Originally, the arrangement of windows in a building. Now, windows, glazing, and shading devices.
The transmittance, reflectance, and absorptance of glazing materials for solar radiation.
That portion of the solar spectrum which is visible to the human eye. Too much visible light transmittance creates brightness and glare
problems within the room. Visible–light transmittance must be a primary consideration when selecting a sunscreen shadecloth.
Solar heat gain
The amount of heat admitted through fenestration due to transmitted radiation and the inward flow of absorbed radiation.
Shading coefficient (SC)
The percentage of solar heat gain that passes through a combination of glass and screen. A lower shading coefficient means lower
heat gain (better thermal performance). When used on the interior, light colors have lower shading coefficients than dark colors. Thus,
light colors outperform dark colors. A lower shading coefficient equals lower heat gain, i.e., SC 0.60 = 60% relative solar heat gain;
SC 0.45 = 45% relative solar heat gain.
When these same shadecloths are used on the exterior, this performance is reversed. For exterior shading, dark colors have a lower
coefficient and, thus, outperform light colors. An explanation for this is that the lighter colors not only reflect heat away from the window
but also reflect a substantial percentage back into the building as well.
Solar reflectance (SR)
The percentage of solar energy which is reflected or bounces off the shadecloth. Light colors are more reflective
with lower heat gain and shading coefficients but with a higher percentage of daylight and solar transmittance. Light colors are
brighter when sunlit (which causes high surface brightness, or bare–light–bulb syndrome) and may transmit excessive, debilitating light onto
computer screens and workstations.
Solar absorbance (SA)
The percentage of solar energy which is absorbed by shadecloth. Dark colors absorb light and heat and are
less energy efficient than lighter colors. They transmit less light and have a lower surface brightness which lessens the reflectivity and provides
excellent glare–free environments on computer monitors and workstations.
Openness factor (OF)
The density of a shadecloth’s weave. To assure personal comfort near the window wall,
it is necessary to control the direct solar–radiant energy (sunshine) that penetrates the glass/shade combination. This is accomplished with
proper selection of shadecloth density in conjunction with the visible light transmittance of the glass.
The distance between successive peaks or valleys of radiation waves: Measurement is in millions of a meter.
A measurement of the conductive inward or outward heat flow expressed as a percentage.
The ability to give off radiant energy when compared to a perfect absorber. Different materials emit stored energy at different
temperatures. Shadecloths emit much lower temperatures than, as examples, polished–aluminum or satin–aluminum finishes.
Long–wave emittance is sensible heat which heats the air.
White and dark surfaces
Most shadecloth surfaces have a high long–wave emittance. Light–colored fabric surfaces will reflect more short–wave
solar radiation and, therefore, absorb less. Dark–colored fabric surfaces absorb more short–wave radiation and reflect less.
Equivalent sphere illumination which is provided by the luminous hemisphere.
In degrees, the angle between a solar ray and the horizon.
In degrees, the angle between the north–south line and the horizontal projection of the solar ray.
The control of the admission of heat and light through windows by means of adjustable shading devices.