How to achieve 0.2 u-value cheaply?

[ipoppy]

Hi,
I am trying to find the best insulation in terms of price for my pitched roof (vented, 600mm between rafters and 190mm depth). It need to be done as per regulations with u-value of 0.2. I have found with this calculator that I need thickness at least of 150mm of Celotex insulation which will be very expensive since I need 100m2 of it. Don't know about Kingspan; can't find their calculator. Unfortunately reflective foil over rafters won't be accepted by local building standards Officer.
So what my options to keep u-value and use cheaper insulation then?

Thanks

 

[freddiemercurystwin]

There is no magic solution, if there was a cheap way to achieve it everyone (well, with a brain/conscience) would do it. I've found that Kingspan is usually the preferred choice by builders as it seems to be a bit cheaper than Celotex, you'll likely need a very similar thickness. Phone up their technical advice line and they'll tell you there and then.

 

[r896neo]

the only cheaper option is to hang some 6 x 2 or similar from the rafters which will give you more depth, then you will be able to get away with rolls. It is a lot of extra work and not worth your time if being paid but is a fav with the self builder who has cheap/ free hours to devote.

Of course it has its obvious draw backs too and by the time you buy the timber it does work out cheaper usually but not by much..

 

[ipoppy]

Thanks all for replies. I think I will stick to normal Kingspan pitched roof insulation. However to achieve my u-value I will need certain thickness and every mm counts.
Is there any online Kingspan calculator to check which type and thickness I should use to get 0.2 u-value?

Thanks

 

[freddiemercurystwin]

As mentioned previously phone them up: http://www.insulation.kingspan.com/uk/services04.htm Online calculators are not 100% accurate and as every mm counts as you put it, phoning them up is the best way of getting a very accurate result without calculating it yourself. They'll work it out there and then and tell you exactly which type to use.