Jon12345

My heating bills are high, but it is difficult to get a 15 year payback. This is the issue I am facing. I will write to Building Control and hope they reply!

Sorry, bit confused what you mean by your first couple of sentences.

Does Building Control not have to follow the 15 year payback rules, and so if it was going to be too costly for the gain then they give you a pass?

There is no insulation at sloping rafter level. The is only some insulation at the ceiling joist level, around the edges, because most of the attic has floorboards (except the edges). Joist depth is 22cm. I am thinking the cost to remove the carpets and floorboards in the attic to put thinner insulation may not meet the 15 year payback rule? If I use loft legs, then it will reduce the usability of the attic due to the sloping ceilings. Isn't there a building regs rule against reducing usability? The rafters are 11.8cm deep. Some I could wedge in insulation, but the main room in the attic does not have rafters visible because there are boards over them and painted. So they have sarking boards one side, and other board the other side. Removing them to put thin insulation in might not meet the 15 year payback rule? What do you think?

1907 detached house, High Weald AONB, EPC Band G. Stripping front and right roof slopes (over 50%), so Part L triggered. Sarking boards, 115mm rafters, bitumen underfelt. First-floor bedrooms have sloping ceilings. Attic above has no fixed heating, ladder access only. NFRC contractor has quoted £9,652 + VAT for between-rafter insulation as a separate line item. On a G-rated house with uninsulated cavity walls, I estimate the annual saving at £75–200 — giving a payback of 48–154 years, well beyond the 15-year test in para 5.9. Three questions: If the attic has no fixed heating, is the roof above it NOT a thermal element — making the attic floor the relevant element instead? Has anyone successfully used the 15-year payback argument with Building Control on an older property? Above-rafter insulation would raise the roof height in an AONB, needing uncertain planning permission. Is that "not technically feasible" under para 5.9? Thanks, Jon