Louvers FAQ

Start with the required airflow volume (CFM) from your HVAC engineer. Divide by the desired face velocity (typically 400-800 FPM for intake louvers). The result is the minimum net free area. Then divide by the louver free area percentage to get the gross face area needed. Always verify that the resulting pressure drop at design velocity falls within the air-handling unit capacity.

Drainable louvers have blade profiles designed to channel water that enters the louver to internal gutters, where it drains to the exterior. They provide superior wind-driven rain resistance and are recommended for any application where weather protection is important. Non-drainable louvers have simpler blade profiles that rely on blade angle alone to shed water; they offer higher free area and lower pressure drop but less rain protection.

High Velocity Hurricane Zone approval is required for any building product installed in Miami-Dade County or Broward County, Florida. These areas are designated as H.V.H.Z. under Chapter 44 of the Florida Building Code. Products must be tested to TAS 201 (impact), TAS 202 (cyclic pressure), and TAS 203 (static pressure) and carry a valid Product Evaluation Report or Notice of Acceptance.

AMCA Standard 550 classifies louvers based on water penetration at specific velocities. Class A louvers allow no water penetration at the beginning of water penetration velocity (typically tested at 29 mph). Class B louvers allow a controlled amount of penetration. For critical applications like data centers or electrical rooms, always specify Class A.

Steeper blade angles (closer to vertical) increase free area and reduce pressure drop, allowing more airflow. However, they provide less rain protection and reduced line-of-sight screening. Shallower angles (closer to horizontal) improve rain rejection and visual screening but restrict airflow. Most architectural louvers use 35-45 degree blade angles as an optimal compromise.

Yes, most louver profiles work for both intake and exhaust applications. However, intake louvers benefit more from drainable blade designs since wind-driven rain is a greater concern when negative pressure draws moisture inward. Exhaust louvers operating under positive building pressure naturally resist rain ingress, so non-drainable profiles are often acceptable.

Key factors include blade spacing (closer blades = more resistance), blade angle (shallower = more resistance), blade depth, frame depth, the presence of bird screens or insect screens behind the louver, and air velocity through the free area. Pressure drop increases with the square of velocity, so doubling airflow quadruples the pressure drop.