Aluminium Louvre Window Water Management: Blades, Frames and Weather Boundaries

A louvre window is the only common window type that is expected to keep weather out while it is open. That single sentence explains almost every water problem associated with the product. A casement, an awning or a sliding window is tested, sold and warranted in the closed position, where a continuous perimeter seal and a single pane of glass do most of the work. A louvre is asked to perform in a partly open position, with a stack of blades angled against the rain and a permanent aperture through the frame. Water management is therefore not an accessory to louvre design. It is the design.

This article works through the water story of an aluminium louvre window in the order water experiences it: the relationship between louvres and screens, the blade and its overlaps, the frame as a drainage body rather than a picture frame, the route water takes through and out of the assembly, the behaviour of wind-driven rain at an open aperture, the limits of seals, the detailing of glazing that sits beside a louvre bank, corrosion and coating choices, cleaning, testing, and the compliance framework in Australia and New Zealand. It deliberately avoids blade sizes, prices, thermal and acoustic values and performance ratings, because those belong to a specific tested system on a specific project rather than to louvre windows as a category.

Why a Louvre Poses a Different Water Problem

An Aperture That Is Never Fully Closed

Every window has joints, and every joint is a potential water path. What separates a louvre is the number and orientation of those joints. A fixed window has four frame corners and a glazing perimeter. A louvre bank of several blades adds a horizontal junction between every pair of blades, a blade-end junction at each jamb, and a set of operating components that must move while remaining part of the weather boundary. The result is a large number of horizontal lines, and horizontal lines are where water rests.

The geometry also means that the assembly cannot rely on a single plane of defence. Water that passes the outer face of a blade is not automatically outside the building; it is inside the louvre frame, where it must be collected and returned to the exterior. Understanding that intermediate zone, and designing it as a drained space rather than a sealed one, is the foundation of good louvre performance.

The Difference Between Excluding Water and Managing It

A sealed window tries to exclude water. A louvre manages it. The distinction is practical rather than philosophical. Exclusion depends on the integrity of gaskets and sealant, both of which degrade with movement, ultraviolet exposure and time. Management assumes that some water will arrive, gives it a defined path, and gets rid of it before it reaches the wall, the lining or the floor structure.

That is why two louvre installations that look identical from the street can behave completely differently. The one that works has a continuous line of collection and discharge behind the blades. The one that fails has the same blades, the same frame and the same sealant, but water arriving behind the blades has nowhere to go except inward.

Where the Weather Boundary Actually Sits

On a well-resolved louvre, the primary weather boundary is the outer face of the blade stack and the outer face of the frame. Behind that boundary sits a secondary zone, drained and ventilated, which copes with whatever passes the first line. The wall’s weather-resistive barrier and flashing connect to that zone, not to the blades themselves.

Confusion about this boundary is the most common source of defects. When the wall membrane is terminated against the back of the frame, every drop that passes a blade edge is already inside the building envelope. When the frame’s drainage is blocked or the sill is not flashed, the same drop ends up in the wall cavity. The boundary must be drawn on the detail, and the trades must be told which side of it they are working on.

Louvre Windows Versus Screens

Two Components, Two Jobs

The word screen covers two different things in louvre specification, and mixing them up causes real design errors. The first is an insect screen: a fine mesh, usually in a removable or hinged frame, whose purpose is to keep insects out while allowing air through. The second is a fixed louvre screen or blade screen: an array of blades mounted on the facade, often as a sunshade or privacy element, which does not form part of the weathertight window at all.

An insect screen has no meaningful water-excluding function. It can intercept large droplets and it will slow airflow, but it does not create a pressure boundary, and water driven against it passes through the mesh and onto whatever sits behind. A fixed blade screen sheds a proportion of incident rain and reduces the kinetic energy of what reaches the facade, but it is a shading device, not a window, and it is not tested as one.

What Screens Contribute to Water Management

Screens still matter to water management, mainly by changing the environment around the louvre. A fixed blade screen set out from the facade reduces the volume and velocity of rain reaching the window, and it can reduce wind pressure at the wall if it is detailed to let air escape rather than trap it. A screen mounted tight to the frame with no separation can do the opposite: it becomes a trap for debris and a capillary bridge between the outside and the louvre.

