Insulation For Between Roof Rafters

Modern u value targets mean installing insulation between rafters only is rarely a viable option.

Insulation for between roof rafters. We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe. 7 staple sheets of 6 mil plastic over unfaced insulation to create a vapor barrier. You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood rafters. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings.

It allows insulation to be installed in a watertight roof either after the roof covering has been fixed on a new build or without disturbing an otherwise sound existing roof covering as part of a renovation. Unfaced insulation has no tabs and stays in place with friction between the fiberglass and the rafters. Where the insulation does not fill the total rafter depth the low emissivity foil facings can gain additional thermal benefit from the air spaces they face. When you use solid insulation board to create a warm loft the key thing to remember is ventilation you must keep a 50mm gap between the roof and the rigid insulation board.

The general advice we give is that you should always insulate between and above the rafters or between and under the rafters on our u value calculator we don t give an option for putting insulation between the rafters. In this blog post we will be looking at insulating pitched roofs and why putting insulation just between the rafters isn t a viable solution.