Here is the code I was looking for: In the 2017 NYS Supplement:
AJ604.3 Automatic Sprinkler Systems
A habitable attic may be created in an existing attic located above the second or third story above grade plane without requiring the installation of a sprinkler system throughout the entire dwelling, provided all of the following conditions are met:
- The building was legally occupied before January 1, 1984.
- The habitable attic and its means of egress to the exterior are equipped with a limited area sprinkler system installed in accordance with NFPA 13D.
- The habitable attic is provided with:
- A second exit stair meeting the requirements of Section R311.7, or
- An emergency escape and rescue opening, meeting the requirements of Section R310, located directly above a roof or other structural appurtenance from which access to grade does not exceed a vertical distance of 14 feet.
- The entire dwelling is equipped with smoke alarms in compliance with Section R314 and monitored by an approved supervising station in accordance with NFPA 72.