The network of rectangular, round and oval ducts that branch through the walls, floors and ceiling are designed to continuously control the humidity, freshness and comfort level of the air in your home. Properly connected and insulated, the ducts in your home can provide significant levels of comfort as well as energy efficiencies that can lower your heating and cooling costs.
This guide will help you understand how venting works in your home and offer solutions to help you get the most out of your venting system.
There are three types of venting in your home: venting for supply air, return air and exhaust air. The effectiveness of these venting systems is facilitated by a combination of heating and air system materials, duct sizes, duct sealant and insulation.
Supply Air: A mixture of recirculated and outside air which has been conditioned and delivered into your home. This can be either 100 percent recirculated air, 100 percent outside air or any mixture of the two.
Return Air: Air that has circulated through your home as supply air and is returned to the HVAC system for additional conditioning or release from the home. Return ducts help pull air into vents that is being pushed in by supply ducts.
Exhaust Air: Air that is removed from a space and not returned, removing airborne impurities, like smoke from cooking or moisture from bathrooms and washing machines. This keeps the air clean and prevents damage from excess moisture and dust.
Ducts can be made from galvanized steel, fiberglass duct board/insulation panels or flexible ducting. They are available in a range of sizes but ducts, in-wall stacks and registers have standard sizes commonly found in homes.
Common Duct and Vent Sizes
Ducts: 4, 5, 6, 7 or 8 inches
In-wall stacks: 3.25 x 10 inches, 3.25 x 12 inches or 3.24 x 14 inches
Registers: 4 x 10 inches, 6 x 10 inches, 4 x 12 inches, 6 x 12 inches
Insulation & R-Values
Insulating ducts in unconditioned spaces increases energy efficiency and prevents condensation from forming so you can avoid problems with mold and mildew.
Return air ducts only need to be insulated if they pass through environments that adversely affect the return air temperature.
Supply air ducts don’t require insulation if they run exposed through the space being conditioned.
Exhaust air ducts normally do not need insulation.
Insulating your ducts can be a simple project for DIYers. Sheets are cut to fit and attached to one another with high-quality foil tape or other attachment mechanisms.
- Shorter lengths
- Available for various elbow and tee joints
- The most commonly used insulating material
Self-adhesive foam insulation with aluminum foil backing
- Effective where space is at a premium
- Suitable for hot and cold pipes
6-foot lengths of 3/8-inch tubular polyethylene foam
- For use with long runs of pipe
- Pre-slit tubes come in different internal diameters
- Tubes snap into place quickly and easily on pipes from ¼-inch iron to 1¼-inch copper
- Available as rubber tubes
- Used for new installations
- Used for spot repairs and leak sealing
Duct insulation is measured in terms of R-value, which is a measure of resistance to heat flow.
The higher the R value, the better the degree of insulation.
Duct insulation ranges in thickness from 1 to 2 ½ inches and provide an R-value of about R-4.0 per inch of thickness.
- R-Values for Unconditioned Attic: R-4 to R-8
- R-Values for Unconditioned Basement/Crawlspace: None to R-4
- R-Values for Unconditioned Attic: R-4 to R-8
- R-Values for Unconditioned Basement/Crawlspace: R-2 to R-8
- R-Values for Unconditioned Attic: R-6 to R-11
- R-Values for Unconditioned Basement/Crawlspace:R-2 to R-11
Upkeep & Features
Leaky air ducts can raise a home’s heating and cooling costs by 20 percent to 40 percent, and can contribute to health issues. Keep an eye on duct leaks and clean the ducts if mold or excessive dust is present.
Look for air leaks in ductwork in unconditioned areas, like attics and crawlspaces.
Check for separation in areas where sections join and for obvious holes.
If your duct joints have been sealed with cloth duct tape, look for cracks and loose or peeling tape.
Small repairs are fairly easy to make, using duct mastic/sealant, mastic tape or high-quality duct tape approved for heating and air conditioning systems.
Bigger repairs may need to be made by a professional. Contact The Home Depot’s Installation Services for more information.
Maintaining a Balanced System
Forced air distribution systems are designed to be a closed, pressure-balanced loop, with the same amount of air entering and leaving conditioned zones through the ductwork. Maintaining a balanced air system not only makes your home more comfortable but also makes the system run more efficiently, which translates into lower utility bills.
While a well-designed system should not need adjusting, if you find some rooms too hot and others too cold, you can tweak the balance yourself by adjusting levers on air registers and balancing dampers in rooms.
Cleaning air ducts periodically removes allergens like pollen as well as other contaminants like dust and dirt. Check debris accumulation in your ducts at least once a year and have them cleaned immediately if:
Mold is visible
Ducts are infested with vermin
Ducts have excessive dust or dirt that is being released through supply registers
Cleaning techniques range from using a brush, rag and vacuum cleaner to remove loose dirt and dust on registers, grilles and duct walls to professional whole-house duct cleaning services that clean the entire HVAC system with services like duct sealing and biocide applications.
Features to Consider
Decorative grilles and registers are available in a variety of materials and finishes and are an easy way to change your decor.
In-line booster fans boost heated and cooled air for increased comfort.
Register vent boosters pull more air from registers and increase comfort in rooms that aren’t served by your HVAC system.