Energy and Atmosphere (EA)

The Energy and Atmosphere aspects of LEED are probably the best known, and rightly so since they are typically weighted to carry the most points in the rating system. The prerequisites and credits of this category address the reduction of energy consumption through a performance-based approach allowing designers and facility managers to tailor energy reduction measures to their specific buildings. Improving the energy performance of facilities is well known to lower operating costs, reduce pollution, and enhance occupant comfort, which can lead to healthier, happier students, teachers, and staff.

Building Envelope

The most cost effective and highest potential for controlling energy use in a building starts with the design of the building envelope—the place that architects typically have the most direct control over. For schools, that usually means a reliable, high-performance system is needed to prevent heat loss, eliminate thermal bridging, and provide safety and comfort over the operating lifetime of the facility. This is particularly true in the exterior wall system selected for a school building.

An alternative high-performance option instead of common steel framed, block, or brick walls is catching on through the use of insulated concrete forms (ICFs). Such systems start with pre-formed rigid insulation in the shape of large, hollow “blocks” that can be straight, cornered, or custom configured. The inner and outer layers of insulation are held apart by connectors with low thermal conductance spaced appropriately. The hollow area is then filled with concrete once the ICF blocks are in place with the connectors serving as form ties and providing support to locate reinforcing steel. Once the concrete is set, the system provides a solid, durable concrete wall that is covered inside and out with continuous insulation, creating a very efficient thermal wall envelope. The interior and exterior can then be finished in conventional manners of choice.

By designing and building with ICFs, buildings can achieve high-performance values by vastly reducing air infiltration due to the continuous nature of the walls. The system also offers superior performance when it comes to eliminating thermal bridging, resulting in even temperatures throughout the building with reduced drafts and cold spots to optimize energy performance. An added benefit is that insulated concrete forms act as an effective sound barrier by dampening sound vibrations from unwanted outside noise, such as traffic, trains, and neighbors. Since the main structural element in an ICF building is reinforced concrete, it offers substantially better durability and requires less maintenance and repair over its lifetime compared to some other systems.

Photo courtesy of NUDURA Integrated Building Technology

Insulated concrete forms (ICFs) achieve high energy efficiency and provide other attributes, such as sound deadening and durability in green schools.

CASE STUDY: BUILDING ENVELOPE AT THE RICHARDSVILLE ELEMENTARY SCHOOL

The Richardsville Elementary School, a 77,285-square-foot school located in Bowling Green, Kentucky, was built using concrete-filled ICF blocks and has been noted for setting green school building standards in the United States. Utilizing insulated concrete forms for the high-performance building envelope in conjunction with solar panels on the roof, Richardsville Elementary is able to harvest enough energy to offset the total energy consumed by the school, sending 300 kilowatts of power back to the grid and achieving a net-zero footprint. The high-performance building envelope is key to this success and is designed to use only 18 kBtu/square foot. This is impressive energy conservation, reflecting 75 percent less annually than the ASHRAE 90.1 design standard for elementary schools. By means of comparison, the average monthly utility bill for an elementary school in the United States is approximately $7,000. Richardsville generated enough solar energy (in eight sunny days in the course of a month) that it covered more than $4,300 in utility charges and received a credit of $300 for selling the energy back to the electric company.

Photos courtesy of NUDURA Integrated Building Technology

The high-performance, net-zero Richardsville Elementary School designed by Sherman Carter Barnhart Architects of Lexington, Kentucky, was built using insulated concrete form walls.

Heating and Cooling Systems

Conventional HVAC systems have served the needs of most buildings for many decades. However, achieving high levels of performance often requires going beyond the conventional. Considerable success has been found in the use of variable refrigerant flow (VRF) systems, which operate in a zoned manner as an energy-efficient method of providing precise comfort control to indoor environments. Zones are defined as single or multiple room spaces that are conditioned to a set temperature and are operated independently from other rooms within the same structure.

VRF systems move conditioned refrigerant directly to the zone to be cooled or heated, allowing the temperature of that area to be more precisely controlled. They can simultaneously cool some zones while heating others or just provide comfort control to zones that are in use. In addition, VRF systems do not require ductwork for cooling and heating, thus providing more building design flexibility, which can result in more usable space. Ducted systems allow multiple rooms or a large open area to be combined into a single zone. Either way, VRF systems are often simpler in design and more energy efficient than conventional HVAC systems due in part to inverter-driven compressor technology, which is highly responsive and efficient. The systems overall allow for compact, quiet units, flexibility of placement, and give architects and owners more design freedom with individualized controls.

VRF systems tend to differ from conventional HVAC systems in three ways: low noise levels, design flexibility, and long-term reliability and efficiency of the systems. The very quiet indoor unit operation (as low as 19 decibels) leads to uninterrupted learning within classroom environments. The design flexibility and potential space savings means more attention can be placed on school design while indoor air quality is enhanced through the elimination of ductwork, providing a higher indoor air quality to the classroom. The efficiency and long-term reliability speak to the green school design requirements for energy performance and sustainability with personalized comfort control.

Photos courtesy of of Mitsubishi Electric Cooling & Heating/Joe Loehle Photography

A VRF system is an energy-efficient alternative to conventional HVAC systems using high-performance compressors, ductless or ducted indoor units, and individual zone controls.

CASE STUDY: HEATING AND COOLING WITH VRF AT THE SCREVEN COUNTY ELEMENTARY SCHOOL

The Screven Elementary School located in Sylvania, Georgia, serves 1,400 pre-K to fifth-graders in a 143,000-square-foot facility that was built in 1989. William Bland, superintendent of the Screven County School System, said, “There was no question about the need for a renovation of the HVAC system at the elementary school.” The original plan was to repair the old system, but the cost of that work was going to be substantial and was not going to increase energy efficiency. The direction changed when Bland and other school representatives learned about VRF systems. Maintenance Director Mike Dixon said, “It was the energy efficiency that grabbed our attention. We were also interested in the ability of the units to maintain the temperature within one or two degrees and the quiet operation.” Choosing one make over other brands involved comparing attributes and offerings. “We talked with several companies regarding the features, capabilities, controls, and warranty before deciding on the right system for us to go with,” said Dixon.

The VRF system allows Preston Dees, director of school safety and energy manager, Screven County School System, to monitor and control the cooling and heating in each classroom. Dees said, “Now we’re on a control system, and we can manage our energy usage. We were able to cut out another big part of our energy costs when we installed the new system because we were able to remove the old boiler and cooling tower,” Dees said. The boiler had provided heat, which was no longer necessary with the new system. “We saved about two-thirds on our gas costs, so we’ve saved on energy and gas,” Dees added. Overall, the school has documented a 25 percent energy savings compared to the prior conventional system.

Photos courtesy of Mitsubishi Electric Cooling & Heating/Joe Loehle Photography

The Screven County Elementary School in Sylvania Georgia realized a 25 percent energy saving by switching from a conventional HVAC system to a VRF system.