Careful planning and design, as well as educated equipment purchases, can help launch today's energy-efficient.
As utility bills continue to increase and budgets decrease, energy efficiency is at the top of most schools' priority lists. While there are many obvious ways to reduce energy usage-turning off lights in unoccupied areas, sealing windows, etc.-designing an energy-efficient school is a multi-faceted effort, requiring close coordination among the school, architect and engineer.
Because each school is in a different location with its own climate and usage requirements, there is no one formula that fits all. However, by following some guidelines, energy efficiency can be within any district's grasp.
Initiating the process A critical step in designing for energy efficiency-development of an architectural (usage) program-occurs before design begins. The usage program identifies existing and new spaces, and provides a usage schedule, both during and outside normal school hours. In addition, the program addresses current and projected needs. A successful program helps create a design that: -Accommodates the facility's many functions. -Provides for energy-efficient operation and low-cost maintenance. -Supports changes in technology, equipment and usage. -Has efficient mechanical systems.
Usually, heating, ventilating and air conditioning (HVAC) comprise approximately 40 percent of a building's energy costs. The right HVAC system with the proper controls can create significant operating savings. Several programmatic elements affect system selection, including: -The number of people served and their distribution by location and time. -The number and distribution of computers, printers and actual field-measured electrical load values. -Any long-range technology improvement plans.
These elements will impact system and zone size, level of system controls needed, and how best to allow flexibility for technology growth and changing equipment. Inclusion of spare capacity in main mechanical and electrical services, as well as slight oversizing of distribution systems, is one means of providing flexibility. Keep in mind that oversized equipment might cycle frequently and provide poor dehumidification when only lightly loaded.
A variety of system types and add-on features is available. The best selection depends on location, building size and usage, and local utility rates. A few systems and features include: -Water-source heat pumps deliver heating and cooling in different zones concurrently. Individual rooms and central-system components easily can be expanded. -Variable-air-volume (VAV) systems provide good energy efficiency because they are sized for a diversified "block" load, rather than a sum of zone "peak" loads. Additionally, decreased building loads and supply-air volume reduce fan horsepower. If central-system components and duct distribution mains are sized adequately, these systems are expandable. -Heat reclaim systems, such as from swimming-pool mechanical dehumidification systems, preheat incoming water and air. -Air-to-air and coil run-around energy-recovery or transfer systems transfer energy from exhaust air to incoming air streams, lessening the impact of ASHRAE 62-1989's increased outdoor-ventilation air-quantity requirements. -Carbon-dioxide sensors control outdoor-ventilation air quantity by sensing actual room or zone carbon-dioxide levels where different or varying occupancy levels exist.
Application of several concepts tends to improve energy efficiency, regardless of system type. Be sure to match equipment and zone size to fit odd- or after-hours space usage, which eliminates the need to operate larger pieces of equipment to satisfy only a small zone. Also, implement systems and control energy-reduction strategies at individual rooms or space levels, which is more effective than in larger zones. Another way to save energy is to design in the ability to maintain and adjust operating hours and temperature set points at school, zone and room levels.
Lighting and controls Approximately 30 percent of a building's energy costs are for lighting. Prudent balance of natural and artificial light, lighting controls, appropriate artificial lighting sources and reflective interior finishes can reduce this amount.
A simple, cost-effective way to increase light levels without increasing the number of fixtures is with light-colored reflective ceilings, walls and floors. Keeping ceiling reflectances near 80 percent, walls at 50 percent and floors at 20 percent contributes significantly to brightness, therefore reducing required installed lighting wattage and resultant air-conditioning load.
Carefully balanced natural and artificial light also can result in significant reductions. Natural light lowers artificial-light requirements and cooling loads. Artificial-light sources increasingly are more energy efficient and cost effective. A number of energy-efficient lamps, electronic ballasts and fixtures are available. For instance, the latest
T-8 lamps and electronic ballasts bring up to 40 percent savings over conventional T-12 lamps and magnetic ballasts. Occupancy and daylight sensors increase energy efficiency even more.
