Glossary

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L

Laminated glass
Two or more sheets of glass with an inner layer of transparent plastic to which the glass adheres if broken. Used for safety glazing and sound reduction.
Lift
Handle for raising the lower sash in a double-hung window. Also called sash lift.
Light
A window; a pane of glass within a window. Double-hung windows are designated by the number of lights in upper and lower sash, as in six-over-six. Also spelled informally lite.
Light-to-solar-gain ratio
A measure of the ability of a glazing to provide light without excessive solar heat gain. It is the ratio between the visible transmittance of a glazing and its solar heat gain coefficient. Abbreviated LSG.
Lintel
A horizontal member above a window or door opening that supports the structure above.
Liquid crystal glazing
Glass in which the optical properties of a thin layer of liquid crystals are controlled by an electrical current, changing from a clear to a diffusing state.
Long-wave infrared radiation
Invisible radiation, beyond red light on the electromagnetic spectrum (above 3.5 micro meters), emitted by warm surfaces such as a body at room temperature radiating to a cold window surface.
Low-conductance spacers
An assembly of materials designed to reduce heat transfer at the edge of an insulating window. Spacers are placed between the panes of glass in a double- or triple-glazed window.
Low-emittance (Low-E) coating
Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of long-wave infrared radiation.
Low-emissivity (low-e) coating
Microscopically thin, virtually invisible metal or metallic oxide layers deposited on a window glazing surface and sealed in an insulating glass unit to reduce the U-factor by suppressing radiative heat-flow through the window.
Luminous Efficacy (Light-to-Solar Gain Ratio)
The visible transmittance of a glazing system divided by the solar heat gain coefficient (or shading coefficient). This ratio is helpful in selecting glazing products for different climates in terms of those that transmit more heat than light and those that transmit more light than heat.