Peer-Reviewed IAQ StudiesUnlike many anecdotal claims or self-serving analyses, a recent scholarly study of the impact of OA rates and lost productivity clearly shows a quantifiable link between better ventilation rates and reduced absenteeism due to sick leave.
Published in December 2000 in the Indoor Air Journal (Vol. 10 Issue 4), "Risk of Sick Leave Associated with Outdoor Air Supply Rate, Humidification, and Occupant Complaints" (by Donald K. Milton, P. Mark Glencross, and Michael D. Walters), is a summary of a study performed over several years on a commercial multibuilding facility in the Northeast. Careful measurements were taken of airflow, humidity, contaminants, etc., and corrections made for a variety of factors (including age, gender, seniority, shift, ethnicity, crowding, and type of work). The bottom line: A $1.00 spent on additional OA yields (on average) about $3.00 in greater productivity due to reduced sick leave.
This study valued sick leave absence due to insufficient OA at about $240 of lost productivity per worker per year (about 0.6%, based on the salary used in the study). At typical personnel space distributions, that's $1 (or more) per square foot of employee output. The study's cost calculation for energy to condition OA cost was (at $3.22 per additional OA cfm per year) a bit high (energy costs in the Northeast were used), but this means that the relative value of adding more OA (if its reductions in sick leave are accepted) is even greater than indicated in the study.
Since companies typically pay 100 times or more for people than they do for energy, even a small increase in productivity should be worth the cost. The study did not, however, consider one-time costs involved in increasing coil or plant capacity that might be needed to condition OA on very hot or cold days. The study found "consistent associations of increased sick leave with lower levels of outdoor air supply and IAQ complaints" and concluded that "The cost of providing additional ventilation may be more than offset by the savings that result from reduced sick leave."
The paper may be accessed at www.blackwell-synergy.com. To download load it, one must register at the site (which is free) and then pay $19 via credit card.
IAQ resources from the EPAA much higher estimate of improved productivity may be found at the EPA webpages on IAQ (www.epa.gov/iaq/). This is a very good (and free) informational resource on the issues.
One of the site's more interesting resources is the I-BEAM computer program (which stands for Indoor Air Quality Building Education and Assessment Model). This process can help a building/facility manager study and simulate IAQ issues on a PC. Find I-BEAM and its useful accompanying text modules at: www.epa.gov/iaq/largebldgs/ibeam_page.htm.
With regard to improved employee productivity, the EPA I-BEAM manual states:
"Significant measurable changes in people's ability to concentrate or perform mental or physical tasks have been shown to result from modest changes in temperature and relative humidity. In addition, recent studies suggest that similar effects are associated with indoor pollution due to lack of ventilation or the presence of pollution sources. Estimates of performance losses from poor indoor air quality for all buildings suggest a 2% to 4% loss on average."
A 2% change in performance would be worth roughly $2.00 to $4.00 in improved productivity per square foot of occupied workspace. By comparison, the cost to heat and cool OA, even in high cost hot/cold areas, rarely exceeds $0.30 to $0.50 per square foot (assuming 20% OA is supplied). If improved performance translates into a quantifiable result (e.g., more widgets made properly, less overtime to make up for absenteeism), even doubling that cost is small compared to the potential savings.
The text also includes some useful nuts-and-bolts ways to "sell" tenants and owners on better IAQ. Under "Market Your IAQ," I-BEAM offers various ways to promote improved air quality and provides a calculator for the costs/benefits involved. ES