IRC R304.1 Required Heating. When the winter design temperature in table R301.2(1) is below 60F every dwelling unit shall be provided with heating facilities capable of maintain a minimum room temp of 68F at a point 3 feet above the floor and 2 feet from exterior walls in all habitable rooms at the design temperature. The installation of one or more portable space heaters shall not be used to achieve compliance with this section.

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