- Author
-
Wallace, L. A.
|
Emmerich, S. J.
|
Howard-Reed, C.
- Title
- Continuous Measurements of Air Change Rates in an Occupied House for 1 Year: The Effect of Temperature, Wind, Fans and Windows.
- Coporate
- US EPA, Reston, VA
National Institute of Standards and Technology, Gaithersburg, MD
- Journal
-
Journal of Exposure Analysis and Environmental Epidemiology,
Vol. 12,
No. 4,
296-306,
July 2002
- Keywords
-
residential buildings
|
indoor air quality
|
temperature effects
|
wind effects
|
fans
|
windows
|
infiltration
|
tracer gas
|
ventilation
|
air change rates
|
quality control
|
meteorology
|
statistics
|
wind direction
|
wind velocity
|
regression rate
|
floors
- Identifiers
- comparison with Dulles Airport; differences by floor level; effect of opening the windows; comparison of meteorology measurements at Reston house versus Dulles Airport; air change rate percentiles; monthly variation of indoor and outdoor temperatures and the absolute indoor-outdoor difference; monthly variation of indoor and outdoor RH and the absolute indoor-outdoor difference; monthly wind speeds measured at rooftop level; diurnal wind speeds averaged over 1 year; distribution of logarithms of air change rates over the year; monthly air change rates by floor; regression of air change rate on absolute indoor-outdoor temperature difference - overnight values; regression of air change rate on absolute indoor-outdoor temperature difference
- Abstract
- A year-long investigation of air change rates in an occupied house was undertaken to establish the effects of temperature, wind velocity, use of exhaust fans, and window-opening behavior. Air change rates were calculated by periodically injecting a tracer gas (SF6) into the return air duct and measuring the concentration in 10 indoor locations sequentially every minute by a gas chromatograph equipped with an electron capture detector. Temperatures were also measured outdoors and in the 10 indoor locations. Relative humidity (RH) was measured outdoors and in five indoor locations every 5 min. Wind speed and direction in the horizontal plane were measured using a portable meteorological station mounted on the rooftop. Use of the thermostat-controlled attic fan was recorded automatically. Indoor temperatures increased from 21°C in winter to 27°C in summer. Indoor RH increased from 20% to 70% in the same time period. Windows were open only a few percent of the time in winter but more than half the time in summer. About 4600 hour-long average air change rates were calculated from the measured tracer gas decay rates. The mean (SD) rate was 0.65 (0.56) h-1. Tracer gas decay rates in different rooms were very similar, ranging only from 0.62 to 0.67 h-1, suggesting that conditions were well mixed throughout the year. The strongest influence on air change rates was opening windows, which could increase the rate to as much as 2 h-1 for extended periods, and up to 3 h-1 for short periods of a few hours. The use of the attic fan also increased air change rates by amounts up to 1 h-1. Use of the furnace fan had no effect on air change rates. Although a clear effect of indoor-outdoor temperature difference could be discerned, its magnitude was relatively small, with a very large temperature difference of 30°C (54°F) accounting for an increase in the air change rate of about 0.6 h-1. Wind speed and direction were found to have very little influence on air change rates at this house.