ᐅ Rafter insulation

Hello,

I am planning to convert my attic and want to insulate the rafters with 8cm (3 inches) wood fiberboard and cellulose. Do I need to leave a ventilation gap between the vapor barrier (outside) and the wood fiberboard (inside), or can I install it tightly against the barrier between the rafters?

Thank you in advance!

Hello,

Leaving space for ventilation is certainly a smart step.
I would prefer the Isofloc insulation with cellulose.
It has proven to be effective several times.

Best regards

Vollpfosten schrieb:
Hello,

I am planning to convert my attic and want to insulate the rafters with 8cm (3 inches) wood fiberboard and cellulose. Do I need to leave a ventilation gap between the vapor barrier (outside) and the wood fiberboard (inside), or can I place it tightly against the vapor barrier between the rafters?

Thank you in advance!

Hello,

Will the roof be stripped and rebuilt?

Best regards

K.Brodbeck

Hello,
the roof will not be stripped and will remain as it is because it is new. I only decided later to renovate, otherwise I would have, of course, used the wood fiber boards as insulation above the rafters. Now it is different, and I want to install the wood fiber boards from the inside. The question remains: should there be an air gap or not?
Best regards, Thomas Riepen

Vollpfosten schrieb:
Hello,
the roof will not be uncovered and will remain as it is since it is new. I only decided later to convert the attic, otherwise I would have of course used wood fiber boards as insulation above the rafters. But now it is different and I want to attach the wood fiber boards from the inside. The question remains: ventilation gap or not?????
Best regards, Thomas Riepen

Hello,

a ventilation gap is a good idea, but it remains just an air gap unless there is ventilation at the eaves and ridge areas.

In my case, I am also opting for a solution with wood fiber boards cut to fit between the rafters. However, our roof is already 80 years old and will likely need to be replaced in the foreseeable future, so then I will be able to install the underlay over the rafters. This method is a temporary measure that I would not use on a newly built roof (because it is a “perpetual” provisional solution).

Best regards

K.Brodbeck