Garage Roof Rafter 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.

Garage roof rafter insulation.

There should be a continuous ridge and soffit ventilation. Roof insulation configurations for unvented rafter truss assemblies. Covering up the soffit vents with loose fill or batts which can happen if you stuff insulation along the eaves is a huge no no. It s a popular misconception that insulation adds warmth.

If you re not adding heat there s little point in insulating. For the same reason insulation shouldn t touch the roof s underside. Make sure you have enough ventilation on your roof as well. It pays to insulate your garage if you re adding heat whether on a permanent or as needed basis.

Blown cellulose insulation will require the installation of netting over the rafter pockets. 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. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. 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.

Garages built without attics are also prime candidates for insulation into rafter bays the name for those spaces between rafters. 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. Images courtesy simpson gumpertz heger. In a warm roof structure the insulation is placed above or above and between rafters in order to avoid heat loss and energy transfer.

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.