ENVE 4105 Lecture Notes - Lecture 5: Shortwave Radiation, Thermal Comfort, Passive Solar Building Design
19 Jan 2016
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Fenestration - lecture five - 3 february 2015. Good passive solar/ daylighting design is complex. Windows and the associated leakage often represent the single greatest source of heat loss in buildings. Longwave radiation between building surfaces: multi-paned windows. Low-e (emissivity) coatings reduce the long-wave radiation between window surfaces. Low-e coatings have emissivities of about 0. 1 - 0. 2 (compared to about 0. 9 without) Heat transfer between surfaces that are not in contact and does not require a medium (air, water, etc) Any surfaces that see each other exchange thermal energy via longwave radiation, For example, a floor that is directly in the sun will redistribute that thermal energy via so long as they"re at different temperatures longwave radiation to all surfaces it sees . Qnet = net heat transfer from surface 1 to surface 2 (watts) Is the stefan-boltzmann constant (= 5. 669 x 10-8 w/m2k4) F12 view factor from surface 1 to 2.
