Planning for the future is a sound goal handed down from generation to generation. It spans personal and professional spheres, and campuses that follow this directive can reap significant financial and environmental benefits for many years.
Energy-efficient buildings on K-16 campuses don’t just happen; they result from a thorough, long-range plan carried out by a team of experts. A combination of strategies and tools is needed to design a sustainable master plan that design firms, school districts and universities can use to maximize operational efficiencies and utility cost savings.
A sustainable master plan incorporates a holistic approach to future campus needs via the inclusion of energy use, needs and sustainable practices.
Tools and strategies
•Benchmarking: Analyzing energy consumption of a building and comparing it with peer building types in the region. Evaluating the performance of a building compared with similar buildings helps gauge its efficiency.
•Energy audit: A visual inspection of a building to identify energy-conservation opportunities. Professionals observe existing lighting systems, air handlers, variable-air-volume systems and other items that can be updated to reduce energy consumption.
•Commissioning: Verifying performance to evaluate the design intent of the building. Experts confirm the owner project requirements and carry out tests to determine if the project team delivered the building the owner expected. Commissioning also seeks to confirm whether the building is performing as the energy modeling in the design projected. The process is conducted during the first year of operation or through seasonal cycles.
•Post-commissioning: Commissioning of a building that has been modified for energy efficiency via benchmarking, energy audits and subsequent solutions.
Case study: Red Wing High Public School District
Fifty miles southeast of the Twin Cities, the Red Wing (Minn.) Public School District serves a population of 16,000. The district outlined a sustainable master plan, followed through, and now is experiencing the rewards.
"Red Wing School District wants to be good stewards of its tax dollars," says Kevin Johnson, director of buildings, grounds and technology. "We cut more than $400,000 out of our annual energy budget, and we are paying 6 percent less in gas and electric than we were 10 years ago."
One of Johnson’s first assignments after being hired a decade ago was benchmarking to evaluate energy consumption in district-owned buildings. The building inventory includes five academic school buildings, one early-childhood center and two ice arenas.
"The importance of benchmarking is to understand your energy consumption as an entity," says Johnson. "You can’t reduce until you understand how much energy you consume."
In the initial analysis, several potential savings opportunities were identified and put into place.
"These were simple tweaks that districts typically can accomplish with little to no cost or outside assistance," says Johnson. "For example, we changed every light bulb to a T8 25-watt version. The gymnasium alone attained an eight-month payback, saving $11,000 per year in electricity costs."
By educating staff on the "hows" and "whys" of living and working sustainably, the district achieved these annual cost savings:
•Adjusting temperature control set points to 68ºF for heating and 76ºF for cooling saves $50,000.
•Low-flow plumbing fixtures save $5,000.
•Lighting sensors save $9,500.
•Better use of building automation system for scheduling saves $16,000.
Johnson used his background in facility management to perform an initial energy audit of the HVAC systems, focusing on the heating water systems. He found that many of the boiler systems at the district’s high school were supplying heating water at 180 degrees year round. In response, the district installed a condensing base-load boiler to operate in the summer and off-peak times to maintain supply water temperature of 90 to 125 degrees for dehumidification control.
"It doesn’t make sense to send 180-degree water through the boiler system when significantly cooler heating water will suffice for summer reheat. By taking advantage of the efficiency of a condensing style boiler and adjusting the water temperatures, we immediately cut our utility costs by $48,000," says Johnson.
The district also continues to monitor its boilers and recommends annual preventive maintenance.
"If a boiler is off just 1 percent, the cost of the tune-up outweighs the cost of the inefficiency," says Johnson.
After consulting with an architect to quantify additional savings, the district carried out an ENERGY STAR analysis of its five academic buildings and compared their energy consumption with surrounding districts. ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy.
For the analysis, the district compiled building specifications and evaluated gas and electric bills, and measured the performance of district buildings vs. peer buildings. This helped the district:
•Measure energy performance.
