This Old House Video: Energy-Efficient HVAC | Season 9, Episode 12 (2010): Not familiar with ductwork? Watch plumbing and heating expert Richard Trethewey helps a pair of homeowners reduce their utility bills by installing a new forced-air furnace and air conditioning system. HVAC portion ends at 10:18 minutes
Nationwide ACCA Manual D Duct Design Service - Call 801-949-5337 Today!
What is Manual D? ACCA Manual D duct design properly sizes HVAC supply and return ducts and registers to ensure heating and cooling is distributed properly to each room. The ANSI-recognized national standard for residential HVAC duct is Manual D, from the Air Conditioning Contractors of America (ACCA), and provides a single set of duct sizing principles and calculations that apply to all duct materials. Manual D provides system operating point (supply Cfm and external static pressure), and a method for determining the impact of duct friction and fitting pressure drop on blower performance and air delivery
Manual D VIDEO: Please watch This Old House define different duct items that Manual D sizes - video is towards middle of page
Developed by Hank Rutkowski
Why is a residential Manual D duct design important? You're ready to replace an old HVAC system or perhaps you're building your dream home. Before purchasing ANY HVAC equipment, there are 3 important HVAC design factors to ensure optimum comfort in your home for many years to come. This webpage addresses the 3rd step - sizing HVAC supply & return duct properly using ACCA Manual D duct sizing techniques developed by Hank Rutkowski.
Why do many permit offices require an ACCA Manual D duct design before issuing an HVAC permit? Because Manual D Residential Duct Systems has a proven track record over many decades just like the ACCA Manual J load calculations & Manual S HVAC sizing. In proper duct sizing techniques, your HVAC designer will utilize:
The Manual D procedures creates a "duct blueprint" that code officials can inspect, a home owner can review and an HVAC installer can use.
Residential HVAC ductwork that is too large will result in rooms becoming uncomfortable - This duct work is TOO Big! Duct work that is too small will increase your utility bills and perform inefficiently - This duct work is TOO Small!
Why Should You Insist on a Proper Residential Manual D HVAC Duct Design?
Like everything, there is a right way and a wrong way. Many contractors use improper duct sizing techniques because they want to save materials, time and labor. Their shortcuts result in a spider web of duct work of varying sizes and lengths. Supply registers deliver inconsistent comfort and the returns are often undersized. Do you really believe all your rooms are receiving the required CFMs consistently?
If the ductwork is not installed properly you cannot expect your comfort system to be effective. Your system may be properly sized using ACCA certified Manual J load calculation results, and you may have selected a great HVAC unit, but your poor residential duct design will result in HVAC ducts that don't deliver the required airflow to each room. Or sometimes contractors will add an addition onto an existing system and the new heating and cooling system is too small to cover both the existing space and the new addition.
Many municipalities and permit offices are requiring an residential ACCA certified Manual D duct design along with a Manual J load analysis and Manual S HVAC equipment sizing to meet code requirements. These residential HVAC duct designs accurately size the duct work needed for your properly sized heating and cooling system.
Some things to look for in a good home HVAC duct design are:
Improperly sized return trucks:
When your home duct system is properly designed, air will distribute evenly throughout your home. Each duct will carry the proper amounts of CFMs. Save yourself money, time and aggravation. Invest in an ACCA Manual J load calculation and Manual S equipment sizing to ensure you select the properly sized HVAC unit and an ACCA Manual D duct design and enjoy years of comfort. Your home will no longer be a Goldilocks home - instead it will be Just Right!
The residential duct system is designed to match the heating and cooling equipment blower capacity. The Manual D duct layout provides the contractor with a "duct blueprint".
How to accurately design HVAC duct based on ACCA Manual D
Properly sized grilles and registers are essential to proper room comfort. You can have a properly sized HVAC system, proper equipment selection and a properly sized duct system but improperly sized grilles and registers could ruin all that hard work.
How to accurately size HVAC registers and grilles with ACCA Manual T:
Avoid having Goldilocks ductwork. Confirm your HVAC duct designer uses ACCA approved residential Manual D duct sizing software and theory to size your duct work. You are investing a lot of hard earned $$$ - with proper heat loss/heat gain results (Manual J), you can select a properly sized system (Manual S), and proper duct sizing (Manual D). Then your Comfort System will be Just Right