B-vent ducting is commonly used for furnaces and water heater installations. It is made up of a double wall, metal pipe that exhausts gas fumes out of your home. B-venting may exit your wall or ceiling. Consult your local inspector or contractor on all specific code requirements. Otherwise, a do-it-yourselfer is capable of installing B-venting.
Things You'll Need
- Eye protection
- Ear protection
- Roto saw (for drilling and cutting holes)
- Extension cord
- Cordless drill
- Drywall screws
- Screw bits
Put on all protective gear.
Drill a series of holes in the wall or ceiling, where your B-vent will exit your wall or attic. Do the same for the roof. Use the roto saw for this. Make drill holes in a circular pattern and then cut out the hole. Hole size will depend on the unit you are venting. The most common vent size is 4 inches. Check with a local contractor for help with vent sizing.
Press the draft vent over on top of the furnace or water heater vent pipe exhaust. It clips in place. Attach the first section of B-vent pipe onto the draft vent. Each piece of B-vent connects to the next by twisting it in place.The pieces are interlocking and are held in place by two locking tabs. Unlike regular venting, which you can cut to size, B-vent only comes in pre-determined lengths.
Install a 45-degree elbow onto the first section of B-vent, if you are exhausting your furnace or water heater through the wall. Codes generally don't allow 90-degree elbows to be installed for B-venting because it can trap gas fumes.
Connect each section of B-vent to the next by sliding it down and twisting it in place, until it locks. Once you reach the wall or ceiling, hook up the through-the-wall connection. Generally, you will install a flat fire stop at the wall or ceiling, which your B-vent pipe will pass though to the attic or outside. A fire stop is a flat piece of metal that sandwiches the B-vent as it exits the wall or ceiling and prevents fire from spreading from inside to outside of the house.
Install the attic insulation shield on top of the fire stop, for roof exit venting, and connect the next section of B-vent to it. Install the last piece of B-vent through the hole in the roof or wall that you previously cut out.
Go outside and install a vent cap on the end of the B-vent. Roof installations will require flashing and a collar to be installed first, before you place the B-vent cap on.
Install pipe strapping tape to the B-vent piping as it exits the ceiling and then the roof. Install pipe-strapping tape to the wall exit of your B-vent for wall exit installations. Pipe-strapping tape has holes in it to allow you to screw it to the studs. Use a cordless drill and screw bit to do this.
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