The Walter Library Reading Room on the University of Minnesota campus opened in 1924. Historical and traditional buildings, such as this, used large windows for natural ventilation, illumination, and a connection to the outdoors. Photo courtesy of the University of Minnesota; Photo: Tom Foley

The Occidental Chemical Corporation in Niagara Falls, NY shows the technological facade development through the use of a double-envelope system and louvres in the system cavity. Photo: Canon Design

Windows can have a significant impact on building operating costs, health, productivity and occupant well-being. The traditional purpose of windows was to provide light, view, and fresh air for the occupants. As completely sealed, mechanically ventilated, and electrically lit commercial buildings have become the norm in the last half of the twentieth century, the role of the window in addressing occupant needs has declined. However, there is a growing recognition that the benefits of windows are valuable and contribute to the satisfaction, health, and productivity of building occupants. In addition to the trend toward more human-centered design, there is an urgent need for significant improvements in building energy performance.

Energy & Cost

Windows can be one of the most important components influencing a building's energy use, peak electricity demand, and environmental impacts. By providing natural light, windows can reduce electric lighting loads. Proper window selection and design can also cut peak electricity and cooling loads, thereby avoiding costly peak demand charges. In addition, high-performance windows impact mechanical systems, not only contributing to reduced operation expense but also to potential equipment downsizing, saving capital costs.

Human Factors

Windows have a direct impact on occupant health, well-being and productivity. Windows directly affect design attributes such as daylight, glare, view, and thermal comfort. The benefits of daylight, view, and natural ventilation can be achieved with careful design that mitigates the potential negative effects of increased glare and reduced thermal comfort.

Energy Codes and Standards for Commercial Fenestration

In most places in the United States, building energy codes are based on the International Energy Conservation Code (IECC), which references ASHRAE Standard 90.1 as a compliance alternative for commercial buildings and residential buildings with more than three stories. Both the IECC and ASHRAE Standard 90.1 set energy efficiency provisions for new construction, additions, and new systems and equipment in existing buildings.

More information on the commercial chapter of the IECC »
More information on ASHRAE Standard 90.1 »

While the IECC and ASHRAE Standard 90.1 have been developed to provide minimum energy efficiency baselines, other standards have been developed with more ambitious energy efficiency and sustainable design requirements. Prominent examples are ASHRAE Standard 189 and the International Green Construction Code (IgCC). These sustainable design standards establish baselines for green construction that can be adopted and enforced by jurisdictions.

More information on ASHRAE Standard 189 and the IgCC »

For all of these codes and standards, certified fenestration energy ratings are required. These must be determined by independent laboratories in accordance with National Fenestration Ratings Council (NFRC) standards. A recent method for generating certified NFRC ratings for commercial fenestration is the Component Modeling Approach (CMA).

More information on CMA »

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