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.

Half inch drywall is usually sufficient but check with local building officials before installing. The technically correct approach depends on a number of factors. I would personally use celotex cut tightly in between the rafters. 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.

To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. 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. Place the plastic sheeting on top of the rolled insulation. If there is a floor you will need to remove it to properly insulate the roof rafters.

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 between rafters will do no good because the attic should be ventilated and the rafter insulation would be between two unheated spaces. 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. You can add insulation to the floor.

You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood 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. Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator. However rigid foam insulation must be covered with a fire rated material when used on the interior of a building.

You can use rigid foam panels or do as tom silva does with nearly all houses these days. Do not use plastic sheeting in this case. You could then simply clad the area with plasterboard etc. 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.

Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. Hire a pro to install spray foam insulation. 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.