City College’s board wants to minimize the college’s expenditures on physical facilities over time and so has asked the physical facilities department to consider choosing double-pane windows when replacing old windows. Compared to single-pane windows, double-pane windows provide much more insulation to a building, thus reducing energy costs. Moreover, the labor and other costs associated with installing double-pane windows are the same as those for single-pane windows.
Which of the following would it be most useful to know in determining whether switching to double-paned windows would be likely to help minimize City College’s physical facilities expenditures?