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Beelzebub4 Oct 2019 18:28Hello everyone,
I have the following question: insulating valley rafters.
I’m aware there are many discussions on this topic, but not every loft conversion is the same. I’m wondering whether to fully wrap the valley rafters because, as you can see in the picture, there is an air gap between the valley rafters and the purlins nailed onto them.
If the vapor control membrane is run around the valley rafters up to the ridge, in my opinion, cold air from the cavity insulation could reach the loft and cause condensation there. That’s why I want to make it airtight.
Solution 1:
Insulation boards up to the ridge, fully wrap the valley rafters, then seal with membrane onto the rafters. Basically, wrap all visible surfaces with proClima Intello.
Solution 2:
Insulation boards up to the ridge, run the vapor barrier underneath the valley rafters. (In my opinion this is risky because the loft can get cold.) This is what the carpenter suggested as the simplest solution.
Solution 3:
Loosen the purlins on the valley rafters slightly, apply sealing adhesive between them, then nail them back in place. Then seal the membrane tightly at the valleys.
Fully wrap the ridge beam? Or just seal the membrane onto the beam?
The roof is new with 6cm (2.4 inches) wood fiber rigid insulation above the rafters. Ventilating the loft is not possible. I’m willing to do all the fiddly work—I have time over winter.
Thanks in advance for hopefully constructive answers.
I have the following question: insulating valley rafters.
I’m aware there are many discussions on this topic, but not every loft conversion is the same. I’m wondering whether to fully wrap the valley rafters because, as you can see in the picture, there is an air gap between the valley rafters and the purlins nailed onto them.
If the vapor control membrane is run around the valley rafters up to the ridge, in my opinion, cold air from the cavity insulation could reach the loft and cause condensation there. That’s why I want to make it airtight.
Solution 1:
Insulation boards up to the ridge, fully wrap the valley rafters, then seal with membrane onto the rafters. Basically, wrap all visible surfaces with proClima Intello.
Solution 2:
Insulation boards up to the ridge, run the vapor barrier underneath the valley rafters. (In my opinion this is risky because the loft can get cold.) This is what the carpenter suggested as the simplest solution.
Solution 3:
Loosen the purlins on the valley rafters slightly, apply sealing adhesive between them, then nail them back in place. Then seal the membrane tightly at the valleys.
Fully wrap the ridge beam? Or just seal the membrane onto the beam?
The roof is new with 6cm (2.4 inches) wood fiber rigid insulation above the rafters. Ventilating the loft is not possible. I’m willing to do all the fiddly work—I have time over winter.
Thanks in advance for hopefully constructive answers.
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