Solar gain (also known as solar heat gain or passive solar gain) refers to the increase in
temperaturein a space, object or structure that results from solar radiation. The amount of solar gain increases with the strength of the sun, and with the ability of any intervening material to transmit or resist the radiation.
Objects struck by sunlight absorb the short-wave radiation from the
lightand re-radiate the heat at longer infrared wavelengths. Where there is a material or substance between the sunand the objects struck that is more transparent to the shorter wavelengths than the longer, then when the sun is shining the net result is an increase in temperature - solar gain. This effect, the greenhouse effect, so called due to the solar gain that is experienced behind the glass of a greenhouse, has since become well known in the context of global warming.
When discussing the properties of fenestration (e.g. [window] s and [door] s) and shading devices, shading coefficients are commonly mentioned properties. Shading coefficients measure the solar energy
transmittancethrough windows. "G-value" is the coefficient commonly used in Europe and "solar heat gain coefficient (SHGC)" is used in the United States. "Shading Coefficient" is an older term that is still sometimes used in the United States. The relationship between SHGC and SC is as follows: SHGC = SC × 0.87. G-values and SHGC values ranges from 0 to 1, a lower value representing less solar gain. Shading coefficient values are calculated using the sum of the primary solar transmittance (T-value) and the secondary transmittance. Primary transmittance is fraction of solar radiationthat directly enters a building through a window compared to the total solar insolation, the amount of radiation that the window receives. The secondary transmittance is the fraction of inwardly flowing solar energyabsorbed in the window (or shading device) again compared to the total solar insolation.
Solar gain and building design
In the context of
passive solar building designthe aim of the designer is normally to maximise solar gain within the building in the winter (to reduce space heatingdemand), and to control it in summer (to minimise cooling requirements). Thermal massmay be used to even out the fluctuations during the day, and to some extent between days.
In direct solar gain systems, the composition and coating of the building glazing can also be manipulated to optimise the greenhouse effect, while its size, position and shading can be used to optimise solar gain. Solar gain can also be transferred to the building by indirect or isolated solar gain systems. For further details, see "
passive solar building design".
Heating degree day
** Low-emissivity coatings
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Solar Gain — The amount of energy that a building absorbs due to solar energy striking its exterior and conducting to the interior or passing through windows and being absorbed by materials in the building … Energy terms
Direct solar gain — Solar energy collected from the sun (as heat) in a building through windows, walls, skylights, etc. California Energy Comission. Dictionary of Energy Terms … Energy terms
Indirect Solar Gain System — A passive solar heating system in which the sun warms a heat storage element, and the heat is distributed to the interior space by convection, conduction, and radiation … Energy terms
Isolated Solar Gain System — A type of passive solar heating system where heat is collected in one area for use in another … Energy terms
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