Dear Jim: We have a gas furnace with central air conditioning and my son has an all-electric house. He is planning to install a super-efficient geothermal heat pump. Would this make sense for my home too? – Paul G.

Dear Paul: When people hear the word heat pump, they often think heat pumps are only for all-electric homes. With rising costs of natural gas, propane and oil, geothermal heat pumps may be a money-saving option for any home. They produce warmer, more comfortable air than standard air-type heat pumps.

A geothermal heat pump both heats and cools your home like an air-type one, but that is where the similarities end. It pulls free heat from the earth for super-high efficiencies. For example, with a coefficient of performance (COP) of 4, it produces an extra $3 of free heat for each $1 on your utility bills.

In the summer, the savings can be as high as 60 percent. Some models have efficiencies as high as 22 as compared to your old air conditioner at about 8. The dehumidification is also better for improved indoor air quality.

In the air-conditioning mode, most geothermal heat pumps use the heat from your house to heat your hot water for free, instead of exhausting it outdoors. The newest models use ozone-friendly R410A refrigerant instead of Freon.

Geothermal heat pumps are so efficient because they use the ground as the source of heat in the winter; and in the summer, they deposit heat to the ground. Since the ground temperature, several feet below the surface, stays relatively constant, the heat pump requires less electricity to heat and cool.

Even though it feels cold outdoors when it is 30 degrees, there is still energy in the air that a standard heat pump can “pump” into your house. At the same time, the ground temperature may be 55 degrees. It makes sense that it is easier to pull heat from 55-degree ground than from 35-degree air.

To install a system, a small pipe is placed in a narrow trench in your yard. (Vertical holes can be used instead. A solution runs through the pipe, which is connected to a heat exchanger in the heat pump. Another efficient design (DX) uses copper tubing with the refrigerant running directly through it.

Since a noisy outdoor condenser fan is not needed, most geothermal units are located entirely inside your house. There are designs to fit utility rooms, basements or attics. This makes servicing them easier. New outdoor units are also available if you plan to keep your gas furnace.

For ultimate comfort and efficiency, select a two-stage model with a variable-speed blower. This allows it to constantly fine-tune the heating and cooling (and electricity usage) to the varying needs throughout the day.

Dear Jim: Our house has a tar and gravel roof with exposed beams underneath in the room below. The roof should have some additional insulation. What is the best method to add insulation? – Nick M.

Dear Nick: You will not be able to add insulation indoors, so it will have to be added over the roof. Spraying on and inch or two of polyurethane foam insulation is a good method to use. This is generally not a do-it-yourself job.

The foam will hold up well and blocks water, but it must be coated to protect it from the sun’s ultraviolet rays. Roofing contractors can apply a protective white coating. This also reflects the sun’s heat in the summer.

Write for (instantly download – www.dulley.com) Update Bulletin No. 644 – buyer’s guide of 13 single, two-stage geothermal heat pump manufacturers listing efficiencies, heat-cool outputs, features, fuel cost comparison chart and ground loop details. Include $3.00 and a business-size SASE and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244