Insulate Unvented Roof

An unvented attic differs from a conventional vented attic in that there is no direct venting of the attic.

Insulate unvented roof.

If you don t want to use sips or nailbase there are four basic approaches. When hvac equipment is in the attic insulation and. We re big fans of fine homebuilding. 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.

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. Insulating unvented roof assemblies. We agree that avoiding sheathing rot is critical and that air permeable insulation such as fiberglass or cellulose cannot be used alone. Advantages of unvented attic assemblies.

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. Low slope and steep slope unvented roof systems i e. 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. You need enough exterior foam to prevent condensation on the inside of the roof sheathing by keeping that plywood warm.

In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies. Don t stay stuck in the sci fi nightmare of foam foam foam. 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.