Insulation

[rs6mra]

I have searched through the threads but still non the wiser.
A friend has had this summer house erected and now wants to insulate it. The plan is to do the walls with 50mm PIR insulation. The roof has timber slats and a felt roof. Would it be acceptable to have a battens in the slots thus creating a gap between the celotex (50mm) and the boards? Thanks

 

[rs6mra]

Photo attached

 

[eribaMotters]

The air gap would be fine and should reduce the risk of condensation. I'd tack some 3/4" battens to the rafters 50mm in from the edge and then board over the underside to get your ceiling. Alternatively you could set the battens closer to the timber slats so that after the insulation board has gone in you could set ceiling boards into the gaps leaving the bottom edge of the rafter on show.

Colin

 

[rs6mra]

Will there be a need for a vapour barrier before it is plasterboarded?

 

[harryc]

Will there be a need for a vapour barrier before it is plasterboarded?

No the silver foil will act as the vapour barrier, just make sure you tape over any gaps to prevent thermal bridging.