Indoor Air Quality in Schools

Oregon Elementary School

During the conditions audit at the Oregon Elementary School three concerns were identified as targets for possible retrofit work:

control ventilation based on occupancy as indicated by CO2 sensors to maintain recommended ventilation and potentially save on heating cost by reducing periods of over-ventilation
general maintenance for 27 unit ventilators to increase outside air to recommended levels while maintaining temperature control
adding mechanical ventilation for a six classroom portable with restrooms that were without any mechanical ventilation.

It was anticipated that the energy savings from more efficient operation of the ventilation provided to the common core of the building (gym, cafeteria, and auditorium) would offset the added cost of providing proper ventilation to the classroom areas. Based on available funding, it was decided to address the first two items.

Maintenance performed by the district to address the unit ventilator recommendation was completed during the summer of 2003. Unit ventilators were cleaned, including outside air intakes, and calibrated. Dampers, controls and valves were checked, adjusted, and replaced as needed. Ventilation of the gym, cafeteria, and large auditorium was also improved. The multizone fan system was reconfigured so that these areas could be operated as isolated zones by the operation of dampers controlled by CO₂ sensors for the cafeteria and auditorium and an occupancy sensor for the gym. Temperature, relative humidity and CO₂ levels in the cafeteria and auditorium and selected classrooms were monitored pre and post retrofit. Maintenance on the unit ventilators in the classrooms produced a significant improvement in measured flows of outside air provided to each room with average outside air flows going from 149 cfm pre-retrofit to 356 cfm post-retrofit. Sixteen out of 20 rooms were adequately ventilated post retrofit versus only two of 20 pre retrofit. CO₂ monitoring also confirmed improved ventilation rates. Based on an energy audit performed by a private company as part of the state of Oregon’s SB 1149 program, energy savings from the multizone fan system retrofit were estimated at 308 MMBtu/year with a dollar savings of $1,997/year. This yields a simple pay back of 4.5 years for a $9,000 investment.