extra insulation???

[matholme]

I am having my dormer re-roofed and re-clad (well a builder is doing it). The plan was to strip the felt back to the weather board then lay butyl membrane. Strip off the rotting cladding to the weather board and replace with western red cedar. I am pretty sure the weather board is sound as we have had no damp or leaks on the inside. I am now thinking of upgrading the insulation, I think we have about 4 – 6” of glass fibre. To strip off the weatherboard and replace the glass fibre insulation with kingspan and reboard will add about 1500 pounds to the bill.

The dormer is 4.25m long by 3m deep.

Snow on the roof does not thaw much quicker than other parts of the roof which are insulated.

It tends to get hot in the summer, but we have large patio doors which get direct sunlight. It use to get cold in the winter until we put in heating. I have also insulated the non lived in pitched roofed attic space which previously had no insulation.

I am wondering if it is worth the expense to upgrade the insulation in the dormer?

Any comments welcome.

[JohnD]

If the old board is showing signs of age, it could be worth re-doing it, but on insulation energy-saving grounds alone, I don't think there is an economic advantage. I haven't got my tables for heat losss to hand, but I doubt you lose as much as £50 worth of heat through that little dormer area in a year, as it is already insulated, so to get your extra £1600 back in saved energy could take you 32 years... You might do better to invest it in Centrica or BG shares.

http://www.moneyextra.com/stocks/LSE/BG.
http://www.moneyextra.com/stocks/LSE/CNA

[chappers]

Someones extracting the urine mate £1500 extra to replace that roof deck.
Materials £300 tops and thats being very generous probably be able to reuse the roof deck anyway. Work would take 2 men a day tops and thats being very generous too. Thats £600 each a day when they are on site
already working .