celotex shed roof heat transfer question

[Matt@]

Hi all, I'm looking for some pointers re. using celotex for lining an outbuilding roof.

I have a 20' x 12' outbuilding with cement fibre corrugated sheet roof. The sun beats down on the roof thus making the roof inside the building (made very hot by the sun) to act like a radiator by way of heating the inside to stifling temperatures. Now looking at lining the inside of the roofing sheets with celotex. The celotex boards wouold have a void of 2" between roof sheets. What thickness celotex would I need so the heat will not transfer through ie still be cool to the touch even thouigh the roof sheet is red hot? I need approx 6 sheets and dont want to spend needlessly nor do I want to skimp....

thanks

 

[woodfarmer]

I used 1 1/4 inch thick pine planks for the ceilings of my poultry houses with 60mm thick celotex ( tightly fitted) above. for some reason they are always warm, summer or winter. roof is corrugated iron. Very pleased with them.