window repair - wood filling water proof

1. Would it be more economical in the long run to have a professional installer replace the window (& frame) with a modern one? If not:
2. Replace all rotted wood that you possibly can.
3. Fill voids around all edges with expanding foam insulation from a spray can. This provides a good thermal barrier but is not waterproof: i.e. you may need also to:
4. Inspect/repair exterior flashing.

This company makes excellent products:

Sorry I did not mean not replying but I posted a new post with internet links (pictures of my windows) but it did not get posted!! I thought I am not allow to post pictures. I will try again to send pictures (maybe I do not know how to do it correctly)

When you get the basic damage repaired, use 3M Bondo for your filler/ reconstruction. Obviously if it can stand the environment in vehicle repair, it will work well on your project. Fast cure, tough and paintable...all the the attributes you need. Much cheaper than epoxy kits, and UV resistant, too.

Joe

Second Joe's comments. As long as it will be painted, bondo is great, sticks very well to any non-greasy surface, sets up quickly and sands fairly easily.

I've been using Bondo All Purpose Putty for years. It's usually my "go to" product for big repairs. HD used to sell it in gallon cans but now they sell it in 1/2 gallon sizes and charge about the same. IMO it's the best stuff for tricky repairs when you don't want to do a tear out. Paintable, drillable, long lasting etc....

Remember - it is NOT waterproof - so it MUST be sealed and painted - sealed to keep water from getting behind it, as well as sealed and painted on the outer surface. Unpainted Bondo (polyester filler) pops off if it gets wet and freezes. The old rotten wood needs to be DRY before it is applied, as well. It does heat substantially as it cures - so don't put it on too thich at a time.