Infiltration and Ventilation in a Very Tight, High Performance Home

The Net Zero Energy Residential Test Facility (NZERTF) was constructed at the National Institute of Standards and Technology (NIST) to support the development and adoption of cost-effective net zero energy designs and technologies. Key design objectives included providing occupant health and comfort through adequate ventilation and reduced indoor contaminant sources. The 250 m2 two-story, unoccupied NZERTF was completed in 2012 with the following design goals: meeting the comfort and functional needs of the occupants; siting to maximize renewable energy potential; establishing an airtight and highly insulated building enclosure designed for water and moisture control; providing controlled mechanical ventilation; and installing highly efficient mechanical equipment, lighting and appliances. The NZERTF achieved its goal of generating more energy than it consumed during its first year of simulated occupancy by a single family, despite a severe winter at the building site. The airtightness goal was achieved through detailed envelope design, careful construction, and during- and post-construction commissioning techniques. The NZERTF is one of the tightest residential buildings in North America with a whole building pressurization test result of roughly 0.6 h-1 at 50 Pa. The ventilation goals were met with a heat recovery ventilator sized to comply with ASHRAE Standard 62.2-2010, which corresponds to roughly 40 L/s or 0.1 h-1 for this building.
This paper describes the design and construction methods used to achieve such a tight building as well as the performance measurements made to verify that the building achieved its airtightness and ventilation goals. Tracer gas measurements of air change rates are reported, as well as multizone airflow model predictions of these same rates for comparison. This study highlights some of the measurement and modelling challenges in very tight buildings.