Gas and Oil Home Heating Furnaces - Ventilator turbine covers during winter

I don't really know which forum to ask this question, so if there is a more appropriate one, please let me know. First my details: I live in Dallas, TX in a small (about 1000 sq. ft) house built in 1950. The cold weather extends from now (11/24) until late Feb. Temperatures range from the low 50's's down to the low 20's, sometimes a little colder. We have electric A/C and gas heat. We have two ventilator turbines on the roof. My sister buys and installs covers (made for this purpose) on her turbines every winter with the thinking that it keeps any heat that's in the attic from escaping into the atmosphere. This supposedly cuts down on heating bills, somewhat, and keeps her house warmer. I've never heard of doing this and wonder if it's is true and a good idea and/or if there are any problems associated with doing this. Thanks for your input!

David

David:

By covering the ventilators up in the colder weather you run the risk of forming condensation inside the roof space.
The attic must be at the same temperature as outside.
It is the insulation in the ceiling that keeps the cold out.

Thanks! Makes sense. If the attic is warmer than the surrounding air (outside air), then condensation forms on the boundry surfaces. Just like a glass of ice water in the summer. Then you get rotting wood under the shingles. Duh, I should have realized that. I'll relay this info. to my sister. Thanks again...

David

Not just rotted wood, but the dreaded mold.

From several years of experience (covers both on and off...), turbine covers in our area probably won't do any harm (they won't be on that long), but they don't help the heating bill much either. What they do accomplish is getting you up to look at the turbines 2 times a year, at which time hopefully you're checking for proper operation and tightness of the screw that holds them on. Otherwise most of us tend to ignore them until they blow off in the middle of a Texas drenching and we have far far more water damage than condensation could ever cause.;) On another note, the covers sold for this purpose don't stay on very well - a plastic bag and duct tape works much better, especially now that duct tape comes in a variety of colors.:D

All kidding aside, I would skip the covors, but do go up and check the turbines once or twice every year.

Doug M.

Nice to have someone with local knowlege.