The Purpose of Louvres for Ventilation

Where solid steel doors are completely sealed, louvre doorsets are engineered specifically to provide ventilation without compromising on security. They can be found in buildings such as toilet blocks, bin stores, kitchens, and utility buildings.

Ventilation is critical in mechanical plant areas to:

•  Remove excess heat generated by machinery
• Reduce the risk of overheating and associated failure
• Dilute or remove gases such as carbon monoxide
• Manage humidity and reduce condensation or mould risk

Louvred doorsets can also work in conjunction with mechanical ventilation systems, helping to provide controlled airflow paths where required.

The Type of Louvres Available

At Metador, we provide an extensive range of louvres suited to many different doorsets, as well as standalone panels, ranging from standard aluminium to high-security steel and even fire-rated configurations.

Our range of in-door louvres include:

• Standard Aluminium Louvre

Available predominantly with our Safeguard steel personnel doorsets for environments where ventilation is needed and security demands are lower.

• High security Louvre

Used where increased strength is required compared to aluminium, particularly in high-traffic or more demanding environments.

• Extra High Security Louvre

These reinforced steel louvres are fitted with additional steel mesh to the rear. They are tested to both LPS 1175 B3 (SR2) and PAS 24 security ratings to achieve Secured By Design accreditation.

• Extra High Security Fire Rated Louvre

These louvres hold the same construction as our extra high security louvres and are suitable for our External Fire Rated or External Fire and Security Rated doorsets.

• Standard Fire Rated Louvres

These fire rated louvres are available for use on our Fireshield internal fire rated doorsets.

• Xtreme 3 LPS Rated Louvres

These louvres are suitable for use with our Xtreme 3 LPS 1175 C5 security rated doorsets.

Louvred Side & Overpanels

Our louvred side panels and over panels consist of a heavy-duty rebated outer frame fitted with multiple adjustable fixing points. They’re fitted first into the opening and adjusted for level and plumb. The louvre cassette is then fitted into the frame and secured from the inside.  Available cassette options are as follows:

• Standard Aluminium – 45mm or 65mm louvre cassette depths, 50mm blade pitch
• High Security Steel – 60mm cassette, 50mm blade pitch (+/- 5mm)
• Extra High Security Steel Louvre – 60mm cassette, 50mm blade pitch (+/- 5mm). (Available for LPS 1175 B3 (SR2) and PAS 24 Security Ratings with SBD accreditation)
• Extra High Security Fire Rated Louvres  – 60mm cassette, 50mm blade pitch (+/- 5mm)

Metador’s louvre doors are built from heavy-gauge galvanised or stainless steel to withstand harsh, continuous use and provide a long service life with minimal maintenance.

Understanding Louvre Performance

When specifying a louvre, it’s important to look beyond appearance or size. Performance is driven by how effectively the louvre allows air to pass through — while balancing any additional requirements such as security, weather resistance or fire performance.

There are three key concepts to understand:

1. Visible Free Area

The visible free area is the portion of the louvre that appears open when viewed from the front.

• It represents the open area you can physically see
• It does not account for blade profile or airflow path through the louvre
• As a result, it can significantly overstate actual performance

In simple terms: it’s a visual reference, not a measure of airflow

2. Actual (Effective) Free Area

The actual free area is a more meaningful indicator of performance.

It represents the smallest effective opening through which air must pass, measured perpendicular to the direction of airflow.

Because airflow through louvres is typically deflected by the blades, this measurement is often taken at an angle (commonly around 45°), reflecting the real airflow path rather than a straight-through opening.

This means:

• The effective opening is usually smaller than it first appears
• Blade geometry and spacing have a significant impact
• Additional elements such as mesh, security bars or filters further reduce the free area

 This gives a more realistic representation of airflow potential, but still needs to be considered within the wider system.

3. Airflow (Volume and Pressure)

True louvre performance is defined by the actual volume of air passing through under real operating conditions.

This is influenced by multiple factors, including:

• Effective free area
• Blade geometry and angle
• Pressure differential across the opening
• External conditions (e.g. wind exposure)
• Additional components such as mesh, dampers or filters
• Positioning and installation within the building

Airflow is typically expressed as a volume flow rate (e.g. L/s or m³/s) at a given pressure.

Important: Responsibility for Airflow Design

While louvre selection can influence airflow performance, the required airflow rate and system design must be determined by the project’s mechanical or building services engineer.

Metador can support with product selection based on known performance characteristics, but final airflow requirements and system calculations should be established as part of the overall ventilation design.

What This Means for Specification

When selecting a louvre:

• Don’t rely on visual appearance or nominal opening size alone
• Use actual free area as a more meaningful indicator
• Allow for reductions caused by mesh, security, or fire-rated configurations
• Ensure the louvre is selected as part of the overall ventilation strategy, not in isolation.

Louvre Sizing and Style

Louvres are available in a wide range of sizes and configurations, allowing them to be tailored to each application.

• Larger louvre areas generally allow increased airflow
• Smaller or partial louvres may be more appropriate where ventilation demands are lower
• Doorsets can incorporate single, double, or full-height louvres
• Side and overpanels can be used to increase ventilation area without altering the primary door opening.

Bespoke sizing is available on selected configurations, depending on application and design requirements.

Meeting Your Requirements

Our louvre doorsets can be delivered across a wide range of our products, and, importantly, our louvre panels are available with anti-vermin, insect, and bird mesh, addressing any concerns about unwanted entry by small animals and wildlife.

Accreditations

As with all of our doors and ironmongery, our range of louvre doorsets is manufactured in line with established internal quality procedures and is supported by certification to recognised quality management standards such as ISO 9001.  

Where security performance is required, doorsets can be specified to align with recognised standards such as:

• LPS 1175
• PAS 24
• Secured by Design (SBD) frameworks

Certification and performance claims should always be considered in relation to the complete doorset configuration and supporting evidence.

Speak to Our Experts

If you’d like to find out more about our louvre door options and independent wall panels, please speak with our experienced and knowledgeable team, who will be happy to help with specifications and requirements.

📞 Call: 01642 337119

✉️ Email: sales@metador.com