Louvers

An aluminium louvre, spelled louver on American drawings, is a bank of angled blades doing three jobs at once: letting air through, keeping rain out, and cutting sun and sightlines. The blades are extruded profiles, fixed or operable, carried in a frame that builds into facades, screens, doors, and plant room walls. We extrude louvre blade and frame profiles at our facility in Indonesia, for the decorative end of the market and the engineered end alike, and the first thing this page will do is explain why those are two different products.

What a Louvre Is

The working part is the blade: an extruded section set at an angle, typically between 37 and 45 degrees, repeated at a regular pitch up the frame. Air passes between the blades. Rain, arriving at a steeper angle, strikes the blade faces and runs off. Sun, arriving from above, is shadowed out. The geometry does all the work, which is why blade shape, angle, and pitch are the entire specification, and why the same idea scales from a door vent to a forty-metre facade screen.

Louvre or Louver? One Letter, Two Markets

The split is purely spelling, and it is one of the cleanest in the trade. The UK, Australia, Canada, India, and most of Europe write louvre. The United States writes louver. Same blades, same frames, same physics. We quote against both spellings, in aluminium or aluminum to match, and our drawings carry whichever convention your project documents use.

Architectural or Ventilation Louvre? Decide This First

Here is the confusion that costs buyers money in both directions. Architectural louvres are looks-led: facade screens, sun shading, privacy banks, and equipment screening where airflow is incidental. The blade profile is chosen for shadow and rhythm, not performance data. Ventilation louvres, sometimes called performance or mechanical louvres, are engineered products: they exist to pass a known volume of air into a plant room, generator room, or air handling space while defending it from driven rain.

Specifying a performance-grade louvre on a privacy screen wastes money. Putting a decorative screen on a generator room starves the engine behind it. Tell us which job the louvre has, and the blade recommendation follows.

Free Area: The Number That Matters

For ventilation duty, one figure rules the specification: free area, the percentage of the louvre's face that is actually open once the blades and frame are subtracted. A typical 50 mm pitch blade bank delivers roughly 50 percent free area, with real products ranging from around 35 to 60 percent depending on blade profile and depth.

The practical consequence: a louvre is not a hole. A generator that needs one square metre of open intake needs about two square metres of 50 percent free area louvre to breathe properly. Order the louvre by face size without checking free area and the equipment behind it runs hot and throttles. It is the single most common louvre specification error we see, and the cheapest one to avoid: it costs one question at enquiry stage.

Drainable or Non-Drainable, Fixed or Operable

Two more decisions complete the specification. A drainable blade carries a gutter along its leading edge that catches water and channels it sideways to drain down the frame's jambs, rather than letting it cascade from blade to blade. At the same depth, drainable blades defend against driven rain markedly better, which is why they are the default for exposed elevations and conditioned spaces. Non-drainable blades are simpler and cheaper, and entirely adequate under canopies, on sheltered faces, and where what sits behind the louvre can tolerate occasional moisture.

Fixed blades suit most duties. Operable blades, pivoting on the frame, belong where airflow must close: smoke control, seasonal ventilation, and spaces that are conditioned part of the year.

Sun Control: One Rule Worth Knowing

Blade orientation should follow the sun's path, not the building's styling. Horizontal blades shadow high-angle sun, which makes them effective on elevations that face the midday path. Low morning and evening sun slips under horizontal blades, which is why east and west elevations are better served by vertical fins. In the tropics, where midday sun is nearly overhead, shallow horizontal blades achieve shading that would need much deeper profiles at higher latitudes. We extrude both orientations from the same die logic.

Where Louvres Get Used

• Building facades, as continuous screens and feature bands.
• Plant, generator, and pump rooms, the core ventilation duty.
• Sun control, on glazed elevations where cooling load is won or lost.
• Privacy and equipment screening, hiding rooftop plant and service yards.
• Acoustic banks, where lined blades trade some free area for noise reduction.

Custom Louvre Profiles from Indonesia

Standard blade and frame sections ship cut-to-size against your elevation schedule. Beyond that, the die library covers alternative blade depths and pitches, and a custom die can produce a proprietary blade profile, including aerofoil sections and integrated gutter details, against your drawing. Send the elevation, the duty (decorative or ventilation), and the free area or shading target, and our team will reply with a blade recommendation, price, and lead time from our factory and warehouse in Indonesia.

Louvres rarely travel alone on a facade. The panel that closes the zone between window bands lives on our Spandrel page.