KR> what kind of foam to use in kr2 buiding

[E.D]

Hi,

I would like to know what kind of foam to use in kr2 building
uréthane,styrène,polystyrène or polyuréthane ???? and what density
I know the foam must not be cut by hot wire because about  production 
of  toxic gas  (cyanidrique gas)
Some people can tell me what ref.. of  foam i must to buy from  aircraft 
spruce.
Thanks.
Eric Dewet.