Insulate Unvented Roof

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.

Insulate unvented roof.

In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies. Insulating the underside of roofs making the case for the unvented attic assembly background. If you don t want to use sips or nailbase there are four basic approaches. Don t stay stuck in the sci fi nightmare of foam foam foam.

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

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. When hvac equipment is in the attic insulation and. Insulating unvented roof assemblies. An unvented attic differs from a conventional vented attic in that there is no direct venting of the attic.

We re big fans of fine homebuilding. Four options for building an unvented roof assembly. 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.