Sri Lanka asks a window to do two things that pull in opposite directions. It has to let the breeze through for most of the year, and it has to keep a monsoon out for the rest of it. Almost every specification mistake we see on this island comes from someone optimising for one of those jobs and quietly failing the other.
This page is written for whoever is assembling the window and door schedule for a Sri Lankan project — an architect, a quantity surveyor, a contractor, or an owner who has been handed a quotation and wants to know what is missing from it. It is not a product brochure. Where we publish a number, we give it to you. Where we do not publish one, we say so and tell you what to ask for instead, because a value nobody has published is not a worse value — it is simply an unanswerable comparison.
One thing up front, so nobody has to work it out later: ALPES is a factory in China. Our published project experience is in the Gulf and in Australia. We do not claim a completed Sri Lanka project, and you should not accept a claim like that from anyone without addresses you can visit. What we can do is supply a system, the test evidence behind it, and the documentation your clearance needs. Whether that is worth the freight is a question this article tries to help you answer honestly.
Sri Lanka has a deep, well-earned tradition of building for air movement. The verandah, the deep overhang, the courtyard, the louvered opening that stays cracked open all night — that is not decoration, it is a climate strategy that predates air conditioning by a very long way. Tropical modernism on this island is essentially that strategy executed with real architectural ambition.
A sealed, thermally broken aluminium system belongs to a different building. It belongs to a building that is air conditioned, that is expected to be quiet, and whose openings are shut for most of the day. That is increasingly true for Colombo apartments, for hotel rooms, for offices, and for the upper floors of anything tall where the wind makes an openable sash unpleasant anyway.
So before anyone talks about frame widths, settle this: is this window being bought to keep the weather out, or to let it in when required? A fully sealed casement specified for a house that will never be air conditioned is money spent on performance that will never be used, and it will feel stuffy. A louvered opening specified for a bedroom that will run air conditioning every night is a permanent heat and humidity leak. Most real projects are a mix, and the schedule should say which elevation is which.
Everything below follows from these four. If a quotation does not mention them, it is not a specification, it is a price.
| Load | What it does | What it attacks first | Write this into the enquiry |
|---|---|---|---|
| Wind-driven monsoon rain | Rain arrives close to horizontal and keeps arriving for hours, from two different monsoons at different times of year | The perimeter seal, then the drainage path behind the outer seal, then the weep outlets | Water penetration test result — with the tested size, the glass build-up and the pressure all stated |
| Salt-laden coastal air | Chloride deposits sit on the coating and stay damp in high humidity, so corrosion never gets a dry break | Coating defects, cut edges, fasteners before frames, then hinges and rollers | Coating standard and test hours, pre-treatment, and the fastener grade — as separate line items |
| Heat, humidity and air conditioning | A large temperature difference across a thin assembly, with moisture on both sides of it | The glass build-up first, then the thermal break, then any gap in the seal continuity | SHGC and U value for the exact glass you are buying, under one named standard |
| High-rise wind and stack effect | Pressure rises with height and with exposure; it acts on the sash in both directions | Mullion stiffness, sash retention, then the anchors into the structure | Design pressure calculated for your building, plus the anchor detail that goes with it |
Two more that are not loads but belong on the schedule anyway. Insect screening is a practical requirement for most of the year, and it should be specified at the same time as the window, because a screen retrofitted to a window that was not designed for it is the single most common source of complaints after handover. And in Colombo, traffic noise is often the reason a client asks for an upgrade in the first place — which makes the acoustic build-up a stated requirement, not an upgrade option.
Sri Lanka has its own national wind loading standard. The Sri Lanka Standards Institution publishes SLS EN 1991-1-4 with a National Annex, and the current revision of that annex incorporates an updated wind map for the island prepared from wind data collected over several decades at the University of Moratuwa. In practice, Sri Lankan structural consultants also work from BS 6399-2, BS EN 1991-1-4 and AS/NZS 1170.2 depending on the project and the age of the design. There is also a Sri Lanka Standard covering Eurocode 9, the design of aluminium structures.
What that means for you is simple and worth insisting on:
A quotation that says "wind resistant" or "suitable for high-rise" has told you nothing. A quotation that gives you a pressure, a tested size and a report number has told you everything you need to compare it.
