Construction Specialties - CS lists out a few important tips to help correctly specify architectural louvres.

Building and architectural louvres are installed to move air. But how can one be sure if the specified louvre will actually deliver the desired air volume? Sizing and specifying louvres on free area alone can cause problems for both architects and owners. For instance, what does the homeowner get when a 50% free area architectural louvre is specified?

Free area is affected by the size of the louvre. The industry typically quotes free area using a 1.2m x 1.2m square louvre but in reality, louvres are never precisely this size.

Additionally, other factors also impact airflow. For example, louvre frames add resistance to airflow while mullions, structural supports, bird screens and insect screens will also reduce airflow.

A more efficient specification for architectural louvres is based on the needs of the building.

Construction Specialties – CS recommends that the following factors be considered when specifying louvres: site location and exposure; severity of local (site) weather conditions; location and exposure of louvres on the building; airflow rate and direction through louvre; maximum acceptable pressure drop; acceptable degree and depth of water penetration; and aesthetic of the building.