Why and when do I need a class ‘A’ louvre?

A Class ‘A’ louvre is the highest-performing rain defence louvre classification under BS EN 13030, offering excellent resistance to wind-driven rain while still permitting airflow. You typically need a Class A louvre when preventing water ingress is critical to the safety, functionality, or longevity of the equipment or spaces located behind the façade opening.

Class A louvres are commonly required where:

· Rain ingress could damage mechanical or electrical plant, such as AHUs, switchgear, generators, or UPS systems.

· Mission-critical or continuously operating facilities—including data centres, hospitals, laboratories, or telecoms hubs— which cannot tolerate moisture intrusion.

· Enclosed plant areas which are highly exposed, such as elevated rooftops or wind-prone elevations.

· Ventilation openings lack secondary weather protection, meaning the louvre is the primary defence against rain.

· Designers need to maintain airflow efficiency while still ensuring robust weather protection.

A Class ‘A’ louvre is not always necessary, however. In many applications, lower-class rain defence louvres (Class B, C, or D) can be entirely appropriate where plant is non-critical, secondary weathering is provided, or the building’s orientation and shielding reduce exposure to wind-driven rain.

At Solinear, our Aquarius X-LINE Rain Defence louvre profiles include Class ‘A’ options engineered to deliver exceptional rain protection and airflow performance. We work closely with architects, façade engineers, and M&E consultants to determine whether a Class A louvre is genuinely required—or whether a more cost-effective solution can be used without compromising performance.

If you’re unsure whether Class A is genuinely required for your project, see “Do I REALLY need a Class ‘A’ louvre?”