Anytime you have opposing temperatures at work,there is a chance of a condensation problem.You may recall when superdomes were first constructed,engineers were faced with the problem of how to control the "weather"inside.The solution to your problem is to bring the opposing temps. closer together.Shades on the skylights,relocating vents,lowering ac temps are possibilities.Don't be to rough on the manufacturer(s),they have no control over final installation variables.Also,you may want to look into lowering the moisture content of the air in the house as this can be a contributing factor.Good Luck.

[This message has been edited by Matches (edited August 11, 2001).]

The simple physics is this: Warm, moist air is condensing-out on a cool, dry surface. It's that simple.

Perhaps there's stale warm, moist air in the ducts that occurs when the A/C is off. WHen it comes on, it 'mixes' w/the cool, dry vent. It's possible that there's an insulation problem if your ductwork is at the roof-line, or running up an outside wall that happens to get very warm.

Jay J -Moderator

Thank you both for your input on this matter. I guess we will just have to continue narrowing down the numerous possiblilities. Darn....I wanted an easy out. Oh well, I'm going to relay your suggestions to them anyway. Thanks, again.
Babs

If it makes you feel better, you're not alone. I've noticed that some metal vent covers seem to rust every few years. Now I know why. Probably best to replace those with plastic or other material that doesn't rust.