Insect screens introduce a maintenance issue rather than a water issue in the strict sense. Mesh clogs with dust, pollen and salt, airflow drops, and the occupant opens the louvre further to compensate. The window then sits in a more open position than the design assumed, and water management is being asked to handle an aperture it was never detailed for. That is a design lesson as much as a cleaning one: the screen and the louvre should be specified together, with access for cleaning on both faces.

The Blade: First Line of Defence

Profile and Edge Detail

The blade is the part of the system that meets the weather first, and its performance is mostly a matter of profile rather than material. A blade intended for wet exposure usually carries a shaped leading edge, a hollow or folded body that adds stiffness, and an edge detail that mates with the blade above or below when the stack is closed. The edge detail is where most of the water resistance lives, because it is the line that water crosses to get from the outside face to the inside face.

Blade material matters for durability rather than for shedding. Aluminium blades resist corrosion and hold their shape; glass blades offer transparency and clean easily but depend entirely on their edge treatment and on the frame’s ability to protect those edges. In both cases the frame, not the blade, is the structural and drainage element, and the blade is a movable panel within it.

Overlap, Pitch and the Closed Stack

When a louvre is closed, adjacent blades overlap. The overlap is what turns a stack of separate panels into a continuous barrier, and it is also the feature that allows the assembly to drain: water running down the outer face of one blade reaches the top of the blade below and is directed outwards rather than inwards. The amount of overlap and the angle at which the blades sit when closed are properties of the specific system and should be taken from the manufacturer’s tested configuration, not adjusted on site.

In the open position the blade works differently. It becomes a series of angled deflectors, each throwing water outward and downward while admitting air across the aperture. The angle chosen by the occupant changes the balance completely, which is why the operating range and the intended “rain position” should be explained at handover rather than left to trial and error.

Operation and the Moving Joint

The operating mechanism is the least discussed and most vulnerable part of the water boundary. Blades are carried on clips, carriers or end pivots, and each of those connections is a gap that must be toleranced so the blade can move without binding. Too tight, and the mechanism strains the blade ends; too loose, and the end gaps become water paths and rattle points.

Because the mechanism is inside the frame, it is also where debris accumulates. Dust, salt, pollen and insects collect around carriers and pivots, hold moisture against the aluminium, and gradually stiffen the operation. A louvre that no longer closes fully has stopped being the product that was tested, and its water performance has changed without anyone noticing. Regular operation through the full range is therefore a water-management task, not just a convenience one.

The Frame: Structure, Collection and Discharge

A Drainage Body, Not a Border

In a fixed window the frame is largely a border that holds glass and transfers wind load to the structure. In a louvre the frame is a machine housing. It carries the blade carriers, contains the operating linkage, provides the end seals at each jamb, and forms the collection chamber at the sill. Its depth is driven by those functions, and its internal geometry is what determines whether water that passes the blades leaves the building or enters the wall.

The head, jambs and sill each have a different job. The head deflects and, where the system provides for it, collects and discharges to the ends. The jambs carry the blade-end seals and must remain straight enough for those seals to work through the full operating range. The sill collects everything that reaches the bottom of the assembly and is the only member with a genuine discharge responsibility.

The Sill as the Critical Member

Almost every louvre water complaint resolves to the sill. The sill must be able to receive water from the blade stack, hold a small volume without overflowing inward, and discharge it to the exterior through openings that remain clear. That requires an internal upstand or baffle on the room side, a floor that falls outward, and outlets that are large enough and positioned where water actually collects.

The sill also has to connect to the wall. Its exterior projection, its relationship to the flashing, and the way the wall’s weather barrier laps to it determine whether discharge water runs clear of the facade or tracks back into the cladding. A sill that drains correctly onto a wall that is not flashed is still a leak; the two details are one detail.

Fixing, Movement and the Interface

Frames are fixed through their perimeter into the opening, and every fixing is a potential water path if it penetrates a drainage chamber or a seal line. Fixings should land in the structural zones the system provides for, with the recommended isolation washers and, where specified, sealed according to the manufacturer’s detail. Random screwing through a sill or a jamb is one of the most common ways a good system is turned into a leaking one.

Aluminium also moves. Frames expand and contract with temperature, and a louvre bank on a west-facing elevation will see more movement than a shaded one. The perimeter joint must be sized to accommodate that movement without tearing the sealant or loading the frame, and the joint geometry, backing material and sealant type should be shown on the detail rather than decided by the applicator on the day.

How Water Leaves a Louvre Assembly

The Intended Path

Water arrives at the blade stack from wind-driven rain and from runoff above. Most of it is shed by the blades to the exterior. What remains reaches the blade ends and the sill chamber, where it is collected and discharged through the sill outlets, over the flashing, and clear of the facade. Air movement through the same chambers helps dry them between rain events, which is why a drained assembly is also a ventilated one.

The path only works in one direction. Internal upstands, baffles and the overlap between frame sections are there to stop water travelling inward under wind pressure, and pressure equalisation openings are there to reduce the driving force across the assembly. Removing or blocking any of those features, for appearance or for convenience, changes the pressure regime and typically moves water to a place it was not designed to go.

Weeps, Outlets and the Debris Problem

Discharge openings are small by necessity and vulnerable by nature. They block with mortar, render, paint, sealant, insect nests and general debris, and once blocked the sill behaves as a tray. Water then stands against the internal upstand until it finds a fastener, a joint or a capillary path, and the leak appears indoors at a point that seems unrelated to the blockage.

Protecting the outlets during construction is more effective than clearing them afterwards. That means keeping them taped or plugged until the facade trades have finished, checking them at the hold points before linings close, and leaving the front edge of the sill clear so that discharge does not have to travel through a bed of sealant. Outlets that can be inspected and cleaned without dismantling the window are worth specifying.

Wall Interfaces and the Flashing Connection

A louvre frame is set into an opening in a wall that has its own water management. The wall’s weather barrier must lap over the frame’s flashing at the sill and behind the frame at the jambs and head, in the correct shingle order. Where the wall is masonry, the cavity must remain open and the flashing must include ends that turn up. Where the wall is framed and clad, the drained cavity behind the cladding must connect to the same discharge path.

The interface is where responsibility usually divides between trades, and it is where most defects originate. A window installed correctly into an opening that was never flashed, or a flashing installed after the frame so that it cannot lap behind it, produces a detail that looks complete from both sides and leaks from the first storm.

Wind-Driven Rain and the Open Aperture

What Makes Rain Penetrate

Rain enters an assembly for three reasons: momentum, pressure difference and gravity. Momentum carries droplets through an opening before they can be deflected. Pressure difference, created by wind on the windward face and suction elsewhere, pushes air and water through any path that connects the two. Gravity moves water down whatever surface it finds. A louvre blade stack addresses momentum and gravity well and pressure difference less completely, because an open aperture is by definition a path between outside and inside.

That is why the performance of an open louvre is a matter of degree rather than a binary rating. Angled blades can shed a large proportion of incident rain, but in severe wind-driven conditions some water will reach the inner face of the assembly, and the design must expect it. The relevant question is not whether the louvre is waterproof when open, but where that residual water goes and how quickly the assembly dries.

Exposure, Height and Building Geometry

The same louvre behaves differently at ground level and at height. Wind speed increases with height and with exposure, and a building on a coastal headland, a hilltop or an open plain sees more driving rain than one in a sheltered suburban street. Corners, recesses, parapets and adjacent structures all change the local pressure field, and a louvre bank in a recessed balcony can be wetter than one on an exposed wall because the recess concentrates runoff and reduces drying.

Orientation matters as much as exposure. In southern Australia and New Zealand, the prevailing rain-bearing winds are frequently from the west or south-west, and in northern Australia the wet-season driving rain arrives with tropical systems from particular directions. A louvre on a sheltered elevation may perform perfectly for years while an identical one on the exposed elevation of the same building becomes a maintenance item, which is why elevation-by-elevation assessment is more useful than a single building-wide specification.

