Features: Features a powerful 77 CFM blower, specifically designed for continuous use application Retains heat from the exhausted stale indoor air to temper incoming fresh air for an energy efficient whole house solution Heat recovery core reduces utility bills by capturing energy in exhausted air to heat incoming air Integrated balancing dampers and pressure taps automatically calibrate and balance air flow Includes port straps and hooks providing a simple and flexible installation experience Sealed bearings motor is totally enclosed and maintenance free for a product that will last for years of use Equipped with side ports for horizontal ventilation Covered under a 5 year parts and a limited lifetime Heat Recover Core manufacturer warranty Energy Star qualified and HVI certified Specifications: CFM: 37, 77 Length: 19.8125" Width: 15.625" Height: 16.3125" Duct Size: 4" Round Amperage: 0.5 Wattage: 60 Voltage: 120 Hardwired: No Filter Type: Washable Foam Filters HVI Certified: YesProduct Variations: HRV80S (This Model): 77 CFM Heat Recovery Ventilator with Side Ports HRV80T: 77 CFM Heat Recovery Ventilator with Top Ports