Problem: Cold, drafty rooms. Many homes - even new homes built to code - have one or two rooms that are plagued by drafts, remaining cold even with the heat cranked.
Solution: While the traditional fix is to put on a hat or a sweater (or avoid the room altogether), there are a number of improvements to the building envelope that will significantly reduce drafts, so that you can comfortably utilize your neglected room all winter long. More specifically, drafts are usually indicative of ineffective insulation in the walls, a bad air leakage problem, or both. While windows can play a part (because they may be leaky, or insulate poorly), focusing on air sealing and insulation before replacing your windows will almost always give you a better return on your investment than buying expensive new windows.
Consulting with a certified home performance professional is the best way to determine the cause of your discomfort, because their fancy infrared cameras can pinpoint exactly where air leakage is taking place, as well as where insulation is performing poorly (or where your walls may be lacking insulation altogether). This eliminates guesswork, and lets you focus on where you'll get the most bang for your buck. An energy auditor or home performance contractor can also give you an estimate of how much money you might save by making the recommended improvements, as well as how much those improvements are likely to cost. Rest assured, a proper combination of insulation and air sealing (possibly including insulating and air sealing those windows with some combination of storm windows, window films, or insulating window shades) will eliminate your drafts once and for all, so you can save your hat for the ski slopes.