Seals, Gaskets and Their Limits

Blade Edge Gaskets

Blade edge gaskets do the fine work of the system. They close the line between adjacent blades, absorb tolerance, and provide the friction that keeps a closed stack stable. Their performance depends on compression: too little and the line leaks, too much and the blade will not close without force, which distorts the blade and opens the ends. Gasket material must tolerate ultraviolet exposure, repeated compression and the local climate, and it must be replaceable without replacing the blade.

Gaskets are consumables, not permanent components. They harden, shrink and take a set, and a louvre that has been closed in the same position for a decade will not seal as it did when new. Including gasket condition in routine maintenance is the difference between a window that lasts and one that is replaced early.

Jamb Seals and End Gaps

The ends of each blade run against the jamb, and that interface is the hardest to seal because it must seal while the blade rotates. Manufacturers use end caps, brush seals, wiping gaskets or shaped carriers depending on the system, and each has a different tolerance for debris and misalignment. The end gap is also where water that has passed the blade face is most likely to travel inward, because it is directly connected to the frame chamber.

Inspection should focus here. A blade that sits proud of its neighbours, a carrier that has worn, or a jamb seal that has been painted over will all show as dampness at the reveal rather than as an obvious defect at the blade. This is one reason louvre maintenance is diagnostic rather than cosmetic: the symptom appears some distance from the cause.

Sealant Is Not a Substitute for Drainage

Sealant has a legitimate role at the perimeter of the frame and at junctions between the window and other materials. It has no legitimate role in closing drainage openings, bridging a gap that should be flashed, or replacing a gasket that has failed. A continuous bead across the front of a sill, a common response to a leak, traps water in the assembly and accelerates the corrosion it was meant to prevent.

Sealant also has a service life. Movement, ultraviolet radiation, dust and moisture all degrade the bond, and a joint that was intact at handover may not be intact after several summers. Joints should be designed so that their failure does not compromise the water boundary, and they should be inspected on a schedule rather than discovered during a storm.

Glazing Adjacent to Louvres

Fixed Glazing Beside an Operable Bank

Louvre banks are frequently combined with fixed glazing in the same opening: a louvre for ventilation above or beside a fixed pane for view. The junction between the two is a hybrid condition, because the fixed pane is a sealed assembly and the louvre is a drained one. Water that is managed behind the louvre must not be allowed to reach the glazing rebate of the fixed panel, and the fixed panel’s drainage, if it has any, must not discharge into the louvre frame.

The mullion between them is the detail that decides this. It should be continuous, should preserve the pressure boundary, and should carry the louvre’s collection zone past the fixed glazing without interruption. Where the two products come from different systems, the interface needs a purpose-designed adaptor rather than a site-made junction of sealant and angle.

Insulating Glass Units and Edge Protection

Where the adjacent glazing is an insulating glass unit, the edge seal is the vulnerable part. Units are manufactured and tested to AS 4666, which sets requirements for the unit itself, but that performance assumes the edge seal is protected from standing water and from prolonged contact with moisture. A rebate that holds water against the unit’s edge will eventually produce haze, delamination or seal failure, and the failure will be attributed to the glass rather than to the detail that kept it wet.

Drainage and ventilation in the glazing rebate therefore matter as much next to a louvre as anywhere else. Setting blocks should be positioned so they do not dam the rebate, weep paths should remain open, and the frame’s internal geometry should keep water away from the unit edge. In exposed locations the combination of a louvre’s wet-side discharge and an adjacent unit’s edge seal deserves explicit attention at the detailing stage.

Safety Glazing and Human Impact

Glazing in and around louvres is subject to the same safety requirements as any other glazing. AS 1288 governs the selection and installation of glass in buildings, including the determination of wind loads on glass and the identification of locations where human impact must be considered, and AS 2208 sets the requirements for safety glazing materials. A louvre blade at low level, a fixed panel beside a door, or a glass blade in a school or public building may all fall within those provisions.

The practical point for water management is that safety glazing choices change the assembly. Laminated glass behaves differently at its edges, and the frame’s glazing detail must suit the glass type that the safety assessment requires. Specifying the glass and the frame separately, then discovering at fabrication that the two are incompatible, is a familiar and expensive sequence.

