With 6 inch joists, you are laughing. If you can afford celotex, just use
the complete thickness and board over if you wish.


You should not do that - the regs insist on an airgap to allow air to
circulate over the joitsts etc.

How can you have a floor, if you must leave an air gap between the joists
and the boards?

Can I presume you thought I was still talking about insulating the roof, not
the floor?

Christian.