Renson marked the golden anniversary of their very first ventilation louvre launched 50 years ago by introducing an upgraded model.

While Renson has made its mark in many fields as an international trendsetter in ventilation, sun protection, and outdoor living, it still excels in what this Belgian family business first launched 50 years ago: ventilation louvres.

411 – the revolutionary louvre

Renson revolutionised the field of natural ventilation in the 1970s with this louvre made up of L.033.01 blades. They were the first ventilation louvres in which the blades were clipped in rather than welded or affixed with rivets. At that time, it was a revolutionary step forward in the field of louvre production.

The upgraded 411

It’s the L.033 blades (also used in the 414 and 431 louvres and bladed walls) that have been upgraded. These louvres can now boast a free airflow of 50% rather than 45% and an air permeability upgrade from class 4 to class 3. This has no impact on the method of installation and the other components of these louvres, but it does create a ventilation louvre that can meet the requirements of today even better.

Old and new

Old ‘411′ louvre - New ‘411′ louvre. Thanks to an upgrade to the L.033 blades, Renson’s new 411 louvre can now boast a free airflow of 50% rather than 45% and an air permeability upgrade from class 4 to class 3

Renson and ventilation louvres: a successful marriage of 50 years

Renson’s continued status as an international trendsetter in the field of ventilation louvres is due first and foremost to the enormously wide scope of applications for this product range. Our range includes not only wall louvres, but also surface-mounted, window, door, and floor louvres. And they’re all available in every possible size, shape, and colour.

As most ventilation louvres also remain visible in the shell of a building, Renson pays a great deal of attention to their aesthetic aspect: impeccable coatings, no visibility when looking perpendicular to the louvre, no water damage due to good drainage, and a completely rust-free and durable finishing in aluminium contribute to its success.

Renson ventilation louvres also stand out on a technical level. To this day, the combination of air permeability and water resistance is continually being optimised for the entire range. Renson’s extensive range of louvres can meet a wealth of technical requirements: from acoustic attenuation, burglary prevention, water resistance, and fall-through safety to fire resistance, thermal sealing, and specific filter properties. This comes from the continued investment in research and development and the objective testing programmes carried out by independent institutes on each of these ventilation louvres.

50 years of ventilation louvres: the evolution

In the 1970s, Renson launched the very first 411 louvre with aluminium clips blade (L.033.01) for in-wall mounting. It was a first because the blades had always been mounted in the louvre frame with rivets or welding up to that point. The 411 was followed by the 414 and 431 louvres built with the same type of blade, but with a different frame for window and surface mounting, respectively.

411 louvres

For Renson, the 1980s represented various innovative developments in the field of louvres. Lockable louvres made their appearance, along with louvres with movable blades (427), and tablet and floor louvres. With the 425 louvre, there was now also a version with a larger ‘blade pitch’ (of 95mm) in the pattern of the clipped-in blades, and the ‘421′ was a heavier version with larger blades. When data centres and electrical boxes first appeared on the radar, Renson specifically began developing stick-proof/water-resistant louvres (412).

From the 1990s onwards, Renson dedicated itself to the so-called construction cabinet system in the field of louvres, in which local partners follow a thorough training for the independent assembly of a number of popular louvres from the Renson range. It was a wise move by Renson, as it enabled a significantly faster response to market demand. The service was well received by many customers all over the world. At the same time, Renson’s international growth as a company enabled it to specialise and respond better to specific market demands in the field of R&D and pre-sales. Since then, Renson has been contributing actively and with solution-focused collaborations with customers to offer the appropriate louvre for each application. This customer-focused thinking resulted in louvres that were originally developed for specific projects that eventual become ripe for introduction in the standard range. The exemplary projects listed below are proof of this development.

Now, the first series of louvres (411, 414, 431) that started it all 50 years ago will be equipped with newly developed L.033.01 blades. This new step forward in the field of air permeability ensures that Renson is still a pioneer in the field of ventilation louvres. Their extensive experience and close connection with market trends, together with the vast internal know-how and R&D capacity, mean that Renson is now able to meet the most specific wishes in the production of ventilation louvres, both technically and in terms of design.

The possibilities with Renson ventilation louvres

These 5 pilot projects illustrate the endless applications with the Renson 411, 414, 431, or Linius 0.33 louvres:

High Flow: the ultimate in air permeability


Hamburg (DE), Airbus Production Hall, 2000

Type of ventilation louvre: L050 – 2000 ‘high flow’

This project required 60% air permeability, requiring the inclusion of the 481/484 louvres in the product range. Building on this, Renson looked at how far it could go with air permeability, and the 480 and 483 louvres were created for applications where a louvre is installed in a building component while still requiring high airflows.

At the foundation of ‘night cooling’

Renson Head Office

Waregem (BE), Renson Head Office, 2002

Type of ventilation louvre: 431

Renson’s own head office along the E17 was the ideal test environment for integrating large louvres into the windows. The shutters behind are open at night to help cool the indoor air on hot days.

Ventilation and acoustics going hand in hand

Elbe Einkaufzentrum

Hamburg (DE), Elbe Einkaufzentrum, 2009

Type of ventilation louvre: 446/225 with acoustic blade L.150ACL

This car park in the centre of Hamburg had to be sufficiently ventilated due to the heat emitted by the engines of the cars. At the same time, a minimum level of noise was permitted to escape, especially the low frequencies of roaring engines. In our own Renson laboratory, we tested how the shape of the blades and acoustic material could meet these requirements. This process brought forth the range of acoustic louvres.

Burglary resistance: from RC2 to RC3

EWT Wind Farm

Anna Paulowna (NL), EWT Wind Farm, 2019

Type of ventilation louvre: 421RC3

Renson has been producing burglar resistance class RC2 louvres since 2010. For this specific project, among others, the louvre was upgraded to class RC3.

Fall-proof louvres

Verona Pro Offices

Tielt (BE), Verona Pro Offices, 2019

Type of ventilation louvre: 431RC2

Fall prevention became a theme at Renson in 2018. This is an absolute necessity for dormitories, childcare centres, offices, and schools with window louvres on storeys above the ground floor.

Unlimited colours and materials

Renson ventilation louvres – straight or curved – are available in an extensive range of shapes, materials and colours.