Insulating Exposed Enclosed Porch Roof Rafters

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.

Insulating exposed enclosed porch roof rafters.

You can install r 49 of spray foam between the rafters. The boards are secured by a screw fixed counter purlin running from eave to roof ridge above each rafter or top chord. Make sure that you wear gloves and a mask for protection. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.

To create a warm pitched roof insulation such as kingspan kooltherm k7 pitched roof board should be fitted between and over the rafters. As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation. For the same reason insulation shouldn t touch the roof s underside. The insulation should fit snugly to prevent air from getting through.

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. This is often a layer of tongue and groove boards nailed to the exterior side of the exposed rafters. This can be stapled up between the floor joists. Roll out the fiberglass insulation sheets between the joists facing side up making sure it is snugly in place.

In essence the boards are laid horizontally over the timber across the roof area beginning and ending on a rafter or top chord. If you can crawl under your porch insulate from below by nailing plywood boards to cover any openings. You can prevent this by installing foam insulation board against the underside of the roof between the rafters. 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.

Use a vapor barrier to keep your floor above free from condensation caused by the new insulated area. 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.