The wall of a house consists of three layers: a wooden outer wall with an R factor of 1.0,a 3-in layer of fiberglass insulation with an R factor of 11,and a gypsum-board inner wall with an R factor of 0.33 (all R factors are in h · ft² · Fº/Btu).When the temperature is 68ºF inside the house and - 4.0ºF outside,what is the rate of heat loss through an 8-ft by 15-ft section of this wall? A)700 Btu/h B)780 Btu/h C)5.8 Btu/h D)130 Btu/h E)350 Btu/h

Question

Quizplus · Accepted Answer

The correct answer is A because the rate of heat loss through a wall is given by the equation Q = (T1 - T2) / R, where Q is the heat loss in Btu/h, T1 is the temperature on the warm side of the wall in ºF, T2 is the temperature on the cold side of the wall in ºF, and R is the thermal resistance of the wall in h · ft2 · Fº/Btu. In this problem, T1 = 68ºF, T2 = -4.0ºF, and R = 1.0 + 11 + 0.33 = 12.33 h · ft2 · Fº/Btu. Therefore, Q = (68ºF - (-4.0ºF)) / 12.33 h · ft2 · Fº/Btu = 700 Btu/h.

The Wall of a House Consists of Three Layers: a Wooden