Unvented Low Slope Roof

Low slope and steep slope unvented roof systems i e.

Unvented low slope roof.

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. Whatever method is used the amounts of insulation must achieve r values mandated by local codes. 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. 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.

Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek. Insulation and air barrier are applied directly to the underside of the roof deck are common in applications where designers are seeking cost effective and energy efficient roof assemblies. Drying of unvented roofing assemblies is by definition only provided to the interior. The insulation can go below the roof deck above the roof deck or both.

In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane. Unvented low slope roofs are never designed to dry to the exterior because low slope roofing membranes are vapor barriers.