With the exception of projects where louvres are specified purely to provide vision screening, their effectiveness in letting the air in and out of a building will always be a critical performance consideration.

Traditionally, louvres were specified and sized based on the Free Area alone. The industry commonly uses a nominal 1m2 louvre size when quoting Free Area. In reality, louvres are never precisely this size.

What’s more, when Free Area calculation includes the louvre’s frame, the value will be affected by the overall louvre size.

Finally, Free Area itself does not take into account how the air flows through the louvre.

All louvres restrict the passage of air, creating a pressure differential between the air pressure at the front and back of the louvre, known as Pressure Drop.

The pressure drop of a louvre will increase with increasing air intake velocities. Too high a pressure drop, and not enough air will be allowed through, causing any HVAC or generator equipment located behind to work harder and overheat.

Therefore, Aerodynamic Free Area, expressing true ventilation performance of a louvre, should be used instead of Free Area.

Many projects require protection from wind-driven rain ingress. Prevailing weather conditions in a building’s location and position of louvres on the building should be taken into account in assessing the risk of water entering the building and potential damage it could cause.

One way of mitigating that risk is to allow for a ducted plenum chamber and suitable drainage to keep sensitive equipment safe. In those situations, standard ventilation louvres would often be selected for their excellent airflow characteristics.

A more space saving approach is to specify weather louvres, which are designed to deliver both efficient airflow and rain defence.
The products should be independently tested to EN 13030 to substantiate their performance claims.

Where noise emission to the outside environment is a concern, acoustic louvres should be considered.

Acoustic louvres may be required to reduce factory or plant room noise, particularly in areas close to pedestrian walkways or other buildings.

They can be installed as standalone screens, or integrated into the façade. Where required, they can be fitted behind rain defence or ventilation models.

Their depth (typically between 150mm and 600mm, depending on acoustic performance) and weight should be considered early to ensure sufficient support structure is provided.

Some projects, such as government or military buildings, data centres or power plants, may require particularly robust solutions to meet increased security demands.

Often fitted in building openings, louvres can be seen as a weaker point of the façade, alongside doors, windows or shutters.

European standards EN 1627 to EN 1630 prescribe test methods for determining burglary resistance of those products under static loading, dynamic loading and in manual forced entry attempts.

Tested products are certified with one of six RC classes.

• RSH-5700 Rain Defence Louvres
• RSV-5700 Rain Defence Louvres

For buildings vulnerable to explosive threats, a range of our louvres can be configured to resist blast.

These models are designed to withstand up to a 12.6 psi blast pressure, at an impulse of 77.8 psi-msec. They will remain in their frame and anchored adequately, preventing them from becoming a projectile.

• RSH-5700 Rain Defence Louvres
• RSV-5700 Rain Defence Louvres
• RS-5605 Rain Defence Louvres
• RS-5900 Rain Defence Louvres
• A-4085 Ventilation Louvres

All louvres can be supplied with additional accessories and fittings.

Bird / vermin guards or insect meshes can be fitted to the back of the louvres if required.

It is important to remember that inclusion of guards will likely have an impact on the airflow performance of the louvre and relevant test data should be examined.

In non-active parts of the façade louvres are typically blocked off with single skin blanking plates, or insulated blanking panels.

Motorised or manually operated dampers can also be used behind louvres, typically where natural ventilation is utilised.

Finally, where access to the building through the louvred area is required, louvred doors featuring the same blade type and pitch as surrounding wall units can be supplied for a uniform look.