A window measures 36 inches x 50 inches and there are 20 of these windows in a structure. The U-factor for this single pane metal window is 1.3 Btu/hr-ft2-oF. U-factor is the conduction factor (and thus the reciprocal of an R-factor) and is equal to conductivity of the material k over the conducting pathlength L. Assume conduction only.

a. Estimate the heat transfer (in Joules per day) through these 20 windows when the inside temperature is 20C and the outdoor temperature stays at -15C.

b. The U-factor of replacement windows (double pane, argon filled, low-E vinyl frames) is 0.31 Btu/hr-ft²- How much heat is transferred in a day for this case?