Minimum Air Gap On Metal Roof

On the south side of the roof there are solar pv tiles with an air gap under them and a ridge vent.

Minimum air gap on metal roof.

Also on the south side the deck has an impermeable membrane red line in attachment. The international energy conservation code prescribes the minimum r values of insulation based on climate zones and typically the required amounts for energy control also assure condensation control. It doesn t matter which side the air gap is on the foil will work the same whether it is using reflectivity or emissivity to block the heat transfer. The ridge vent only currently vents the air space under the tiles not under the deck.

The beams are 2x6. Thanks for the info. The better option is to install 1x4 purlins creating a 3 4 thick air space. I m doing a warm roof with breathable membrane so didn t think i needed this 50mm air gap.

I m doing a renovation on an unusual roof. As the metal roof heats up in the summer time the added air gap in between will act as a buffer instead of the the metal heating up the below shingle roof. The renovation is from the interior of an attic space room. Research has confirmed that creating an air space under a metal roofing system will increase energy savings during both summer and winter months.

Metal roof coatings with solar reflectance can help building owners save substantially in annual cooling costs. No air gap no radiant heat it won t work. An unvented roof assembly is possible only if you keep the roof sheathing warm enough to prevent conditioned air from condensing against it. In order for radiant heat to exist you must have this air gap.

Metal panel roof systems require a minimum 3 8 air gap between the underside of the metal panel and the covered or uncovered insulation board. Above sheathing ventilation asv is achieved by having continuous air flow between the roof sheathing and the metal panel system. This installation method also allows you the flexibility of adding a radiant barrier under the metal roof to help with heat transferring into the house which should help the air. Purlins parallel to the eave seem called for as the metal roof panels run perpendicular to the eave.

As it is i will probably be needing some insulation below the rafters to get down to the 0 2u but not needing the 50mm gap obviously helps reduce the size needed.