It costs a small fortune to keep your home comfortable over the winter, not only because energy prices keep rising, but also because, in the average home, all that heat can escape through countless cracks, gaps, and small holes. Fortunately, you can lower your bills significantly by finding and filling those costly openings. True, without a formal energy audit, it may not be possible to hunt down and correct each and every one. But begin by looking especially closely at the windows and doors. If you detect air leaks around their perimeters, seal them with weatherstripping, caulk, or a combination of the two. Meanwhile, use spray foam to plug any openings around cables, vents, or pipes that penetrate the exterior.