Insulation Slate Roof

The underside of the roof sheathing will dry rapidly to the exterior through the slate due to ventilation drying and diffusion.

Insulation slate roof.

Check the depth between your trusses and the slates then install the correct thickness of kingspan in the gaps allowing for a 25mm air gap between the kingspan and the slates. A well ventilated roof space is good this stops your timbers rotting. Answered 14th jan 2013 like 2. 3 before you start do your homework.

Where the felt is impervious any contact condensation will run down the felt and make the insulation damp. Understand headlap read about the common mistakes people make when installing slate roofs. If you create an air space under the roof sheathing boards as dana suggests there is no need to have any soffit vents or ridge vent. 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 alternatively polystyrene.

Insulation laid so that it covers the eaves significantly reduces ventilation to the roof. It is vapor permeable and air leaky. Ice water shield. Insulation is often laid in contact with the roofing felt.

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.