Another best practice is to have a vented air cavity directly under the roof.
How to insulate a roof against heat.
The easiest unless you re having a new roof put on the house and most effective way to boost the insulation in your home is to insulate the attic.
Think of how much cooler it is under a canopy or tree than in the direct sun.
Don t forget to insulate the loft hatch.
This allows a lot of the heat to be reflected and dissipated before it even gets to the roof insulation.
Many homes have at least some access to this space and because of the size attics can hold quite a bit of insulation.
Like a canopy a vented roof basically shades the rest of the house.