Unvented Hot Roof Design

What type of foam is best.

Unvented hot roof design.

This type of roof assembly is sometimes called a hot roof. Unvented roofs unvented roofs are increasingly common due to design priorities. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. Potential pitfalls to avoid include.

Hot roof designs aka dense packed insulated sloped roofs. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. This article describes various cold climate building solutions for un vented cathedral ceilings and similar under roof spaces offering advice on how to avoid condensation leaks attic mold structural damage when roof venting is not possible. The drawing shows exterior foam over an unvented conditioned attic but the details are similar for cathedral ceilings.

If you don t want to use sips or nailbase there are four basic approaches. Any type of rigid foam can be used above roof sheathing. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation.

An understanding of heat air and moisture as well as the causes of condensation is critical in detailing unvented roof assemblies. Practicality is also enhanced. Four options for building an unvented roof assembly. As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes.

Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation. This definition allows simple unvented roof design just don t install vents in a previously recognizable climate zone ashrae s hot humid zone. A powerful argument can be made for unvented roof construction in hot humid climates in order to control interior moisture. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation.