All the info I could obtain talks about heat loss through windows and doors. I am trying to get several store owners in my town to close there doors in the middle of winter and summer. The average door is 28 sq ft. I am assuming the inside temperature is 68 degrees and the outside temperate is 34 degrees. How much energy are they wasting? This is not a homework question. I am 65 years old. Too old to remember any of my physics.