What real-world applications are class A, B, C and D louvres suitable for?

BS EN 13030 classifies weather louvres from Class A (highest rain defence performance) to Class D (lowest). Each class is suitable for different types of projects, depending on plant sensitivity, building exposure, and the presence or absence of secondary weather protection. Selecting the right class ensures the louvre is fit for purpose, without unnecessary cost or performance compromise.

Class A Louvres — High Rain Defence / Mission-Critical Applications

Best for:

· Data centres (air intake and exhaust)

· Hospitals, laboratories & clean environments

· Telecoms & broadcasting infrastructure

· UPS rooms, switchgear, electrical plant

· Exposed elevations & rooftop plant

· Tall buildings & coastal sites

Why: Class A louvres deliver the highest resistance to wind-driven rain, making them essential where even small amounts of moisture could damage equipment or disrupt operations. They are also used where the louvre is the primary weather barrier or where high wind exposure makes rain ingress more likely.

Class B Louvres — Balanced Airflow & Weather Protection

Best for:

· General commercial plantrooms

· Light industrial ventilation

· AHU intakes/exhausts with some secondary weathering

· Moderately exposed façades

· Educational buildings, offices, mixed-use developments

Why: Class B systems offer a good balance of airflow and rain defence. They are suitable where some rain protection is required, but the consequences of minor ingress are low—especially when internal drainage or secondary screening is present.

Class C Louvres — Airflow-Focused / Low Weather Risk Areas

Best for:

· Internal plantrooms with secondary weather protection

· Back-of-house areas

· Sheltered façades or recessed louvre locations

· Plantrooms with drip trays or sumps

· General ventilation systems where airflow is the priority

Why: Class C louvres prioritise free area and lower pressure drop, making them suitable for applications where rain defence is helpful but not critical. They are often used behind overhangs, architectural features, or on elevations shielded by adjacent structures.

Class D Louvres — Screening & Basic Ventilation

Best for:

· Architectural screening (visual concealment of plant or equipment)

· Unenclosed rooftop plant zones

· Car parks & open-sided service areas

· Acoustic screening assemblies (where weather protection is provided elsewhere)

· Low-risk, non-critical ventilation

Why: Class D louvres deliver minimal rain defence but offer high free area, lower cost, and simple installation. They are ideal where weather protection is not a critical requirement, or where the louvre is not providing meaningful defence in the first place.

Summary: Selecting the Right Class

Class Rain Defence Typical Use Cases Key Benefit

A Highest Mission-critical plant, exposed sites Maximum weather protection

B High General plantrooms, moderately exposed areas Balanced performance

Class Rain Defence Typical Use Cases Key Benefit

C Moderate Sheltered locations, secondary weathering Higher free area & lower pressure drop

D Low Screening, non-critical areas Cost-effective ventilation / aesthetics

Solinear’s Approach

At Solinear, we help design teams identify the appropriate BS EN 13030 class based on environmental exposure, plant sensitivity, secondary protections, and overall façade design. Our Aquarius X-LINE family includes systems which offer Class A, B, C, and D weather performance, enabling us to provide a solution that is technically appropriate, cost-effective, and architecturally consistent.

To understand how environmental and design factors influence these classifications, see “What affects the weather performance of a louvre?”