Dave Rowell wrote:
We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25 to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks, Dave

This sounds very expensive
I have just had 70 mm Kingspan tp10 for 19.99+VAT for a sheet 1200*2400
( althougt I think £23.00 + VAT is nearer the mark.

What I think has probably happened was that your builder went to
sheffield insulations and has quoted retail price which is £46.00+VAT
per sheet. He will get 50% discount on this

Ring Minster Insulations for a proper price for the area you need

HTH Phil