How to Get to Ducts Between Floors

Many of us have been surprised at how much we can improve airflow in the ducts even if the only access we have is near the unit and through the grilles. Occasionally, we need to access the ducts between the floors to improve the airflow.

Here are several ways to access ducts:

Add a False Return Grille
Cut an access hole in the ceiling of the first floor in a central area to gain access to the ducts. The most common size duct used is 14-in. x 24-in. This size fits just between most floor joists. Most installers report they can get to a 100 sq. ft. area through this access hole.

When the work is completed, install a 14-in. x 24-in. return air grille with a piece of sheet metal attached to the back of the grille that has been painted flat black. There will be no duct attached, there’s just a return grille doubling as an access door that will “disappear” in about a week as the occupant gets used to it. It can easily be removed to run phone lines or computer cables in the future.

If more access is needed, install false grilles behind an adjacent wall, or in the next room, so they’re not all visible from one point.

Pull Back the Carpet
In the past 30 years or so, plywood or particle board is all that’s been installed under most carpets. To gain access to the duct between the floors, simply pull back the carpet, and cut through the plywood.

This is easier than it first appears. Most carpet is held in place by tack strips at the edge of a room. Small spikes hold the carpet in place as the carpet is stretched onto the tack strip. A ½-in. lip at the edge of the carpet is tucked under the wood trim at the bottom of the wall.

Use a pair of pliers to pull up the edge of the carpet at the corner of the room. Continue to pull, and the carpet peels back easily. Carefully remove the padding, that’s normally tacked with staples every four ft. on center to expose the plywood.

Cut an access hole through the plywood with a skill saw. Cut on the joists where the plywood is nailed down. Remove the plywood and perform the duct renovation work.

Replace the plywood that was removed and screw it down with drywall screws. Fill in the cracks in the floor with “Fix-All” or another brand of quick-dry construction filler. Let it dry, and tack the padding back down with a staple gun.

Purchase a “carpet kicker” tool from a carpet accessories distributor (normally less than $100) This tool grips the carpet and stretches it with a kick from the installer’s knee. This forces the carpet back on the tack strip. Simply tuck the lip at the edge of the carpet below the wood trim and it looks good as new.

If you’re a little timid, hire a carpet installer and watch him do the work. You’ll see there’s not much to it.

By using these methods you will rarely need the services of a drywall expert. If you do, there are many carpenters that are experts and are quick to lick up a side job on the way home at very competitive rates. Many contractors refer the drywall contractor to their customers and let them work together outside of the duct renovation agreement.

Rob “Doc” Falke serves the industry aspresident of National Comfort Institute a training company specializing in measuring, rating, improving and verifying HVAC system performance. If you're an HVAC contractor or technician interested in a procedure addressing HVAC system duct renovation, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at for free information, technical articles and downloads.

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