Chp 29 - Defintions Flashcards
Balance-Point Temperature
the outdoor temperature at which a building makes a transition from a heating need to a cooling need
[DF] Daylight Factor
the ratio, expressed as a percentage of the indoor illuminance at a point on a horizontal surface to the unobstructed exterior horizontal illuminance direct sunlight is excluded.
[EA] Effective Aperture
the product of visible transmittance multiplied by the window to wall ratio
Glazing Factor
a LEED based number calculated by taking into account window area, floor are, a window geometry factor, light transmission, and a window height factor.
Ground Light
visible light from the sun and sky, reflected by exterior surfaces below the plane of the horizon
Light Shelf
a horizontal element positioned above eye level and designed to reflect daylight from the ceiling for improved daylighting effectiveness.
Net metering
the requirement that a utility pay and charge 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.
Radiative Cooling (or Nocturnal Cooling or Night Cooled Mass)
a passive or active design strategy that uses thermal mass to collect and store heat during the day for release at night. This works best in climates where there is a significant difference between daytime and nighttime temperatures, such as the Southwest or in temperate climates.
[SC] Shading Coefficient
the ratio of the solar heat gain through a glazing product to the solar heat gain through an unshaded 1/8 in thick (3), clear, double-strength glass under the same set of conditions. This is a value for the glass only and does not include the frame. The SC is a value between 0.0 and 1.0. Because this rating includes only the glass, the solar heat gain coefficient is considered a more accurate rating.
[SHGC] Solar Heat Gain Coefficient
the ratio of the solar heat gain through a fenestration to the total solar radiation incident on the glazing. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted, or converted into the space. This rating includes the effect of the frame and glass space. The SHGC is a value between 0.0 and 0.87.
[VLT] Visible Light Transmittance -the fraction of visible light that passes through glazing material.
the fraction of visible light that passes through glazing material.
[WWR] Window-to-Wall Ratio
the net glazing area (glass only, not including frame or mullions) in a room or space divided by the gross exterior wall area.
Workplane
the assumed height at which work is performed, usually considered to be at desk height, 30 in above the floor.
