thin insulation equivalent to 270mm

[katespencer]

Can anyone recommend a product that will provide the equivalent of 270mm insulation, but is thin enough to fall below the height of our 100mm joists? We need to meet both these criteria to a) apply for solar energy grant or similar b) still be able to board our loft for storage (and it has a very low pitch, so we can't run more joists on top of and at right angles to the originals)

I can see that screwfix sell some thin stuff; but it's described as "equivalent to XXmm polystyrene" Is the insualation value of polystyrene equivalent to fibre? What I mean is, if I bought enough thin product to be equivalent to 270mm polystyrene would it meet the government's latest target depth?

(Not sure why I'm bothering though, as good old Gordon Brown will probably change the goal posts again by the time I've saved up for the solar. I'm sure it's just his way of ensuring low take up for the grant) ;(

Thanks for any help,
Kate

[JohnD]

see also
http://www.diynot.com/forums/viewtopic.php?t=29860&start=0

http://www.diynot.com/forums/viewtopic.php?t=1331&highlight=Warmroof

[royalnavalreserve]

Which company are you thinking about to install your solar heating? Check blagger.com first.