It's sensible to begin by diagnosing the situation. Instead of giving your home a complete energy inspection, play Sherlock Holmes and pinpoint the most critical areas for heat loss. For example, a chronically cold kitchen with large north-facing picture windows is probably a good place to start. Assess where the heat loss is coming from: Is there an obvious draft from the sills or sashes? If so, weather-stripping may be the best line of defense. Give some attention to what type of windows you're thinking of insulating. Perhaps part of the problem is a lack of insulation at the window jambs -- where the window meets the wall -- or behind moldings.
Before you select a method of insulation from the available options, you should also consider your objectives. Obviously, temperature regulation is a primary objective, but how much do you need to increase the insulation value, and what tradeoffs are you willing to make? Will you compromise the view, limit the influx of light or block access to the window? Are you looking for a year-round form of insulation, or will a seasonal fix suffice?
Of course, you'll need to factor in cost. Some remedies can be obtained for modest costs, such as rubber or foam weather-stripping or plastic sheeting. More lasting solutions, such as spraying or inserting insulation in the jambs, will cost more money and may require the help of a contractor or handy person -- but they may prove a worthy investment in the long run. You also may want to think about aesthetics: Tasteful window treatments or homemade thermal shades certainly make a different kind of statement than caulk, foam and vinyl.
After you've considered all these matters, it's time to get to work. Make careful measurements of the windowpanes, casings and frames. If you plan to mount shades or blinds, decide whether insulating inside or outside the casing best fits your needs, remembering that insulating the inside will more efficiently reduce airflow [source: Pandolfi].
Let's move on to learn about what steps to take and with what kinds of tools to use along the way.