In a monsoon, water will get past the outer seal. Every system is designed on that assumption. The questions that actually separate a good specification from a bad one are the next three: where does the water go once it is inside the profile, can it get back out, and does anything stop it reaching the inner barrier before it does.
This is why the drainage details on our sliding systems are worth reading rather than skimming:
| Series | How it handles water | What that means for a Sri Lankan opening |
|---|---|---|
| SL112/167 | 45 mm high-ｄｒｏｐ bottom track, with an optional 85 mm water barrier | The one to look at for an exposed balcony or a west elevation that takes the monsoon squarely |
| SL126/182 (96) | Patented eave-style waterproof design, bottom track water-blocking edge, high track 43 mm or low track 8 mm | Choose the track height deliberately. The 8 mm low track is a trip-free threshold; it is also a lower dam |
| SL126/182 (75) | Butyl rubber gasket at the frame-to-sash joint, interchangeable drip-eave inserts, 27A insulating glass | Panoramic elevations where you want the narrow 75 mm interlock without giving up the drainage path |
| SL155 | Passive check valve drainage, four-sealing design, single sash up to 2800 × 2600 mm | Large terrace openings. The check valve matters where a drain is exposed to driving wind |
| TS130 | Four-sided continuous sealing strip plus sealant between the upper track and the frame, side-pressure closing, 200 kg pulleys | The answer when you want sliding but cannot accept sliding-grade sealing. The sash presses in at the last few centimetres |
| C116 | Flat-channel obstacle-free drainage, triple sealing strips with seamless welded corners, 34–44 mm multi-chamber insulation strips | Casement elevations on upper floors, where a blocked drainage channel is nobody's maintenance priority |
| C113 | Triple sealing, full glue-injection process with glued corner brackets, glass centreline / thermal break / equal-pressure strip on one axis | Where the opening is large enough that the corner is the weak point rather than the seal |
| C120 | Frame, sash and mesh fully sealed with injection-moulded structural adhesive, complete corner sealing, integrated window-and-mesh unit | Wherever the screen is not optional, because a screen that is part of the unit is a screen that seals |
Be clear about what this table is and is not. These are construction features of the systems. They are not a tested water penetration classification, because we do not publish one on our spec sheets, and we are not going to imply one. If your consultant has written a water penetration requirement into the specification — and on a monsoon-exposed building they should — then send us the number and ask for a test report that covers the size and glass you are actually buying.
Coastal Sri Lanka is not one condition. Colombo, Galle, Negombo, Bentota and Hambantota all carry salt, but a beachfront villa and a fourth-floor apartment several kilometres inland are not exposed to the same thing, and specifying them identically wastes money in one place and loses it in the other.
| Band | Typical locations | What to specify | What to be honest about |
|---|---|---|---|
| Inland hills | Kandy, the central highlands, hill-country villas | Standard powder-coated finish is usually sufficient. Spend the money on the thermal build-up instead, because the nights are cooler | A cooler climate changes the condensation question — ask which face is expected to run wet before you choose the glass |
| Coastal city | Colombo, and the dense coastal belt | Confirm the coating standard and pre-treatment in writing; specify stainless fasteners as a separate line item; add a rinse-down regime to the maintenance manual | Most corrosion complaints on city buildings start at the fastener, not at the frame |
| Beachfront | Galle, Negombo, Bentota, the southern coastline | Higher coating specification, upgraded fastener grade, drainage that will be flushed regularly, and a maintenance contract that is actually funded | No window is maintenance-free in this band. If the client will not fund rinsing, specify a cheaper window and expect to ｒｅｐｌａｃｅ it |
Two honest points about our own numbers here. The 240-hour salt spray result published for the AW90 series is a test result on that series. It is not a coastal qualification certificate, and it does not transfer to any other series. If your project specification requires a stated corrosion resistance, write the required hours into the enquiry for the specific series you intend to buy and ask for the report.
Second, the C116 lists 304 stainless steel high-load hinges. That is a good material, and for a beachfront project it is worth asking whether a higher-grade stainless is available on the fixings and hardware. We would rather you asked and got a straight answer than discovered it in year three.
A thermal break in Sri Lanka is not doing the job it does in Europe. In Europe it keeps paid-for heat inside the building. Here, the same strip is doing two different jobs: reducing the amount of heat that travels from a hot frame into a conditioned room, and keeping the interior face of the frame warm enough that humid air does not condense on it when the air conditioner is running.
