What K (or U or R) value will building regs want?

ipjodan · 30 Sep 2006

Hi all, doing a loft conversion and am investigating the insulation. My architect has stated i need 90mm of celotex inbetween rafters and 45mm on the inside of the rafters. This will give me a R value (?) of 5.85. How can i convert this to compare it to other products? also what is the minimum value building regs will want?

Thanks

^woody^ · 1 Oct 2006

Loft conversions need a roof with a U-value of 0.2 Wm2K.

The R-value is just for individual materials and if you just compare R-values then you may also need ot factor in other things like air space to achieve the required U-value.

Most manufacturers websites will give information about suitable products and R and U values

jeds · 9 Oct 2006

Compare with which other products? I think you'll struggle to find a viable alternative.

^woody^ · 10 Oct 2006

Tri-Iso Super 10?

jeds · 11 Oct 2006

There is no evidence that TRi-Iso super 10 is comparable with PIR foam. For that reason its certificate for use was withdrawn in February this yaer and it is not at present accepted by BC or NHBC.

^woody^ · 11 Oct 2006

Are you sure? The LA's around me are still accepting it, and from what I can tell other LA's are accepting it too

The testing was done via TRADA wasn't it, so I presume it adds some credibility.

jeds · 12 Oct 2006

I'm sure there are individual inspectors letting it go but they shouldn't be really. The September issue of NHBC news officially declared it not allowed by NHBC until comparable test results become availabe. The manufacturers have been working on this for at least 2 years now and haven't been able to come up with the figures so I suppose that tells us something.

You are right that the original 12 month licence was granted because of tests that were carried out on a timber frame house and supervised by TRADA. But that licence ran out in February and hasn't been renewed.

rangersman · 26 Oct 2006

jeds said:
You are right that the original 12 month licence was granted because of tests that were carried out on a timber frame house and supervised by TRADA. But that licence ran out in February and hasn't been renewed.

They claim to have a BM Trada certificate from April 2006 onwards on their website.

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What K (or U or R) value will building regs want?

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