Compare and contrast

Which is the right louver for your project?

FL-D series or D-HFA series?

United Enertech’s FL-D and D-HFA series fixed louvers offer high-performance and protection from water intrusion for openings in the exterior walls of buildings. And while both have some similar benefits, choosing the correct sized louver for your application can ensure you have the right protection and the right-priced product.

Here are some key points when selecting and sizing fixed louvers and a comparison of our D-HFA and FL-D series louvers to help with your next project!

Selecting and Sizing Fixed Louvers

Three Things to Consider

  • Square Feet of Free Area
  • Free Area Velocity at beginning point of water penetration - Measured in Feet Per Minute (FPM)
  • Pressure Drop (loss) - Measured in Inches of Water Gauge (inches W.G.)

The Magic Formula

Air Volume (CFM) / Free Area (SQ. FT.) = Free Area Velocity (FPM)

D-HFA Series



  • More economical price point
  • More free area with 60% Free Area


  • D-HFA-4 (4” Deep Alum.) VIEW
  • D-HFA-6 (6” Deep Alum.) VIEW

FL-D Series



  • Better performance for water penetration

Drainable Models

  • FL-D-2 (2” Deep Alum.) VIEW
  • FL-D-4 (4” Deep Alum. ) VIEW
  • FL-D-6.1 (6” Deep Alum.) VIEW

Want to learn more about United Enertech's louvers?

Watch our recorded webinar: All About Louvers Part 1

Learn about Standard 500-L and a range of United Enertech Louvers including fixed, adjustable and combination, and wind driven rain louvers. This webinar also discusses louver finishes, special louver details, and installation recommendations.

Louvers Webinar

Visit the Resources section of our website to view this webinar recording and others.

UE AHR Expo 2023 Banner

We're looking forward to AHR Expo 2023 taking place in Atlanta in February. Check out our page on the AHR Expo Exhibitor site to view videos, product photos, and more.

January 24, 2023