[_1miket]

Are insulated recess housings required on the first floor of a two story residence if the first floor ceiling is not insulated?

[tkrussell]

Generally, no. A standard non- IC can should be allowed.

You do need to check local codes as some may want fire proofing done, or use air tight housings to prevent loss of heat or cooling.

[tkrussell]

Thought I should mention, most of the rules for recess lighting does not come from the NEC.

It comes mostly from building codes, others come from State Energy codes, and UL Listings.