MEP Flashcards
Enthalpy
a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
Demand control ventilation
A system designed to adjust the amount of ventilation air provided to a space based on the extent of occupancy, the system normally uses carbon dioxide sensors but may also use occupancy sensors or air quality sensors.
Light Shelf
A horizontal element positioned above eye level and designed to reflect daylight on the ceiling for improved daylight effectiveness.
Shading coefficient (SC)
The ratio of solar heat gain through a glazing product to the solar heat gain through an unshaded 1/8 inch thick, clear, double strength glass, under the same set of conditions.
SHGC
Solar Heat Gain Coefficient.
The ratio of solar heat gain through a fence station to the total solar radiation incident on glazing. Solar heat gain includes directly transmitted solar heat absorbed solar radiation, which is then re-radiated, conducted, or convected into the space.
Solar time
This time is defined by the sun in its position relative to earth. Because the length of the solar day varies, most references use the mean solar day as a basis for time keeping, this is the average length of a solar day.
Graywater recycling
The collection, treatment, storage, and distribution of wastewater from sources that do not contain human waste such as showers & sinks.
Analemma
The figure-eight curve that represents the angular offset of the sun from its mean position as viewed from the earth. At any given point on the earth, if the position of the sun is noted at the same time every day for a year, the figure of the analemma is produced.
balance-point temperature
The outdoor temperature at which a building makes a transition from a heating need to a cooling need.
daylight autonomy (DA)
Also referred to as spatial daylight autonomy (sDA). The percentage of an area that meets a minimum daylight illuminance level for a specified fraction of the operating hours per year (e.g., 300 lux for 50% of the time). It is one of the options for receiving LEED credit in the Daylight category.
equation of time
The factor used to account for the difference between solar time and clock time. Solar time is based on the position of the sun. Its basic unit is the solar day, the time the earth takes to make one complete rotation on its axis. A solar day may be slightly more than or less than 24 hours by clock time; its exact length changes from day to day due to the earth’s elliptical orbit around the sun and the tilt of the earth’s axis. Depending on the time of year, solar days may pass more quickly or more slowly than days on the clock. As the small differences accumulate, solar time can be ahead or behind clock time by as much as about 161 2 minutes. The equation of time is also expressed in the analemma. The dif- ference between solar time and clock time is also affected by one’s position east or west within a time zone; this is a separate factor from the equation of time.
glazing factor
A LEED-based number calculated by taking into account window area, floor area, a win- dow 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.
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.
radiation spectrum
The entire range of electromagnetic radiation extending from 0 Hz to about 1023 Hz. This includes visible light as well as infrared radiation, radio waves, and gamma rays, among others.
