insulation

[spoonse]

okay so the board in question has no foil on it ,would it still reflect the heat from outside as well as keeping the heat in?

Or shall i splash out and get the kingspan?

 

[mointainwalker]

The effect of the foil is quite modest. There is nothing stopping you just placing cooking foil on top of your board to achieve the same effect and since you already have it at a cost of zero, this would be a huge saving over buying a new product

 

[spoonse]

thanks for that mate maybe ill get some foil for the south facing side of the roof ,nice one cheers

 

[noseall]

The main effect of foil is a vapour barrier. Installed correctly (sealed around joins and edges) foil backed products are reasonably successful at preventing moisture escape.

 

[mointainwalker]

@noseall.

Sorry, have to disagree with you in this case. The boards are themselves impervious to water-vapour and so the foil can only be for added insulation ( or a marketing-aid).

When plaster-board is foil-backed, then the foil is serving both as a vapour-barrier and (slightly) added insulation.