Green Building Advisor Venting Flat Roofs

2 if you re going to vent the roof then vent the roof.

Green building advisor venting flat roofs. When installing or repairing a flat roof you must adhere to building regulations. So much information has been devoted to the subject of roof venting that it s easy to become confused and to lose focus. He says ruling out a layer of exterior rigid foam. An air permeable insulation like mineral wool cannot be installed between rafters if the assembly is unvented.

If you are planning to install mineral wool insulation on the interior side of the roof sheathing you will need to include a ventilation channel between the top of the insulation and the underside of the roof sheathing. Wash the underside of the roof deck with air. Part h of the building regulations regarding drainage state that water should drain to one or two edges. That means the entire perimeter of the roof needs to have air inlets meaning continuous soffit ventilation.

The flat roof overhead is framed in full depth 2x6s finished with what jordan believes is roll roofing a type of asphalt roofing. A vented attic where insulation is placed on an air sealed attic floor is one of the most underappreciated building assemblies that we have in the history of building science. If you re actually going to vent the roof let s be serious about venting the roof. Venting of flat roofs.

There must be a slope of 1 80. A qualified roofing contractor will be able to advise on this but here are some of the main guidelines. Musings of an energy nerd. Originally published may 1976.