Dear Jim: Our old gas furnace is noisy and the room temperature swings up and down a lot. With record high gas prices this winter, our utility bills will bust our budget. What type of new gas furnace should we get? – Reg M.

Dear Reg: What you have described is typical for an older gas furnace in many homes. The noise you hear is from open, unsealed combustion and an old-style, probably worn, blower motor. Natural gas is in short supply this winter and you will likely have your highest heating bills ever.

The uncomfortable temperature swings may be caused by a faulty thermostat or from the furnace itself. If you have made some efficiency improvements to your home, such as new windows, doors, more insulation, etc., your old furnace may now be oversized for the heating needs of your home. This causes it to cycle on and off too often, causing the swings you feel and high bills.

Installing a new high-efficiency gas furnace should cure these problems. Depending upon your climate and local gas rates, installing a new one can pay back its cost in five years or less. With a 40 percent energy savings and lifetime heat exchanger warranties, its return is hard to beat.

There is a huge range in prices among high-efficiency gas furnaces. These include models with AFUEs (annual fuel utilization efficiency) above 90 percent. Your existing furnace is likely in the 60-percent AFUE range.

Since you mentioned noise and temperature swings as primary concerns, consider a modulating or a two-stage gas furnace. Both of these furnace designs vary the heat output of the gas burners depending on the changing heating needs of your house throughout the day and night. This results in the furnace running in longer, more comfortable and efficient cycles.

A modulating furnace increases the burner heat output in just 5 percent increments. It offers the best comfort and efficiency, but, with its sophisticated controls, it is considerably more expensive than a two-stage model with just two heat output levels. For most families, a two-stage model will be adequate and offer a faster payback period.

These multistage furnaces utilize a General Electric variable-speed blower motor. When the furnace is running in the low-heat-output stage, the blower also runs slower. This makes it quieter. It also has quiet soft-start feature to slowly ramp up to speed and eliminate the initial chilly draft each time it starts.

These furnaces use two small pipes (no chimney). One brings in outdoor combustion air and the other forces the fumes outdoors. The combustion process is totally sealed from indoor air. With sealed combustion and a variable-speed blower, you may not even notice when the furnace starts and stops.

Write for (instantly download – www.dulley.com) Update Bulletin No. 773 – buyer’s guide of 16 efficient gas-propane furnaces listing AFUEs, number of heating stages, blower motor type, warranties, comfort features, and sizing and savings charts. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.