Vapor Barrier or Not?

Guest User
Hi, I am building a barn and have been trying to figure out how to do my steel roof without running into issues down the road. This will be a heated barn with about 15" thick of blown in insulation in the attic and vented sofit. (i live in mid-michigan) My question is, can I lay the steel roof on 2x4 purlins and not have to worry about condesation due to the attic being insulated? I have been told by one place that they recommend putting osb on the trusses followed by 30lb felt, then lay the steel directly on that. Is this right? What should I do?
Eric Novotny
An informed customer is the Best Customer!
Air seal the attic floor and as long as the roof is vented, you should be fine. Best thing to do it to keep the moisture from even getting into the attic at that point. Air seal round all the penetrations and if you want, you can incorporate a vapor barrier into the attic ceiling. If the roof is effectively vented via ridge and soffit combination, and you are controlling moisture at the attic interface, you should be fine. Folks that have condensation issues don't have an intermediary level between the roof and the moisture generation source as you do in this scenario.

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.

Find a Professional

Get Started Today

Take the first step to increasing the value of your home with a great looking, durable, fire resistant and energy efficient metal roof. Browse our list of qualified MRA Member Roofing Professionals in your area for a free consultation and estimate.