Energy Loss Through Windows

Hello. I work in a very old building and there is little money available for repairs. However, one improvement that I think could save the company money is to insulate the windows. My challenge is to prove this to the boss! The windows are obviously inadequate as, aside from being single glazed and vey thin, they are also stuck open. There are about 10 windows along one corridor, and at least 5 won't close, leaving a gap of about 1 cm each. The temperature inside is probably about 18 degrees C and outside 3 degrees, but temperatures are plummeting this time of year, so the difference will be greater. How do I calculate the approximate energy lost through the windows? If I can figure that out, I can then work out how much money is being wasted through the open windows. Thanks for your help.
- Sarah (age 35)
UK

That sounds like a great idea. I wish that we could use basic physics to calculate the energy loss, but the problems of wind etc. are too complicated for that. Instead, we can just quote figures from reliable groups with practical experience in these matters. E.g.  estimates a 25% to 50% reduction in heat loss from replacing really poor windows. Replacing the ones you have that don't even close probably would save even more. 

People say that the payback time for fixing really bad energy leaks is short, just a few years. In addition, of course, there are benefits for our shared environment. This sounds like it would be a smart move by any standard.

Mike W.

(published on 01/29/2014)