The Sensible Home: Select air conditioner carefully

Q. My central air conditioner is 16 years old, noisy and probably inefficient. I want to replace it with a quiet, efficient model. What are the best ones available for 2011 and which provide the best comfort?

A. If your central air conditioner is that old, any new model you install will be much quieter and efficient. Depending upon its condition, your old one likely has an SEER (seasonal energy efficiency ratio) of less than 10. The most efficient new ones are as high as 24.5 SEER, which would cut your cooling costs by 60 percent or more. As with most products, higher efficiency models that provide the greatest savings also cost the most to install. Always request your contractor to provide payback analyses on several models of various efficiencies.

With this information and other intangible factors such as comfort, conservation and environmental concerns, etc., you can make your selection decision. While you are getting quotations on various systems, also consider installing a heat pump instead of just a central air conditioner. Their cooling efficiencies are only very slightly less and installing one may also cut your winter heating bills even if you have a gas furnace.

Nordyne (www.frigidaire.net) makes one of the most efficient designs of central air conditioners using a variable-speed rotary compressor. It offers up to 24.5 SEER with a cooling output ranging from about 25 to 100 percent of maximum. It uses inverter technology to control the speed of the compressor efficiently and thus the cooling output.

In addition to the super-high efficiency, the variable output can greatly improve comfort and indoor air quality. The computerized matching thermostat and controls are constantly varying the compressor speed to target the cooling output to the instantaneous cooling needs of your house.

When the cooling needs, as on a mild day, are not great, the compressor runs slower and quieter, but longer than a simple single-stage cooling model. This not only maintains constant room temperature, but provides precise humidity control for comfort. A single-stage model, unless it has a variable-speed blower motor, can make a house feel cool, but damp.

Another option that provides good comfort and high efficiency (often in the 21 SEER range) uses two-stage cooling instead of completely variable output. The lower-output is often 60 to 70 percent of maximum. Most major companies offer these two-stage models and many use quiet scroll compressors.

Lennox now offers its best two-stage model with a solar feature, SunSourceT. It is designed to connect with up to 15 independent solar panels. Depending upon the climate, as little as six panels can completely power the air conditioner.

On sunny cool days when the air conditioner is not running a lot, the solar panels can power other appliances in your home. Some utility companies will pay you for extra (more than you are currently using) electricity your panels generate. Since each panel has its own built-in mini-inverter, more panels can easily be added anytime as your budget allows.

Q. I recently had a house built and the exterior foundation foam insulation is exposed to the weather. Should I cover it with something to protect it?

A. The weather should not harm the extruded polystyrene insulation, but the ultraviolet rays from the sun can degrade it. Exposed foundation insulation also looks bad.

The insulation can be covered with panels such as cement board, vinyl, or pressure-treated lumber. There also are several brush-on foundation paint coatings available. Another choice is brushing or troweling on stucco or plastic stucco-like materials.

Ÿ Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit dulley.com.