Insulate Unvented Roof

Don t stay stuck in the sci fi nightmare of foam foam foam.

Insulate unvented roof.

To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents soffits etc which make it difficult to achieve an airtight ceiling plane. Advantages of unvented attic assemblies. Low slope and steep slope unvented roof systems i e. 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.

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. When hvac equipment is in the attic insulation and. Insulating the underside of roofs making the case for the unvented attic assembly background. Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons.

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. Exterior insulation solves a lot of thermal nosebleeds but the amount of foam you put on the outside needs to be proportional with the amount of insulation on the inside within the rafter cavity. We agree that avoiding sheathing rot is critical and that air permeable insulation such as fiberglass or cellulose cannot be used alone. Four options for building an unvented roof assembly.

Insulating unvented roof assemblies. We re big fans of fine homebuilding. In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies.