QUESTION: I want to air-condition my house, but I cannot afford central air. Also, a room addition has no duct system. How efficient are mini-split ductless systems and are they quieter than room air conditioners?
ANSWER: Super-efficient mini-split ductless air conditioners and heat pumps are very quiet and can be less expensive to operate than a central air conditioner. Ductless systems are about the only whole-house cooling option for houses without an air duct system (hot water or electric baseboard heat).
A ductless air conditioner is somewhat like a central air conditioner in that the noisy compressor and condenser unit is located outdoors. In fact, it looks very similar in size and shape to a typical central unit.
Instead of having one large cooling coil in the furnace duct, a ductless system has small quiet indoor fan/cooling coil units in each of one to four rooms. A system with three or four units will adequately cool even a large house.
These small indoor units are only about 6 to 8 inches deep and can be mounted flush on the wall or ceiling or recessed in a dropped ceiling. Because they are high in the room and cool air naturally drops, they provide even room temperatures and comfortable air circulation.
Installation labor costs are lower than having to add a duct system. For wall mounting, a 3-inch hole is sawed through the wall. The condensate drain, refrigerant lines, power and control cables from the central outdoor unit all pass through this single hole.
The advantages of a ductless system are many. Each indoor unit has its own thermostat, and all the functions (temperature, fan speed, timed setbacks, etc.) are controlled by a hand-held remote (like a TV remote).
This allows you to set different temperatures at different times in various rooms of your house (called zoning). The times can be programmed differently for each day of the week or changed manually with the remote control.
The electricity savings from zoning are significant. Also, you will no longer have problems with rooms that are too hot or too cold. Installing a heat pump model with electric backup will save electricity in winter too.
If you have allergies and want to keep your bedroom air allergen-free, a ductless system allows you to isolate that room while keeping it cool. Many also have built-in filters to further clean the air.
Some convenience and comfort features to consider are motorized louvers to improve air circulation. A nighttime setting option operates at a quiet low fan speed. An economical high-dehumidification setting improves comfort.
Write for Update Bulletin No. 730, a buyer's guide of ductless air conditioners, cooling/heating outputs, efficiency ratings, features, prices and typical installations. Please send $2 and a business-size self-addressed stamped envelope to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.
Temperature Changes Create an Air Leak
Q: In the winter, a one-eighth-inch gap forms where the walls meet the ceiling, and I am afraid that it leaks air. In the summer, the gap disappears. What causes this and how can I stop it?
A: The cause of the gap in the winter is temperature differences between the exposed top members of the truss and the bottom members buried in the attic insulation. These thermal stresses cause truss uplift.
This gap can leak some indoor air into the attic. It can be quite a job to fix it permanently. The easiest method to correct it now is to just nail a molding strip to the ceiling. This looks better and blocks some of the air leaks.
Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244. To read 150 previous columns, e-mail Dulley at http://www.dulley.com