Best 50mm Insulation Material to Use With Air Gap Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[Zacccc]

I am insulating above the ceiling of my back bedroom. The ceiling slopes down and there is only 4 inches between the ceiling plasterboard and the roof felt above. Since I have to leave 2 inches for air flow, this means I can only put in 2 inches (50mm) of insulation so I'm wondering what the best type would be. Any advice welcome.

[welsh brickie]

kingspan, foilbacked insulation board 50mm

[Zacccc]

Thanks welsh brickie, I'll have a look at that.

[Zacccc]

Is it ok just to put the insulation boards in or should there be a vapour barrier under them?

[Zacccc]

Thanks again for all the advice I've had on here.

I bought two sheets of Xtratherm and I intended to put them between the joists/rafters by sliding them down into place from the loft. A couple of people advised me (quite correctly as it turned out) that this would be very difficult to do and just about impossible without leaving gaps everywhere. Well, I did try but soon realized it couldn't be done and therefore decided to take down the whole ceiling (or at least the sloping part to the eaves - horrible dirty job!) I've now completed this and am next going to put the Xtratherm boards in, getting as tight a fit as I can.

After I've put the boards in I'm going to put up insulation backed plasterboard, preferably a type that has a built in vapour control layer. Does anybody have any recommendations on what type would be best? Thanks.