About Vapor Retarders
A vapor retarder, or vapor barrier, is a specialized material installed within a commercial roof assembly to restrict the movement of moisture vapor into the insulation and roofing system. In certain climates and building types (like indoor pools or manufacturing facilities with high humidity), warm, moist air from inside the building can travel upward and condense within the cooler roof assembly. A vapor retarder prevents this condensation, protecting the insulation’s R-value and preventing structural rot and mold.
Frequently Asked Questions
When is a vapor retarder required on a commercial roof?
It is typically required in cold climates or over buildings with high internal humidity to prevent condensation within the roof assembly.
Where is the vapor retarder installed?
It is usually installed directly over the roof deck, beneath the rigid insulation layers.
Can a roof have too many vapor retarders?
Yes, installing multiple vapor retarders can trap moisture within the roof assembly, leading to significant damage. Proper hygrothermal analysis is required.
