Garage Roof Rafter Insulation

Blown cellulose insulation will require the installation of netting over the rafter pockets.

Garage roof rafter insulation.

If you are insulating the garage ceiling not only by the truss level but also up by the roofline then you must leave at least 1 1 2 to two inches of air between the fiberglass and the underside. In a warm roof structure the insulation is placed above or above and between rafters in order to avoid heat loss and energy transfer. Make sure you have enough ventilation on your roof as well. If you re not adding heat there s little point in insulating.

It s a popular misconception that insulation adds warmth. There should be a continuous ridge and soffit ventilation. Roof insulation configurations for unvented rafter truss assemblies. In reality insulation merely slows the transfer of heat through the insulated barrier wall ceiling floor etc.

Images courtesy simpson gumpertz heger. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. Ibc dictates acceptable placement and composition of roofing materials in chapter 15 but describes required thermal efficiency of the roof in chapter 13 which references the international energy conservation code iecc the minimum required thermal resistance varies. Garages built without attics are also prime candidates for insulation into rafter bays the name for those spaces between rafters.

For the same reason insulation shouldn t touch the roof s underside. Opening vents in the soffit would allow air to flow from the low edge of the roof up along each channel between the rafters and up to your ridge vent. You can either install faced batting insulation which has a paper. This netting serves to hold the blown insulation usually recycled newspaper inside the rafter pockets until such time that ceiling materials can be installed over the insulation.

In the case of a cold roof structure the insulation is placed between or between and under the rafters or at ceiling joist level and the roof is ventilated by leaving a 50mm gap above the insulation which vents air to the outside.