You are reading a single comment by @JonoMarshall and its replies.
Click here to read the full conversation.
-
I was told talk to (negotiate with?) building control. Especially true if you're in a conservation area. They'll want the best possible performance given the structure you have to work with. For us that means internal insulated board for sloping ceilings that gets close to (but doesn't meet) building reqs (U-value of 0.15).
Ventilation path is meant to be 50mm, eaves vents are meant to be equivalent to continuous 25mm gap.
JonoMarshall
Insulation question:
Kitchen has a hipped roof (slate), and the rafters are only 75mm deep.
Will I need to build out (in?) off these rafters to give a load more room for air gap and heftier thickness of PIR board - assuming 120mm?
Can’t tell if this is a mandatory building regs thing, or just what they prefer to see (and could I get away with 60mm PIR and 15mm between that and the membrane under the batons).
Previously had a suspended ceiling and zero insultation at all.