Total Solar Transmittance
|
The ratio of the
amount of total solar energy in the full solar wavelength
range (300-2,100 nanometers) that is allowed to pass through
a glazing system to the amount of total solar energy falling
on that glazing system. Value is usually expressed as a
percent. |
Total Solar Reflectance
|
The ratio of total
solar energy which is reflected outward by the glazing
system to the amount of total solar energy falling on the
glazing system. On filmed windows this reflectance is a
function of the side of the film facing the window surface.
Value is usually expressed as a percent. |
Total Solar Absorption
|
The ratio of the
amount of total solar energy absorbed by a glazing system to
the amount of total solar energy falling on the glazing
system. Solar absorption is that portion of total solar
energy neither transmitted nor reflected. Since solar
transmittance and solar reflectance are measured directly,
the following equation should be used in calculating solar
absorption. Solar absorption =1.00 - (solar transmittance) -
(solar reflectance) |
Visible Light Transmittance
|
The ratio of the
amount of total visible solar energy (380-780 nanometers)
that is allowed to pass through a glazing system to the
amount of total visible solar energy falling on the glazing
system. Value is usually expressed as a percent. Glare is
influenced by visible light transmittance through a glazing
system. |
Visible Light Reflectance
|
The percent of
total visible light to be reflected by a glazing system that
can be seen visually. |
Ultraviolet (UV) Transmittance
|
The ratio of the
amount of total UV solar energy (300-380 nanometers) that is
allowed to pass through a glazing system to the amount of
total UV solar energy falling on the glazing system.
Ultra-violet is one portion of the total solar energy
spectrum which greatly contributes to fading and
deterioration of fabric and furnishings. |
U-Factor
|
The overall heat
transfer coefficient of the glazing system, U -Factor is a
measure of the heat transfer that occurs through the glazing
system, and its outer and inner surfaces. This value is a
function of temperature, and is expressed in BTU per square
foot per hour per degree Fahrenheit (BTU/ sq. ft./hr.
degrees
F). The lower the U- Factor, the better the insulation
qualities of the glazing system. |
Shading Coefficient
(SC)
|
The ratio of the
solar heat gain through a given glazing system to the solar
heat gain under the same conditions for clear, unshaded
double strength window glass (DSA). Shading coefficient
defines the sun control capability or efficiency of the
glazing system. |
Total Solar Energy Rejected
|
The percent of
incident solar energy rejected by a glazing system equals
solar reflectance plus the part of solar absorption which is
reradiated outward. |
BTU-British Thermal Unit
|
The amount of heat
required to raise the temperature of one pound of water one
degree Fahrenheit. 1 BTU = 252 Calories (CAL) |
TON-HR
|
One ton of air
conditioning = 12,000 BTU/Hour (3.52kW) |
