Majority of home owners still believe that replacing windows is the best way to lower energy bills and make a home more comfortable. In almost every scenario, this thought process is not valid.
If a window is not functioning properly (i.e. it will not open or close properly – it cannot be locked) than it should be replaced, but these are the only reasons we see fit. The adjacent photo shows air leakage occurring through the window frame – this image shows hot summer air that is infiltrating the home through the window frame and seeping through the finished trim work surrounding the window. On a cold winter day a home owner could walk past this window and feel a draft, the first thing they may think is that they need a new window – after seeing this photo however, they would realize all they need to do is remove the trim around the window and apply some expanding spray foam or silicon caulking. Once cured, they could replace or re-install the trim and have a window that performs great.
An issue that may arise: removing trim around windows and doors can be difficult and expensive if it is not done by a professional (especially if it breaks during removal), but this cost will be much less than replacing all your windows – and it will give you improved results.
Another option is caulk the trim - make sure to caulk any and all seams that are cracked or have gaps between the window and the stops and the window to the wall surface (drywall/plaster). If there is cold air permeating through this location, these seams/gaps may need to be re-caulked every few years depending on how bad the draft actually is.
Tip: Spend the money on the expanding spray foam, it is phenomenal stuff. Make certain that you have more than one small area to foam though, the foam will harden in the plastic applicator tube before you have used all the foam (unless of course you are using a professional foaming gun). Most homes that have 1 window with air leakage around the window frame have many more like this. Remove the trim on all affected windows first and then spray foam
Tip: Stuffing fiberglass insulation into the window/door frame will not stop air leakage. Air will always find a way through fiberglass.