The PROJECT

We are studying the impact that new and traditional ventilation control methods have on worker productivity, energy use, and indoor air quality.

SIGNIFICANCE

More than 90% of the total operating cost of commercial office buildings is the salary cost of workers. Our working hypothesis is that better ventilation control will improve indoor air quality, reduce sick building syndrome (SBS) symptoms, and consequently improve worker productivity. If proved true, this project would significantly increase the value of improved ventilation system design and operation. It would also increase the significance of past indoor air quality research results that lack a productivity outcome. Recent results support our working hypothesis.

DELIVERABLE

We have written an interim report describing an analysis of worker performance acquired from a call center (Federspiel, 1999). We have found significant correlations between work performance and factors that affect indoor air quality. A second report containing a more detailed analysis will be completed by the October 1999 CBE meeting. Results from the field intervention will be available by the April 2000 CBE meeting.

DESCRIPTION

In most buildings, ventilation is not controlled. Instead, the dampers are adjusted so that at the minimum position the ventilation rate is sufficiently high to meet code requirements. This approach causes overventilation under many operating conditions. Since ventilation loads are a significant fraction of the total heating and cooling load, demand-controlled ventilation strategies have been proposed and implemented. Demand-controlled strategies adjust the ventilation rate so that when there is less demand for ventilation (i.e., fewer occupants), less fresh air is supplied to the building in order to save energy. The most common of these strategies provides ventilation air in proportion to the indoor CO₂ concentration. The CO₂ concentration is a lagging indicator of the number of occupants, so this strategy causes a lag between the time that a space is occupied and the time that the ventilation is activated. This lag is suspected of causing poor indoor air quality and consequently impairing worker productivity. An alternative demand-controlled strategy called On-Demand Ventilation Control (Federspiel, 1996) eliminates this lag.

This study will involve a comparison of three ventilation strategies: constant ventilation, proportional demand-controlled ventilation, and ODVC. The study will be conducted in collaboration with William Fisk and David Faulkner of the Indoor Environment Department at Lawrence Berkeley National Laboratory.

TECHNICAL APPROACH

This study will involve two parts. The first is an observational analysis of work performance metrics and control system variables such as ventilation rate and temperature. Statistical correlations between control system variables and work performance metrics will be investigated.

The second part is a double-blind, controlled field intervention. The control strategy type will be the independent variable. We will compare constant ventilation, proportional demand-controlled ventilation, and ODVC. Indoor air quality metrics will be derived from laboratory analysis of air samples and statistical analysis of symptom intensity surveys. Performance metrics will be derived from the automated call distribution (ACD) system in the call center. Measurable disturbance variables such as sound pressure level and temperature will be recorded with portable dataloggers and via the existing building control system. We will determine whether or not there is a statistically significant difference between the three strategies on the basis of work performance, health symptoms, contaminant concentrations, and energy usage. We will also perform a cross-correlation analysis between the outcome metrics.

RELATED WORK

Other research activities related to this project include the Workplace Productivity Database project, which is funded by the National Institute of Standards and Technology (NIST), and the CBE project on Productivity and Indoor Environmental Quality in the New Office.

REFERENCES

Federspiel, C. C., W. J. Fisk, D. Faulkner, and D. Wyon, 1999, Statistical Analysis of Work Performance in a Call Center, CBE Interim Report.

Federspiel, C. C., 1996, "On-Demand Ventilation Control: A New Approach to Demand-Controlled Ventilation," Proceedings of INDOOR AIR '96, Nagoya, Japan, 3, 935-940.