In new home construction and in retrofits, proper duct system design is critical. Many existing duct systems lose a lot of energy from leaks and poor insulation. Efficient and well-designed duct systems distribute air properly throughout a home without leaking to keep all rooms at a comfortable temperature.

Duct systems should provide balanced supply and return flow in order to maintain a neutral pressure within a home. Maintaining a neutral indoor air pressure is important to the health, safety, and comfort of a home's occupants, as well as to the energy efficiency of the home. An unbalanced system reduces the home's comfort and energy efficiency. It can also draw mold spores, dust, humidity, radon gas, and other contaminants indoors.

Air return duct systems can be configured in two ways. In a distributed return duct system, each room has a return duct that provides a pathway for air to flow back to the air handler. In a central return duct system, or whole-house return, return grilles are installed in central locations on each floor, usually close to the air handler.

Central returns vs. distributed returns
Traditionally, central returns have been less popular than distributed returns because of privacy problems and noise transfer. A central return duct system that has been installed using Best Practices®, however, exhibits none of these issues.

The benefits of central returns:

• Less ductwork is required, because the HVAC system is in a centralized location.
• There’s a more direct path for air flow, because fewer connections are required.
• The system is more efficient, because there are fewer seams and joints and potential leaks are minimized.
• Energy costs are lower, because the system minimizes the surface area of the ductwork.
• There's less pressure loss too, since the duct size is larger overall.
• Less installation time is required, and the cost of materials is lower.

So despite criticism, central return duct systems are the better choice in duct system design. Good duct design provides a home with proper air distribution, economical heating and cooling system operation, and economical duct installation. Central return duct systems are a good way to provide a comfortable indoor environment for homeowners.

For more information:

• Review our related article “Central Return Duct Systems: How they work” to learn more about the Best Practices® and building science behind these systems.
• Review the U.S. Department of Energy’s fact sheet on duct systems: "Air Distribution System Design: Good duct design increases efficiency."
• Sign up your team for BuildIQ University’s online training course, “Mechanicals: HVAC,” for more Best Practices® for ductwork design, heating, ventilation and air conditioning.