Corrosion, Coatings and Long-Term Water Performance

Alloy, Finish and Environment

Aluminium is chosen for louvres because it resists corrosion, holds fine profiles and can be finished in ways that survive weather. It is not immune. In coastal and industrial environments, salt and airborne pollutants settle on surfaces, hold moisture and attack the metal wherever the protective finish is breached. The severity of the environment, not the colour of the finish, should drive the specification.

Powder coating and anodising are the two common finishes, and both rely on pre-treatment for their performance. Coating thickness, pretreatment quality and the detailing of cut edges and concealed faces all affect how long the finish lasts. Cut edges, drilled holes and site-cut sections are where corrosion usually starts, because they are the places where the protective layer is absent.

Fasteners, Fixings and Dissimilar Metals

Water management and corrosion are the same subject seen from two directions. A detail that holds water will corrode, and a corroded detail will eventually stop draining. Fasteners are the usual weak point: steel screws in an aluminium frame, or aluminium components bearing on stainless steel, create galvanic couples that accelerate attack precisely where water collects.

The correct approach is to specify fasteners and accessories that are compatible with the frame and appropriate to the exposure, to isolate dissimilar metals where contact is unavoidable, and to avoid creating crevices that trap water. Site practice matters here as much as the specification, because a bag of the wrong screws is always closer to hand than the correct ones.

Maintenance and the Appearance of Performance

A coating that looks intact may still be failing at a cut edge or inside a drainage chamber, and a louvre that looks clean may have blocked outlets. Maintenance should therefore include the parts that cannot be seen: sill chambers, blade carriers, end seals and fixings. Washing removes the salt and debris that drive corrosion, and it also reveals the staining that indicates a water path.

Where a finish has failed, the repair should restore the protective system rather than cover the symptom. Painting over corrosion without removing it traps the attack and produces a failure that returns within a season.

Cleaning and Routine Care

Cleaning a louvre is mostly about restoring two things: airflow and drainage. Blades should be cleaned on both faces, with the stack operated to expose the surfaces that are normally hidden, and the frame should be flushed so that debris leaves through the outlets rather than collecting in the sill. Fresh water and a mild detergent are usually sufficient; abrasive cleaners and aggressive solvents damage coatings and gaskets.

The frequency depends on exposure. A coastal louvre may need attention several times a year, while a sheltered inland installation may need it annually. The schedule should be driven by inspection rather than by the calendar, because the failure modes are local: one blocked outlet, one hardened gasket, one loose carrier. Records of what was found are more useful than records of what was washed.

Operation belongs in the same routine. Blades should be cycled through their full range, the mechanism lubricated only with products the manufacturer approves, and any change in effort or alignment reported. A louvre that has become stiff is a louvre whose seals are being loaded unevenly, and that is a water problem in its early stage.

Testing, Evidence and What a Report Covers

Product Testing Under AS 2047

AS 2047 is the Australian product standard for windows and external glazed doors, and it addresses structural performance, water penetration and air infiltration, with testing carried out under the AS 4420 series. For a louvre system, the relevant evidence is a report for that system in its tested configuration. The report identifies the size tested, the configuration, the glazing and the performance achieved, and it is only valid for products built to the same specification.

One point deserves emphasis. Water penetration testing is conducted with the specimen closed. A louvre is not required to be weathertight in the open position, and no rating should be inferred for an open blade stack. Claims that an open louvre “meets” a water rating are a misreading of what the test does, and they are worth challenging during specification review.

Facade Testing Under AS 4284

AS 4284 provides methods for testing building facades, including performance under wind pressure and water penetration, and it is used both in laboratories and on site. For projects where a louvre bank forms part of a larger facade system, or where the architect wants evidence of the installed assembly rather than the product alone, facade testing gives a more representative result because it includes the junctions, the supporting structure and the installation sequence.

In-situ testing has limits. It samples a portion of the facade, it is affected by weather and access, and it cannot prove the performance of every unit. It is best used as verification of a detail that has already been designed and built correctly, not as a substitute for design.

Reading a Test Report Honestly

A test report is evidence about a specimen, not a guarantee about a building. The useful questions are: what exactly was tested, at what size, with what glazing, with what seals, and in what condition; was the test laboratory accredited for that method; and does the project’s configuration fall inside the scope of what was tested. A report that answers those questions is valuable. A certificate number quoted without a scope is not.

