The Natural Philosopher wrote:
Ian Stirling wrote:
wrote:
Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?

Take sheet of non-vapour barrier plasterboard.
Dilute PVA to milk-like consistency.
Arrange some way to prop up the sheet so that it's off the floor,
vertical, or sloping slghtly backwards, with the long side parallel to
the floor.
Spray a meter with the PVA solution from a small pump-up sprayer.
Lay two lines of kitchen foil, slightly overlapping.
Spray another meter, repeat.

This gets you a foil coated bit of plasterboard for well under 30p, and
in under 5 min or so.


Whereas the extra cost of the foil backed plasterboard is probably about
10p for the same area..

Oh well.
I got quoted an extra fiver per sheet.
Kitchen foil is only 10p/sheet or so.