Solar radiation heat gain

The part of the bus enclosure installed outdoors is exposed to solar radiation which is a cause of additional heat gain by the enclosure. ANSI C-37.24 has provided a basis to determine its effect in terms of heat generated as follows ... 

Outdoor air is generally less polluted than the system return air. However, problems with reentry of previously exhausted air occur as a result of improperly located exhaust and intake vents or periodic changes in wind conditions. Other outdoor contamination problems include contaminants from other industrial sources, power plants, motor vehicle exhaust, and dust, asphalt vapors, and solvents from construction or renovation. Also, heat gains and losses through the building envelope due to heat conduction through exterior walls, floor, and roof, and due to solar radiation and infiltration, can be attributed to effects from external sources. 

Heat gain by radiation through transparent surfaces - usually solar but occasionally by other means (radiant heat from a process, such as furnaces)... 

After the proper inside and summer outside temperature conditions for comfort and temperature conditions for process air conditioning have been selected, the next step is to calculate the space cooling load, which is made up of sensible heat and latent heat loads. The sensible heat load consists of (1) transmission through walls, roofs, floors, ceilings, and window glass, (2) solar and sky radiation, (3) heat gains from infiltration of outside air, (4) heat gains from people. 

The fraction of incident solar radiation that enters through the glazing is called the solar heat gain coefficient (SHGC) and is expressed as... 

Draperie.s reduce heat gain in summer by reflecting back solar radiation, and reduce beat loss in winter by forming an air space before the window. 

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