| dc.description.abstract | Shading devices are frequently used to control solar gain through windows. Solar
optical properties are very important in the energy analysis of windows. Transmittance,
absorptance and reflectance are required to quantify solar heat gain through
complex fenestration systems, which consist of combinations of glazing and shading
layers.
In this research the solar transmittance of a sheer blind was measured using a
Broad Area Illuminating Integrating Sphere (BAI-IS). More specifically, the spectral
directional-hemispherical transmittance was measured in the wavelength range
of 0.4 µm to 2.0 µm.
A “sheer blind” consists of soft fabric vanes, similar to a venetian blind, suspended
between two vertical layers of sheer fabric. This arrangement is popular because it is attractive and it has potential application for daylighting. The vertical sheer fabric reduces the solar intensity and diffuses incident radiation; generally reducing
solar gain and producing soft, natural illumination. The fabric vanes control
the amount of light entering the room.
Shading devices such as venetian blinds, sheer blinds and drapes have spatially
non-uniform and light scattering surfaces. Hence, measurement error occurs if
the solar optical properties are measured by traditional narrow-beam measurement
techniques typically used in commercial spectrophotometers. To reduce this error,
a BAI-IS is recommended.
The BAI-IS apparatus consists of a 20-inch diameter integrating sphere, sample
mounting system, monochromator, radiant source, lock-in-amplifier, photo sensor,
optical chopper and various auxiliary devices. In order to improve reliability of the measurement the BAI-IS has recently been upgraded by replacing most of the key
control and measurement equipment.
The refurbishment of the BAI-IS apparatus was successful. The directionalhemispherical
transmittance of a sheer blind from BAI-IS measurement was found to agree well with an analytical model. | en |
