Hear Recovery, IAQ, Residential
Heating and cooling for residential buildings consumes a lot of energy in the United States every year, which leads to Energy Recovery Ventilator (ERV) systems becoming more common for residential applications. An ERV is a relatively simple air to air heat exchanger with supply and exhaust fans. The supply fan pulls outdoor air into the house while the exhaust fan pulls stale air from the house. The ERV preheats outside air during cold weather and cools/dehumidifies outside air during warm weather. These systems are a good investment because they typically achieve a simple payback of 2 years or less based on energy savings. Â ERVâ€™s also have an important role for Indoor Air Quality (IAQ) in modern energy efficient homes that are carefully sealed to minimize the infiltration. One challenge is determining an optimal strategy for when to turn on the fans for the ERV.Â Unnecessary run time wastes energy by running equipment when it is not necessarily needed for IAQ. This paper explores a demand controlled ventilation strategy that has been deployed in a net zero energy home which was designed and built by Purdue University for the 2011 Solar Decathlon.Â The control strategy only runs the ERV when direct measurements for IAQ indicate that fresh outside air is needed. CO2, VOC, and relative humidity levels are monitored in the home on a continuous basis. When any of these measurements rise above a specified threshold, the heat recovery system turns on and continues to run until the IAQ levels return to healthy levels. This paper summarizes the results of several years of demand controlled ERV performance in terms of IAQ and energy savings. The results clearly show that this optimized control strategy should be considered in more ERV installations.