Roof Insulation Board Between Rafters

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.

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. The usual way to do this is by inserting rigid insulation boards between the rafters. Fit the cut quinn therm qr insulation boards tightly between the rafters with the quinn therm branded side facing into the building. Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall.

Being lightweight they do not impose significant additional loads on existing structures. Modern u value targets mean installing insulation between rafters only is rarely a viable option. 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. To get the required 270mm thickness of insulation you may have to insulate over the rafters as well using insulated plasterboard.

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. To create a warm pitched roof insulation such as kingspan kooltherm k7 pitched roof board should be fitted between and over 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.

We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings. They should be cut to exactly the right size so they fit snugly and don t allow any draughts through. As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation.

Time to get the insulation finished and get this place warm. Check out our how to video at the link below. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face.