ic rated can lights

[infinity]

OP was not asking about insulation just tight to the structure.

Now I've got it.

 

[Team-MEI]

Non-Type IC (1⁄2 in.) from combustible materials AND Thermal insulation shall not be installed above a recessed luminaire or within 75 mm (3 in.) of the
recessed luminaire?s enclosure

2008-NEC
410.116 Clearance and Installation.
(A) Clearance.
(1) Non-Type IC. A recessed luminaire that is not identified
for contact with insulation shall have all recessed parts
spaced not less than 13 mm (1⁄2 in.) from combustible materials.
The points of support and the trim finishing off
the opening in the ceiling or wall surface shall be permitted
to be in contact with combustible materials.
(2) Type IC. A recessed luminaire that is identified for
contact with insulation, Type IC, shall be permitted to be in
contact with combustible materials at recessed parts, points
of support, and portions passing through or finishing off the
opening in the building structure.
(B) Installation. Thermal insulation shall not be installed
above a recessed luminaire or within 75 mm (3 in.) of the
recessed luminaire?s enclosure, wiring compartment, or
ballast unless it is identified for contact with insulation,
Type IC.