Project-Specific Performance and Compliance

The NCC and the ABCB

In Australia, the National Construction Code, maintained by the Australian Building Codes Board, sets the performance requirements that a building must satisfy, including weatherproofing and the performance of external glazing. The NCC offers performance solutions and deemed-to-satisfy provisions, and for windows and facade elements those provisions point to the relevant Australian Standards and to evidence of compliance.

Compliance is therefore a project question. The wind classification of the site, the height and geometry of the building, the exposure of each elevation, the class of the building and the chosen compliance path all combine to define what the louvre must do. A product that is compliant on one project may be unsuitable on another with the same drawings but a different site classification, and the responsibility for that judgement sits with the project’s designers and certifiers, not with a brochure.

Australian Standards in the Specification

Four standards recur in louvre and glazing specifications. AS 2047 defines the product performance and testing regime. AS 4284 provides the facade test methods used when the assembly, rather than the product, is being verified. AS 4666 governs insulating glass units, which matters wherever a louvre sits beside fixed double glazing. AS 1288 governs the selection and installation of glass, including structural and human-impact considerations, and works alongside AS 2208 for safety glazing materials. Wind actions are determined separately, using the wind load standards applicable to the building type.

The specification should say which of these apply, what evidence is required, and who is responsible for the interface details. Vague references to “compliance with all relevant standards” are common and almost useless, because they leave the critical decisions to fabrication and site.

New Zealand References

New Zealand regulates the same physics through a different framework. The Building Code sets performance requirements, and Clause E2, external moisture, is the provision that governs how a wall and its openings must manage water. E2/AS1 provides an Acceptable Solution for timber-framed construction, and its risk matrix approach to cladding, wind zone, eaves and storeys is directly relevant to how much protection a louvre installation needs and how the wall interface should be built.

Window performance is addressed through SNZ TS 4211:2022, the technical specification for windows and doors, which covers classification and performance including watertightness for the defined wind zone. Glazing is addressed through NZS 4223, and framing through NZS 3604 where the building is timber-framed. A New Zealand louvre specification should reference these documents explicitly, along with the manufacturer’s tested configurations for the relevant wind zone.

The regulatory logic differs from Australia, but the construction logic does not. A drained sill, a continuous flashing, a lapped weather barrier, a ventilated cavity and clear outlets are the same requirements on both sides of the Tasman, and a detail that works in Brisbane will work in Auckland for the same reasons.

Specification Checklist

Confirm the exposure of each elevation and the wind classification that applies to the site.
Select a louvre system with published test evidence for the configuration being specified.
Define the weather boundary and show the drained zone on the detail.
Detail the sill with an internal upstand, outward fall and inspectable outlets.
Detail the flashing, the wall weather barrier lap and the cavity closure at jambs and head.
Specify blade edge and jamb seals, and state that they are replaceable.
Coordinate adjacent fixed glazing, its glass type and its edge protection.
Specify frame finish, fasteners and isolation for the corrosion category of the site.
State the inspection hold points before linings and cladding close.
Define the maintenance regime, including outlet clearing, gasket inspection and blade cycling.

Frequently Asked Questions

Are louvre windows waterproof when they are open?

No window is waterproof when open, and a louvre is no exception. Angled blades shed a large share of incident rain, and the frame is designed to collect and discharge what gets past them, but an open aperture remains a path for wind-driven water. The realistic expectation is a controlled amount of wetting on the inner face of the assembly, drained away before it reaches the building interior.

Do insect screens stop rain entering a louvre?

Only marginally. A screen intercepts large droplets and reduces the velocity of some of what passes, but it is not a pressure boundary and it does not seal. A fine mesh can even hold water against the louvre by surface tension and capillary action, which is one reason screens need cleaning and should be mounted with some separation from the blades.

Why does water appear inside the room rather than at the window?

Because water travels along the path of least resistance, which is often a fixing, a frame joint or a capillary gap that leads away from the point of entry. By the time it appears at a skirting or a ceiling line, it may have travelled some distance. Finding the entry means inspecting the sill chamber, the outlets, the end seals and the perimeter joint, not sealing the visible stain.

