HVAC Duct Work Installation

Choosing Ducts

• The best type of ducts for your home depends on the amount of space you have available behind the walls or above the ceiling. Traditional ducts are boxy tubes of sheet metal that are large and need a straight line between rooms. Flexible ducts use metal wire and fiberglass or aluminum covers. Bending these smaller tubes around wall joists or around light switches allows for installation in tighter spaces.

Preparation

• You'll need to prepare the space inside the walls, floors or ceilings where you'll be installing the duct work. Ensure that you have a clear path that is free of obstructions to run the ducts to each room with as few turns and bends as possible to prevent air flow problems. The size of the ducts needs to be calculated using the formula from the Air Conditioning Contractors of America. Ducts of the wrong size cause temperature variations and waste unnecessary energy.

Securing

• The duct work will need to be laid out in the order of installation and then assembled and attached to the floor or ceiling supports with metal straps. Clamping a few pieces together at a time, then lifting them up for hanging, ensures a tight fit between duct work sections, according to Nordfab Ducting. Flexible ducts need more hangers than stiff metal duct work, but attaching sections of it together is harder and requires adhesives.

Finishing

• After checking each joint and seam for air leaks after the duct work is connected to a furnace or air conditioner, many homeowners add a layer of insulation around the metal to reduce the amount of heat lost as the air travels through the ducts. Most flexible duct work doesn't require additional insulation, because the inner layer of the duct is fiberglass batting.