We've been trying to get quotes to install roof insulation in our Victorian pitched-roof building. Technically it's a "Room-in-Roof" installation, although the rooms are not remotely habitable yet. We've calculated that we'd need around 80m3 of insulation. Access is easy.
After a long delay, we finally received a quote for a Green Homes Grant-eligible installation (figures approximate):
Materials ~£9000
Labour ~£500
Sundries ~£1500
Total ~£11000
For comparison, we also had a quote from a non-GHG local installer: ~£2250 for both labour and materials.
Both quotes seem to be for the same coverage - the former for just under 80m3, the latter for ~30no. sheets of 100mm foam insulation.
A very quick search online suggests that 80m3 of 100mm foam insulation on the open market is around £1100 inc. VAT.
My questions are therefore:
Which quote seems to make more sense?
Judging by their vast difference in price, is either quote likely to have missed some crucial factor?
Has anyone had any experiences of receiving GHG-eligible quotes for insulation? If so, have they been hugely inflated?
Thanks for any advice.