Insulating A Vented Roof

That is create a vent channel above the insulation with low and high vents.

Insulating a vented roof.

In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof cavities. You could insulate the roof the traditional way. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. For the same reason insulation shouldn t touch the roof s underside.

Vented roofing the typical vented roof has a vent at the lower eave and a vent at the higher. Spray foam with air permeable insulation. In this energy smart homes article senior editor martin holladay explains how to insulate a vented low slope shed roof using a combination of intake vents and cupolas. When hvac equipment is in the attic insulation and an air barrier at the roof line brings that equipment within the conditioned enclosure envelope thereby allowing it to operate in more favorable temperature and humidity conditions without air leakage and heat loss gain directly to the exterior.

You must meet the same minimum code requirements for the spray foam layer and the total assembly as for the rigid foam plus air permeable insulation approach. Covering up the soffit vents with loose fill or batts which can happen if you stuff insulation along the eaves is a huge no no. Rigid foam and spray foam are two of them. All insulation materials require proper venting.

Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof. Then insulate below with fiberglass or cellulose add a vapor retarder and your finish ceiling. In a vented roof foam can seal the openings and serve as an air barrier and a vapor retarder in addition to its insulating function. Air can move through the attic space freely and the floor of the attic is insulated to thermally separate the unconditioned attic from the living spaces below.

A layer of spray polyurethane foam can be installed against the underside of the roof sheathing with the rest of the rafter cavity filled with air permeable insulation. Foam insulation can play an important role in both vented and un vented roof assemblies.