Insulating Attic Room Under Slate Roof

Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

Insulating attic room under slate roof.

To meet all three goals insulating your finished attic ventilating the roof and maximizing headroom use a combination of dense batt insulation rigid foam sheeting and air chutes. You may have to build out on the inside a bit to get enough insulation. Install wood between the rafters maintaining a 1 gap between the wood the underside of the roof deck. Insulating your roof and attic space will help retain energy in your home often leading to cost savings and comfort improvement.

Water is insulation s enemy. The gap should be on the cold side of the insulation. Insulating in and around your roof attic space also prevents long term damage from moisture build up or ice damming which results from the warm air trying to escape through the apex of the roof but instead heating up the snow. Additionally insulation serves as a way to enhance sound proofing on the uppermost envelop of your house.

Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. I would advise as much insulation between the rafters as you can get in but leaving a 25mm gap and another 40 or 50mm continuous layer beneath the rafters. Then use spray foam insulation after that finish the ceiling how you would like. Box out light fixtures.

Normally it would be 50mm but if you have no undertile felt then 25mm would be reasonable.