•Identify maintenance needs.
•Target buildings needing improvement.
This analysis enabled the district to direct its resources to facilities with the biggest opportunities. An architect carried out a detailed energy audit and retro-commissioning study of the high school.
"School districts have limited resources," says Johnson. "The goal of commissioning is to identify where the opportunities are and invest in those opportunities that return the best value."
The audit identified 11 energy-conservation opportunities that Red Wing could pursue immediately to reduce energy consumption at the high school by 10 percent—an annual energy savings of almost $30,000. As the school incorporates more of the recommendations, it hopes to join the ranks of the district’s other schools and receive an ENERGY STAR award for its energy performance.
Among the high school’s energy conservation opportunities:
•Run-time reduction of air-handling units that more accurately reflect the building’s occupancy periods.
•Demand-control ventilation in the auditorium, little theater and cafeteria. Carbon dioxide is a byproduct of human respiration and is considered a trace gas. By measuring the carbon-dioxide levels in the space, the amount of outside air can be modulated to more closely reflect the amount of people in the space and prevent over- and under-ventilation.
•Relocate chilled- and hot-water differential pressure sensors closer to the main fan rooms, enabling the pumps to operate at faster speeds and maintain space temperatures with lower discharge air temperatures.
•Reduce the artificial head pressure on the chilled-water system while maintaining the same system performance. By reducing pressure, the system will consume less power.
•Adjust the chilled-water setpoint to be based on outside air temperature and load of the building vs. a constant 42 degrees.
•Utilize ASHRAE 62 and recalculate the amount of ventilation air based on the real occupancy levels in any given zone, while maintaining the indoor air quality within each zone.
•Use duct static pressure optimization control algorithms for VAV systems. Adjusting the static pressure based on meeting the demand of the space has an estimated 10 percent expected energy reduction over maintaining a constant static pressure.
•Repair dampers in terminal boxes that are stuck in full open position to reduce the fan speed necessary to maintain the static pressure setpoint.
•Utilize enthalpy economizer vs. temperature economizer. Enthalpy control compares the amount of energy in the return air with the energy in the outside air. The control system then will calculate the most energy-efficient combination of return- and outside-air cooling of the building.
•Modify the energy-recovery wheel control to maintain an exhaust air temperature setpoint that is 2 degrees above the outside exhaust air dew point when the exhaust air temperature is below 34 degrees. This modification will extend the time that energy recovery is operational in the winter, thus reducing the heating needs of the building.
To carry out projects such as commissioning, benchmarking and energy audits, districts have many funding options. For example, a utility in Minnesota provided a $25,000 grant to cover a portion of the Red Wing High School commissioning.
"Districts should take advantage of whatever funding sources are available in your state," says Johnson. "Check with your local utility companies for grant opportunities."
Case study: College of Saint Benedict
College of Saint Benedict (CSB) is an all-female student community founded in 1913.
The college shares its academic programs with Saint John’s University.
In 2007, CSB became a charter signatory of the American College and Universities Presidential Climate Commitment (ACUPCC), which aims to eliminate net greenhouse gas emissions from specified campus operations.
CSB serves 3,938 undergraduates in 40 buildings spread over 1.2 million square feet. A 2007 master plan identified the need for three additional buildings on campus to accommodate growing student enrollment. The master plan seeks to expand the campus by 50 percent over the next five years, including an addition to the athletic center, a new academic building and campuswide renovations.
In 2009, CSB issued a request for proposals to evaluate its utilities to confirm the college had the capacity to meet the 2007 master plan. This evolved into a comprehensive utilities master plan.
An architect was hired to evaluate campus utilities and recommend ways to pursue sustainable growth in accordance with ACUPCC.
A three-phase approach was recommended to achieve sustainable growth:
•Phase I evaluated and developed recommendations about CSB’s utilities capacity.
•Phase II assessed the energy performance of all campus buildings and recommended ways to reduce energy use.
