Do you need a vapor barrier between the attic and living space?
In addition to an air barrier, should a vapor barrier (non permeable) be used to hault moisture flow between the attic and living space. Thinking permeable is better but I'm hearing differently.
Where and when to use vapor barriers in construction and renovation can vary depending on a few things – the climate you are building in, whether it is above grade or below, and the composition of the wall. The answer is more simple for homes in Canada, but the lack of a U in vapor indicates you are likely in the US.
If where you live requires vapor barriers by code, then you would need to continue with that on the ceiling, and no, it should be permeable. Tell us more and we can help – what climate zone do you live in, and is this a new construction project or a renovation?
Here is a good page to read as a starting point, that may answer your question but feel free to write a follow up.
The difference between air barriers and vapor barriers
Yes, I'm building new construction in Virginia, climate zone 5, I believe. If no code dictates the use of vapour (lol!) barriers, how might the barriers between the inside ceiling and attic be applied for my zone?
Thanks! You guys are great
Thanks for the kind words Jim,
Depending where you are in Virginia you may be in climate zone 4 but possibly 5, so I think you’re best to go with the advice of local general contractors who would know the code requirements for exactly where you are. If it was the basement there is simply no climate zone where a vapor barrier makes sense, but for an attic I'm reticent to offer advice from a thousand miles away that may conflict with the contractor parked in your laneway.
As for how to do air barriers and vapor barriers, presumably if it is a new home you would have a designer or architect on the team? They would have proposed on in the plans, no? There are options of course, if you’re looking to explore some here is the link to air barriers in the Ecohome Building Guide, have a look here and see if anything resonates.