N.J. Admin. Code § 5:10-14.4 : COMMUNITY AFFAIRS — MAINTENANCE OF HOTELS AND MULTIPLE DWELLINGS — HEATING —14.4 - Minimum temperature

(a) From October 1 of each year to the next succeeding May 1, every unit of dwelling space and every habitable room therein shall be maintained at a temperature of at least 68 degrees Fahrenheit between the hours of 6:00 A.M. and 11:00 P.M. and at least 65 degrees Fahrenheit between the hours of 11:00 P.M. and 6:00 A.M. The heating system shall be capable of maintaining the minimum required temperature in all habitable rooms without the necessity of heating adjoining rooms more than five degrees higher than said minimum required temperature. The design of the heating system shall conform to the ASHRAE Guide and Data Book. The heating standard herein set forth may be modified by the Commissioner by emergency rule.
(b) In meeting the aforesaid standards, the owner shall not be responsible for heat loss and the consequent drop in the interior temperature arising out of action by the occupants in leaving windows or doors open to the exterior of the building.
(c) The owner shall be obligated to supply required fuel or energy and maintain the heating system in good operating condition so that it can supply heat as required herein, notwithstanding any contractual provision seeking to delegate or shift responsibility to the occupant or third person, except that the owner shall not be required to supply fuel or energy for heating purposes to any unit where the occupant thereof agrees in writing to supply heat to his own unit of dwelling space and the said unit is served by its own exclusive heating equipment for which the source of heat can be separately computed and billed.

N.J. Admin. Code § 5:10-14.4