definitions - ballast 29 Flashcards
are chromogenic fenestration products that change their characteristics based on particular envi- ronmental conditions or through human intervention.
switchable glazings
consists of a multilayered thin film, applied to glass, that changes continuously from dark to clear as low-voltage electrical current is applied. This type of glazing allows variable transmittance in the visible por- tion of the spectrum while reflecting in the infrared spec- trum, thereby reducing solar heat gain.
electrochromic glazing
darkens under the direct action of sun- light, in the same way that some sunglasses do. As the light intensity increases, the window becomes darker.
Photochromicglazing
changes darkness in response totem- perature. Like photochromic glazing, this technique offers less control than electrochromic glazing does.
thermochromic glazing
csmake it possible to have a glazing material that changes from transparent to
reflective.
Transition-meta!hydride e!ectrochromi
When a new outer layer of glazing is built around an exist- ing building, the system is known as a
dynamic buffer zone
This is the ratio, expressed as a per- centage, of the indoor illuminance at a point on a horizon- . tal surface to the unobstructed exterior horizontal illuminance. Direct sunlight is excluded.
daylight factor DF
:the outdoor temperature at which a building makes a transition from a heating need to a cooling need
balance point temperature
:the product of visible transmittance mul- tiplied by the window-to-wall ratio
effective aperature
a LEED-based number calculated by taking into account window area, floor area, a window geome- try factor, light transmission, and a window height fac- tor.
glazing factor
visible light from the sun and sky, reflected by exterior surfaces below the plane of the horizon
ground light
the requirement that a utility pay and cliarge equal rates regardless of which way electricity flows as part of the utility grid. Thus, excess electricity generated with photovoltaics or wind systems can be sold back to the utility
net metering
the ratio of the solar heat gain through a glazing product to the solar heat gain through an unshaded 1 /, in thick (3), clear, double-strength glass under the same set of conditions.
shading coefficient
the ratio of the solar heat gain through a fenestration to the total solar radiation incident on the glazing.
solar heat gain coefficient SHGC
the fraction of visible light that passes through a glazing material
visible light transmittance VLT
