What would be the best products to use to refinish sun damaged window sashes and panes?

Question:I would like to refinish two windows showing excessive heat and sun damage. They are southern exposure, sixteen yr old, PELLA windows with a separate metal-framed glass insert to give the double pane insulating protection for our tough northern winters. That double pane creates excessive heat between the glass and affects the wood grills. The previous stain and varnish has faded, peeled and seems to be down to raw wood. Any "tested" ideas would be greatly appreciated. Thanks

Answers:
You need to use a "SPAR" urethane, go to your local paint store, not the big box stores, you need a professional to talk to, Good luck Les the painter