I've just moved into a house where I'm concerned that an energy audit might find problems. The clue is that the windows appear to be old single-pane windows. Once it's cold out I can borrow an infrared camera and go around checking to see how bad things are and exactly where the greatest heat losses are. But it's hard to install new windows in winter. What can I do now to anticipate where the problems will be?
One way is to heat the whole house so it is above the outside ambient temperature, say 24 degrees C, then use a thermal camera to take pictures of the outside walls and roof surfaces of the house.
Those walls, windows etc that are loosing heat faster than other surfaces or parts of surfaces show up. If the camera is calibrated then it will provide a scale showing the relative temperatures.
The general principle to use is that actual air leaks are a lot worse than just having poor insulation.
Look around your doors, windows, plumbing, attic/basement/crawlspace access hatches, fireplace, and anywhere else where there's a hole in the wall. Anywhere you feel air movement is an issue. Anywhere you can see daylight (that's not glass) is an issue.
My answer is old school but it has worked for me many times. Get a roll of that semi clear plastic and tape a piece to the entire inside window frame, basically sealing it. Any air leaking will either bow or suck in the plastic. you can then work on fixing any leaks and will know when you've succeeded because the plastic will quit moving. here is a link to the type of plastic I used. https://www.amazon.com/Premier-Clear-Plastic-Cloth I also used the blue painters tape so i wouldn't damage the walls or frame.