It takes more energy—and money—to heat a drafty house. That's why it pays to address drafts before you even switch on the furnace. Inspect window frames and door jambs, both inside and out, for holes, cracks, or crumbling caulk. Install weatherstripping to fill gaps in door frames and windows, and apply fresh caulk where needed to seal up your home. In a few months' time, you'll be glad you took the time to keep whistling winter winds at bay.