Minnesota Researches Energy Conservation, Ventilation and IAQ in K-12 Schools
By Consulting Specifying Engineer Staff
New research recently completed in schools provides additional insight into energy conservation, ventilation and indoor air quality (IAQ). The research utilized continuous IAQ monitoring technology, which measures temperature, relative humidity, carbon monoxide, carbon dioxide and odors and gases (TVOCs).
Two comprehensive studies, conducted simultaneously in more than 100 classrooms in 11 Minnesota K-12 schools, will assist education professionals and decisions makers in all levels of state and federal government.
“Schools Air Monitoring Project for Learning & Energy Efficiency” (SAMPLE 2). The study was funded by a Minnesota public utility company as part of the State of Minnesota’s Conservation Improvement Program (CIP). CIP requires energy utilities to invest a portion of their annual revenues into energy conservation programs. This one-year, three-school study is complete.
“Continuous Indoor Air Quality Monitoring in Minnesota Schools.” This study is funded by the State of Minnesota and is the first known example of state funding for continuous IAQ monitoring in schools in the U.S. This one-year, eight-school study is at the mid point.
The two projects are identical in design, timeframe and project team. The SAMPLE 2 program’s primary focus was energy conservation opportunities made possible by continuous IAQ data, with the secondary emphasis on IAQ improvement. The state-funded program reverses these two priorities, emphasizing IAQ improvement.
Results: Energy Conservation
SAMPLE 2 identified significant energy conservation opportunities realized by continuous IAQ monitoring. The opportunities included:
Temperature Management: In each school, actual room temperatures were, at times, warmer than target temperatures during the school’s heating season. This difference resulted from the following:
Inoperable, inaccurate or incorrectly-set thermostats
Lack of temperature setback capability during winter unoccupied hours
Lack of training regarding thermostat operation
The continuous monitoring data identified specific rooms that needed better temperature management. The biggest opportunity is during unoccupied hours on nights, weekends and holidays.
Demand Control Ventilation (DCV ) : All three SAMPLE 2 schools use constant volume ventilation. Large quantities of energy are used to condition cold, outside air for heating during the winter. (The converse would be true for cooling in the summer in an air-conditioned building.) Study results validated that participating schools can conserve significant energy if ventilated based on actual occupancy in rooms, as measured by real-time IAQ monitoring. Savings occur despite the fact that all three schools were ventilated at constant rates but lower than current ASHRAE standard of 15 CFM of outside air per occupant.
Computer Labs : All computer laboratories were warmer than other rooms, whether occupied or not. Overheating was caused by multiple (typically 30 to 40) personal computers in the labs. No participating school shut computers down during unoccupied hours. A relatively simple and inexpensive solution is to shutdown computers during unoccupied hours, which would save significant energy.
In total, the project identified potential energy conservation savings of 13 to 20 percent for the three schools’ total thermal, winter season heating requirement. Corresponding savings, using the same conservation strategies, are possible in warmer climate, air-conditioned schools.
Results: IAQ Improvement
Both studies identified IAQ improvement opportunities.
Due to increased occupancy or activity, some rooms frequently experienced carbon dioxide (CO 2 ) levels above industry standards. More ventilation is needed in those rooms during specific times.
In the state-funded project, CO 2 regularly and significantly exceeded industry standards in multiple rooms in at least half the schools. Causes for higher CO 2 levels include the following:
Broken ventilation equipment
Control systems designed for maximum energy conservation (to the detriment of IAQ)
Ventilation pathways blocked due to building changes or fire code compliance
In one case, complete ventilation system failure
Note: These needed repairs or equipment conditions were often unknown to school administration prior to the project.
Three schools participating in the state-funded project recently invested in system changes to improve ventilation rates, per a state requirement to achieve 15 CFM of outside air per occupant. As a result, these schools have better ventilation, as measured by IAQ monitoring, than the five schools that have not yet complied.
(Note: One school reported high utility bills and had difficulty keeping the school warm in the winter. Results from SAMPLE 2 indicate that while a constant CFM level delivers excellent IAQ, excessive energy may be used.)
All participating schools have very low (single digit) relative humidity in winter. During cold winter months, relative humidity of 20-to-30 percent is desirable. When relative humidity is below 15 percent, dry eyes, scratchy throats and static electricity complaints increase.
All three SAMPLE 2 schools had low odors & gases (O&G) readings except during maintenance activities in the summer. Also, elevated carbon monoxide readings were observed in rooms in two schools during summer maintenance activities.
Constant Volume vs. Demand Control
Relative energy requirements differ between the traditional, constant volume compliance versus variable, demand control ventilation based on real-time IAQ monitoring.
Until now, actual IAQ conditions were unknown, so industry standards and approaches have been conservative, and traditional methodology has been relatively energy-intensive. SAMPLE 2 data suggests that energy savings can be achieved when actual, real-time IAQ data is used.
Note : A major national research organization has recently completed a study that demonstrates a link between elevated carbon dioxide levels and student absenteeism. The study will be published in an upcoming “Indoor
The Project Team
Schulte Associates LLC ( www.schulteassociates.com ) is an independent executive management consulting firm with offices in Minneapolis and Cleveland and a specialty practice in energy-related industries. SA is the project developer and manager.
Sebesta Blomberg & Associates, Inc. ( www.sebesta.com ) is a leading energy consulting firm. Barry Bridges, P.E., senior recommissioning engineer, is the lead Sebesta consultant for the project. Among other activities, he is currently active in recommissioning efforts of heating, ventilation and cooling systems at the Pentagon for the Department of Defense.
Altec Energy Systems, Inc. ( www.alteces.com ) is an energy services company with deep experience in real-time monitoring, energy programs and control systems.
Grimsrud & Associates: Dr. David T. Grimsrud is a retired professor at the University of Minnesota, where he was director of the Cold Climate Buildings Institute. He is author of numerous published papers for the U.S. Department of Energy and others on indoor air quality and energy relationships.
PureChoice, Inc. ( www.purechoice.com ) is the developer and supplier of the PureTrac
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