ENERGY IMPACTS OF VARIOUS RESIDENTIAL MECHANICAL VENTILATION STRATEGIES

Abstract

The Building America program has been working with home builders for more than a decade using a variety of strategies for bringing fresh air into the homes. Many of these strategies utilize the central air handler fan from the HVAC system to ventilate when the system runs. Controllers can be purchased to force the air to enter for minimum periods of time or to shut off outside air dampers after some period of runtime. EnergyGauge USA, a detailed hourly residential simulation program, has been modified to simulate the various runtime strategies, as well as supply- or exhaust-only ventilation strategies and an enthalpy recovery ventilation system. This paper compares simulation results for each of these ventilation strategies. Runtime ventilation tends to bring in very little extra air. When forced to turn on for 25% of an hour, the typical HVAC fan uses significant energy making the overall energy penalty more than that from a continuous supply or exhaust fan supplying the same nominal air flow. Enthalpy recovery ventilation units tend to use more energy overall - despite the heat recovery - than supply or exhaust only ventilation systems, due to using twice as much fan energy. This paper presents simulation results for eight ventilation strategies compared to no ventilation, and it presents the changes in energy use for each.