Aluminium Weather Louvre Guide

What is an Aluminium Weather Louvre?

Aluminium weather louvres are framed openings fitted with fixed horizontal slats which allow air and light to enter, while protecting against rain. This provides necessary airflow, both intake and exhaust, to HVAC units.

How Do Aluminium Weather Louvres Work?

Aluminium louvres are designed for two opposing functions: allowing air in and out, while preventing water from entering.

To do this, the aluminium blades are angled so that rain runs off, while the openings allow airflow. 

Where are Aluminium Weather Louvres Used?

You will most commonly find aluminium weather louvres in commercial buildings and industrial warehouses as good airflow is often essential in order to provide clean air for people and machinery.

In these areas, it’s also just as important to prevent rain from entering, so electrical equipment doesn’t become wet and damaged and so that flrs don’t become slippery and unsafe.

Louvre systems offer airflow to building systems without letting in any rain, making them ideal for businesses in the UK where rain can be expected all year round.

Aluminium Weather Louvre Fitting Guide

The way in which you fit your weather louvre depends on whether there are pre-drilled fixing holes or not.

Standard Fixing

Most weather louvres are supplied with no fixings. In this instance we recommend drilling through either the louvre flange or the neck, and screwing directly into the supporting structure with an appropriate fixing.

Pre-Drilled Face Fixing Holes

​​5mm fixing holes (not countersunk) will be drilled into the louvre frame before powder coating, allowing quick and easy fitting on site. Number and layout of fixing holes will be appropriate to louvre size.

Are There Different Types of Louvres?

There are three main types of louvre commonly fitted in industrial and commercial buildings:

Performance (Weather) Louvre

The primary objective of performance, or weather, louvres is to allow airflow. These types of louvres are preferred in areas where water entering the premises would cause significant problems, such as rooms with electrical equipment.

Standard Louvre

Standard louvres provide maximum airflow with some degree of rain protection. 

Screening Louvre

Screening louvres are commonly used on top of buildings in order to conceal HVAC and make them look less unsightly.

What is the Louvre Free Area?

Every louvre has a calculated ‘free area’. This is the total open area between blades, divided by the area covered.

A high percentage of open area that meets airflow and water resistance requirements is usually the most effective solution thanks to the low costs.

However, specifying the type of louvre you want on free area alone can cause problems for both architects and owners.

This is because the percentage of free area of a louvre can be affected by size and other factors such as louvre frames, structural supports, bird screens and insect screens can all have a negative impact on airflow.

How to Specify the Louvre You Need

In order to correctly specify the right kind of aluminium louvre you need, you first need to consider the compromise between airflow and water ingress.

For example, car park projects may require maximum ventilation, so a standard or screening louvre would be suitable. 

However, a factory containing special machinery and electrical equipment may require high levels or ventilation, making a performance (weather) louvre the most appropriate option.

Therefore, it is important to consider the following factors when specifying louvres:

  • Airflow
  • Severity of weather conditions
  • Site location
  • Building use
  • Water penetration
  • Maximum pressure drop
  • Building aesthetics


When it comes to selecting weather louvres, one of the key aspects is the air velocity at the louvre face.

You can calculate this with the following formula:

Face Velocity (m/s) = Volume Flow Rate (m³/s) / Face Area (m²)

E.g. If the volume flow rate is 4m³/s and the face area is 2m², the face velocity will be 2m².

Aluminium Weather Louvres at eFans

At eFans, we have over 40 years experience in HVAC, Building and Facilities services, working with expert site engineers to deliver the solution you need. 

We can also offer highly competitive and flexible prices to help suit your budget, so don’t hesitate to get in touch with your aluminium weather louvre requirements today.