Quote:
Originally Posted by Ormston
AC
If you download the data sheet from the page you linked to a couple of posts back you will see what I mean about the insulation value in various constructions.
It looks like there multifoil is only a radiant barrier and still requires a more conventional type of insulation to tasked care of conduction.
Battons are just 2x1" lengths of timber used as spacers and so on.
|
OK, I think I'm seeing how this goes...
When UK vendors are describing insulation values and say, "up to", they assume a cumulative R-value that includes all of the insulative layers summed up, given unspecified, but generally understood building practices.
I'm assuming that this is common practice in the UK, and everyone expects this to be interpreted in terms of cumulative R-value, and would be able to shift their expatiations accordingly.
In the US, it is the practice to cite R-value as pertaining to the insulating material only. I think this is because of 'fair labeling laws' or something.
So a cultural adjustment is called for here.
When I look at this Fixing Instruction:
I do see that the multi layer insulation has a resistance value of 1.52, for the 40 mm thickness, which would equate to:
(1.52 / 0.17611) / (40mm / 25.4) = R 5.39 per inch, in US terms.
Hmmmm..... not at all so good as I thought.
And PIR, which I think is similar to what we refer to as "Poly Iso", come out in the example as:
(2.174 / 0.17611) / (50 / 25.4) = 6.27 per inch. in US terms. Pretty much standard.
OK, it isn't looking like quite the miracle material I had thought it to be.
-AC