How to Install Air Conditioning in a House With No Forced Air Heating

Cost to Add Central Air

• Adding central air to a home with no forced air heating requires a substantial investment. Not only do you have to pay for the new cooling unit, but you also face costs associated with adding ductwork, including costs to modify the home to accept these ducts. As of 2013, installing central air and new ducts in a 2,000-square-foot house costs between $7,000 and $8,000, according to This Old House. In homes with existing ducts, a new cooling system costs between $3,500 and $4,000. The cost of a high-performance system and accompanying ductwork can easily top $10,000, according to Bob Vila Home Improvement.

Sizing Central Air Unit

• Air conditioning units may be rated in British thermal units or tons, and one ton equals 12,000 Btu. To properly size your new system, consult a contractor who uses the Air Conditioning Contractors of America's Manual J sizing system. Manual J serves as the industry standard for sizing cooling systems, and takes into account the location of a home, its orientation toward the sun, type and placement of windows and doors, insulation, and other factors that impact cooling needs. As a general rule of thumb, the U.S. Department of Energy suggests using 21,000 Btu for 1,000 to 1,200 square feet, 30,000 Btu for 1,500 to 2,000 square feet, and 34,000 Btu for 2,000 to 2,500 square feet.

Construction Considerations

• While a new cooling system can be installed outdoors or on the roof, the ducts used to distribute this cool air often require extensive remodeling work. Installers may have to lower ceilings, build out walls, or add soffits to hide ducts, which generally measure 12-by-6 or 10-by-8 inches. In a ranch-style home, the ducts can be hidden in the attic with relative ease. In a two-story home, builders may be able to hide supply runs in the closet to keep these ducts out of the living spaces. Cooling contractors also have to cut some holes in walls and ceilings to accommodate supply and return grills.

Mini-Split Systems

• If you don't have existing ducts, a mini-split system may serve as a more affordable and effective method of cooling your home than a new central air system. These systems consist of an outdoor compressor and an indoor air handling unit. Each outdoor compressor can accommodate up to four air handling units to cool four different rooms. The systems connect via a small conduit, and there's no need to add ductwork. The DOE estimates you'll spend $1,500 to $2,000 per ton of cooling capacity to install mini-split air conditioners as of 2012.