•Phase III will incorporate the findings of the first two phases to provide a comprehensive sustainable master plan for heating and cooling the campus.
As part of Phase I, a team of experts evaluated the central heating plant, central cooling plant, domestic hot and cold water, and the central medium-voltage distribution switchgear, along with the associated distribution infrastructure and campus telecommunications infrastructure. The existing conditions of each system were documented and future loads projected based on campus expansion plans.
The team evaluated CSB’s high-pressure steam heating system and its chilled-water cooling system. The challenge with a high-pressure steam system is monitoring equipment continually. Maintenance staff must check gauges every two hours to ensure the system is operating as intended. The evaluation determined that pipe sizes varied and the systems were not looped, which leads to operational inefficiencies. A utilities study found that the heating system was at maximum capacity with current loads.
"The study revealed CSB’s systems were piecemealed together," says Sue Palmer, vice president for finance and administration. "There were several expansions over the years, and unfortunately the pipe sizes are not consistent, which leads to energy waste."
Phase II identified energy-savings opportunities:
•Use loop pipes for maximum efficiency.
•Install a low-pressure steam and hot-water condensing boiler.
•Reassign maintenance workers to improve staffing efficiency.
"While these are attractive options, replacing all central plant piping is cost-prohibitive," says Palmer. "Rather, we prioritized and adopted a long-range plan CSB can both afford and implement for optimal efficiency."
Phase III will address how to reduce the overall load on campus utilities by further analyzing the individual building demands and developing strategies to reduce energy use at the building level. Electrical and mechanical strategies will be presented with a cost estimate and simple payback analysis.
Phase III steps:
•Conduct a building-by-building energy-consumption analysis and identify energy-conservation opportunities (ECOs) to bring the building to the lowest possible energy footprint.
•Carry out ECOs with simple paybacks.
•Develop a plan to continue the retrocommissioning of buildings.
•Determine viability of renewable resources, and develop a plan to incorporate renewable energy into new buildings as well as existing structures.
A plan has been identified to decentralize and use the current central plant as a hot-water plant. Piping will be looped for maximum efficiency, and a ground-source heat pump will be installed in a new academic building to meet CSB’s energy efficiency goals related to ACUPCC.
"The strategy is to right-size," says Palmer. "CSB doesn’t want to oversize, which would be inefficient. Rather, CSB strives to right-size now with the intent to expand as needed in the future."
CSB obtained a grant from a local utility that offset some of the costs of the evaluation. The grant also positions the campus for additional rebates as projects are completed.
Sidebar: College of Saint Benedict
Estimated master plan financial savings and schedule:
Capital Cost: $4,411,413
Annual Maintenance Savings:: $360,020
Annual Energy Savings:
Simple Payback:7.4 years
Sidebar: Red Wing Scores
The Environmental Protection Agency has recognized Red Wing School District as an ENERGY STAR Leader Top Performer for achieving a portfolio-wide average energy performance score of 78. A score of 75 or higher achieves ENERGY STAR status. In 2010, only 9 percent of all public school districts in the nation earned this status. Below are some of the schools’ energy performance scores:
Burnside Elementary: 90
Sunnyside Elementary: 75
Twin Bluff Middle: 90
Jefferson Elementary: 100
Red Wing High: 65
Sidebar: Red Wing Reductions
Red Wing School District has reduced 1,865 metric tons of CO2 per year, which is equivalent to:
•Saving more than 360 acres of Douglas Fir pine trees (+48,300 trees).
•290 automobiles removed from service for one year.
•Meeting the heating, cooling, cooking and electricity needs of 155 homes for one year.
Horkey, PE, LEED AP, is principal and mechanical engineer and Laue, PE, LEED AP, is senior associate and mechanical engineer at DLR Group, Minneapolis. The firm worked on the Red Wing and College of Saint Benedict projects. They can be reached at [email protected] and [email protected].