(1) Except as provided in Sentence (2), heat recovery ventilators with rated capacities of not less than 25 L/s and not more than 200 L/s shall be installed in accordance with Article 9.32.3.11.
(2) Where electric space heating, other than forced-air electric heating system, is provided in buildings of residential occupancy within the scope of Part 9, the mechanical ventilation system shall include heat recovery ventilators designed to provide a minimum 55% sensible heat recovery efficiency when tested to the low temperature thermal and ventilation performance test method set out in CAN/CSA-C439, “Rating the Performance of Heat/Energy-Recovery Ventilators”, at a Station 1 test temperature of -25°C at an air flow not less than 30 L/s.