Insulation For Between Roof 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.

Insulation for between roof rafters.

Modern u value targets mean installing insulation between rafters only is rarely a viable option. 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. We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe. Being lightweight they do not impose significant additional loads on existing structures.

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. You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood 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.

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. Consider using high density r 30 batts which are as thick as r 25 batts but fit into 2x10 framing.