Dear Jim: My old central air conditioner is getting noisy and it doesn’t keep the house as cool as it used to. With all the advertisements I see, I am confused about what new type to install. What do you suggest? – Pat M.

Dear Pat: If your central air conditioner has not been serviced recently, have it checked before you go to the expense of replacing it. The noise may be just from something loose and the refrigerant levels may need attention to restore its cooling output. If the noise is a compressor going bad and the system is leaking, then installing a new air conditioner is likely your best option.

There is not one best central air conditioner for every home. Many factors of the house, such as size, construction, number of windows and orientation toward the sun, affect the selection. If you want the most efficient two-stage heating during winter in cold climates, you will also need to install the most efficient indoor air conditioner blower system.

For many families, a simple single-stage central air conditioner is adequate. These are the least expensive models to install, but still offer some high efficiencies. As the efficiency of the model increases, so does the price. A contractor can project the electricity savings payback for various models.

Using scroll compressors is the trend in single-speed models. These are reliable and quiet designs with few moving parts to wear out. Look for models which use R410A refrigerant, even though they cost a little more, instead of old R-22. R410A does not harm the environment as R-22 can.

If your primary comfort concern in your climate is removing humidity, single-speed models with the absolute highest efficiency may not be a good choice. These models are ideal for Phoenix, but probably not for Cincinnati or Washington DC. Standard high-efficiency ones may dehumidify better for these more humid climates.

Another comfort and efficiency option for all climates, but especially for humid ones, is installing a variable-speed indoor blower motor. This will increase the initial cost by several hundred dollars, but because it is 75 percent more efficient, it will save much electricity over its lifetime.

I have this motor with a matched thermostat in my own home. When the air is cool enough indoors, the blower switches to a very low, efficient speed. At this lower speed, the air moving over the cooling coils has more time to be dehumidified.

If your budget is open and you want the most efficient system with the best comfort, select a two-stage model. Depending upon the instantaneous cooling needs of your home throughout the day, it switches between low and high output.

The following companies offer high-efficiency central air conditioners: Bryant, (800) 428-4326, www.bryant.com; Carrier, (800) 237-7437, www.carrier.com; Goodman, (877) 254-4729, goodmanmfg.com; Lennox, (800) 953-6669, www.lennox.com; and York, (877) 874-7378, www.york.com.

Dear Jim: I am considering building a house using foam core panels. My builder said I should just build a standard home with foam sheets attached to the outside walls. Which is a better way to build? – Chuck H.

Dear Chuck: Either method can provide the same wall insulation levels, but I prefer the foam core panels. They very strong and are specifically designed for high insulation. They are also very airtight.

Check your local building codes for the recommended amount of wall insulation. With this information, have your builder provide quotes for both methods. If the costs are similar, go with the foam core panels.

Send inquiries to James Dulley, Newspaper Name, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.

dulley.com.