Retrofit Heat-Recovery Ventilation for an Office Building with Exhaust Heat Recovery

Abstract

This study evaluated a retrofit heat recovery ventilation (HRV) system for a 70,000 ft², seven-story office building to reduce ventilation-related heating energy, improve indoor air quality (IAQ), and integrate with existing HVAC controls while minimizing disruption. A compact plate-type HRV with CO₂-based demand controls was selected. Phased installation and commissioning included test and balance procedures, control interlocks with the rooftop unit, and staff training. Twelve-month monitoring with 15-minute logging of energy and IAQ metrics showed a mean sensible heat-exchanger effectiveness of 72%, an 18% annual reduction in ventilation-related space-heating energy, and a reduction in occupied-hour CO₂ peak concentrations from values exceeding 1,200 ppm to sustained levels below 950 ppm. Integrated controls prevented overventilation and maintained occupant comfort. The estimated simple payback period ranged from 5 to 7 years. The retrofit demonstrated that a compact, well-commissioned HRV with demand control delivered measurable energy, IAQ, and operational benefits for midrise office buildings. Key Terms: Demand controlled ventilation (CO2 based), Retrofit commissioning, Sensible heat exchanger effectiveness, Ventilation related energy savings.