Building America Technical Highlight

BUILDING TECHNOLOGIES PROGRAM

ventilator, and DX dehumidifier. Space Key Research Results Evaluation of relative humidity, thermal comfort, Humidity Control and whole-house source energy Achievement consumption were compared for indoor Researchers worked with EnergyPlus Options in Hot-Humid relative humidity set points of 50%, developers to add in moisture capacitance 55%, and 60%. model to analyze the moisture buffering Climate Homes effect. Combined effect of mechanical The study revealed why similar trends ventilation (per ASHRAE 62.2) and of high humidity were observed in infiltration is one of the major culprits of As the Building America program high indoor RH excursions in hot-humid all three homes regardless of energy researches construction of homes climate homes. For the first time, this effect efficiency, and why humidity problems that achieve greater source energy was analyzed accurately to predict humidity are not necessarily unique in the high- level in homes. Whole-house dehumidification savings over typical mid-1990s performance home. Thermal comfort equipment energy penalty was evaluated construction, proper modeling of and summarized at different space RH analysis indicated that occupants are whole-house latent loads and operation control points. unlikely to notice indoor humidity of humidity control equipment has problems. Result become a high priority. Long-term high relative humidity can cause health Confirmed that supplemental The study confirmed that supplemental dehumidification must be provided in a and durability problems in homes, dehumidification is needed to maintain high-performance home in the hot-humid particularly in a hot-humid climate. space relative humidity (RH) below climate to maintain space conditions below 60% in a hot-humid climate home. 60% relative humidity. Energy penalty In this study, researchers at the introduced by the various supplemental Researchers also concluded that while National Renewable Energy dehumidification equipment is sensitive on all the active dehumidification options Laboratory (NREL) used the latest the indoor RH control levels: at an RH set included in the study successfully point of 60%, all explicit dehumidification EnergyPlus tool equipped with the controlled space relative humidity technologies result in similar insignificant moisture capacitance model to analyze excursions, the increase in whole-house increases in source energy consumption the indoor relative humidity in three and thus are equally competitive. energy consumption was much more home types: a Building America sensitive to the humidity set point than high-performance home; a mid- Benefit the chosen technology option. In the 1990s reference home; and a 2006 This research informs homeowners and high-performance home, supplemental International Energy Conservation home builders of house humidity issues dehumidification equipment results in a with and without whole-house Code (IECC)-compliant home in hot- significant source energy consumption dehumidification in the hot-humid climate, humid climate zones. They examined and source energy penalty introduced by penalty at 50% RH set point (12.6%– the impacts of various dehumidification dehumidifiers at different space humidity 22.4%) compared to the consumption equipment and controls on the set points. at 60% RH set point (1.5%–2.7%). At high-performance home where the 50% and 55% RH set points, A/C with Funding Support dehumidification equipment energy use desiccant wheel dehumidifier and This research was sponsored by the U.S. can become a much larger portion of A/C with ERV and high-efficiency Department of Energy’s Building whole-house energy consumption. Technologies Program. DX dehumidifier stand out as the two The research included a number of cases resulting in the smallest increase simulated cases: thermostat reset, of source energy consumption. At For more information A/C with energy recovery ventilator, an RH set point of 60%, all explicit Fang, X., Winkler, J., Christensen, D. (2011) heat exchanger assisted A/C, A/C with dehumidification technologies result in “Using EnergyPlus to Perform Dehumidification condenser reheat, A/C with desiccant similar insignificant increases in source Analysis on Building America Homes.” wheel dehumidifier, A/C with DX energy consumption and thus are HVAC&R Research. Vol. 17(3), 2011. dehumidifier, A/C with energy recovery equally competitive. doi: 10.1080/10789669.2011.564260.

EERE Information Center Prepared by the National Renewable Energy Laboratory 1-877-EERE-INFO (1-877-337-3463) (NREL), a national laboratory of the U.S. Department of www.eere.energy.gov/informationcenter Energy, Office of Energy Efficiency and Renewable Energy; NREL is operated by the Alliance for Sustainable Energy, LLC. Printed with a renewable-source ink on paper containing at least 50% wastepaper, DOE/GO-102011-3235 • December 2011 including 10% post consumer waste. CLEAN CITIES CLEAN