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Data To Measure IAQ Is Complex Proposition
December 5, 2012
Today's tip is to understand that measuring IAQ is more complicated than a metric such as energy use. Measuring indoor air quality means amalgamating several different metrics to give a holistic IAQ picture.
"There is not just one measurement that can assess the dynamic relationship between the presence of air contaminants and the ventilation to effectively dilute and remove them," says David Bearg, president of Life Energy Associates. "Instead, assessing the healthfulness of an indoor environment is more a matter of measuring key parameters" such as effective ventilation rates, contaminant levels, absolute humidity, and even occupant satisfaction.
"The most important thing is measuring and maintaining airflow rates and exhaust," says John McFarland, director of operations, Working Buildings, Inc. Luckily, air flow is also the easiest IAQ-related metric to measure and benchmark, says McFarland, who is also the vice chair of the ASHRAE 62.1 committee.
ASHRAE 62.1 is generally thought of as a design standard, but facility managers can use its recommended ventilation rates toward IAQ. Determine the cubic feet per minute (CFM) of airflow per person, then use 62.1 to determine if the current airflow rates meet the minimum requirements for the space occupancy, especially if space functions have changed.
Also, a high percentage of completed preventive maintenance bodes well for good IAQ. It means you're regularly checking filters, examining dampers to make sure they're opening and closing properly, and making sure drain pans aren't full of water. Essentially, you're continuously commissioning your systems to make sure they're behaving as they should.
ASHRAE 62.1 also provides a standard for relative humidity (maximum of 65 percent in the 2007 edition), which is another part of the IAQ whole. "Extremes of moisture, either too dry or too humid, can adversely impact IAQ," Bearg says. If the air is too wet, mold can form. But air that is too dry (especially in the winter), makes occupants uncomfortable, says Bearg. So measuring the dew point temperature and humidity, and benchmarking that data, is one of the more important, yet overlooked, parts of getting a holistic IAQ view.