I am about to insulate and finish my garage interior. The garage is barn-style with dense roofing felt on top of tongue-and-groove boards. There is no opening for air to escape in/out from the sides or at the ridge.
How do I insulate and finish this structure and what materials should I use?
Is an air gap needed? I think the air doesn't really have anywhere to go anyway?
If it's not possible to vent moisture away, should I use something other than construction plastic right next to the ceiling?
Hope you understand me - in urgent need to move forward, but I want to build correctly
How do I insulate and finish this structure and what materials should I use?
Is an air gap needed? I think the air doesn't really have anywhere to go anyway?
If it's not possible to vent moisture away, should I use something other than construction plastic right next to the ceiling?
Hope you understand me - in urgent need to move forward, but I want to build correctly
Self-builder
· Stockholm
· 8 224 posts
Isover writes a bit about diffusion-tight roofs vs. no air gapF Flipar said:I am about to insulate and complete my garage construction internally. The garage is barn-style with dense roofing felt on top of the roof boarding. There is no opening for air to escape from the sides or at the ridge.
How do I insulate and close up this structure, and what materials should I use?
Is an air gap needed? I'm thinking that the air doesn't have anywhere to go anyway.
If there is no way to ventilate moisture, should I use something other than building plastic closest to the ceiling?
I hope you understand me - I'm in urgent need to move forward, but I want to build correctly
https://www.isover.se/oventilerad-konstruktion#diffusionstatt-yttertak
In a small timber cabin, I have used Hunton boards (hygroscopic insulation made of wood fiber) and a vapor barrier, but with diffusion-tight paper on top of the roof boarding. This will not be inhabited and will only be partly heated (kept above 0), but we'll see in a few years if this technique works.
The theory is that moisture can be buffered in the insulation and exit inward through the vapor barrier, but the vapor barrier will still prevent air from entering the construction from inside.
Apart from wanting to preserve ceiling height, it is quite tricky to have ventilation in the roof sections in a timber construction. And with a hygroscopic construction, it should withstand some moisture variation over the seasons. If it were to be used as living space, with constant moisture pressure (kitchen, bathroom, and people 24/7), I might have built a ventilated construction, although I still like hygroscopic construction with a vapor barrier rather than a barrier since I don't really trust that the construction remains completely moisture-tight over time in all situations.