Theo <
theom...@chiark.greenend.org.uk> wrote:
> In terms of conduction, this SF6 has an R value of 0.99 ('core performance')
> and various bigger numbers 'including air spaces' (roof R=1.9, wall R=2.32,
> floor R=3.64), the exact conditions are unspecified. R-values are thermal
> resistance, like electrical resistance.
>
> By contrast foil-backed Celotex GA4000 has the following R values:
> 50mm: R=2.25
> 75mm: R=3.40
> 100mm: R=4.30
The numbers I did for my roof calculations for the other thread:
I started off looking at aerogel products since they have the lowest
conductivity per thickness, but then they have to be bonded with
plasterboard.
Spacetherm 32.5mm = 20mm Aerogel + 12.5 PB
R(plasterboard) = 0.125/0.19 = 0.066
R(aerogel) = 0.02/0.015 = 1.33
Total R = 1.4
Spacetherm 17.5mm = 5mm aerogel + 12.5
R = 0.4
Celotex 37.5mm = 25mm PIR + 12.5 PB
R = 1.2
Celotex 27.5mm = 15mm PIR + 12.5PB
R = 0.7
Thermaline 22mm = 12.5mm EPS + 9mm PB:
R = 0.35
Spacetherm Multi:
6mm MgO PB + 10 / 15 /20mm aerogel
R(plasterboard) = 0.006/0.19 = 0.0315
R(10mm aerogel) = 0.01/0.015 = 0.66
R = 0.7
15mm aerogel + 6mmMgO
R = 1.03
20mm aerogel + 6mm MgO
R = 1.33
PIR foam (celotex) without plasterboard
40mm R = 1.8
30mm R = 1.36
20mm R = 0.9
Pavatex Reveal Board (wood fibre)
30mm: R = 0.65
40mm: R = 0.90
Wediboard (XPS laminate)
20mm R = 0.15
30mm R = 0.8
40mm R = 1.086
https://www.knauf.co.uk/store/xps-laminate-plus/c-23/p-105
27mm R = 0.58
So, given the SF6 superfoil is 30mm thick, if we believe the numbers for a
roof it's R=1.9, and that compares with 30mm of PIR at R=1.36. And the PIR
gives a smooth surface while the superfoil would need a plasterboard or ply
surface to make it flat. If we only take the core numbers, the superfoil
has an R=0.99 so not as good.
On the other hand the superfoil can be useful if you need a flexible product
rather than a board, eg for fitting between timbers.
Theo