Should I Insulate My Roof Rafters

If you re considering turning your attic into conditioned storage or living space it s worth changing tactics to insulate between the rafters and wall joists instead of the floor.

Should i insulate my roof rafters.

Place the plastic sheeting on top of the rolled insulation. If you have vents in the walls of the attic or in the roof ridge then the insulation can go all the way to the roof. You need to leave a gap to the rear of the insulation between the membrane and the insulation to allow air to circulate around the roof space. Insulating the pitched roof if your attic is often used or perhaps you plan to convert it in the future you will need to insulate the inner surfaces of the roof.

Attic moisture problems are often the result of heated air from the living space rising up into the attic which is not heated. You only need those if you have vents in the soffits under the eaves. You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood rafters. I would personally use celotex cut tightly in between the rafters.

The idea is to allow some air to circulate through some part of the attic under the roof but outside the insulation to prevent moisture build up. The technically correct approach depends on a number of factors. 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. If the plastic sheeting is in pieces overlap the pieces by 8 inches and staple it in place directly to the roof rafters and the wall.

Whether or not there is an inner roof lining and the total thickness of the roof structure. Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator. To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. Do not use plastic sheeting in this case.

You can add insulation to the floor. In order to avoid damage to the roof deck you should insulate ceilings to create an air barrier between the living space and an unfinished attic or airspace underneath the roof deck. If there is a floor you will need to remove it to properly insulate the roof rafters. However rigid foam insulation must be covered with a fire rated material when used on the interior of a building.

Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. Half inch drywall is usually sufficient but check with local building officials before installing. You could then simply clad the area with plasterboard etc.