The government will issue fresh guidance on insulation after a successful judicial review brought by a product supplier.

Actis, which makes thermo-reflective insulation products, obtained the ruling from the High Court after it complained that the communities department had failed to consult properly over a testing method that discriminated against its “multifoil insulation” product.

Mr Justice Charles, the judge at the hearing, said of the guidance, known as BR 443, that “a fair procedure was not followed in making the revision”.

He ruled that the use of BR 443 to test multifoils would be unenforceable until the proper procedures had been complied with. He also instructed the government to circulate guidance on multifoil insulation and an explanation of the judgment to building control officers.

Actis said its market share had been damaged after changes to rules on performance testing last year when the communities department wrote to building control bodies saying they should only accept results from a test called the “hotbox”.

A fair and appropriate procedure was not followed on BR 443

Mr Justice Charles

Actis said its products suffered as the test favoured conventional insulation products, and that conventional insulation manufacturers had been involved in the consultation.

It added that although the communities department had offered multifoil manufacturers a period of grace to develop their products to meet European standards, during which BR 443 would not apply, the communities department then withdrew this concession without explanation.

The communities department will now write to building control bodies advising them on how insulation can comply with the Building Regulations.