Air-conditioning ducts are usually part of an integrated heating, air-conditioning and ventilation, or HVAC, system that uses shared ducts to distribute cooled air from an AC unit and heated air from a furnace. In many systems, heating and AC ducts are essentially indistinguishable and both benefit from the same methods of insulation. Although several preinsulated duct materials are available, bare sheet metal remains the industry standard. To reduce temperature loss through the bare sheet metal, HVAC professionals cover the ducts either with rigid insulation boards or flexible insulation wrap. Both types of insulation are relatively easy to install, but rigid insulation board usually is more costly. Regardless of type, duct insulation increases your HVAC system's efficiency and reduces your home's energy requirements.
Things You'll Need
- Tape measure
- Foil-faced duct wrap
- Utility knife
- Outward clinch staples
- Outward clinch staple gun
- Foil seam tape
Measure the perimeter of the duct that you are insulating with a tape measure. On square or rectangular ducts, measure and add all four sides to determine the perimeter. On round ducts, the perimeter is equivalent to the duct's circumference. To determine circumference, multiply the round duct's diameter by pi. The result is the round duct's circumference.
Determine the "stretch-out" value of the perimeter. Stretch-out values are units of length that you must add to the duct's perimeter to achieve the duct wrap's listed insulation value. Duct wrap manufacturer's include stretch-out charts with their products. Find your insulation's thickness and corresponding value on the stretch-out. Add the stretch-out value to the duct's perimeter. The result is the cut length for the duct wrap.
Unroll the duct wrap on a flat surface with its foil side facing down. Mark the cut length both sides of the wrap, lay a straightedge between the marks and draw a knife along the straightedge's side to sever the length of duct wrap from the roll. Mark roughly 2 inches in from one corner of wrap's cut edge. Create a corresponding mark at the opposite corner. Lay the straightedge across the marks.
Draw the knife along the straightedge's side to score through the insulation portion of the duct wrap. Do not completely cut through the wrap; leave the underlying foil intact. Remove the 2-inch strip of insulation from the end of the duct wrap to expose the underlying foil flap. This flap will overlap the opposite end of the duct wrap during installation.
Load outward clinch staples into an outward clinch staple gun. Drape the duct wrap around the duct with its foil side facing out. Lap the flap that you created over the intact, opposite end of the duct wrap. While holding the flap over the wrap's opposite end, fasten staples through the flap every 6 inches along the seam.
Cut and install successive pieces of insulation to cover the entire duct. Slip the intact ends of adjacent pieces beneath the integral flap of previous pieces. Cover both the stapled and butt-joint seams with foil seam tape.
- Photo Credit Comstock/Comstock/Getty Images
How to Cut Metal Ductwork
Cutting metal it to length and cutting holes in for taps are two common reasons to cut metal ductwork. The thin sheet...
How to Insulate 90-Degree Water Pipes
Insulation around your water pipes can prevent condensation and help save on your energy bills. When cold water flows through pipes installed...
How to Insulate Return Air Ductwork
For maximum efficiency, ductwork needs to be insulated in certain circumstances. Ductwork warrants insulation when it is concealed above a drywall ceiling,...
Standard Method of Measurement of Pipe Insulation
Pipes have wide and varied applications, including some that cause the pipes to be placed in environments with undesirable temperatures. This means...
How to Insulate a Metal Duct
If you have metal heating and/or air-conditioning ducts in your home that aren't insulated, they are probably costing you energy dollars. The...
Sheet Metal Duct Types
Ducts are integral parts of ventilation systems, including heating and air conditioning. They are the pathways for airflow and are important for...
AC Duct Insulation Methods
Air conditioning ducts supply cooled air to the living area and return the same volume of air to the air conditioning unit...