Builders should check the claimed thermal performance of multi-foil roof insulation

(11/06/2008)

Builders and contractors using multi-foil roof insulation remain at risk of failing to meet Building Control energy efficiency requirements and being denied an Energy Label if they rely on some manufacturers’ claimed “R” values from non-standard tests, Building Control guidance is warning.

The revised Technical Guidance Note from Local Authority Building Control (LABC) has once again raised concerns about the claimed thermal performance of multi-foil roof insulation based on comparative tests, rather than industry-standard “hot box” testing in accordance with National, European and International standards.

“Builders, contractors and loft converters may have to go to considerable extra time and expense to refit insulation and gain an Energy Label if they specify multi-foil products based on the claimed “R” values of the comparative tests,” says Crispin Dunn Meynell, General Secretary of Eurisol, the insulation trade association.

The guidance advises caution in accepting R values claimed by some multi-foil manufacturers of 5 to 6m2K/W in ‘comparative tests’, rather than the 1.69 to 1.71m2K/W indicated in National Physical Laboratory tests conducted in accordance with BS EN ISO 8990, concluding “if such values are accepted now, there is a significant risk that approved buildings will fail to achieve the required level of energy performance.”

The recently revised LABC guidance follows the findings of a Judicial Review, which considered LABC’s previous guidance in August 2006. The review found in favour of a specific group of multi-foil manufacturers wishing to use non-standard evaluation methods, which caused confusion in the market about the accepted use of multi-foils following the review. The revised guidance has now provided clarification.

“The judgement had been purely on the grounds that a proper notification process had not been followed. The LABC guidance affirms that the judge made no comment on the technical issues surrounding the use of multi-foils. The LABC states that there had been claims by some multi-foil manufacturers that the judgement requires Building Control Bodies to accept comparative testing as a valid means of demonstrating compliance with Building Regulations but that was not correct,” Dunn Meynell continues.

BCBs remain entitled to make their own judgement about manufacturers’ compliance with regulations, but LABC went on to recommend: “.. the thermal performance of all insulation materials should be determined by testing to National, European or International standards by organisations which have been accredited to do so. On this basis we are not aware of any multi-foil product currently on the market that can meet the normal roof “U” value requirement of 0.2 when used as a single layer without the need for additional insulation.”

Dunn Meynell concluded: “We welcome Building Control’s revised guidance and clarification on this matter. Eurisol advises contractors to proceed with extreme caution in specifying those multi-foil products making unrealistic claims. To avoid risk and potential liability it is advisable to specify insulation products meeting current BS EN standards.”

Related categories:  Energy Conservation   Legislation and regulations 

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