Residential Duct WorkMA Duct Work Inc.

The purpose of Residential Ductwork Design is to properly distribute the airflow, produced by your heating/cooling system, to your house. This involves Return Air (unconditioned) coming into the heating/cooling system. Then, by heating/cooling that air, delivering the newly conditioned air to your home. An improperly designed ductwork systems can cost money through inefficiencies, and in some cases, cause premature failure of heating and cooling equipment. This means that your home's ductwork system is just as important as the equipment used to heat and cool your home.


Residential Ductwork Designs

The 3 Most Important Things to Understand About Residential Ductwork Designs are:

Furnaces and air conditioners require a certain amount of airflow, measured in CFM (Cubic Feet Per Minute), to be passed through the equipment (supply and return ducts) in order for the equipment to function properly and efficiently.

All homes have unique requirements and construction that pose obstacles when designing the ductwork system to accommodate each room with proper airflow. (This is especially true with older homes.)

The Ideal Ductwork System achieves both goals by providing enough airflow to and from the heating/cooling equipment as well as the home. For maximum efficiency, this "ideal" system should also be sealed at all seams with aluminum tape, and should be properly insulated when exposed to unconditioned environments (i.e. crawl spaces and attics).

Residential Ductwork Designs


Basic Guidelines for Ductwork Fittings and Placement

  • Supplies are located on outside walls.
  • Returns are located on inside walls. They should not be located in the same area as the furnace, nor should they be located by moisture sources such as kitchens or bathrooms.
  • Return Air CFM must be equal or greater than Supply Air CFM.
  • Wyes commonly reduce.
  • Tees split, but do not reduce, and an appropriate reducer must be added.
  • Dampers on take-off duct runs allow for adjustments of air distribution.
  • In order to maintain velocity, reduce duct size.
  • Never locate ducts at the end of the trunk line run. Last take-off run to be located 12" - 18" from end.
  • Always stagger take-off ducts by 12" to maintain pressure.
  • Use insulated duct or duct board in unheated spaces.
  • Flexible duct work must be stretched tightly for maximum air flow.

  • Example:
    System is designed to move 3 Ton of A/C or 1200 CFM.
    Sample Design

    Video Clips on Some Projects