Smart Ventilation Control of Indoor Humidity in High Performance Homes in Humid U.S. Climates

Elevated indoor humidity levels in homes represent a risk to occupant thermal comfort and health, as well as building durability. The improved thermal properties of high performance homes lead to less cooling system run time and associated moisture removal. High performance homes often have elevated indoor humidity, as a result. Current technologies for addressing this high humidity include dehumidifiers, energy recovery ventilators and enhanced cooling strategies. A strategy that has not been assessed to-date is the smart control of ventilation systems to better manage indoor moisture and reduce humidity loads. Such smart controls time-shift ventilation to reduce the duration and number of hours of high indoor humidity, while providing annual pollutant exposure equivalent to a continuously operated fan sized to ASHRAE Standard 62.2-2013. The REGCAP simulation tool was used to assess 13 smart ventilation control strategies. Elevated indoor humidity was mostly problematic only in smaller homes with higher moisture gains. The best controls were able to achieve significant reductions in indoor humidity without excessive energy penalties (e.g., 16% of annual hours reduced below 60% RH in a small Miami home, using 277 kWh annually). They also maintained equivalent air quality to a continuous 62.2-2013 fan. In the cases with highest indoor humidity, smart ventilation controls did not eliminate the need for supplemental dehumidification, with 20 to 25% of annual hours remaining >60% RH.