Roof Insulation Between Rafters

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

Roof insulation between rafters.

Insulation can be installed between the rafters using a ventilated roof construction or an un ventilated roof construction. Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe. You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood 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. Modern u value targets mean installing insulation between rafters only is rarely a viable option. The decision on which method to use is usually dependent on the sarking or underlay. 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. Water is insulation s enemy. Unfaced insulation has no tabs and stays in place with friction between the fiberglass and the rafters. A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.

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. 7 staple sheets of 6 mil plastic over unfaced insulation to create a vapor barrier. Box out light fixtures. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings.

Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow. Although there are many different. Being lightweight they do not impose significant additional loads on existing structures.

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. For example if the space beneath the rafters is going to be used for a living area then you will need to insulate the roof rafters.