Celotex Thermal Performance

[ADLIan]

See Celotex website , www.celotex.co.uk.

Appears they have not been exactly truthful with their thermal performance!

[ProDave]

So they have been under stating the values. So it is better then they have said?  And the problem is.....?

[ADLIan]

With lamba value lower = better so ‘understating’ is not good. Since 2009 they’ve been claiming 0.022 W/mK when it should have been 0.023 W/mK. Makes all your U-values higher (worse). Not good for their certification and CE mark especially on the back of Grenfell and incorrect quoted fire performance - all on website.

[CC45]

How much difference will this make in the real world?

[Jeremy Harris]

22 minutes ago, CC45 said:

How much difference will this make in the real world?

 

Very roughly the performance will be around 4.5% worse that predicted.  Down in the noise, really, but interesting, because at the time that Celotex claimed a lambda of 0.022 it was lower than any of their competitors who were selling near-identical PIR foam insulation, so it probably helped gain them market share.

[A_L]

Something else is the reduction in R value as the temperature drops with falling exterior temps. This is American so have to divide by about 5.7 to get S.I. R values

 

https://buildingscience.com/documents/information-sheets/info-502-temperature-dependent-r-value

 

The R values of fibrous insulation tend to increase with falling temps.

[ADLIan]

+1 JSH. PUR manufacturers sell heavily on conductivity - try selling 0.023 product against 0.022 product and you’re dead in the water! 4.5% degradation does not sound much but on 8 years production it adds up.

 

Temp variation effect on conductivity is not important here compared to USA which has massive changes in climate from north to south. Under BS conductivity is normally measured at mean 10K (0C - 20C).