How To Insulate An Old Slate Roof

Answered 14th jan 2013 like 2.

How to insulate an old slate roof. If you want to avoid internal changes you can do so by insulating externally. The best way is to insulate the attic floor. An advantage of spray foam is it s quick whereas foam board needs to be cut and measured which can be a chore. Equally the reverse is true.

With an assumed pre existing u value of 2 23w m the best options are as follows. You would first have to create a vent channel under the slates by installing 1x1 sticks at the top of each rafter bay followed by stiff material like rigid foam or plywood. The materials used to insulate under the roof include batts of mineral or glass wool insulation held in place by battens of wood attached to and across the rafters. To insulate the roof itself you either use spray foam or retrofit with it with rigid foam board.

U value 0 38w m. Plasterboard 50mm pur insulation in 50mm timber stud with 50mm vented cavity to the existing wall. A well ventilated roof space is good this stops your timbers rotting. If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters.