Hi,

I live in a 1930s semi which has a void underneath the living room
that is about 6 foot deep. Although the wooden floor is carpeted,
would it help to insulate underneath the floor with something like
celotex between the joists? If so, do I need to leave a gap between
it and the floor and/or put any membrane layer somewhere? The void has
a concrete floor that has always been bone dry.

Grateful for any advice as to me the living room does not seem to heat
up to well.

TIA