painting window sash

[heteroscedastic]

I have Andersen double-hung windows. I finished the wood sash with polyurethane 10 years ago. It is generally in fine shape except for windows which experience a certain amount of condensation in the winter, mainly early in the heating season before the house has dried out. I wipe it off every morning but that's not enough, and the varnish has deteriorated on the beveled part of the bottom of the sashes. I think if I just paint the sash, the paint will hold up better than the varnish has, though I don't expect perfection here. I can't totally prevent condensation, mainly because I heat with wood, and the bedrooms are cooler than the rest of the house.

Are there any tips for getting the best possible result with paint, i.e. maximum resistance to damage from condensation?

[DerbyDad03]

Have you talked to anyone at a dedicated paint store - not a big box paint counter, but a locally owned business that has been around for a while?

I've had so many instances where the big boxes and the kids at the national chains (Sherman-Williams, etc) knew less than I did about what I was trying to accomplish. However, there is a small local chain that's been around since the 80's as well as a family owned single store (that I'm pretty sure sold paint to the pilgrims) where I can go in, they understand what I am trying to do and offer suggestions that make sense.

[ransley]

One big benefit is you can see mold and kill it with bleach before it turn to rot, do you have black areas, with paint you wont know of big problems until its to late and the window is ruined. Will paint last longer, maybe not, and you wont know about rot. Run a dehumidifer or open windows when condensation occurs, you have good expensive windows, loosing them to rot is not right.

[norminn]

I don't know your brand of window, but for wood windows in general the problem is moisture running down the glass behind the wood. Only tip I know of for interior window finish in regard to this problem is to paint or varnish onto the glass - provides a seal so the water doesn't get behind the wood. If your hand isn't steady, you can tape the glass and allow 1/16" or so of glass to be finished. I have also used a metal rule and razor blade to even the line after finish is dry.

[norminn]

I forgot to mention - since the wood is damaged, should allow it to dry well and sand down to clean wood. Strong sunlight can also damage finish, and clear finish acts like a "heat trap"; if that is the case, paint would likely be better than clear finish.

If you get a lot of condensation in cold weather, a fan might help. Heavy drapes also help.

[Phisherman]

Most of the work is preparing the surface and that will determine the overall quality of your work. Sand, repair defects, remove caulk. Inspect your work at various light angles to correct flaws. After surface is clean and dry caulk cracks, prime, and apply two finish coats. Use a high quality angled sash brush. Lightly sand between coats with 220 grit and remove any dust.

Condensation can be controlled by better air circulation, lower humidy, triple-pane insulated windows, etc.

Actually I trust a varnish polyurethane over paint if the surface gets wet. Paint would not be my practical choice. With either finish, you can apply a coat of paste wax after allowing the finish to fully harden (maybe 2 months.)