How to Add a Heating Duct

The addition of a heating duct can increase the circulation in a room or actually add heat to an unheated room. Running a heating vent is simple if the space is clear or the insulation can be removed. If this is not the case then the project should be left to a professional. A single floor ranch house is an example of a duct any homeowner can add. It only requires a few tools and an familiarity with the crawlspace.

Tape Measure
Hammer
2-inch nail
Marker
Drill with a 1/8 inch drill bit (You should also have a Philips bit to screw in the under-mount)
Jigsaw
Tin nippers
Duct tape
Flexible duct work
Prefabricated Floor under-mount (With connector bracket)
Under-mount screws (Provided with the under-mount)
Floor register (Specific to the size of the floor under-mount)

Instructions

- 1
  Enter the crawlspace and measure the distance from where you are placing the opening to the trunk line. Drive a nail through the floor so that it can be located when you go back to the surface.
- 2
  Measure the width of the under-mount and the width of the register. The register should be about 1/4 inch smaller than the under-mount for a good fit. Transfer the width of the under-mount to the area you are placing the hole for the vent. Center the hole around the nail. When this is marked off, drill a hole into one corner with the drill.
- 3
  Pound the nail into the floorboard. This will give you a smooth cutting surface. Cut out the hole for the under-mount and register. Clean the edges so that there are no splinters.
- 4
  Crawl under the house and locate the area you are coming off of the trunk line. Measure the end of the flexible duct work and transfer those measurements to the trunk line. Cut a hole into the trunk line. Place the end of the flexible duct work into the hole. You will have to go in at an angle because when you push on it the duct work will only bend. Straighten the duct work out. Apply duct tape around the outside of the trunk line and where the duct work meet. This will keep the duct from falling out. Make sure that you go completely around the vent to prevent air loss.
- 5
  Run the flexible duct work to the area where the under-mount will be located. It does not have to be attached, just in the area.
- 6
  Attach the under-mount with the drill and the screws provided. These are generally attached to each corner and one in the middle on each side. Cover with duct tape to prevent air leakage.
- 7
  Attach the duct work. This is done with the clamp provided. If you have to cut it to fit the length that is fine. Use the tin nips. You do not want it to sag. It should be close to the sub-floor but not touching it. The clamp will fit around the round under-mount opening and can be tightened by hand. You will also want to wrap a layer of duct tape over this to prevent air loss.
- 8
  Place the register into the new vent. It should fit snugly and also be easy to remove for cleaning out debris and other items that small children will place in there.

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