Efficient building materials Thermal resistance is critical throughout a building, whether through insulation, placement of air space or seals and barriers. Roof insulation may be particularly important in a large, one-story facility, while less important for a multi-story building. Each facade material has its own energy-efficiency characteristics, such as: -Masonry absorbs heat, later releasing it when the atmosphere has cooled. Its wall mass retains heat longer than other materials, delaying the need for space heating in winter, and possibly reducing summer cooling. Masonry alone, however, is not a good insulator or vapor barrier. Good, properly placed thermal and vapor barriers are necessary. -Metal-skinned walls, such as composite sandwich panel systems, achieve high thermal and vapor resistance values, given proper joint seals and maintenance between panels. A high-performance, composite metal wall system may offset masonry's time-delay heat gain/loss advantages.
Windows can be potential points of energy inefficiency; however, proper selection and maintenance can help increase efficiency. Low-emissive windows prevent solar radiant heat transfer, helping reduce and control energy gain. Proper placement and maintenance of vapor barriers, weather stripping and gasketing are highly critical.
When selecting wall and window systems, specific insulation types, and quantities of natural and artificial light to use, the process should include analysis with a computer-based HVAC loads program that will provide annual energy usage. This data, coupled with first costs and utility rates, should be submitted to life-cycle-cost analysis.
The quality of maintenance is critical. Components subject to contact, and wear and tear (such as gaskets, weather-stripping and caulking), must be periodically checked and maintained. Air-side filters must be changed regularly to keep fan energy at a lower level.
Other opportunities Site orientation, landscaping and building organization also can lower energy usage. Many factors influence site orientation; however, the following should be considered for their impact on energy efficiency: - Glazing (quantity, orientation, angle). - Trees and shrubs (deciduous and evergreen). -Entryways (size, length, single or vestibule, location).
Also, there are a number of constraints on massing and organization that will provide energy savings, including: -Minimizing exterior skin, building shape, or ratio of perimeter exposed wall to overall building square footage directly impacts energy use. - Organizing for efficient operation, including clustering spaces used extensively during evening hours, allows climate control in these areas, while the remaining building moves to the unoccupied mode. - Sharing appropriate spaces, such as a single cooking kitchen serving multiple facilities, with only warming kitchens in remaining schools, conserves energy. Schools sharing a campus provide additional opportunities for shared spaces. - Placing spaces requiring controlled heat, light and humidity in a building's interior where the environment is easier to control. - Recessing entryways along windward exposures and placing vestibules at entryways will reduce direct wind action.
Lang, P.E., is director of mechanical and electrical engineering for Kennedy Associates, St. Louis. The firm was project manager and architect for the Samuel Shepard, Jr. Gateway Educational Park complex; William Tao & Associates provided mechanical and electrical engineering services.
In addition to being an energy-efficient facility, even components of the Samuel Shepard, Jr. Gateway Educational Park's, St. Louis, three schools-elementary, middle and The Michael School for medically challenged students-are learning tools.
For example, students "create" power in the interactive solar-power display. They monitor worldwide weather conditions at indoor and outdoor weather stations and observe an operational windmill turning wind into energy. Exposed, brightly colored ductwork stimulates curiosity and research.
These schools also help conserve energy. Exterior walls of brick and concrete masonry units, exterior insulation finish systems (EIFS), metal panel systems and ceramic tile contain a minimum 2 inches of rigid insulation. Roofs also are insulated heavily. Vestibules at major entryways and inset northern entrances protect from cold winter winds.
Natural and artificial sources combine to provide energy-efficient lighting. Dark-tinted, low-emissive insulated fixed windows comprise all glazing, including those overlooking the courtyard. Electronic ballasts and T-8 fluorescent lamps are used, contributing to lower energy costs and increased lamp life. Insulated, translucent skylights further brighten the library and circulation areas.
With 1,300 students, the outside-air intake requirement is high to maintain proper indoor air quality. Heavy computer use consistent with the math, science and technology theme adds to the energy load. To meet these heavier-than-normal heating and air-conditioning requirements, the school uses a water-source heat-pump system, with heat-reclaim and redistribution capability. Heat produced in one portion of the complex is used wherever needed.
The heat-pump system has an additional bonus-it is inexpensive to install, operate and maintain. Modular and off-the-shelf, a single unit can be replaced when required, rather than an entire system. A single classroom can be removed from use rather than a wing or the entire school. The system also is easily expandable to accommodate further enhancements to the school's technology program. For further energy conservation, spaces with unused high, open ceilings, such as the library and gymnasium, employ air stratification-air in only the lower portion of the spaces is conditioned.