Thermal designs and operations for new residential buildings for which building permits are obtained after March 15, 1979, must at a minimum take into account exterior envelope physical characteristics, HVAC system selection and configuration, HVAC equipment performance, and service water heating design and equipment selection and are not required to meet standards more stringent than the provisions of the Florida Building Code-Energy Conservation. HVAC equipment mounted in an attic or a garage is not required to have supplemental insulation in addition to that installed by the manufacturer. All new residential buildings, except those herein exempted, must have insulation in ceilings rated at R-19 or more, space permitting. Thermal efficiency standards do not apply to a building of less than 1,000 square feet which is not primarily used as a principal residence and which is constructed and owned by a natural person for hunting or similar recreational purposes; however, such person may not build more than one exempt building in any 12-month period.