On Sun, 30 Dec 2007 01:04:01 +0000, a particular chimpanzee, The
Natural Philosopher randomly hit the keyboard and produced:

Andy Wade wrote:

Nonsense - you've forgotten to include the surface boundary layer
resistances.

That was straight out of te building regulations hand book.

I tend to trust them more than you.

But he is right. The Resistance value of all the elements is added
together to give the total R-value; a U-value is the reciprocal of
this. The R-value includes the surface resistances of the inside and
outside surfaces (IIRC, between 0.35m²K/W to 0.04m²K/W depending on a
few factors).
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"