Shed Roof Air Gap

Rising along the underside of the angled purlin until it reaches a gap then rising up to the next purlin and so on to exit at the ridge or gable.

Shed roof air gap.

If you insulate your shed roof be sure to leave ventilation space especially in heated insulated sheds. Purlins at a 45 degree angle still provide sufficient support for installation of the metal roof panels. Air can be flushed out using a whirlybird rotating cowl type vent. Ventilation air follows exactly the opposite path.

Examine the shed during rainfall to see if any water is leaking in. The map at right which is based on table r806 4 of the irc lists the minimum r values required to prevent condensation in unvented assemblies in various climate zones. An unvented roof assembly is possible only if you keep the roof sheathing warm enough to prevent conditioned air from condensing against it. In the absence of rain use a garden hose and spray it over the roof.

Same boat as yerself no vents in the roof space fascia. Fiberglass with r3 8 per inch would need 10 inches to achieve the minimum requirement. Condensation will form without adequate ventilation when the heat rises. You can use shingles metal roofing or fiberglass.

My thinking was to just drill some holes either side of the fascia and leave an air gap but i may just insulate without a gap and insert an air inlet outlet on the walls and hope. This can lead to mold growth and rotting of wood. The ventilators allow air to flow in one side and out the other bringing in fresh air and exhausting the moist and damp air from above the insulation. With active ventilation the natural flow of air is given some help active ventilation gives the air flow a hand by either drawing in cooler air or flushing out the hot air at the top of the building.

This type of vent is situated on the shed roof and is powered by the wind. Different types of shed. Install a roof with a good drainage system. Look inside for signs of leakage.

I m also insulating my shed and also have been wondering wot to do with the roof by way of insulating air gaps. Even more thinking is needed for a retrofit shed with 2 x4 truss or rafter construction. Climate at least 24 in of room between the top floor ceiling and the roof sheathing. If your framing is less than 75mm you may need to use a thinner board of insulation to accommodate the air gap.

The minimum rating of r38 in a roof requires some creative planning in the roof design of a new shed with 2 x6 minimum roof construction. Provide soffit fascia or wall mounted vents at the perimeter of the shallow attic that will allow exterior air to connect with the air gap between the top of the insulation and the underside of the roof sheathing. Leaving a 2 gap above the insulation should be sufficient.