Façade louvres are the building’s breathing apertures — arrays of angled blades that let air pass through the envelope while keeping wind-driven rain, debris and prying eyes out. Where an opening window is sometimes open and sometimes sealed, a louvre is a permanent ventilation opening: feeding fresh air to plant and ventilation systems, exhausting stale air and smoke, cooling car parks and switch rooms, and screening rooftop equipment behind a tidy architectural surface.
This entry covers how a louvre balances free area against rain defence, the weather, double-bank, acoustic, operable and screening louvre types, the special role of acoustic louvres in letting plant breathe quietly, and the sizing, integration and standards that make a louvre perform.
Louvre essentials
- A permanent ventilation opening — air passes through while rain is kept out.
- Free area (airflow) and rain defence pull in opposite directions — every louvre tunes the compromise.
- Double-bank louvres for high rain defence; acoustic louvres to let noisy plant breathe quietly.
- Sized from tested aerodynamic data (EN 13030) for airflow at acceptable pressure drop.
- Functional + matching blank screening louvres give a uniform elevation over plant.
- Integrated with dampers, mesh, drained plenums and the façade’s fire and weather lines.
01What are façade louvres?
Façade louvres are arrays of angled blades set into the building envelope to let air pass while keeping rain, debris, birds and direct sight out. Unlike an opening window (which is sometimes open, sometimes sealed), a louvre is a permanent ventilation opening — a part of the façade whose job is to admit or exhaust air continuously, or to screen equipment behind a coordinated architectural surface. They are the façade’s breathing apertures.
Figure 1. A weather louvre’s blade profile and pitch are designed so air flows freely between the blades while wind-driven rain strikes the blade faces and drains away — the core of louvre performance.
Why a building needs louvres
Buildings must move large volumes of air through their skin: fresh-air intakes and exhausts for mechanical ventilation, plant-room and generator cooling and combustion air, smoke ventilation, car-park ventilation, and cooling of switch rooms and risers. They also need to hide rooftop and façade plant behind a tidy screen. A louvre does this — providing a weatherproof, secure, architecturally controlled opening — where a plain hole or a window would let in rain or look untidy. The art is to pass the required airflow while defending against wind-driven rain, within the architectural language of the façade.
02How a louvre works
A louvre’s performance is governed by the geometry of its blades — their profile, depth, angle and spacing (pitch) — which together set how freely air passes and how well rain is kept out.
Free area and airflow
The key airflow measure is free area — the proportion of the louvre face that is actually open to airflow (the gaps between blades, net of the blades and frame). A high free area passes more air for a given face size and pressure drop; the airflow capacity is characterised by the relationship between air velocity and pressure loss (the louvre’s aerodynamic coefficient), so the engineer can size the louvre area to deliver the required air volume without excessive resistance or noise.
Rain defence
The competing requirement is rain defence — the louvre’s ability to stop wind-driven rain entering. The blade profile is shaped so that air can weave between the blades but water droplets strike the blade faces and drain away down and out, rather than being carried through. Rain defence is rated as the percentage of water excluded at defined wind-driven-rain conditions (per EN 13030). Free area and rain defence pull in opposite directions — more open means more airflow but worse rain defence — so every louvre is a tuned compromise between the two.
03Louvre types
Louvres are made in a range of types matched to the balance of airflow, rain defence, acoustics, control and appearance required.
Figure 2. The louvre families: single- and double-bank weather louvres, acoustic louvres with lined blades, operable (adjustable) louvres and aesthetic screening louvres.
Weather, double-bank and acoustic
Single-bank weather louvres are the standard, balancing free area and rain defence for general ventilation. Double-bank (and storm) louvres add a second row of blades for high rain defence where water exclusion is critical (data centres, electrical plant, exposed and coastal sites), at the cost of free area. Acoustic louvres use deep, sound-absorbing lined blades to attenuate the noise of plant (generators, chillers, fans) passing through the ventilation opening — essential where noisy equipment ventilates near occupied or residential areas.
Operable, screening and specials
Operable louvres have adjustable or closable blades to control or shut off airflow (and double as smoke or comfort dampers). Screening louvres are chosen primarily for appearance — hiding plant, car parks and risers behind a uniform architectural blade pattern with generous free area but modest rain defence. Specials include sand-trap louvres (desert climates), louvres integrated with dampers, bird/insect mesh, and louvres combined with PV or finished to match adjacent cladding.
04Acoustic louvres and plant screening
One of the most demanding louvre applications is letting plant breathe while keeping its noise in — the role of the acoustic louvre.
Attenuating plant noise
Generators, chillers, cooling towers, fans and transformers need large volumes of ventilation air but generate significant noise, and that noise would escape straight through an ordinary ventilation opening. Acoustic louvres use deep blades lined with sound-absorbing material so that air passes through the convoluted path while sound energy is absorbed, attenuating the noise breaking out of (or into) the building. The depth of the louvre and the lining determine the acoustic insertion loss, traded against the free area and pressure drop — a deeper, more absorptive louvre attenuates more but resists airflow more.
Screening and integration
Beyond acoustics, louvres screen rooftop and façade plant behind an architectural surface, coordinated with the building’s cladding so the plant zone reads as part of the design rather than an afterthought. The same louvre line often combines functioning ventilation louvres (where air is actually needed) with matching blank/dummy louvres (pure screening) so the elevation is uniform.
