Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

HVAC Ducts - Air Velocities

Recommended air velocities in HVAC ducts.

Flow velocity in air ducts should be kept within certain limits to avoid noise and unacceptable friction loss and energy consumption. Low velocity design is very important for the energy efficiency of the air distribution system. Doubling the duct diameter reduces the friction loss by factor 32.

Low and Medium Pressure Loss Ducts

  • Maximum friction rate 0.1 - 0.2 inches W.G./100 ft
  • Velocity 1500 - 2000 ft/min (8 - 10 m/s)
HVAC Ducts - Maximum Air Velocities
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 300 < 175 2.5 490
< 1000 < 590 3 590
< 2000 < 1200 4 785
< 4000 < 2350 5 980
< 10000 < 5900 6 1180
> 10000 > 5900 7 1380

High Pressure Loss Ducts

  • Maximum friction rate less than 0.4 inches W.G./100 ft
  • Velocity 2000 - 3500 ft/min (10 - 18 m/s)

Shafts

HVAC Ducts - Maximum Air Velocities - Shafts
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5000 < 2950 12 2350
< 10000 < 5900 15 2950
< 17000 < 10000 17 3350
< 25000 < 14700 20 3940
< 40000 < 23500 22 4300
< 70000 < 41000 25 4900
< 100000 < 59000 30 5800

It is common to keep main duct velocity above 20 m/s (3940 ft/min).

Corridors

HVAC Ducts - Maximum Air Velocities - Corridors
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5000 < 2950 10 2000
< 10000 < 5900 12 2350
< 17000 < 10000 15 2950
< 25000 < 14700 17 3350
< 40000 < 23500 20 3940

User Areas

  • Offices, receptions, lounges and similar
HVAC Ducts - Maximum Air Velocities - User Areas
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5000 < 2950 10 2000
< 10000 < 5900 12 2350
< 17000 < 10000 14 2750
< 25000 < 14700 16 3150

Typical Air Velocity Guidelines

Low Velocity Duct Systems

  • typical 400 - 2000 ft/min (2 - 10 m/s)
HVAC Ducts - Maximum Air Velocities - Low Velocity Systems
ApplicationsRecommended max. Velocity
(ft/min)
Main DuctsBranch Ducts
SupplyReturnSupplyReturn
Apartments 1000 800 600 600
Banks 2000 1500 1600 1200
Hospital rooms 1500 1300 1200 1000
Apartments, Hotel rooms 1500 1300 1200 1000
Industrial 3000 1800 2200 1500
Libraries 2000 1500 1600 1200
Meeting rooms, cafeterias 2000 1500 1600 1200
Offices 2000 1500 1600 1200
Residences 1000 800 600 600
Restaurants, stores 2000 1500 1600 1200
Auditoriums, churches, cinemas, theaters 1300 1100 1000 800

Medium Velocity Duct Systems

  • typical 2000 - 2500 ft/min (10 - 12.5 m/s)

High Velocity Duct Systems

  • typical 2500 - 3000 ft/min (12.5 - 15 m/s)

Related Topics

  • Ventilation Systems

    Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

Related Documents

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2005). HVAC Ducts - Air Velocities. [online] Available at: https://www.engineeringtoolbox.com/duct-velocity-d_928.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter


















































12.6.9

.