In article , Steve Jones wrote:
I am sat here watching some roofers on the house opposite. Instead of
roofing felt they are using some thin plastic type stuff which is green
on one side and white on the other. What is this stuff? Surely it won't
provide as much insulation as traditional felt?

Steve

Errm, who says the felt is to provide insulation? That's provided by
the thick layer of name your favourite insulator between the rafters.
AFAIK roofing felt is there to:
a. stop the slates or tiles lifting in strong winds.
b. stop all the filth accumulating in your loft space (several tons of
dust in the 1903 terrace loft space that I hoovered out a few years ago.)

(Ok, it may provide some marginal insulation by reducing the rate
of air change in your loft.)

--
Jan