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Zinc Sheet Coils Halt the Growth of Moss on Roof


QUESTION: We have a problem with moss growing on our roof shingles. The moss is growing mainly on the north and east sides, which are shaded most of the day. We will be building a new home in a wooded (and shaded) area in the same community and would like to prevent this problem on our new home.

ANSWER: Inquiries regarding roof moss are among the most common that we receive. In discussing this problem in the past, we have recommended stretching bare copper wire horizontally about every 5 feet across the roof. We've recently learned of a product that appears to be easier to install and more effective. It can be used on new or old roofs.

The product, Z-Stop, is a coil of zinc sheet 2 1/2 inches wide by 50 feet long. You fasten it to the roof on both sides of the ridge cap. A coil costs about $30. Each coil comes with sufficient zinc-coated, rubber-gasketed roofing nails to apply it to the roof.

An average roof requires about three coils. It can be used on a wood or composition roof shingle. It is not well suited for tiled roofs, however, because their shape does not allow rainwater to flow continuously from the ridge cap all the way down the roof.

For more information, contact Z-Stop, Wespac Enterprises Inc., P.O. Box 46337, Seattle, WA 98146.

Water Heater Blanket Won't Create Rust

Q: For several years, utility companies have recommended installing insulation blankets on our electric water heaters. Some even do it free for customers. I installed one on my own, but I was told that the blanket will drastically reduce the life of my heater by trapping condensation and causing it to rust. I was advised to remove the blanket and use the escaping heat to prevent my laundry room pipes from freezing. Whom do I believe?

A: All tank-type water heaters are insulated by the manufacturer between the storage tank and the outer casing. Even with this insulation, the surface of the outer casing becomes warm to the touch and, as a result it gives up some heat to the room in which it's located. You can reduce this heat loss by covering the casing with an insulated blanket, as was recommended by your utility company.

Condensation is not a problem you have to worry about. For the water vapor in the air to condense, it must contact a surface that's cooler than the room's temperature. Since the temperature of the water heater casing will be either the same as room temperature or above, moisture in the air will never condense on it, regardless of whether the casing is insulated.

If you are concerned about pipes freezing in the laundry room, don't depend on the water heater. Instead, install a thermostatically controlled space heater. This way you can regulate the room temperature to suit your needs and the time of year.

Tips for Proper Venting, Installation of Attic Fan

Q: I am considering installing an electric attic fan. I've been told that because I have only small openings in the gable ends of my house, I'll need more ventilating holes for the fan to work properly. How much venting is needed for the turbine vents that are turned by the wind? Would this be a better solution to my problem?

A: The FHA minimum property standards require that 1/150 of the ceiling area be free ventilating area. A 20-by-30-foot ceiling equals 600 square feet. Multiplied by 1/150, that equals 4 square feet of vents.

You can reduce this to 1/300 of the ceiling area if 50% of the ventilators are in the upper portion of the roof. They must be at least 3 feet above the eaves or cornice vents. An electric powered fan will move air more effectively than a wind turbine.

Ghost Flushing Has a Down-to-Earth Cause

Q: I don't know why, but every so often my toilet flushes by itself. It's quite disturbing. About 10 years ago, I had a water pressure reducer put on my water line in the basement. Is this causing it?

A: When a toilet flushes by itself in the middle of the night, it's enough to make you think you have a ghost living with you. But there is a simple explanation for the phantom flushing phenomenon.

The flushing is caused by a deteriorated flapper or tank ball that covers the flush valve opening in the toilet tank. If either the flapper or ball has deteriorated, water will slowly and quietly leak out of the tank. The water level in the tank will drop far enough so that it will trip the fill valve, and the toilet tank will refill with water. This sounds like the toilet has flushed, when actually it is only the tank refilling with water.

When the ball and flapper are badly deteriorated, the leaking water will be quite noisy and noticeable. When they are not badly deteriorated, as in your case, the water loss is hardly noticeable.

To correct the problem, drain the tank and scrub the valve seat with steel wool to ensure a clean, watertight seal. Then install a new ball or flapper.


To submit a question, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, NY 10019. The most interesting questions will be answered in a future column.

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