Part L payback test on 1907 roof repair in AONB — anyone been through this?

[Jon12345]

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:

1. If the attic has no fixed heating, is the roof above it NOT a thermal element — making the attic floor the relevant element instead?
2. Has anyone successfully used the 15-year payback argument with Building Control on an older property?
3. 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

[Mr Punter]

From your description I cannot work out how much of the upper floor has insulation at sloping rafter level and how much is at ceiling joist level.

 

The ceiling joist insulation is simple with extra loft roll.  You may need to use loft legs if your are storing crap stuff up there.

 

If you can insulate the sloping parts, so much the better.  BC may take a fairly pragmatic approach, especially if you would need to trash ceilings etc.

[Roger440]

6 hours ago, Mr Punter said:

BC may take a fairly pragmatic approach, especially if you would need to trash ceilings etc.

 

Or they may not as has occured with others in this exact same postion.

 

Very interested to see how the OP's job pans out with BC.

[Roger440]

7 hours ago, Jon12345 said:

 

1. If the attic has no fixed heating, is the roof above it NOT a thermal element — making the attic floor the relevant element instead?

 

But the slopey bit IS as the room is the otherside of the plasterboard. If im understanding your layout/build up correctly, ie pretty conventional?

 

Which would mean you only have 115mm to work with. Better than my 75mm though!