Home Improvement : Clean Air Makes Efficient Furnace

QUESTION: Our house is dusty, and I have allergies. Will a furnace-mounted air cleaner adversely affect the efficiency of my air conditioner? What is the difference between an electronic and an electrostatic air cleaner?

ANSWER: A furnace-mounted air cleaner may improve the efficiency of your furnace and air conditioner. An air cleaner is mounted on the return-air side of the furnace, so the air entering is cleaner.

This keeps the heat exchanger and air conditioner evaporator coils cleaner, so they can transfer heat more efficiently. However, you should follow the manufacturer’s recommendations for cleaning the air cleaner elements so that the air flow isn’t impeded.

Both the “electronic” and the “electrostatic” air cleaners work on the same principle. As dirty air enters the air cleaner, the dirt particles are given a negative charge. The second-stage filter inside the air cleaner has a positive charge, so the particles stick to it. The final stage has a negative charge to repel any particles that got through.


The basic difference between an electronic and a self-charging electrostatic air cleaner is in the way in which the electrical charges are created. In an electronic unit, electricity is used to induce the charges, so it must be wired into your furnace’s electrical system.

An electrostatic air cleaner uses special polymer materials that develop their own electrical charge as the air passes through them. This is similar to the static charge built up on your comb when you comb you hair. Therefore, you don’t need electrical wiring and no electricity is used. Also, it won’t produce ozone as electronic models sometimes do.

Electrostatic air cleaners are less expensive than electronic models, and you can install one very easily yourself. It just slips into the slot where your present fiberglass furnace filter is. Select a high-quality air cleaner in which the internal parts are insulated to maintain the charge.

It is important to clean it every 30 to 60 days. You can use a garden hose or clean it in your bathtub. When water hits the air cleaner, the charges dissipate and the dirt particles wash off. Let it dry, and slip it back into the furnace. The electrostatic charges build up quickly again.


Write to me for Utility Bills Update No. 275 showing product information on a high-efficiency electrostatic air cleaner, and for test results of removal rates for allergy-causing particles such as pollen, mold and smoke. Please include $1 and a self-addressed envelope.

Q: I installed a skylight to help cut down on my lighting costs, but it leaks when it rains. What is the best type of caulk to seal the leaky spots?

A: There is never one best type of caulk for every application. The proper selection depends on the exact place it is leaking, the materials to which it must adhere, and the amount of stress it must withstand. Skylights are particularly hard on caulk. With the great temperature swings from the hot afternoon sun to the cold nights, there are high levels of thermal stress in the skylight frame.

One of the better caulks to try first is a polyurethane base. It tends to form a stronger bond to the material than silicone, can be painted and can be used underwater. It also has flexibility about equal to silicone. Therefore, it works well sealing between dissimilar materials that expand and contract at different rates.

Q: We are about to select a new bathroom cabinet. Is there much difference in the electrical usage between fluorescent and incandescent lighting?

A: A fluorescent light uses about one-fourth as much electricity as a standard incandescent light bulb. In many areas of your home, fluorescent lights are the best choice.

In your bathroom, you may be better off with the incandescent light bulbs. Even though incandescent bulbs cost more to operate, they are not switched on very long in a bathroom. For applying cosmetics, the quality of the light is important. Although there are special fluorescent lights made to approximate normal lights, they may not be adequate for you.

Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.