Also worth to look at this case to answer your main question: HMRC v Wetheralds Construction – The reduced rate for energy-saving materials
This case concerned the classification for VAT purposes of a product offered by Wetheralds which is designed for conservatory insulation. The FTT agreed with Wetheralds on its assertion that the supply being made was a single supply of the installation of energy saving materials and therefore attracted the reduced rate of 5%. HMRC disputed this decision, claiming that the installation amounted to more than energy saving materials and should be regarded as a supply of a new roof as new tiles were put down, meaning the supply was standard rated as more than merely insulating material was supplied. The case was referred to the Upper Tribunal (UT).
The UT concluded that the FTT had failed to consider, in enough detail, the extent to which the supply was a roof rather than an addition of energy saving materials to the pre-existing roof UT found that the supply of a roof system did not fall within the reduced rate provisions of VATA 1994 Sch 7A Group 2 and concluded that a replacement roof is not an energy saving material, it is a roof and thus the supply should have been standard rated.