Toplot : Minimum R-value as a function of outside temperature from -20 o F to 50 o F. The graph between the minimum R-value and outside temperature ranging from -20 o F to 50 o F. Given data: Latitude of south facing window = 40 o N Interior temperature = 68 o F Outside temperature (T o ) = -20 o F Initial temperature (T i ) = 68 o F Calculation: Calculate the insulation per unit day in winter: I = Q A Q = Energy A = Area t = time period of one day I = 1000 Btu/ft 2 t t = 1 d a y I = 1000 Btu/ft 2 1 d × | 24 h 1 d | = 42 Btu/ft 2 per hour Calculate the change in temperature Δ T = T i − T o = 68 o F − ( − 20 o F ) = 88 o F Calculate the minimum R-value. R = Δ T I = 88 o F 42 Btu/ft 2 per hour = 2.095 h ft 2 o F/Btu Minimum R-value for different values of outside temperature ranging from -20 o F to 50 o F. The graph between the minimum R-value andoutside temperature ranging from -20 o F to 50 o F.

Sustainable Energy, SI Edition

2nd Edition

ISBN: 9781337672092

Author: DUNLAP, Richard A.

Publisher: Cengage Learning

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Solution Summary: The author calculates the minimum R-value for different values of outside temperature ranging from -20o F to 50oF.

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