Improving school systems
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CSE: Typically in school districts there is a mix of various building types, ages, and MEP systems. Across this diversity, which MEP systems are being kept during retrofit projects? Which systems are being discarded and replaced most frequently?
Dennis Landsberg: Classroom lighting systems are being replaced with super T-8 lighting with occupancy sensors. Metal halide gymnasium lighting is being replaced with T-5 technology. Under major mechanical retrofits, univents are being replaced with air handler systems or geothermal heat pumps if cooling is to be added. VFDs are being added to pumping systems. Boilers are being replaced with modular condensing boilers.
James MacMillan: Unit ventilator (UV) systems are unique and fall into both categories in a 50/50 split. UV systems are commonly replaced with central air distributions, although in many buildings with UV systems, there is limited ceiling space for new air distribution ductwork. In these instances, the UV systems are being replaced with new UV equipment. The new UV equipment and sequences of operation must be designed to effectively control humidity levels in the classrooms.
Vivek Mittall: We have seen that there is a shift toward replacing older hydronic systems with package rooftop equipment. This is mainly for the ease of maintenance of the package equipment as compared to the chilled or hot water systems. On the flip side, we also see that the longevity of the package systems is lesser and they need to be replaced more frequently.
Stu Reeve: Interior lighting has been our major focus for updating MEP systems in the past several years. We also like to update our domestic hot water systems, HVAC boilers, and associated equipment when possible. Automated irrigation control and more efficient pumping options have also been a priority. We try to balance the need for updating our MEP systems with lifecycle and/or other major work that will help us leverage our funding resources.
CSE: As classroom sizes increase, and some schools begin to turn toward unconventional schedules (i.e., year-round schooling, four-day week programs), how are MEP systems retroactively accommodating these types of changes?
Mittall: As a result of year-round schools and longer operating hours of the equipment, the demands for repair and maintenance are much higher, while the window of downtime to carry out these repairs is much shorter. Also due to the varying schedules of the different schools within a district, it's impossible to stay with standard programming and operating schedules, and these are now being handled as one-offs for each facility, leading to nonstandard operating parameters across different buildings.
MacMillan: MEP systems need to be flexible and operate efficiently under part-load conditions. Unconventional scheduling often results in the use of a small part of the building. The MEP systems must be energy-efficient and provide comfort control whether the building is 10% or 100% occupied. A few strategies include the use of incremental equipment such as heat pumps, modular central plant chillers, boilers with properly zoned air-handling equipment, and proper lighting control.
Reeve: In Poudre School District (PSD), we are designing schools today that will help us accommodate the flexibility of the future in both how our schools are being used and how electric, natural gas, and water rates are structured. For instance, time-of-day electric rates drive the design of our MEP systems. Additionally, we can work proactively with school administrators on the most effective methods of managing our MEP systems to accommodate both costs and comfort. Thermal ice storage systems, ground-source heat pumps, indirect/direct evaporative cooling, improved building envelope, natural daylighting, and more BAS for MEP systems provide substantial energy savings and comfort flexibility.
CSE: Due to the past year of economic uncertainty, new construction is down significantly. What tradeoffs are involved when deciding between new construction and school retrofit?
Reeve: We have recently concluded a $175 million bond that was approved and passed in 2000. We're now planning for our next bond possibly in 2010 to go back and address our infrastructure of schools and align them with new schools that were completed in the last 10-year cycle. The recent down economy has helped us leverage our funds to complete our planned projects and stay within our projected budgets. It has also had an impact on our anticipated growth, and we're re-evaluating our future needs and the timing for meeting them in uncertain times. The need for new schools will obviously be impacted, and our focus will be more on the retrofit opportunities in the near future.
Landsberg: The basic financial issues have remained the same—projects that were already in the pipeline are moving forward. School districts are always compromising between investing in their facilities and investing in their programs. New facilities are usually built by districts that are growing, but most districts strive to maintain their existing buildings. They are answerable to the public and are fiscally conservative.
