I have double hung windows. One problem is that the top sash tends to slip down, so that cold air blows in the top. The latch does not work on most of the windows because they are not sized correctly.
One thing I have done is to cut a piece of wood the exact size so that it fits between the lower and upper sash tightly and forces the upper sash closed.
It is kind of inconvenient to make these special props. Are there standard products that are designed to be adjustable and can be used to prop up a window sash?
Best Answer
You really ought to repair the original sash mechanisms. There are many types but most are repairable, albeit with various degrees of difficulty. On the plus side, you will become an expert on how your windows operate.
There are various products made to solve your problem. For an easy solution on wood frame windows the simplest is the gull-wing shaped "hold-up spring", which should be available at any decent hardware store. It basically just sits between the sash and frame, exerting tension on the sash and holding it up yet allowing it to move when needed:
https://www.allaboutdoors.com/Spring-Quickie-Wood-Window-Sash-Wood-Sash-Hardware-Steel