Problem
An older home has windows that are 1 m by 1.67 m in area. The older windows are made of a single pane glass, 5 mm thick with a thermal conductivity of 0.68 W/m/K. If the panes are replaced with thermal panes: two 3 mm sheets of glass (same thermal conductivity) that a sandwich a 5 mm air gap (k_air=0.03 W/m/K). What is the energy savings (W) per window if the inside and outside heat transfer coefficients are 10 and 5 W/m^2/K, respectively and the inside and outside temperatures are 25 and -5 C, respectively?