Adding Central Air | Installing Air Conditioning in an Old …

Because the fan-and-coil unit is mounted in the attic in most retrofit air-conditioning systems, the challenge is to get supply and return ducts to ceiling registers in the first- and second-floor rooms below. Ducts that feed second-floor rooms are typically run across the attic floor and plunge down between the attic floor joists, where they are connected to ceiling registers. Ducts that feed first-floor rooms run down through second-floor closets wherever possible. The first step your contractor will take to determine the position of ducts is to draw a floor plan of the second floor and lay it over a floor plan of the first floor. "In 99 percent of homes," says Frank Scaran-gello, of Staten Island, New York-based Scaran Heating and Air Conditioning, "second-floor closets will give you access to locations for first-floor ceiling registers."

Ducts running in closets take up less space than you might think. Because most ducts are 12 X 6 inches or 10 X 8 inches, even in a relatively small 2 X 4-foot closet, they take up just 4 of the 64 available cubic feet. Some cooling contractors might suggest using "flex duct" (a small, inexpensive flexible hose) instead of rigid square ducts. But avoid flex duct in active closet spaces it doesn't stand up well to wear and tear and is easily punctured.

What kind of mess can you expect if you have to have ducts installed? In most cases, wall and ceiling surfaces are left largely untouched. Holes do have to be cut in first- and second-floor ceilings for registers, and some second-floor closet floors will undergo surgery to accommodate the new ducts. But these holes are relatively small, and the mess is easily contained.

Even if there's no ductwork in your home, if air-conditioning will make your house more pleasant in the summer months, contact HVAC contractors to review the cost of adding A/C and the methods they would use. Choosing the right pro and equipment will ensure you years of comfort, and it's often less expensive and less intrusive than you might imagine.

(Updated with new information, August 2007)

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