I get where you’re coming from with caulk and foam, but I’m not convinced it’s always as effective as it seems—at least not on its own. I did a pretty thorough job caulking and foaming the window trim in my 1915 place, and sure, it cut down on the worst of the drafts. But honestly, my energy bills barely budged. I think a lot of that’s because these old houses just leak everywhere—walls, attic, even through the floorboards.
If you really want to see a difference, you might want to look at bigger-picture stuff: storm windows, heavy curtains, or even interior window film in the winter. Caulking is good for stopping those obvious cold spots, but unless you tackle the other leaky areas too, the gains are kind of limited. Still, I totally get wanting to do something low-cost and non-invasive first. Just don’t expect miracles from a tube of caulk if your house is as drafty as mine was...