Question: Is it a problem when there is moisture around the inside edges of a window? My son and his wife have bought a house that is about 25 years old with casement windows, and often in the winter, there is about an inch of moisture around the edge of many of their windows. What causes that and should the windows be replaced?

Answer: Excessive indoor humidity comes in contact with the cold glass and the inside edges of the window fog up. It happens to the Paladian-style window in our master bedroom when I shower too long on a cold morning and don't turn on the exhaust fan in the bathroom. The other day I noticed that there were water droplets on the plants that sit in front of that window because of it.

Your kinfolk need to find ways to reduce the indoor moisture and get the air circulating - dehumidifier or ceiling fan or exhaust fan. I doubt that window replacement is necessary, since the Paladian is "low-e" and that fact in itself doesn't stop the window from fogging up.

Somewhere I read that you reduce the chance of fogging if you clean the windows with rubbing alcohol. I've never done so, but your son and daughter-in-law might give it a try.

If fogging indicates excessive indoor moisture levels, there is the danger of mold and mildew present. That could be the problem that needs addressing.

Reader assistance. An appeal for help with yellowing vinyl floors brought this from Herbert Ranbow, who wanted to share "our experience with Armstrong vinyl floor tile in our kitchen."

After about five years of wear, his wife decided the "no wax" shine wasn't good enough, and topped it with floor wax. Soon after, a discoloration started appearing, a yellowish hue over the main work area. It got worse with time and spread to other areas.

"We decided that it was caused by an off-brand wax, and switched to Armstrong's own floor-care products, but it was never the same," he said.

It finally got so bad that they put a laminate floor on top. In the process of laying the laminate, he discovered that the discoloration had nothing to do with the floor wax.

"I was laying the new floor in the fall when the sun was lower on the horizon, and the sunbeams were very apparent on the floor - and exactly matched the worst of the discolored areas of the original vinyl tile," Ranbow said. "It was true in both the kitchen and the dinette. Those windows face the west."

So the problem was really UV damage from the sun, and had nothing to do with the floor wax they'd used, or any other floor-care product or wear pattern.

"We immediately added wooden blinds in those windows to help protect the new floor," he said.

Thanks, Herbert.

Tax credits. The end of 2010 marks the end of the tax credit for energy-efficient replacement windows. This credit gives consumers the opportunity to replace the windows in their home and receive a tax credit of up to $1,500.

Although the kin of our lead questioner today probably don't need replacement windows, Chris Pickering, vice president of marketing at Ply Gem Windows, offers four things to keep in mind when thinking of taking advantage of the energy tax credit for windows:

The bill provides a $1,500 maximum tax credit for installing energy-efficient windows that qualify, calculated as 30 percent of the windows' purchase price.

Qualifying windows must have a glass package with a U-Factor rating (the rate at which heat is prevented from escaping) of 0.30 or lower, and a solar heat gain coefficient rating of 0.30 or lower.

To file for the credit, homeowners need their invoice that shows a breakout of window and installation costs; National Fenestration Rating Council (NFRC) labels from all windows and doors, and the manufacturer's certificate.

Once homeowners have the windows installed and have gathered the necessary documents, they need to fill out IRS 5695 form, found at www.energystar.gov, and submit it by April 15.

Questions? E-mail Alan J. Heavens at aheavens@phillynews.com or write him at The Inquirer, Box 8263, Philadelphia 19101. Volume prohibits individual replies. He is the author of "Remodeling on the Money" (Kaplan Publishing). Twitter: @alheavens