4 Solar Gain Through Building
4.2 Type of Window Glasses
4.2.1 Clear Plate or Sheet Glasses
4.2.2 Tinted Heat Absorbing Glasses
4.2.3 Reflective Coated Glasses
4.2.4 Insulating Glasses
4.3 Greenhouse Effect
Window glass allows short-wave solar radiation get into an interior space. This radiation is absorbed by the interior of the building. The interior then radiates long-wave, thermal radiation. Glass is opaque (not transparent) to this long wave radiation. Thus energy is trapped in the building and the indoor air temperature rises. This is known as the green effect.
Figure 6 Distribution of Solar Radiation Falling on 3mm Clear Plate or Float Glass
4.4 Solar Gain Through Fenestration
Figure 7 Solar Transmission through a 6mm Float Glazing Glass (Green)
Figure 8 Solar Transmission through a 6mm Reflective Glass (Gold)
4.4.1 Solar Heat Gain
4.4.2 Shading Coefficient
4.4.3 Solar Heat Gain Factor
2) is the solar heat gain through a sunlit double strength sheet glass at any specified orientation and any day-light hour.
Since SHGF at a fixed window orientation varies through the year because of the continuous change of incident sunlight direction., maximum solar heat gain factor (max. SHGF) is introduced. Max. SGHF is the maximum value of SHGF on the 21st day of each month for a specific latitude. Table 2 lists the maximum SHGFs of the 22 degree north latitude. These max. SGHFs are values on average cloudiness days. At high elevations and very clear days, the actual max. SGHF may be 15% higher, and in very dusty industrial areas, they may be 20 to 30% lower.
Table 2 Maximum Solar Heat Gain Factor for Sunlit Glass on Average Cloudiness Days
4.4.4 Solar Heat Gain through Fenestration Area
where max. SHGF = maximum solar heat gain factor for window glass
Table 3 Maximum Solar Heat Gain Factor of Shaded Area