PERFORMANCE: Energy & Cost
Energy & Cost
Codes & Standards
According to the Department of Energy's 2010 Buildings Energy Data Book, commercial buildings represent just over 18% of U.S. energy consumption of 96.3 Quads. Office, retail, and educational facilities represent about ½ of commercial sector energy consumption. Windows are responsible for 1.88 Quads of energy for heating and 3.86 Quads of energy for cooling.
Windows have a dominant influence on a building's appearance and interior environment, yet windows can be one of the most important components impacting its energy use, peak electricity demand, and environmental consequences. Heat gain and heat loss through windows can represent a significant portion of a building's heating and cooling loads. By providing natural light, windows can reduce electric lighting loads by using design strategies such as dimming controls, automated shading, and light redirection.
Site and Source Energy
The EPA has determined that source energy is the most equitable unit of evaluation of energy consumption of commercial buildings. Source energy represents the total amount of raw fuel that is required to operate the building incorporating transmission, delivery, and production losses. This allows for a complete assessment of energy efficiency in a building by providing equitable rating and consumption in a single common unit.
When primary energy is consumed, the conversion to source energy accounts for losses that are incurred in storage, transport and delivery of fuel to the building. When secondary energy is consumed, the conversion to source must account for losses incurred in the production, transmission, and delivery to the site. Source energy comparisons generally reflect energy costs and carbon emissions more accurately than site energy. The factors used to restate primary and secondary energy in terms of the total equivalent source energy units are called the source-site ratios.