The cheapest solar control available to a Sri Lankan building is the one the tradition already provides: a deep eave, a verandah, a recessed opening, a balcony that shades the glazing below it. Shading stops the energy before it reaches the glass. Upgrading the glass to reject what has already arrived is the more expensive way to solve the same problem. If the elevation has no shading and the budget only stretches to one intervention, fix the shading.
Internal shading should be specified at the same time as the window, not after handover. For inward-opening units this matters more than people expect — blinds for tilt and turn windows have to clear the sash in both the tilted and the fully open position, and that is a dimension you want on the drawing rather than discovered on site.
This question is worth ten minutes at design stage and is almost never asked. In a hot, humid city with air conditioning running, moisture can appear on three different surfaces and they mean three entirely different things:
Our published thermal values are K = 1.3 for AW90, K = 1.6 for C120 and K = 1.7 for C116. Treat them correctly: they are system values obtained under one set of boundary conditions, they are not whole-window values for your particular glass build-up, and they are not interchangeable with figures produced under a different national standard. A number without its standard attached is not a number you can put in front of a consultant. We do not publish a solar heat gain coefficient for any series — ask for it per glass configuration, because in a cooling-dominated climate it is the more decision-relevant of the two.
We sell these systems, so it is worth saying plainly where they are not the right purchase. Aluminium is also not the only material on this island, and the local alternatives are genuinely good at some things.
| Scenario | Why a sealed thermal-break unit is the wrong buy | Specify this instead |
|---|---|---|
| A house that will never be air conditioned | You are paying for a thermal barrier whose only effect, in a free-running house, is to stop the breeze doing its job | A top-hung or louvered opening with a good insect screen, and shading. Save the budget for the roof |
| Small rental units on a tight budget | The payback depends on the air conditioning being used, which in a rental you do not control | A non-thermal aluminium system, with the spend redirected to the glass and the screens |
| Heritage timber restoration | The sightlines, the reveal depths and the whole character of the elevation change | Restored timber, treated for insects and with a realistic repainting cycle agreed up front |
| An opening you want to open completely | A casement sash always leaves part of the opening closed, and an outward sash has a swing arc to protect | A multi-track sliding system, or a folding door if the whole wall has to go |
| An unshaded west or east elevation | The best glazing in the catalogue is still second best to keeping the sun off the glass | Fix the shading first. Then specify the glass, with the shading in place |
| A twenty-window project with no specification | Freight, clearance and lead time will cost more than the performance is worth at that scale | Buy from a good local fabricator. This is not a sales reversal, it is arithmetic |
On the material question, briefly and fairly. Timber is the incumbent and it is beautiful, which is why people keep specifying it despite the maintenance — a wood casement window moves with the humidity, needs repainting on a cycle, and is food for insects unless it is treated and kept treated. uPVC is the other common alternative: a upvc casement window will not corrode and usually costs less than a thermally broken aluminium system, but you should get the maximum span and any restriction on dark colours in writing, because those are the two places where the material's limits show up in a tropical climate. Aluminium's advantage is span and section depth: it holds a larger opening in a slimmer profile, and it does not mind a dark colour.
The frame widths below are the numbers that matter for your wall build-up, because that is the dimension that has to be inside the opening. One warning that catches people out: frame depth is a property of the series, not a function of how many tracks it has. Our four-track SL155 is 155 mm deep, which is shallower than the three-track SL126/182 at 182 mm. Do not let anyone on site assume more tracks means a deeper frame.
