Insulate Unvented Roof

Insulating the underside of roofs making the case for the unvented attic assembly background.

Insulate unvented roof.

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. 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. You need enough exterior foam to prevent condensation on the inside of the roof sheathing by keeping that plywood warm.

Insulating unvented roof assemblies. Advantages of unvented attic assemblies. When hvac equipment is in the attic insulation and. Four options for building an unvented roof assembly.

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. 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. We re big fans of fine homebuilding. An unvented attic differs from a conventional vented attic in that there is no direct venting of the attic.

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