PERFORMANCE: Energy & Cost
Energy & Cost
Codes & Standards
The initial expense of windows is generally more than an equal area of opaque facade, but the need for or desirability of some type of window usually does not require justification—for the purpose of window is for light, view and natural ventilation. An important issue is defending additional cost to provide more windows or higher-performance windows. Yet, the operating energy and maintenance costs of the building usually outweigh the initial costs by a factor of about ten to one. Moreover, the expense of occupant salaries within the building is typically many times more than the operating costs. The window's initial cost drives many decisions, but it is small in comparison to other more critical features.
Since windows can have a significant impact on the operating costs, health, productivity and occupant well-being, a broadly focused life cycle analysis must be used. Such analysis must include monetary, environmental, and human impacts of building design choices. Durability is also a key issue in any life cycle analysis. Window frames, glazings, and sealants may have different useful lives. Yet, window systems are expected to last at least 20–30 years and they can often be much more expensive and difficult to replace than other building systems. Maintaining energy performance properties over the life of the window is an essential aspect of window durability.