Replacing a recirculating hood with a ducted model
BY: ANNA HOLBROOK
Clearing the Kitchen Air
It's not surprising that most kitchens are equipped with a range hood. What is remarkable, however, is that most of these hoods do a lousy job of eliminating steam, smoke, grease and odors. That's because they simply recirculate the air by drawing it through a filter and blowing it back into the room. For a range hood to perform well, it must exhaust the dirty air to the outdoors. In this project, we'll show you how to replace an old recirculating unit with a new ducted range hood. In our kitchen, the range sat against an exterior wall, so we ran the duct out the rear of the hood and through the house wall. However, we could have also run the duct straight up into the upper cabinet and then cut through the roof or turned it down through the eave. For a range placed against an interior wall, the duct can go up into the soffit above the cabinets or between ceiling joists, and then out through the nearest exterior wall. Regardless of where you run the duct, be sure it leads outdoors; never end a ventilation duct inside an attic or other enclosed space. Most recirculating range hoods can be converted to an exhausted type with standard 7-in.-dia. round or 3 1/4 x 10-in. rectangular ducting. We opted to replace our range hood with a newer one that's a lot more effective. We installed the 30-in. Allure III ($399) from Broan-NuTone. It features sleek styling and dual halogen lamps that light up the range top. Plus, its fan operates at only 0.9 sones, which is 50 percent quieter than some comparable units. Drawing a respectable 250 cfm (cubic feet per minute) of air, the fan also features a "boost" setting that kicks the blower up to 400 cfm for extra power. There's even a delay-off mode that automatically turns off the range hood 20 minutes after you set it. The Allure III is designed for easy cleaning, too. Its two large filters are dishwasher safe and the steel cover behind the filters is coated with nonstick SilverStone, which means you can easily wipe off grease stains. The unit comes in 30-, 36- and 42-in. sizes in white, biscuit, almond, black and stainless steel. Prices start at about $200.
Readying the New Hood
Start by removing the two filters and unscrewing the bottom cover (step 1). Take out the damper/duct connector and set it aside (to prevent damage during shipping, the connector is screwed to the inside of the hood). Next, use a hammer and slotted screwdriver to remove the rectangular duct knockout from the rear of the hood (step 2). Work carefully so you don't deform the metal surface around the knockout hole. Then screw the connector over the hole (step 3).
Cutting the Hole
Before removing the old range hood, shut off the electricity to that circuit at the main electrical panel. Flip the light switch on the old hood to confirm that the power is off. Remove the grilles from the stove top and cover the range with a blanket. To remove the old hood, reach up into it and disconnect the electrical cable. Locate the mounting screws that hold the hood in place and remove them. Gently pull the hood from the wall (step 4). Next, mark the centerline of the upper cabinet on the back wall. Measure down 1/8 in. from the bottom of the cabinet and draw a level line across the wall. Use these two references marks to draw a 3 3/4 -in.-high x 10 1/2 -in.-long rectangle on the wall. Cut out the duct hole with a drywall saw (step 5). If you're lucky you won't hit a wall stud or other obstacle. If you do, but it's just at one edge of your hole, you can shift damper/duct connector on the rear of the unit 1 in. to the left or right. This shift is often enough leeway to miss a stud or obstacle. However, if the stud is still in the way, you'll have to remove it and install a header. Here's how: Empty out the wall cabinet that sits directly above the duct location, then unscrew and remove the cabinet. Cut a hole in the wall that's about 14 in. high x 28 in. wide. Use a reciprocating saw to cut the stud 6 in. above the location of the duct hole and 4 in. below it. Pry out the severed piece of stud. Next, make a header by nailing together two 2x4s sandwiched around a 1/2-in.-thick plywood spacer. The header must be long enough to span between the two full-length studs on each side of the hole. (For studs placed 16 in. on center, cut the header 30 1/2 in. long.) Make a double sill plate to the same length by nailing together two 2x4s. Then, reach into the wall hole and screw a 2-ft.-long 2x4 trimmer stud to each full-length wall stud. The trimmers must be level with the top of the just-cut wall stud coming up from below. If you can't fit the trimmer stud into place, enlarge the hole. Slip the double sill into the wall and screw it down into the trimmers. Insert the header and screw up into the bottom of the cut stud hanging down from above. Cut two short 2x4s to fit vertically between the sill and header. Screw one to each of the full-length wall studs inside the hole. Cover up the new framing by replacing the original drywall or cutting a new piece to fit. Conceal the wall patch with drywall tape and joint compound. Reinstall the wall cabinet and cut out the 3 3/4-in.-high x 10 1/2-in.-long duct hole. Next, transfer the duct hole location to the outside by boring a hole through the exterior wall from inside (step 6). Go outside and use the hole as a reference point to saw out a 3 1/2-in.-high x 10 1/4-in.-long duct hole (step 7).
Installation Sequence
At this juncture, the hardest part of the project is done. Installing the range hood takes only about 30 minutes. Start by feeding the electrical cable through the round knockout hole in the rear of the hood (step 8). Be sure the hole is fitted with a cable clamp. Use wire connectors to join same-color wires (black to black and white to white). Tighten the green or bare wire under the grounding screw. Lift the hood into place and press it tightly against the underside of the upper cabinet. Secure it with four screws driven up from the inside (step 9). Now go outdoors to install the wall cap ($23). Run a continuous bead of caulk around the flange of the wall cap, then press it into the hole (step 10). Check to make sure the wall duct on the cap slides onto the damper/duct connector that's attached to the rear of the range hood. If the wall cap is too long, trim it with tin snips. If it's too short, pick up a 3 1/4x 10-in. section of aluminum duct at a home center or lumberyard (a 24-in. piece costs $8). Cut a piece of duct to fit between the wall cap and damper and attach it with professional (not cloth-backed) duct tape. Finish the installation of the wall cap by screwing it to the house. Turn the electricity back on and test the ventilating fan and lights. Go outside to check that the wall cap damper flips open when the fan is on and closes tightly when it's off. Of course to truly test your new range hood, go fry up a batch of fish— you can be confident that the kitchen won't smell like Captain Stinky's House of Haddock.
Step by Step
1. Remove the one-piece cover from the bottom of the range hood. Also, remove the aluminum damper/duct connector that's attached to the inside of the hood. 2. Pry off the rectangular knockout from the rear of the hood for ducting straight back through the house wall. The unit can also be ducted through the top. 3. Attach the damper/duct connector over the knockout hole. You can adjust it up to 1 in. off center if needed to avoid a stud or other obstacle. 4. Pull the old range hood from the wall after removing its mounting screws. Be sure the electricity is off to this circuit. 5. Cut out the rectangular duct hole with a drywall saw. Hold a wet/dry vacuum under the saw to capture any dust that falls. 6. Bore through the exteriort wall with a 3/8-in. spade bit and an extension shaft by drilling exactly at each corner of the hole. 7. Use a sabre saw to cut a duct hole measuring 3 1/2 x 10 1/4 in. through the siding and the plywood wall sheathing beneath. 8. Pass the electrical cable through the round knockout hole in the rear of the hood, then tighten the cable clamp. 9. Secure the new range hood with four large-headed screws driven into the upper wall cabinet above. 10. Slide the wall cap through the duct hole, making sure it joins the damper/duct connector on the rear of the range hood.
REFERENCE: http://www.thisoldhouse.com/toh/article/0,,218403,00.html
