Why today's air conditioners are much more efficient
Q. I need to replace my noisy, old central air conditioner with a more efficient one. I want steady room temperature, humidity control and cleaner air. What system types do you recommend?
A. At best, your old central air conditioner probably has a SEER (seasonal energy efficiency ratio) of 10. By replacing it with the most efficient new system with a SEER above 25, your electric bills savings can be $2,500 over just five years.
These new systems also provide the most constant room temperatures and precise humidity control. Controlling the indoor humidity level is as important for overall comfort as it is for keeping the house cool. Humidity control also impacts indoor air quality, especially for people with mold spore and dust mite allergies.
Consider replacing your old central air conditioner with a heat pump model instead. It is basically the same as a central air conditioner except it has a reversing valve to also produce heat. During mild fall and spring weather, it heats at a lower cost than running a furnace. During colder weather, its efficiency drops and the furnace takes over. Some companies call this a hybrid system.
Your three basic options are fully variable, two-level and single-level cooling output models. Since you are seeking high efficiency, steady room temperatures, humidity control, less noise and cleaner indoor air, a variable-output model is your best choice. It also is the most expensive system so have your contractor do a payback analysis first.
Variable cooling models use variable-speed rotary compressors that are often called "inverter technology." They continually vary the cooling output to the instantaneous cooling needs of your house. The cooling level varies in 1% increments from about 35% to maximum output.
In early morning when cooling needs are low, the compressor slows down to about one-third of its maximum output. At this slower speed, it runs longer and more efficiently. These longer, efficiently run cycles maintain room temperatures within just one-half degree of the thermostat setting.
These systems use a matching variable-speed blower. At the lower compressor speed, the indoor blower and outdoor condenser fans also run slower, making the entire system, indoors and outdoors, much quieter than single-level models.
When you set the desired humidity level on the thermostat, the blower speed automatically varies to control humidity. It can continue to dehumidify even when the room air is already cool enough. This eliminates that cool but muggy feeling that may occur with a single-level system, particularly one that is oversized for your house.
The next step down in comfort, efficiency (SEER in the 20 range) and initial cost is a two-level cooling system. This type of system runs at the more efficient low-output level the majority of the time. On hot afternoons or when you want quick cooling, it switches to the high-output level.
Single-level output models with a single-speed blower speed are the least expensive to install. Because they have only one cooling output level, you can expect a room temperature swing of about two to three degrees between run cycles.
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.
• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit dulley.com.