I like fresh air, but my kids have allergies, so I sometimes close the windows and turn on the air conditioner. I thought about getting a portable air conditioner to use in various rooms. Would that be any more efficient?—Lynne M.
Using natural fresh air ventilation is always the most energy efficient. But outdoor allergens can certainly be a problem. In many cases though, indoor air is more polluted than outdoor air. Check with your doctor to make sure the allergens are truly coming from outdoors.
If you were going to air-condition just for the clean air circulation, but not necessarily for the cooling, there are several other options. Heat recovery fresh air ventilation is a good option for year-round fresh air. Most systems include effective air cleaners to remove allergens from the fresh air before it enters the system.
Another option is ducting fresh air into the return air system. Run the system on “fan-only” with no cooling and allow a high-quality central air cleaner to remove the allergens. This is most efficient if your central air handler has an efficient variable-speed blower that can be run at a relatively low speed.
As you mentioned, using a portable air conditioner—many of which are heat pumps—could also be an effective solution.
I use a portable heat pump in my own home for year-round savings. In addition to cooling the room during summer, it also functions as a portable heater during winter.
The efficiency of a portable air conditioner is similar to a window air conditioner. Although this is less efficient than the newest central air conditioners, using one can still save money. By keeping just one or two rooms comfortably cool with clean air, you can set your central thermostat higher and save electricity overall. Use it in the dining room for dinner, roll it into the living room for television, and then to the bedroom for sleeping.
A portable air conditioner/heat pump operates similarly to a typical window unit. The primary difference is it is on castors and rests on the floor. Most are light enough to easily roll from room to room. The higher-output models are fairly heavy, but still roll easily.
Round air ducts, similar to dryer ducts, connect the unit to a window adapter. You open a window, place the adapter in the opening, and close the window against it. This exhausts the heat outdoors when cooling.
There are two basic designs of portable units. One uses a single duct to the window adapter. This is the simplest system and works well, but it does draw some cooled or heated room air to the outdoors.
The other design uses two ducts, which is more efficient. All of the air flowing through the condenser (which carries the heat away) is drawn from outdoors and exhausted back outdoors. With two ducts, no already-conditioned indoor air is being exhausted outdoors. This is more energy efficient, especially when operating a heat pump model in the heating mode during winter.
Another feature to consider is how the condensed water is handled in the cooling mode. Some evaporative models mix it with the air exhausted outdoors so there is nothing to empty. Other models, which also work well as dehumidifiers, capture the water in a small tank you must empty—I use the distilled water from the tank to water my plants.
The following companies offer portable air conditioner/heat pumps: Fedders, (609) 662-5300, www.fedders.com; Soleus Air, (513) 985-1211, www.soleusair.com; Sunpentown, (800) 330-0388, www.sunpentown.com; Toyotomi, (203) 775-1909, www.toyotomiusa.com; and Windchaser, (800) 405-2943, www.windchaserproducts.com.