Rick wrote:
I have just seen some 25mm quitled roof insulation, that says it
acheives 0.2 U value, its about the same price as 100mm kingspan,
which is also about the same U value.

Does it work ?


There's been a lot of debate about this stuff and the methods used for
testing it. A lot of heat loss is by radiation and the multilayers of
foil separated by foam cut this rather dramatically. It's not cheap
but if your space is limited it could be a good option.
In the cryogenics field where vessels containing liquid nitrogen or
even colder substances need to be kept very insulated from the
environment, multifoil blankets consisting of 30 layers of foil and
paper per inch are used.