When the basement isn't quite as warm or as cool as you'd like it to be, the solution is usually a few well-placed vents in the ceiling. You can't just tap into any piece of duct work, however. Some ducts are sized to the room they serve. Others return air to the furnace and central-air units to be reheated or cooled and recirculated. Whether you're installing a ceiling vent in an unfinished or finished basement, the steps are similar. Often the difference is only in the trim pieces.
Things You'll Need
- Left- or right-cutting sheet metal shears
- Hex-head sheet metal screws
- Drill with bits and hex driver bits
- Duct starter collar
- Large flat-head screwdriver
- Flexible metal duct (for drop or hanging ceilings)
- Rigid metal duct (for no ceiling or drywall ceilings)
- Register box (for rigid duct)
- Register cover
- 1-by-2-inch lumber for mounting the vent
- Duct strapping
- Metal duct tape
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Determine the correct main duct into which to cut. At the furnace, find the air filter. The filter is always on the return duct, right before the air is fed into the furnace. It is the other main duct that you will want to tap into. Follow this duct and mark it as the delivery duct.
Choose a location on the main delivery duct that is closest to where the new vent will be. On the side or top of the main delivery duct, use the starter collar to trace a cutout for the new duct. The path to the new vent should have as few bends as possible, which makes the side of the main duct ideal. Use the top if necessary.
Place the head of the screwdriver just inside the traced circle at a 45-degree angle. Strike the butt of the handle with the hammer to penetrate the duct and start the cut. Use the sheet metal cutting shears to cut out the circle for the starter collar.
Place the starter collar in the new hole and bend the ears back around the inside of the main duct to hold the collar in place. Secure the starter collar with three equally spaced hex-head sheet metal screws.
Run duct to the location where the vent is to be installed, starting at the starter collar. Use duct strapping every 3 to 5 feet as necessary to secure the duct work to the joists with sheet metal screws. Use as few bends and angle pieces as possible. Each bend slows the air flow.
Mount the register box, if required, to the ceiling joists with 1-by-2-inch lumber cut to size and nailed to the joists. This step is not required for suspended or drop ceilings.
Make any adjustments to the installation and secure all the joints. With flexible duct, metal duct tape will permanently join the sections together. Secure rigid duct with three evenly spaced sheet metal screws at each joint. Seal all the joints with metal duct tape regardless of the type of duct.
Install a return air register for each room into which a ceiling vent was added. Follow Steps 1 to 7, except tap into the main return duct rather than the delivery duct. If the basement is unfinished, you probably don't need additional return ducts. Return air ducts can be at ceiling height, or the space between studs in a wall will serve just as well.