Calculate how much thermal energy you save over a 1-hour period with a double-pane (low-e, argon-gas filled) window as compared to a single-pane window. the interior temperature is 70° f and the outside temperature is 40° f. facts include: the single-pane window has an r-value of 0.9. the double-pane window has an r-value of 3.0. you have 250 square feet of window in your home.