ASHRAE OR-16-C040

Abstract

<em>A 2715 ft² (252 m²), two story, residential home of the style typical of the Gaithersburg, Maryland area was constructed in 2012 to illustrate technologies employed to produce a net-zero energy (NZE) home (or ZEH). It functions as a laboratory to support the development and adoption of costeffective NZE designs, technologies, construction methods, and building codes. The primary design goal was to meet the comfort and functional needs of the simulated occupants. The first annual test period began on July 1, 2013 and ended June 30, 2014. During the first year of operation, the home&#8217;s annual energy consumption was 13039 kWh (4.8 kWh ft², 51.7 kWh m²), and the 10.2 kW solar photovoltaic system generated an excess of 484 kWh. During this period the heating and air conditioning of the home was performed by a novel air-source heat pump that utilized a reheat heat exchanger to allow hot compressor discharge gas to reheat the supply air during a dedicated dehumidification mode. During dedicated dehumidification, room-neutral temperature air was supplied to the living space until the relative humidity setpoint of 50% was satisfied. The heat pump consumed a total of 6225 kWh (2.3 kWh ft² , 24.7 kWh m^-²) of electrical energy for cooling, heating, and dehumidification. Annual cooling efficiency was 10.1 Btu W- 1h-1 (2.95 W W¹); the rated SEER of the heat pump is 15.8 Btu W^-1h^-1 (4.63 W W^-1). Annual heating efficiency was 7.10 Btu W^-1h^-1 (2.09 W W^-1); the unit&#8217;s rated HSPF is 9.05 Btu W^-1h^-1 (2.65 W W^-1). These field measured efficiency numbers include dedicated dehumidification operation and standby energy use for the year. Annual sensible heat ratio was approximately 70%. Standby energy consumption was 5.2% and 3.5% of the total electrical energy used for cooling and heating, respectively.</em>