According to the EPA, drafty windows are a major source of wasted energy dollars as they allow warmed and cooled air to escape your home. To find out if your windows are costly culprits, says the EPA, light an incense stick on a windy day and hold it next to the interior side of a window. If the smoke streams horizontally from the stick, your window likely needs caulking and/or weather-stripping to seal it. You can button up the window even further by choosing window treatments
designed to insulate, such as panels or Roman shades with thermal lining, or honeycomb cellular shades.