Many people narrowly focus on energy efficiency when defining a “high-performance” school — a school building that is economical with respect to heating, cooling and electric lighting. That is certainly true, but in the broadest terms, a high-performance school is designed to minimize reliance on fossil fuels — and provide a comfortable, healthful, productive and beautiful learning environment — by optimizing the efficiency of the building form and mechanical equipment.

Working together, architects, engineers and environmental designers can achieve this complex goal by integrating effective school planning, sustainable architecture and sophisticated building performance analyses. In the process, they use energy modeling early in the design process to analyze the building envelope, and mechanical and electrical loads. Daylighting, ventilation and mechanical/electrical strategies are used to develop and refine the design.

Laying the foundation

Design-stage analysis is possible through a range of modeling software, depending on the nature of analysis required. These include a program patented by the U.S. Department of Energy and Lawrence Berkeley Laboratory, as well as proprietary software developed by manufacturers of mechanical systems and independent researchers. Building-performance benchmarks based on a designer's experience with various types of buildings in various locations also serve as useful rule-of-thumb tools for qualitative and quantitative analysis. Ideally, a design team should work together as early as the conceptual design phase to identify the site and climate factors that affect the building envelope.

The thermal performance of a building envelope — roof, wall, window and floor systems — is critical in determining energy consumption for heating and cooling. Likewise, the design of an efficient building envelope lays the foundation for the design of a high-performance school. In an early design-stage building envelope study, a whole-building energy simulation of the school can provide a useful initial assessment of the annual heating and cooling requirements. This study can help determine the energy use that can be attributed to the building envelope. It focuses on massing and the insulating properties of the building envelope.

Building energy simulation typically uses a “base case” for comparison — that is, a building whose roof, wall and underfloor R-values and glazing U-values meet the minimum code requirements set by the ASHRAE 90.1 standard, which is used by the U.S. Green Building Council. The modeling process compares the predicted energy performance of the base case against the design alternatives, whose energy-efficiency measures may have individual or cumulative effects on building performance. Whole-building energy modeling typically focuses more on the sensitivity of the overall envelope than on the localized effects of the envelope on individual spaces.