Roof Insulation Board Between Rafters

The boards creating the slope of the roof are wider than lumber used to build trusses 2x8s 2x10s and 2x12s are most common in rafters vs.

Roof insulation board between rafters.

Being lightweight they do not impose significant additional loads on existing structures. Measure the space between the rafters where the insulation will be placed and cut the insulation boards marginally wider than the space to ensure a friction fit upon installation. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings. 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.

100mm based on 150mm rafters leaving 50mm air flow. 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. R value for fiberglass or wool batts per inch is between r3 and r3 5. 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.

Rigid polyisocyanurate pir foam insulation boards from celotex are among the most thermally efficient commonly available insulation materials on the market. Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. Rolls are usually used for long expanses such as length of floor for entire attic while batts are fit between studs in attic rafters. We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe.

Fit the cut quinn therm qr insulation boards tightly between the rafters with the quinn therm branded side facing into the building. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face. Best material to use is 100mm kingspan or celotex foil backed insulation board easily cut to size to fit between rafters. 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.