Super Insulation

[teta]

Any builders out there?.I am looking for a substitute for 120 cm's of insulation in a warm roof.The internal roof height of our extension will be much lower than the kitchen so we are trying to reduce roof thickness.Any super insulation that you have used and would recommend [including space-age ones!]

Are you with british gas for your gas and electric by any chance (could you change to them) if so you could get this done for free.

Yes,we are!.

Celotex 5cm? Thinsulex?

Thank-you Rollmops.Architect has recommmended 120 mm celotex EL 3000 on 9 mm ply on min. of 25 mm firings on c16 145 times 47 mm joists on 100 times 75 mm wall plate plus 12.5 mm plasterboard.Apart from the fact i am not a builder and don't understand all this how do i cut down on the thickness?.We will be going from a kitchen height of 2.8m to an extension height of maybe 2.3!.

I don't understand all your numbers either , but we have celotex and it is good stuff.

120mm Celotex is a bit of overkill, well, unless you live in Lapland or similar. Have a Google on Thinsulex and different thickness of Celotex and see what would suit your needs best.

Our builder swears by Tri Iso Super10 which is 30mm but gives 210mm of insulation- however there can be issues with building regs using it or something.

They discovered our loft was only held up by a couple of nails- so we ended up keeping what insulation was there and spending the cash on strengthening it!

Thread on Tri Iso Super10.

DIYNOT.com is good place to ask your queries, OP.

Thank-you Thandeka that sounds like a real possibility.Rollmops we are also having a big roof lantern so maybe the celotex is to offset the heat loss via the lantern [but the lantern is supposedly the same insulative value of an insulated brick wall]Ragged i'm glad i'm not the only one to find this incredibly complicated.I am just wondering [from my position of total ignorance]if its possible to pack insulation between the joists to save on space, or will it not be a "warm roof" then.

If it's a flat roof - you can probably get away with 70mm of celotex between the joists and then 50mm over the top to give you the warm roof and to reduce thickness of your roof by 70mm.

Sounds like you need to go back and talk to your architect about more ideas if you're unhappy.

Check you can use Tri Iso Super on flat roofs..not sure you can.

You cannot pack ordinary insulation in (the fluffy fibreglass stuff) between the joists, if that's what you meant. Fibreglass insulation becomes an inefficient insulator when compressed. DH is so worried about compression that he has kittens if I put empty cardboard boxes on our fluffy loft insulation. You really need the specialist compressed foam boards, or something meant for narrow spaces.

The only other idea is to increase the height of the whole structure to above the render line [where there is a natural'drip'] and builder will probably have to insert a cavity tray which he doesn't want to do [ and i think we probably will have to!].it also means asking sub- contracted brickies to change plans slightly which they [or incidentally the builder] don't seem to like.Is it always a battle?