How air tight is your home? All homes will have a certain amount of air leaks, but if there is too much outside air leaking in, you will have heat and humidity coming in during the summer months, while you will have cold air coming in during the winter. Many times, a common source of leaks are your windows. If there are cracks or holes that have formed around your windows, you will see much higher energy bills year round. It might be somewhat tricky to find where the leaks are located, but you can get help from a friend shining a light from the outside while you’re looking from the inside.
To fix a crack, you first need to make sure to remove any wood that has traces of rot or decay, since just covering that over will lead to it spreading once more. You can repair the window frame by using wood filler, and then sand and paint it to make it look like new.