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New Ductwork for Central AC

Don't duck the issue of ducts when considering new central air for your home.

There's nothing standing in your way if you want to finally get rid of your window air conditioners and convert to central AC. It just depends on whether you have existing heat ducts or no ducts at all. Each requires a different approach and investment, with the cost for a house with no ducts running much higher. Here's some information to help you weigh your options.

If you already have furnace ducts in your home, you're halfway there. But you can't just slap AC equipment onto your existing ductwork and equipment. Before you do anything, get your ducts inspected. Your technician can determine if the existing system will work and whether you need to modify it. Some of the typical modifications include sealing the ducts, upgrading your furnace blower, and replacing your furnace registers. Find out the capacity of your blower. If your furnace blower doesn't deliver enough air over the coils or throughout the home, your system will be anemic and your coils could freeze.

In addition, sealing the ducts may improve your system's efficiency during the summer season but don't try this at home. Use a professional to avoid unbalancing your heating system or creating dangerous backdrafts. Finally, don't forget to take a look at your registers, too, and consider replacement. Are they the older models with only inch slits? Newer grilles have wider openings that allow more cool air to pass through, up to 25 percent more.

If you don't have furnace ducts to work with, you're in for more work and a bigger price tag than adding to an existing forced-air heating system. How much more? Adding central air to a 2,000-sq.-ft. home with an existing system costs about $3,500 to $4,000. For a house that needs new ducts, the costs and work time double. But that doesn't mean it can't be done cleanly. You won't be staring at any obvious or ugly ductwork sticking out from the walls. The right contractor will be able to squirrel them away behind walls, in the back of closets and up in the attic. How will it look? The ducts might be almost unnoticeable on your wall and ceiling surfaces. Your contractor will cut holes in first- and second-floor ceilings for registers.

In a duct-from-scratch installation, typically the fan-and-coil unit is mounted in the attic. That means getting supply and return air ducts to reach downstairs as far as the first floor. To determine the best way to route the ducts, your contractor will have to draw a floor plan of the second floor and lay it over a floor plan of the first floor. The second-floor rooms can be serviced by running ducts across the attic, then downward between the attic floor joists. From there, ducts could run down through second-floor closets to feed the first-floor rooms. Don't worry, the new ducts won't squeeze your wardrobe out. Most ducts are only 12 X 6 in. or 10 X 8 in. "Flex duct" is a small flexible hose that can take the place of rigid ductwork. But be careful of installing flex duct where it could be punctured.

Sources used to create this article include Today's Homeowner magazine.