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

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.

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.