Hugo Nebula wrote:
On Mon, 28 Apr 2008 19:12:35 +0100, a particular chimpanzee,
"Tanner-'op" randomly hit the keyboard
and produced:

Jim Alexander wrote:

OK there are now better materials than traditional felt.
You have to use a 'permeable membrane' material now rather than the old
bituminous felt.

You don't "have to"; bituminous felt is still acceptable. I would go
for a breather membrane, though.

Permeable membrane is not needed in a 'cold roof'

Its there to vent 'warm roof' spaces where the joists are covered and
there is very little movement past them as they are insulated, with a
small air gap.