MacMillan: From an MEP perspective, new construction provides an opportunity for evaluating and selecting the optimal MEP system from a wide range of options. For retrofit projects, there may be limitations that exclude certain options. Limitations may include structural clearances, available site area, existing utilities, building orientation, available MEP space, and others. The engineer must be creative with these limitations to provide MEP systems that improve energy efficiency, IAQ, and comfort.
Mittall: The construction of school facilities is a lengthy process. Many new construction projects that we are currently engaged in were initiated and funded before the start of the downturn. We are starting to see some projects put on hold due to current economic conditions. However, the retrofit projects are being delayed, and in some cases are limited to addressing issues related to improving occupant comfort and life safety.
CSE: What water efficiency and lighting systems improvements have been the most effective in schools?
MacMillan: Due to the high use of plumbing fixtures in a school, the use of low water-consumption fixtures is a simple strategy with a high rate of return. Daylight harvesting and daylighting controls will save significant utility costs related to lighting energy use and also lower the air conditioning loads. Lighting within teaching spaces must have adequate zoning and level controls to allow the teacher to adjust the lighting levels to meet the teaching needs.
Landsberg: For water systems, reverse-return aquastats on domestic hot water circulator pumps, low-flow sinks, showerheads, toilets, and urinals have been most effective. With regard to lighting, super T-8 fluorescent systems, replacement of metal halide fixtures in gymnasiums, and occupancy sensors have been the most cost-effective measure.
Reeve: For PSD, the most effective improvement has been interfacing our automated irrigation systems to weather stations that are available throughout our district boundaries. Approximately 80% of the water we use is for exterior landscape. We have also been very aggressive in our landscape options to include drought-tolerant or native species of plants that require less water. We have a very comprehensive approach through our Sustainability Management System, an evaluation and plan of action for all areas of energy management, sustainability, and efficiency in the district.
CSE: What are some cost-effective and practical solutions that educational facilities can implement that will help save money and improve student and teacher comfort?
Landsberg: The most important thing to do is to develop and implement an energy efficiency plan. Track the energy use of every building over time to spot malfunctioning equipment and identify and implement low-cost and no-cost energy conservation measures. The plan must include evaluation of replacing capital equipment with more energy-efficient equipment.
Mittall: Temperature-based economizer controls (integrated with the BAS, not stand-alone) provide a good source of fresh air and free cooling during the early morning hours in most climates. These can also be very easily programmed to be used as night flush to pre-cool larger facilities such as gymnasiums. The use of daylight in the design of new buildings is also an effective way to provide natural light and reduce artificial lighting. Windows are no longer seen as a source of large thermal loads due to the recent improvements in glazing technology.
MacMillan: Controls that automatically set lighting zones and the HVAC system to occupied/unoccupied modes based on the building schedule are critical to controlling costs. Providing temperature controls that are adjustable by the classroom occupants also improves comfort. Finding and controlling sources of existing contaminants can quickly and inexpensively improve IAQ. Common contaminants include standing water, trash, vehicle exhaust near outdoor air intakes, and biological growth, dust, or debris in air distribution systems.
Reeve: Behavior and awareness can be very powerful. We have found that getting administrators, teachers, students, and custodians involved and being proactive can make a 10% to 20% reduction in our energy use and cost. We have a grant with Colorado State University to update a case study on how behavior and awareness has made a difference for us. It's truly a team effort to improve required communications and accommodate the ever-changing use of our schools.
Dennis R. Landsberg, PhD, PE
President, L&S Energy Services Inc., Clifton Park, N.Y.
Jim MacMillan, PE, LEED AP
Vice President, Mechanical, Karpinski Engineering, Cleveland, Ohio
Vivek Mittal, PMP, LEED AP
Cx Project Manager, Enovity Inc., Sacramento, Calif.
Energy Manager, Poudre School District, Fort Collins, Colo.