If you do need to install insulation in the roof assembly take into account some rules.
Insulating sloped attic ceiling.
What you would do is you would install six inches of insulation into that.
Install 4 inches of spray foam on the underside of the roof sheathing and fill the rest of the cavity with fiberglass batts.
1 lay long wide boards or.
Insulating unvented sloped ceilings here are your top insulation choices for unvented sloped ceilings.
However this leaves a lot of uninsulated sloping ceilings with little room around 5 inches between the plasterboard and the roof tiles.
You would not fill up the entire eight inches deep because you want to leave that extra two inch space between the end of the insulation and the underside of the roof sheathing so that you can flush air through that.
Install 7 inches of spray foam on the underside of the roof sheathing and leave the rest of the rafter cavity open.
Unless in air conditioned attics insulation is typically installed on the ceiling plane not on the sloped roof assembly.
Insulating a sloped ceiling.
The horizontal ceiling accounts for around 40 of the total ceiling area and is insulated with glass fibre between the joists accessed via the loft hatch.
For attics with sloping walls formed by the roof s angle stapling the facing to the framing ensures it stays in place protecting both your family and your pocketbook.
Previous owner blew celluose insulation in attic.