Fenestration affects building energy use through four basic mechanisms: thermal heat transfer, solar heat gain, visible transmittance and air leakage. Condensation resistance is considered not to affect energy use and is therefore not a concern of the building codes. However, CRF is an important thermal performance characteristic and is therefore included in this document. This document covers glazed fenestration systems such as windows, curtain walls, window walls, sloped glazing, storefronts, doors and other glazed products that are installed in commercial buildings (buildings other than low-rise residential buildings). For projecting elements that do not increase usable floor space, refer to the generalized equation in Section 7.1 and the specific building application. Products not covered by this standard include fenestration systems (windows, doors, skylights) intended for use in low-rise residential applications.