Indoor Air Quality in Schools

Washington State Elementary School

During the conditions audit at the Washington State Elementary School two concerns were identified as targets for possible retrofit work. Timers set for periods of occupancy controlled the ventilation for both the gym and large multipurpose community room. The occupancy of these areas varies greatly even during normal schools hours. The audit also identified a mixing problem in the gym. Ventilation air was short circuiting from the supply to the return without mixing into the occupied zone. Recommended retrofits included:

controlling ventilation based on occupancy using CO₂ sensors was proposed as a way to maintain recommended ventilation and potentially save on heating cost by reducing periods of over ventilation
modifying and redirecting the supply diffusers to better ventilate the occupied area in the zone

Actual retrofit work at the school included adding CO₂ sensors to the control circuits for the gym and multipurpose room and altering the supply diffusers in the gym to provide more mixing and minimize short circuiting to the returns. Temperature, relative humidity and CO₂ levels in the gym and multipurpose room were monitored for over 3 weeks both pre and post retrofit. Data on natural gas consumption for the monitoring period was collected and ambient weather conditions recorded. Outside air damper positions for the gym and multipurpose room were also recorded for the pre and post monitoring periods.

While initial analysis of the collected data indicated lower energy use in the building post retrofit with normalized weather, a review of recorded damper positions suggested that the control settings may not have been properly set for implementation of the desired control strategy. The control program was reset, and school district personnel confirmed that the changes made have in fact improved the existing air mixing problem, and complaints about odors from off gassing of the floor finish have ended. Also, no problems were reported from going to CO₂ based ventilation control for the multipurpose room and gymnasium.