Spiders are industrious beings. They build their webs where there are air currents. This increases their chances of having dinner fly in. So, where there are spider webs, there are air currents.
You can benefit from their instincts by noticing where the spider webs show up in your basement, attic, or living space. If you see a spider web near a window, along a floorboard, or along the basement foundation, you can find a place where heat will be escaping your house. Seal it up. You will save money and discourage the spider (if you haven’t killed it, that is.)