A number of multi foil insulation manufacturers have claimed in their literature that multi foil archives an R value of 5 under 'real world conditions' and can be compared to 200 mm of mineral wool.

The Advertising Standards Agency (ASA) have taken this claim to task and found against any multifoil insulation company making such claims. In a recent Adjudication ASA found against multi foil and concluded that the R value was in fact in the region of 1.6 to 1.8 or at best conferring a U value of just 0.55, well outside Building Regulations for U values!

It was interesting that the ASA Adjudication report delved into the the 'real world' testing that had been done with multi foil and found that the testing had in fact been designed without plasterboard and without a roof membrane, that the joints of the foil insulation had been taped but not the joins of the mineral wool. In other words, maximum air leakage was possible with the mineral wool both from above and below. Since air movement and air leaks are a big source of thermal heat loss no wonder the multi foil compared favorable and o par with mineral wool at a depth of 200 mm. But this is hardly 'real world' testing as the manufacturers had claimed.

The bottom line is that ASA found against the publicity literature where multi foil manufactures claim R = 5 and they must withdraw all literature making this claim and not publicise this false claim.

This comes on top of the fact that Building Control will no only accept multi fol as best case  R = 1.8 which on its own is hopelessly outside Building Regulations for thermal U values being only of the order on 0.55 U value.

Bottom line? Industry professionals, the Foam Industry, the mineral wool industry, Local Building Control and now ASA do not accept the multi foil industry claims for insulation values.

You can download the ASA adjudication report here.