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Heat gain in buildings: Other factors. Solar radiation Classification of solar radiation Direct radiation: Radiation that reaches earth's surface direct from the sun. Diffuse radiation: Radiation that has been scattered or re-emitted.

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## Heat gain in buildings: Other factors

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**Heat gain in buildings: Other factors**• Solar radiation • Classification of solar radiation • Direct radiation: Radiation that reaches earth's surface direct from the sun. • Diffuse radiation: Radiation that has been scattered or re-emitted. • Total solar heat quantity falling on a surface consists of (1) unshaded direct radiation, (2) unobstructed diffuse radiation from sky, and (3) reflected solar radiation from adjacent surfaces. • Solar heat gain through windows depends on its location on the earth's surface (latitude), time of the day, day of the year, and the direction it faces.**Heat gain in buildings: Other factors**• Formula for calculation of solar heat gain: Q =SF*A*SC, where SF = solar heat gain factor that specifies solar radiation in BTUH/sqft., A = glass area in sqft., and SC = shading coefficient that specifies the percentage of solar heat passing through the glass.**Heat gain in buildings: Other factors**• Equivalent temperature difference (ETD) • ETD is an increased temperature difference that allows for heat gain through opaque surfaces caused by both air temperature difference and direct solar radiation. • Apart from direct solar radiation, ETD is also affected by • Surface color and weight (density) of the materials. • ETD takes into account the density of construction, degree of exposure, time of the day, location, and orientation and design conditions. • Formula for calculation of heat gain through opaque surfaces such as roofs and walls, taking direct solar radiation into consideration: Q = U*A*ETD**Heat gain in buildings: Other factors**• Internal loads • People: • Sensible heat • Latent heat • Both sensible and latent heat components should be calculated using the formula: Q = # of persons*heat generated per person • Lighting • Heat gain due to this factor may be calculated using the formula: Q = 3.4 *watts/sqft*floor area**Heat gain in buildings: Other factors**• The total amount of heat gain due to this factor depends on number of people, duration of occupancy, and activity level. • Electric light fixtures convert electrical power into heat and light. Even light is eventually eventually converted into its equivalent heat energy in the space; so, in effect, all electrical power entering a light fixture ends up as heat in a space.**Heat gain in buildings: Other factors**• Equipment: There is almost an infinite variety of equipment that contribute to heat gain to the conditioned space. The designer has to be thorough in identifying all the heat-producing equipment in a given space. In order to calculate heat gain due to the effect of equipment, the formula for lighting may be used as an approximation. • Kitchen appliances: The total residential equipment loads can be approximated by the major appliances in the kitchen. A value of 1200 BTUH may be used as heat gain from residential kitchen appliances.

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