As the "fix-it" person of my family, I appreciate your good, and thorough, explanations, and I have learned a lot from your column. We would like to add central air conditioning to our 25-year-old split-level home but don't know if it is feasible.

The upper level is heated by radiant ceiling heat, each room controlled individually. The family room (added on in 1993) has electric baseboard heat, as does the lower level. Since it is seldom used as a living space and stays cool, I am not concerned about air conditioning there. Because we have no central furnace or ductwork, what are our possibilities and costs? All our windows open by sliding side to side, but I'd like to do something besides room air conditioners.

With your situation, I believe you will open up a can of worms if you try to add central air to a home that's completely finished. It's not impossible, but most likely it is expensive.

A complete unit (furnace and air conditioner) could be installed in the lower or upper level, but ceilings, walls, and floors will need to be opened to accommodate the ductwork required.

This job calls for a remodeling contractor who will bring in an HVAC (heating, ventilating, and air conditioning) contractor (not the other way around). Ideally, both will be skilled professionals experienced in retrofitting an HVAC system in a finished home. Careful advance planning will be required to work out the details and to hold the line on work and costs.

If you install a complete unit, you can eliminate the baseboard and radiant ceiling heat systems but probably not the wires that feed them. You can disconnect the wires from the electrical panel box but will need to install junction boxes with blank covers where you remove the baseboard heat.

Junction box(s) should already be in place for the radiant ceiling heat. Make sure that the wires are disconnected and pulled out of the panel box. Be sure to mark these wires so if you sell the home, the new owners will know what the extra wires are for.

You could install a heating/air conditioning unit in the attic. It won't be as efficient as a unit installed in the lower level at the time the home was built. What makes this configuration inefficient is the attic ductwork. Because the attic is an uncontrolled environment, the ductwork needs to be insulated with a minimum R-8 insulation.

Another point to consider is that lost heat will warm the attic area, which is not good during the winter because the warm air will melt the snow on the roof. Depending on the outside temperature, ice dams may form at the roof eaves, which can damage the roof, ceiling, and walls. It's important to keep the attic as cool as possible during the winter, and make sure it is adequately ventilated to keep the roof cool.

Because cold air flows down, the lower levels of your home would probably benefit in the summer from this installation. You would still have to open the walls to drop in ductwork for cold air returns.

To hold down costs and because you are only worried about cooling the upper rooms, I suggest you reconsider individual air conditioners in the bedrooms. Purchase wall (not window) units sized for the individual rooms. Many come with convenient hand remotes.

For maximum efficiency, install the air conditioners 3 to 4 feet below the ceiling. A clever electrician should be able to wire the units with minimal wall damage.

Another approach would be to install a Ductless Split System by Friedrich, Hitachi, or Soleus (check them out online). This type of unit offers high efficiency and reduced noise without the large hole in the wall or open window typically associated with standard wall/window air conditioning units. Available in different BTU sizes, the units can be matched to specific room sizes for efficiency. You can easily install these units yourself.

The hole required is only about 3 inches in diameter so the power cable, refrigerant tubing, suction tubing, and condensate drain running from the indoor air handling unit can connect to the outdoor compressor/condenser unit. Separating the AC compressor and condenser coil from the fan and evaporator coil puts the noisiest component outside.

Check the yellow pages to find at least three professionals to speak with about your project. From them, you will get ideas and bids so you will have some direction. Good luck with your project and let me know how it turned out!

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C.R.S., Inc. · Spokane, Washington · USA