Among the quickest routes for heated air to escape from your nice, warm home during the winter are the same ones where cold air finds its way in: through windows and doors. Air leaks are a waste of energy, and they can occur around windows and their frames and even right through the glass.

To find leaks, try this test: On a windy day, light a stick of incense and hold it next to a window. If the smoke travels horizontally, you've found a leak. You can use the same test to find leaks around doors, plumbing fixtures, electrical outlets and other potential escape routes for heated air.

Once you find a leak around a window or a door:

• Caulk and weather-strip. Caulk is an airtight filler for cracks and holes. Weather-stripping takes the form of a narrow piece of foam, metal, vinyl, rubber or felt that seals window joints between the sash and frame, but doesn't interfere with opening and closing the window.
• If you have single-pane windows, install storm windows over them.
• As an alternative, tightly tape clear plastic film to the inside of the window frames when it's cold.
• Replace your curtains with insulating shades, shutters or drapes. Taking a few steps to make windows and doors more energy efficient will also make your home more comfortable. And it could save you some money on your electric bill, too.