Education institutions perpetually are challenged to deliver high-quality education with limited budgets. Part of an institution's success depends on finding creative solutions to reduce building operational costs and still provide an environment that promotes learning. With the recent spikes in energy costs and increased focus on environmental stewardship, maximizing energy performance has become a necessity when planning a new facility or improving an existing one.
Opportunities for affecting a facility's sustainability and energy efficiency start at the earliest conceptual stage with defined goals for performance. Educating administrators about integrated design and sustainability concepts results in informed decisions early in the design process. An integrated team of planners, architects and engineers can proactively consider energy performance as they develop a design.
Once energy consumption is optimized through design of the building envelope, the next step is to select highly efficient systems and materials that further reduce the building's carbon footprint. Energy modeling and life-cycle costing are essential in the design process to ensure the systems make fiscal sense.
Benchmarking tools such as Energy Star and ASHRAE 90.1 commonly are used to judge the energy performance of a building. Designs should strive to obtain an Energy Star rating and exceed 30 percent energy savings over the ASHRAE 90.1 baseline. In a recent study by the U.S. Green Building Council, sustainable schools used 33.4 percent less energy than comparable conventional schools, which saves an average of $47,880 annually in utility costs. Similarly, high-performing Energy Star schools have been shown to cost 40 cents less per square foot to operate.
Laying the groundwork
When analyzing a site and developing a design concept for a school, designers should consider the building's orientation and envelope. Each of these can affect energy consumption greatly. Thoughtful, creative site design that maximizes the landscape's potential provides opportunities to reduce energy use and site-development costs. Orienting the building to minimize southwest and southeast exposures reduces the cooling and heating load for building systems.
Several issues influence the sustainability of a site. These include limiting the development footprint and reducing the heat-island effect. Maintaining existing trees provides shading and protection from prevailing winds, and designing with the slope of the land protects portions of the building from the elements. Using highly reflective pavement, and distributed walkways and parking areas also help reduce heat absorption and the heat-island effect.
It's all about the package
The building envelope functions as one system related to energy usage. The key to maximizing efficiency is an integrated team designing all of the elements together.
The goal for the building envelope is to provide a lasting image that reflects the character of the school while enhancing energy efficiency. Durability, maintainability and student comfort (visual, thermal and acoustic) need to be factored into design decisions. Schools should consider performance criteria when selecting building envelope materials, including the roof, windows, walls and floors.
The ideal materials for energy performance vary widely based on climate, but some generalizations can be made. High-mass materials such as brick and concrete block are effective for exterior walls in much of the United States because they store heat in colder months and temper heat transfer in warmer climates. Highly reflective roofing materials and light-colored walls with a high R-value reflect solar energy and are the best choice in all but the coldest climates. The International Energy Conservation Code is one source that defines the minimum thermal performance for the building envelope.
Determining the appropriate amount and type of windows in the building-envelope design is a balancing act. Daylighting in schools can improve student learning and reduce electricity costs, but too much natural light can reduce energy efficiency. The quality of natural light is more important than the quantity. Inappropriately designed daylighting increases the heat gain of a space. This can offset any energy savings from natural lighting. Excessive daylighting can cause glare and difficulty in viewing electronic media, so schools should include a shading plan in their designs.
Effective daylighting that improves energy performance is achieved through careful placement of insulated, low-emissivity windows and walls with a high R-value, combined with appropriate shading devices and automatic artificial light-level controls. Lighting systems should be designed for each specific space to avoid over-lighting any area and with the approach that artificial lighting supplements the available natural light.
A comforting system
The HVAC system is one of the largest energy consumers in a school and is important for maintaining student comfort year-round. Even small improvements in the performance of an HVAC system can save energy significantly. The climate, building size, utility rates and maintenance capabilities are the primary factors to consider in a life-cycle analysis of an HVAC system.
A geothermal heating and cooling system is considered the most energy-efficient method of mechanically maintaining thermal comfort in a building. These systems use the relatively stable earth temperature to heat or cool a building by circulating water through a continuous loop of buried pipes. A geothermal system is a good choice for a school if the site and sub-soil conditions can accommodate the geothermal wells.
Many other systems and system hybrids can produce similar energy-performance results, including variable refrigerant systems, which are beginning to develop a track record in the United States.
HVAC systems that conserve energy, but do not provide the desired indoor environment, are counterproductive. The first step in selecting an appropriate system is defining important environmental criteria such as temperature, humidity and microscopic consideration. Oversized systems add unnecessary cost to the project, and often struggle to maintain the desired indoor environment and energy performance. Displacement ventilation systems affect the indoor air quality positively and enable schools to minimize the capacity of the mechanical system.
Automated controls for the HVAC system and lighting (either with infrared or ultrasonic sensors) enable the systems to work efficiently and turn off when not in use. Building commissioning is a good way to verify that the equipment installed is operating correctly. Budgetary constraints, and a school staff's ability to operate and maintain a system are important factors in determining which system will work best.
Additional renewable-energy options include active and passive solar systems, as well as wind turbines. These once were viewed as cost-prohibitive for use in schools; now, the technology has become more affordable, and grants can offset the higher initial cost. A school that uses these systems can incorporate curriculum focused on solar and wind technologies to provide students with real-world learning opportunities.
When modernizing existing facilities, institutions can improve indoor environmental quality and energy efficiency most dramatically by replacing roofs, windows, and HVAC and lighting systems. Adding or modernizing a building-automation system often improves the indoor environment and has an attractive life-cycle cost.
Many unique circumstances affect this evaluation, so specific trends are difficult to quantify. Schools should improve the building envelope at the same time they upgrade HVAC or building-automation systems so that the energy does not escape to the outdoors.
French is a senior principal and the K-12 education leader for DLR Group, a design firm with 15 offices nationwide. Rod Oathout, LEED AP, is a principal and mechanical engineer with the firm. They work in the Overland Park, Kan., office and can be reached at (913)897-7811, [email protected] or [email protected].
Percentage of energy saved with sustainable schools vs. comparable conventional schools.