We would always recommend having a breathable membrane in place between the tiles and the rafters too to allow the roof to breathe.
How to install insulation between roof rafters.
This roof type will require a breathable membrane like kingspan nilvent to be.
Garages built without attics are.
Modern u value targets mean installing insulation between rafters only is rarely a viable option.
Then blow another layer on top of the roof rafters.
Fit the cut quinn therm qr insulation boards tightly between the rafters with the quinn therm branded side facing into the building.
It allows insulation to be installed in a watertight roof either after the roof covering has been fixed on a new build or without disturbing an otherwise sound existing roof covering as part of a renovation.
Measure the space between the rafters where the insulation will be placed and cut the insulation boards marginally wider than the space to ensure a friction fit upon installation.
As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation.
Typically you will fill the insulation blower with the insulation and blow it between the attic floor joists.
If you have a solid floor covering the roof rafters use the claw end of a hammer to pull the floor up in several locations and blow the insulation under the boards.
When you use solid insulation board to create a warm loft the key thing to remember is ventilation you must keep a 50mm gap between the roof and the rigid insulation board.