"Dave" wrote in message
...
I am renovating a room with a concrete ceiling. Previous ceiling (wood
paneling)
had been removed. The concrete ceiling is a bit uneven and requires
smoothing
which I'd rather not do.

I am thinking of paneling the ceiling with styrofoam sheet about two
inches
thick. I 've got some good quality styrofoam (smooth - not grainy) I coul
just
glue there.

My question is about the lights. I haven't yet selected any lights but
other
rooms have recessed halogens lights eyebulb style.

Halogens tend to get hot and styrofoam could melt . How much room should I
cut
for the 50w lights? (a ball park estimate)

Not a good idea. Styrofoam is a very good insulation, it is made of a flame
retarding material, but, according to building code it must be covered with
something like drywall. It is not allowed to be exposed. Personally, I'd
not use recessed lighting in foam as the light will get very hot, the
insulation will trap the heat and probably melt.