Practical applications and case study of temperature-based smart ventilation controls

Smart ventilation controls (SVCs) provide energy and indoor air quality (IAQ) advantages through dynamic real-time control of mechanical ventilation rates. Section 4.6 of ASHRAE Standard 62.2-2013 allows for alternative SVC strategies if equivalent annual pollutant exposure is provided. This paper presents results from U.S. Department of Energy (DOE) Building America program stakeholder collaborations on temperature-based smart ventilation control (TSVC) as one potential option. Unlike the “continuous” ventilation typically implemented to comply with ASHRAE Standard 62.2-2013, temperature-based ventilation controls take advantage of the dynamics of stack infiltration, which varies with weather, house height, and envelope leakage. The TSVC strategy turns off mechanical ventilation at times of large temperature difference and moves ventilation to periods with smaller temperature differences. To ensure equivalent annual pollutant exposure, mechanical airflow rates must be increased for temperature-based systems. In this paper, we compare the energy and IAQ performance of a TSVC that shuts the fan off at a specified single cutoff temperature to a continuously operated ventilation system fan that is sized to comply with ASHRAE Standard 62.2-2013. This paper presents simulation analysis results using two simulation tools: 1) REGCAP and its advanced ventilation model for detraining ventilation TSVC equivalency, 2) a new beta version of EnergyGauge^® USA for estimating energy savings. Relative humidity (RH) and carbon dioxide (CO₂) concentrations were monitored in two occupied case study homes in cold and marine climates involving weekly “flip flop” tests between continuous and single temperature cutoff control scenarios. Preliminary investigations of market costs and modeled energy savings suggest simple paybacks of 4–11 years from TSVCs for these case study homes.