The efficiency of your sunroom windows is bound to change over the years. Sunrooms are particularly vulnerable if your window sashes are leaking air. Of course, a lot of things can fade, wear down and break, significantly effecting the efficiency of your windows. One of the most common problems is that the felt weatherstripping along the bottom edge of a movable window wears down over the years. As a result, even when the window is closed and locked, it does not create an airtight seal.