Do you need a vapor barrier between the attic and living space?

J
Jim Williams
Updated: April 25, 2023

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.

Responses (3)

J
Jim Williams 9 months ago

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

Mike Reynolds 9 months ago

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.