05Performance and integration
A louvre must be engineered for airflow, rain defence, structural wind load and the protection of the opening behind it, and integrated cleanly into the façade.
Figure 3. Every louvre balances free area (how much air passes) against rain defence (how much water is kept out) — the two pull in opposite directions and the design tunes the compromise.
Sizing and protection
The louvre area is sized so the required air volume passes at an acceptable pressure drop and air velocity (too high a velocity is noisy and carries rain through), using the louvre’s tested aerodynamic data. Behind the louvre, a drained plenum or builder’s-work opening collects and drains any water that does penetrate, with insect/bird mesh and, where needed, blank-off plates and dampers. The opening must maintain the façade’s air, water and fire lines around its perimeter.
Structure, fire and durability
Louvres — usually extruded aluminium, sometimes steel or stainless — resist wind pressure and suction and are fixed to the structure or façade framing on engineered supports. Where they form part of a fire or smoke strategy, fire and smoke dampers are integrated behind them and the assembly meets the relevant fire requirements; louvre materials are classified for reaction to fire. Finishes (PVDF, anodised) match the façade, and the louvre is detailed for the building’s service life and for cleaning access.
06Design, fabrication and installation
Louvres are fabricated from extruded blades and frames, assembled into panels (often to a modular grid), and installed into openings in the façade or as continuous bands.
Design coordination
Louvre design is a coordination exercise between the architect (appearance, blade profile, finish, alignment with cladding), the mechanical engineer (free area, airflow, pressure drop, acoustic and rain-defence requirements) and the façade engineer (structure, weather perimeter, fire). The blade profile and module are chosen to satisfy the airflow and rain-defence numbers while reading correctly on the elevation — and matching screening louvres are added so functional and decorative areas look identical.
Installation
Louvre panels are installed into prepared openings on adjustable supports, with the perimeter sealed to maintain the façade’s weather and air lines, the back-of-louvre plenum drained, and any dampers, mesh and blank-offs fitted. Setting out controls the alignment of the highly visible blade lines across the façade.
07Applications
Louvres appear on virtually every substantial building, wherever air must enter or leave the envelope or plant must be screened.
They provide intake and exhaust for mechanical ventilation and air-conditioning plant; ventilation and cooling for plant rooms, generator and switch rooms, risers and basements; ventilation for car parks (often large louvred bands or screens); combustion and cooling air for boilers and generators; and smoke ventilation. They screen rooftop and façade plant on commercial, residential and mixed-use buildings; acoustic louvres serve data centres, hospitals, hotels and plant adjacent to residential areas; and high-defence double-bank louvres protect critical and coastal installations. Architecturally, louvre bands and screens are a common element of contemporary façades, often blurring into the brise-soleil and screening families.
08Standards and certification
Louvres draw on the ventilation-performance, façade, fire and structural frameworks together.
Performance and product
Louvre airflow and rain-defence performance is tested and classified to EN 13030 (weather performance: water penetration and aerodynamic characteristics under wind and rain), which gives the free area, aerodynamic coefficients and rain-defence rating used to size and compare louvres. As part of the façade, louvre assemblies meet the relevant curtain-wall/cladding framework (EN 13830, CWCT Standard) for the surrounding weather and air lines, and wind/structural loads follow the Eurocodes (EN 1999 for aluminium). Reaction-to-fire follows EN 13501-1; integrated fire and smoke dampers follow EN 1366 / EN 13501-3/-4 and EN 12101 for smoke. Acoustic louvre attenuation is tested to the relevant acoustic insertion-loss methods.
09Sustainability
Louvres are a modest but genuine contributor to a building’s efficiency and durability.
By enabling efficient ventilation and free cooling and by properly screening and ventilating plant, well-designed louvres support the building’s energy strategy; over-sized or high-resistance louvres, by contrast, waste fan energy, so correct sizing to the tested aerodynamic data has a real efficiency benefit. Aluminium and steel louvres are durable and recyclable, carry standard façade finishes, and are demountable as part of the envelope. Acoustic louvres allow plant to be ventilated without noise nuisance, supporting denser, mixed-use development. The most sustainable louvre is one correctly sized for its airflow and rain-defence duty in a durable, recyclable material — doing its ventilation job with the least resistance and the longest life.
10System suppliers
Louvres are supplied by specialist louvre and ventilation manufacturers, by curtain-wall system houses offering integrated louvre systems, and by acoustic and smoke-ventilation specialists — installed by façade contractors and coordinated with the mechanical and fire systems.
Louvre & ventilation manufacturers
- Construction Specialties (C/S)
- Renson
- Colt International
- Greenwood / Gilberts
- Maple Sunscreening / Levolux
- Ruskin (Air Management)
System houses, acoustic & damper specialists
Curtain-wall system houses (Schüco, Reynaers and others) offer louvre ranges integrated with their façade systems; acoustic-louvre and damper specialists provide attenuating and fire/smoke-rated assemblies; and the louvres are sized and coordinated with the building’s HVAC, acoustic and fire strategies. Many regional façade fabricators also produce aluminium louvre and screening systems to project-specific designs.
Need the exact term? Look it up in the façade glossary.
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