Unvented Roof Assembly Options

Roof assemblies must control for exterior moisture in a monolithic and complete fashion.

Unvented roof assembly options. Insulating unvented roof assemblies. Test roofing membranes for integrity prior to covering from below. However designers of compact roof assemblies must consider vapor permeance and arrangement of the roofing materials to produce acceptable hygrothermal performance and low. Also unvented roof assembles make complicated roof geometries more viable as they are difficult to ventilate effectively.

Four options for building an unvented roof assembly. 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. We re big fans of fine homebuilding. If you don t want to use sips or nailbase there are four basic approaches.

These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. We agree that avoiding sheathing rot is critical and that air permeable insulation such as fiberglass or cellulose cannot be used alone. In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane.

Expanded use and design options. Unvented roof systems where the 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.