August 16, 2009 in Features

Fiberglass insulation prevents drafts

Gene Austin McClatchy-Tribune

Q. I recently had new thermal windows installed and the contractor used pieces of fiberglass insulation to seal gaps around the frames before adding interior trim. I thought spray foam would be better but he said it could expand too much and interfere with the operation of the windows. What do you think?

A. It is important to seal gaps around window frames to improve comfort and energy efficiency, and I think your contractor is using good judgment. This important step is too often neglected when new windows are installed, and the result can be drafts and heat loss that help defeat the purpose of the windows.

I also used fiberglass insulation to fill gaps when I installed my own thermal windows. That was some years ago and I have had none of the draft problems that so many readers have described in mail I receive.

However, there are special low-pressure foam insulations for filling gaps around windows and doors, and they are not supposed to expand enough to cause operational problems. These foams can be bought at most home centers and are labeled specifically for windows and doors. Great Stuff Window & Door is one widely sold brand.

Possibly your contractor has tried these foams and found they do cause operational problems with the windows he installs. My feeling in this case is to trust his judgment.

Q. Our attic floor has some loose insulation of unidentified type. We want to add more insulation. Can we use fiberglass blankets, more loose fill or what?

A. If the existing insulation is a gray, crumbly material, it is probably cellulose, a widely used insulation that is considered basically safe.

However, it would be a good idea to have the material identified before you add more insulation, since some hazardous materials were once used to insulate attics. Any insulation contractor could identify it, or scoop some into a jar and show it to staffers in the insulation department of a home center or building-supply outlet.

If the existing insulation is a safe material such as cellulose, you can proceed to add more insulation on top of it. Either unfaced (no vapor barrier) fiberglass blankets or more cellulose can be used.

If you want to do the work yourself, fiberglass blankets are the best choice. Adding blown-in cellulose requires special equipment and skills, so it is best left to a contractor.

Q. How can we tell if the blades of our ceiling fan are moving clockwise or counterclockwise? We are having a dispute about this at our house.

A. The simplest way to determine if the blades are rotating counterclockwise, which is the proper rotation for summer cooling, is to stand under the fan.

If you feel a cooling current of air coming from the fan, you have the correct rotation for warm weather. If you don’t feel the breezy current of air, which is much like that of a floor fan, the rotation is clockwise.

Some fan owners use the latter rotation during the heating season, when a ceiling fan can circulate heated air that would otherwise collect at the ceiling. Most fans have a switch to change the rotation.

Questions and comments should be e-mailed to Gene Austin at Send regular mail for Gene Austin to 1730 Blue Bell Pike, Blue Bell, PA 19422.

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