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'Air Flow ™' Engineering Spreadsheet Module

Is this MODULE for you?

  • Do you design HVAC systems for new construction or retrofit projects and want to save time and improve the quality of your work?
  • Do you want an easy-to-use software to quickly size ductwork in an organized and presentable fashion, without ever touching the 'ductulator' again?
  • Do you have trouble remembering how to calculate vertical and horizontal throws and other characteristics of diffusers and wish you had a tool to calculate all that for you and tell you how many diffusers of each specific type will be required for each space?
  • How about a tool that will also give you easy-to read schedule-type outputs for all of the above that you can simply e-mail to suppliers or architects of review?

If you answered 'yes' to any of the above, the 'AirFlow' Module is your solution!


'Air Flow' MS Excel Spreadsheet Module will assist you in the design of air distribution system. The Module determines the size and number of room air diffusion outlets and the size of the ductwork delivering the conditioned air from air-handling unit to the air diffusers.

Sizing Air Diffusers

In everyday design of the air diffuser layout, the engineer faces a dilemma: to accomplish proper time-consuming selection based on the air jet trajectory (throw, horizontal projection) calculated using special air dynamic equations and the noise criterion as recommended by ASHRAE handbooks or to do a quick selection based on the noise criterion only. If he or she follows the first path, the project development cost will overspill the budget. If the second path is followed, the occupants in the spaces may feel cold air draft or stale zones because of improper design. The module solves the dilemma- it will assist you to follow the first path without excessive time waste.


  • Select the outlet types and the supply airflow rates simulated by the 'DESIGN MODULE' and read the calculated air jet characteristics.
  • Use the outlet manufacturer catalog with jet characteristics.
Click on the thumbnail to see a sample Space Air Diffusion Calculations Space Air Diffusion

Traditional Ductwork Calculations

Unfortunately, the engineer often simplifies the ductwork design to minimize the design effort and thus compromising the design quality. She uses a standard duct sizing chart to select the duct sizes based on recommended air velocity or and friction loss range and the required airflow rates simulated by a software tool, for example, the Module 'DESIGN LOADS'. She manually enters the sizes into an Excel spreadsheet or drawing and calculates the pressure loss through the sized ductwork using the average friction loss rate and a severe factor accounting for the dampers, transitions and other fitting impact. In the course of the design, the airflow rate is often repeatedly changed, so she needs to repeat the above procedure again. What a time wasting and error prone process!

A different issue arises from the manual primitive approach. If the ductwork consists of multiple branch, after the ductwork is constructed, the summarized airflow rates will deviate significantly from the expected values. The use of the balancing dampers to adjust the air flows in many cases causes prohibitive noise created by the air hissing through an almost closed damper.

'Air Flow' Automated Ductwork Calculations

The 'Air Flow' Module automates and streamlines the process of sizing duct systems for you. It  offers tremendous time savings and dramatically improves the accuracy of the results.

The Module is coded based on the standard Bernoulli equation and the empirical duct material datasets provided by the ASHRAE Handbook 'Fundamentals', 2005.


  • Input duct section sizes and airflow rates (for example simulated by the module 'DESIGN LOADS'). 'Air Flow' Module automatically calculates the dynamic, friction, and fitting pressure losses and the air velocity of the duct sections.
  • Automated sizing process allows for quick rebalancing of the pressure losses in the parallel branches of the ductwork by changing the duct section sizes.
Click on the thumbnail to see a sample Duct Sizing calculations Duct Sizing

Engineers may be interested to follow air pressure balancing procedures as outlined in the guide 'A to Z HVAC Design for Engineers'.

The module accuracy has been validated by comparison with the duct sizing chart in the ASHRAE Handbook “Fundementals”, 2005.

The module is available in both Inch-Pound and Metric (SI) units.


Air Flow

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