celotex 165mm substitute

[dcscoot]

Hello
I am currently buiding an extension and on my plans it is stated to use 165mm celotex between the single storey roof spars, can anyone suggest a cheaper option but still acheiving the required U value

Thanks in advance
D

 

[htgeng]

Hello
I am currently buiding an extension and on my plans it is stated to use 165mm celotex between the single storey roof spars, can anyone suggest a cheaper option but still acheiving the required U value

Thanks in advance
D

Around a metre of rockwool?
Ok ok you did say cheaper but didnt mention anything about the thickness
What is it, around £45 for an 8x4 sheet?

 

[SurreyRoofingEstimator]

Am assuming this is a pitched roof.

The only other way would be lots of loft quilt or a combination that and and PUR (Celotex) though as you have it between rafters this points towards a sloping ceiling situation so sound like you're stuck with the specified system (ps Celotex and similar are all about the same rate, shopping around would be your best bet)

 

[freddiemercurystwin]

Why do you need 165mm for an extension roof? That seems excessive! Assuming your rafters are at 600 centres and you have the plasterboard at rafter level: you could reduce the overall thickness by having a layer between the rafters and then a continuous layer beneath the rafters. Obviously having a tick layer beneath the rafters means longer fixings and it being more fiddly, take slightly longer and the fixings will cost more however it may be worth investigating though. A quick stab on the Celotex U Value Calculator and to achieve a U Value of 0.18 you could get away with 50mm between the rafters and a continuous layer of 70mm beneath so overall 120mm.

 

[^woody^]

Wow ... 165mm Celotex?

Your designer must be on some sort of crusade to save the planet all on his own.

In fact, I will ask building control on my next extension if I can offset heat losses with the savings you make on your extension