Perfect Window™ Fresh Air Energy Recovery Ventilation Systems Energy Recovery Ventilators provide proper levels of ventilation with energy savings by transferring heat and moisture between the exhaust and fresh air streams. Includes heat/energy transfer core, pre-filters, and fan and blower assembly. Provides ventilation that helps contractors meet ASHRAE 62-89. Electronic ventilation fan timer option. Low voltage, high-speed override. Variable fan speed control. Easy-to-clean with a vacuum, cross-flow enthalpic core assures years of trouble-free operation. Insulated cabinet. Rugged steel cabinet. Quiet operation. Permanent (washable) pre-filters. Integral balancing dampers. Includes vibration isolation hardware and duct collars.