Unvented Low Slope Roof

Drying of unvented roofing assemblies is by definition only provided to the interior.

Unvented low slope roof.

Whatever method is used the amounts of insulation must achieve r values mandated by local codes. However architects of these compact roof assemblies must consider vapor permeance and arrangement of the materials to produce acceptable hygrothermal performance and low risk of condensation in the resulting conditioned attic space. The insulation can go below the roof deck above the roof deck or both. Like a wall that is severely out of plumb an unvented roof has insulation packed into the framing cavities aligned with the sheathing.

Unvented low slope roofs are never designed to dry to the exterior because low slope roofing membranes are vapor barriers. If the upper edge of a low slope shed roof intersects a vertical wall the most logical approach in my opinion is to detail the roof as an unvented roof. Five ways to insulate an unvented low slope roof of the various methods to insulate a shallow roof applying insulation to the exterior is easier than working in a space with limited access. Low slope and steep slope unvented roof systems i e.

In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane. Because the attic space is now inside the thermal envelope blowing a little heat up there is not like throwing twenty dollar bills out the window.