Cheaper insulation for flat roof than Celotex/Kingspan

What Polystyrene brands are there? Thanks

I forgot what the handyman said.

Problem with polystyrene is it doesn't give you the same insulation value. Typically, where yolu might use 150mm of Celotex, you would need 250 or 300mm polystyrene to comply. Does that still work for you?

Yes it would be fine I doesn't require the waterproofing properties for it. How much is it typically, what names should I look for?

Thanks

Polystyrene is polystyrene and is much of a muchness. Look to be buying 8x4 sheets from builders merchants for the best value. I believe selco are selling them on special this month. They also do xtratherm, another foil backed board which is slightly cheaper than the brands you mention.

Polystyrene is waterproof foil or not. Ever bought a hot drink from a burger van?

Look for Jablite.

Polystyrene is not a practical flat roof solution, particularly not for a warm deck application.

You could see what these guys have in stock: http://www.secondsandco.co.uk/page_offers/index.html

No connection etc.
HTH,
Bri.

@ Jed's comment.

When new. PIR is 60% more effective than polystyrene, however I have recently read in a couple of different places that after 7 or so years it loses this extra efficiency.

This happens because most of the extra insulating effect comes from the gas that is enclosed in the (closed) cells of the material and this slowly leaks away. Polystyrene is an open-cell material and never has this advantage to start with.

There are apparently attempts underway to re-classify insulating materials in their "aged' or stable state, so that would presumably be a major blow to the PIR and PUR manufactirers as the R values for glass-fibre, polystyrene and PIR would alll be rather similar but with huge price differences.

I'm not a chemist and I am repeating what I have seen elsewhere, albeit in serious publications - hope I'm not spreading nonsense.