Can a leaking louvre be fixed with sealant?

Only where the leak is genuinely a joint failure at the perimeter. Sealant cannot replace a blocked outlet, a missing gasket, a reversed flashing or an absent internal upstand, and applying it across a drainage path makes the underlying problem worse. The correct sequence is to identify the water path, restore the detail, and then seal the joints that were designed to be sealed.

Is a louvre suitable for a fully exposed coastal facade?

It can be, if the system is appropriate to the exposure, the frame is finished and maintained for a coastal environment, the drainage is generous and inspectable, and the wall interface is detailed as a drained assembly. Exposure does not disqualify a louvre, but it raises the standard of detailing and the frequency of maintenance. A sheltered elevation and an exposed one on the same building should not be specified identically.

How often should louvre drainage be checked?

At least as often as the windows are cleaned, and more frequently in coastal, industrial or vegetated locations where debris accumulates quickly. The check is simple: operate the blades, look into the sill chamber, confirm the outlets are clear, and look for staining that indicates a persistent water path. Doing this before the wet season is more useful than doing it afterwards.

What is the difference between AS 2047 and AS 4284 for a louvre project?

AS 2047 is a product standard: it defines how a window system is tested and what performance it must achieve. AS 4284 provides facade test methods and is used when the installed assembly, including its junctions and supports, is being verified. A project may need both, and the specification should say which evidence is required at which stage.

Does a New Zealand project need different louvres from an Australian one?

The product may be the same, but the evidence and the detailing requirements differ. New Zealand projects work to the Building Code, with Clause E2 and E2/AS1 governing external moisture, and to SNZ TS 4211:2022, NZS 4223 and NZS 3604 as applicable. The wind zone and the E2/AS1 risk matrix determine how robust the wall interface must be, and the documentation should reflect that framework rather than an Australian one.

Conclusion

A louvre window manages water rather than excluding it, and everything that follows from that principle is practical. The blade stack sheds most of what arrives; the frame collects what remains; the sill discharges it; the flashing and the wall’s weather barrier carry it clear of the building. Each of those steps is simple on its own, and the assembly fails when one of them is missing, blocked, reversed or bypassed.

Good practice is not exotic. Draw the weather boundary and keep it at the outer face. Give the sill an upstand, a fall and clear outlets that can be inspected. Flash the opening before the frame goes in, and lap the wall membrane in the right order. Keep screens and shading devices separated from the blades so they do not become debris traps. Match the finish and the fasteners to the exposure. Test what can be tested, read the report for its scope rather than its headline, and maintain the parts that cannot be seen. Those steps apply to a tropical school, a coastal apartment, a suburban renovation and a New Zealand timber-framed house alike, and they are what separates a louvre that quietly works for decades from one that is blamed for a leak it was never detailed to prevent.

References

Australian Building Codes Board. National Construction Code, Volume One and Volume Two, including the Housing Provisions. https://ncc.abcb.gov.au
Standards Australia. AS 2047, Windows and external glazed doors in buildings. https://www.standards.org.au
Standards Australia. AS 4284, Testing of building facades. https://www.standards.org.au
Standards Australia. AS 4666, Insulating glass units. https://www.standards.org.au
Standards Australia. AS 1288, Glass in buildings – Selection and installation. https://www.standards.org.au
Standards Australia. AS 2208, Safety glazing materials in buildings. https://www.standards.org.au
Standards Australia. AS/NZS 1170.2, Structural design actions – Wind actions. https://www.standards.org.au
Standards New Zealand. SNZ TS 4211:2022, Windows and doors – Performance. https://www.standards.govt.nz
Standards New Zealand. NZS 4223, Glazing in buildings. https://www.standards.govt.nz
Standards New Zealand. NZS 3604, Timber-framed buildings. https://www.standards.govt.nz
Ministry of Business, Innovation and Employment. New Zealand Building Code, Clause E2 External moisture, and E2/AS1. https://www.building.govt.nz

Aluminium Louvre Window Water Management: Blades, Frames and Weather Boundaries