I think maybe the best way to judge the age of a house, like counting tree rings, is to look at its basement and see how many generations of infrastructure you can identify. This picture doesn't show all of them, but it does present a pleasing array of pipes of various description.
Also note the bit of insulation tacked to the wall -- to keep air out? -- and the apparent vine to the far right of the picture. I didn't notice it when taking the shot, but ... when you have a vine in your basement, it's really kind of a warning bell when it comes to air entry.
Another good way to judge airtightness (or dire lack thereof) is to go into the basement during the day with the lights off. If you can see, you might have a problem. I found a one-inch hole in the foundation just today. And gaping holes into a crawlspace under the kitchen which has a grate to the outside -- and that was just a casual note. At any rate, I'm not having troubles seeing why the pipes tended to freeze under the kitchen. (How could they not? They were basically outside!)