Manual D Duct Sizing

Balanced Comfort has over 30 years of HVAC design expertise. Our licensed mechanical engineer (PE) is ready to assist you with your next project. Whether you need help with a residential or commercial project, our team has you covered. From mechanical engineering to fire protection design and other energy efficiency services, our professionals are happy to help!

Residential and Commercial Manual D Duct Design

Designing the ducts of your air and heating system in line with ACCA’s manual D duct design is often required by residential building codes, and furthermore, failing to design your ducts in this manner will have many negative side effects. If the system of ducts which carries the hot or cool air throughout the house is improperly designed, then not only may you be breaking your local building code, but you may be putting the occupants’ health at risk, putting undue stress on your heating and cooling system, and ultimately driving up your own energy bills.

The details of the manual D duct design process will normally require treatment by a professional technician, but we will sketch out the basic details of this process:

  • Consider the strength of the blower which moves the hot or cool air throughout the system of ducts.
  • Match the size of your ducts to the power of your blower.

Friction Rate in Manual D Duct Design

Perhaps the most important step in the manual D duct designing process concerns the friction rate of the ducts. Again, this is quite complex, but we will sketch the basic idea. Friction rate is based on the length of the duct system and therefore can vary drastically from system to system.

  • Figure out your friction rate
  • Use a duct calculator in order to determine the perfect size ducts for your system

The main goal here is to make sure that the air gets blown through the duct system with the perfect velocity so that it exits the vents with the right amount of speed. If your blower power is so low that it ultimately does not push the hot or cool air out of the vents, then your house temperature will not be regulated correctly; and yet if it is pushing out the air too strongly you may be putting unneeded pressure on your system and raising your energy bills.

Frequent Asked Questions