The culprit isn't your furnace or your insulation—it’s the invisible gaps around your windows.

Snip the caulk tube nozzle at a 45-degree angle. You want a bead the size of a pencil lead, not a garden hose. Poke the inner seal with the wire on the gun.

You’ve felt it. That mysterious shiver while sitting on the couch. The way the curtains puff inward on a windy day. The sudden spike on your heating bill that makes you double-check the thermostat.

Pull the gun smoothly along the crack. Don't go back and forth. Aim to fill the void, not just cover the top.

Wet your finger (or a plastic spoon) with soapy water. Run it lightly over the bead to push the caulk into the crack and smooth the surface.