currently considered options for an extension on our house. Anyone got any experience with this system? positive or negative?

Are you anywhere near London? Nudura and other ICF suppliers will be at Ecobuild 8-10 March, might be worth popping in to see what they say for themselves.

For more info on ICF in general see http://www.concretecentre.com/pdf/publicationlibrary/mb_insulatingconcreteformwork2012.pdf

no but we have a nudura dealer a couple of miles away. he’s been to look at the site and give us some advice.

Anyone else?

What are your reasons for using it?
Personally I’m not keen and wouldn’t specify it – I don’t like the use of EPS, the amount of on-site concrete and potential for that to go wrong, the solid-wall construction that you potentially end up with etc.