Thermal element upgrade requirements for major renovations

Where an individual thermal element is being renovated through undertaking an activity listed in paragraph 3.57, and the renovation – (a) constitutes a major renovation; or (b) is greater than 50% of the surface of the individual thermal element; the whole of that thermal element should be upgraded to the improved U-value given in column (b) of Table 3.3. When assessing this area proportion, the area of the element should be taken as that of the individual element, not the area of all the elements of that type in the building. The area of each individual thermal element should be taken in the context of whether the element is being renovated from inside or outside. For example, if the renovation involves stripping plaster from the inside of a solid brick wall, the area of the element is the area of the external wall in that room; however, if the renovation is stripping external render the area is the area of the elevation of which that wall is part. This means that if all the roofing on the pitched roof of an annex to a dwelling is being stripped down, the area of the element is the roof area of the annex, not the total roof area of the dwelling. Similarly, if the rear wall of a single storey extension was being re-rendered, it should be upgraded to the standards of Table 3.3 column (b), even if it was less than 50% of the total area of the building elevation when viewed from the rear. If plaster is being removed from a bedroom wall, the relevant area is the area of the external wall in the room, not the area of the external elevation which contains that wall section. This is because the marginal cost of dry lining with insulated plasterboard rather than plain plasterboard is small. When a building undergoes a major renovation this may represent an opportunity to consider and take into account the technical, environmental and economic feasibility of installing high-efficiency alternative systems.