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Energy Use Consequences of Ventilating a Net-Zero Energy House

Published

Author(s)

Lisa C. Ng, William V. Payne

Abstract

A Net-Zero Energy Residential Test Facility (NZERTF) has been constructed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to demonstrate that a home similar in size, aesthetics, and amenities to those in the surrounding communities can achieve net-zero energy use over the course of a year while meeting the average electricity and water use of a family of four in the United States. The facility incorporates renewable energy and energy efficient technologies, including an air-to-air heat pump system, a solar photovoltaic system, a solar thermal domestic hot water system, and a heat recovery ventilation system sized to meet American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) Standard 62.2-2010 ventilation requirements. The top energy end use within the home was space conditioning, which included heat loss through the building envelope, ventilation air supplied by the heat recovery ventilator (HRV), and internal loads. While it is often touted that an HRV is able to save energy when compared to ventilating without heat recovery, there have been no HRV studies using a full year of measured data that determine the thermal load and energy impact of ventilation to the central heating and cooling system. Over the course of a year, continuous operation of the HRV at the NZERTF resulted in an average annual savings of 7 % in heat pump energy use compared with ventilating without heat recovery. The heat pump electrical use varied from an increase of 5 % in the cooling months to 36 % savings in the heating months. The increase in the cooling months was due to times when the outdoor temperature was lower than the indoor temperature, and for which the availability of an economizer mode would have been beneficial. Nevertheless, the heat pump energy saved using an HRV compared with ventilation without heat recovery was offset by the additional fan energy required to operate the HRV at the NZERTF. This paper descr
Citation
Applied Thermal Engineering
Volume
96

Keywords

air-to-air heat pump, heat recovery ventilator, net-zero energy buildings, ventilation energy use
Created December 2, 2015, Updated February 19, 2017