We have loft insulation about 6-8 inches think of the itchy stuff but in a pink bag at the moment. Just aquired a load of B&Q vouchers and noticed they are doing massive discounts on loft insulation. Is there any benefit in putting another layer down or is the money better wasted elsehwere?
Loft insulation - how deep
Based on my latest calcs for my new house:
K Depth mm R
R1 Roof tiles 0.85 20 0.02
R2 Felt 0.50 3 0.01
R3 Insulation 0.044 300 6.82
R4 Pasterboard 0.16 15 0.09
U Value 0.14
roof has a target U value of 0.16
300mm of rockwool just beats the target.
EDIT: Sorry, tables dont work in phorum.
Anyway, 7" gives you a U value of only 0.22
I've 8" (snigger) with some loftboards on top, I think any more than that and you're not going to see a lot of benefit
B&Q have their insulation this cheap every year. They have 15% off if you spend over £50 tomorrow onwards (but they do that quite often too).
suggests going 5cm-25 isn't a huge benefit, so I recon 20-30cm is even less?
I'd waste your money on some spades, and build a nice trail. Or, some loft boards, board it, stick the wife up there and turn the dining room into a bike workshop
Most of it is already floorboarded. Double garage with beer fridge and sauna for work on the bike. I live a gifted life.
keep an eye out on Money saving expert (or Npower) as Npower do a thing of £1 per roll of rockwool insulation.
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