the rest of the house.
That will be done by the builder, not me.
This is considered separately from the attic; insulating the attic is an additional, later step.
Why does it have to continue seamlessly? Is the concern that moisture could escape through the OSB layer or the insulation layer beneath the OSB?
So that the insulation is ventilated toward the vapor control layers, in case water droplets or moisture penetrate from outside.
Could you explain? When I research this, I read everywhere that under no circumstances should even a tiny hole form in the vapor barrier film. For example, because the warmer, moist air creates positive pressure and is then pushed through any holes, leading to condensation forming there.
This was even explained to me by an advisor at the building materials market.
Not at all yet. Why is that relevant?
Could you explain? Do leaks actually occur due to plastering? The architect told me that plastering is what actually ensures the airtightness of the house. That makes sense because the bricks are not laid airtight.
Thanks for any further replies.
Unfortunately, you did not address the question about the electrical installation.
Nevertheless, your concerns are of course interesting.
Lumpi_LE schrieb:
1st problem: The windows in the unheated attic are certainly not thermal insulation windows, are they?
Yes, they’re standard, just like in the rest of the house.
Lumpi_LE schrieb:
The vapor barrier on the upper floor must continue seamlessly into the attic. If you have already insulated and clad the upper floor, you would have to tear everything down again.
That will be done by the builder, not me.
This is considered separately from the attic; insulating the attic is an additional, later step.
Why does it have to continue seamlessly? Is the concern that moisture could escape through the OSB layer or the insulation layer beneath the OSB?
Lumpi_LE schrieb:
Why do you want to leave a 4 cm (1.6 inch) gap there?
So that the insulation is ventilated toward the vapor control layers, in case water droplets or moisture penetrate from outside.
Lumpi_LE schrieb:
All your worries about gluing, screwing, and taping are not quite correct.
Could you explain? When I research this, I read everywhere that under no circumstances should even a tiny hole form in the vapor barrier film. For example, because the warmer, moist air creates positive pressure and is then pushed through any holes, leading to condensation forming there.
This was even explained to me by an advisor at the building materials market.
Lumpi_LE schrieb:
How was the upper part plastered?
Not at all yet. Why is that relevant?
Lumpi_LE schrieb:
That inevitably leads to leaks... And so on.
Could you explain? Do leaks actually occur due to plastering? The architect told me that plastering is what actually ensures the airtightness of the house. That makes sense because the bricks are not laid airtight.
Thanks for any further replies.
R
readytorumble29 Jun 2017 19:58Staple nails are not an issue; no additional sealing is required.
What type of underlay do you have on the roof? It is always important that the layers get progressively less permeable from the outside to the inside.
You can skip the 4 cm (1.6 inches) gap then.
Otherwise, I think you’ve done good research so far.
I would recommend a vapor retarder; it doesn’t have to be a climate membrane.
What type of underlay do you have on the roof? It is always important that the layers get progressively less permeable from the outside to the inside.
You can skip the 4 cm (1.6 inches) gap then.
Otherwise, I think you’ve done good research so far.
I would recommend a vapor retarder; it doesn’t have to be a climate membrane.
K
Knallkörper30 Jun 2017 12:25The most important point is that you need an airtight connection between the two vapor barriers. Compared to that, stapling and nailing are the least of the problems.
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