Insulating Exposed Enclosed Porch Roof Rafters

This is often a layer of tongue and groove boards nailed to the exterior side of the exposed rafters.

Insulating exposed enclosed porch roof rafters. The insulation should fit snugly to prevent air from getting through. Use a vapor barrier to keep your floor above free from condensation caused by the new insulated area. This is a more rustic choice and you can use contrasting planks with the exposed rafters to add dimension and visual interest to your porch. In essence the boards are laid horizontally over the timber across the roof area beginning and ending on a rafter or top chord.

You can install r 49 of spray foam between the rafters. The screws secure the counter purlin to each rafter or top chord. The insulation for exposed rafters is installed on the exterior side of the finish ceiling. An open ceiling is another option where the rafters that support the roof are left exposed.

You can prevent this by installing foam insulation board against the underside of the roof between the rafters. Large foam insulation sheets can be nailed directly against the floor above or held in place by chicken wire or other metal elements with the facing against the underfloor. For the same reason insulation shouldn t touch the roof s underside. Roll out the fiberglass insulation sheets between the joists facing side up making sure it is snugly in place.

One drawback to this is that the layer of insulation placed above the ceiling is missing which can subject the area of the house with the exposed rafters to extreme temperature changes. The boards are secured by a screw fixed counter purlin running from eave to roof ridge above each rafter or top chord. This can be stapled up between the floor joists. You can install a combination of r 20 rigid foam above the roof sheathing and r 29 or more of air permeable insulation fiberglass batts or cellulose for example between the rafters and in direct contact with the roof sheathing above.

Many homeowners like a classic drop ceiling with painted or stained beadboard for a traditional look. As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. If you can crawl under your porch insulate from below by nailing plywood boards to cover any openings.