| Series | Frame width | Glass sash | K value | Where it fits in Sri Lanka |
|---|---|---|---|---|
| AW90 | 90 mm | 90 mm | 1.3 | Tilt and turn, inward opening. The right answer for upper floors, because the outside face is cleaned from inside. Winkhaus hardware, with ROTO optional. Best published thermal figure we offer |
| C113 | 113 mm | 57 mm | Not published | Outward casement built around the corner: full glue injection, glued corner brackets, CMECH hardware. For large openings and exposed upper floors |
| C116 | 116 mm | 81 mm | 1.7 | Outward casement where sightline and drainage lead: 28 mm oblique press line, 22 mm mullion face, flat-channel drainage, 304 stainless high-load hinges, Wehag upgrade available |
| C120 | 119 mm | 62 mm | 1.6 | Outward casement with the screen integrated into the unit and a seamless threshold. ROTO transmission and anti-pry lock points. Choose it where the insect screen is not negotiable |
| TS130 | 130 mm | 55 mm | Not published | Side-press sliding: the sash presses in at the end of its travel and seals like a casement. 200 kg pulleys, eight-point locking. The compromise when you want ventilation and sealing from one opening |
| SL112/167 | 112 / 167 mm | 43 mm | Not published | Heavy-duty multi-track, up to 220 kg per sash, 45 mm high-ｄｒｏｐ bottom track. For exposed balconies and monsoon-facing elevations |
| SL126/182 | 126 / 182 mm | 55 mm | Not published | Large openings, sliding or lift-sliding, single sash up to 2.5 × 3.0 m. Locally reinforced to 3.0 mm. The 75 mm interlock version gives the panoramic elevation; the 96 mm version is the general-purpose one |
| SL155 | 155 mm (four track) | 54.5 mm | Not published | Terrace openings: 400 kg twenty-wheel pulley system, single sash up to 2800 × 2600 mm, check valve drainage. Note it is shallower in the wall than the three-track above |
This is the table we would want a buyer to hold us to. The right-hand column is the useful one.
| Item | What we publish | What you should ask for on your project |
|---|---|---|
| Thermal transmittance | K = 1.3 (AW90), 1.6 (C120), 1.7 (C116). Nothing for C113 or any sliding series | A whole-window value for your size and glass, calculated under one named standard, from every supplier you are comparing. Missing is not worse — it is unanswerable |
| Solar heat gain | Not published, for any series | SHGC for the exact glass build-up you are buying. In a cooling climate this is the number that moves the energy bill |
| Air, water and wind | No classification is published on our spec sheets | The report itself: tested size, glass build-up, pressure, direction, and the laboratory that issued it |
| Corrosion | 240-hour salt spray, AW90 only | The coating standard, the pre-treatment and the test hours for the series you are actually ordering. A result on one series does not travel to another |
| Shear strength | 5,000 N, AW90 | Confirm what the figure was measured on. It is a test result, not a project rating |
| Hardware cycles | 30,000 cycles, CMECH, on C113 | Ask what was cycled. A hardware rig test is not a service life, and different test setups are not comparable |
| Profile and insulation | 6060-T66, 1.8–2.5 mm depending on series, PA66GF25 multi-chamber strips | Put the alloy, the temper and the wall thickness on the order as contractual terms, not as marketing copy |
| Insect screens | 40# and 80# stainless mesh, anti-PM2.5 mesh, high-elastic mesh depending on series | Specify the mesh at tender. A screen is opened far more often than the sash, so its cycle life matters more than the window's |
This is the part of an island project that has nothing to do with windows and can delay one by weeks. The Sri Lanka Standards Institution is the national standards body. It operates a mandatory import inspection scheme under the Imports and Exports (Control) Act, and the list of products covered by it is set out in gazette notifications that have been revised more than once. Check the current gazette before you ship. Do not take the word of a supplier's blog for what is on the list — including this one.
Where the scheme applies, SLSI accepts conformity evidence from a few routes: a certificate from a laboratory accredited by the exporting country's national accreditation body, a certificate from the exporting country's national standards body, or a certificate from a manufacturer registered with SLSI. Consignments are subject to random checks, and product that arrives without valid documentation is sampled and tested. The consequences of getting this wrong are testing delay, penalties, and in the worst case re-export of the consignment.
The paperwork side is unglamorous and worth getting right the first time: commercial invoice, packing list, bill of lading, the customs declaration, and evidence of country of origin. Sri Lanka also has its own accreditation body, which accredits testing laboratories to ISO/IEC 17025 — if you are relying on a test report, that accreditation is what makes the report worth the paper it is printed on.
One point about the SLS certification mark, because it is widely misunderstood. The mark is issued under a permit to a specific permit holder, and holding it requires factory surveillance along with testing of factory and market samples. It attaches to a manufacturer's quality system under supervision — it is not a sticker that travels with a photograph of a product. If a supplier shows you a certification mark on a quotation, ask whose permit it is and what product scope it covers.
And the honest boundary: we can supply material declarations, drawings, test reports and samples. We cannot be the importer of record on your consignment, and we cannot hand you an SLS permit. Those sit with the importer and the manufacturer's registration respectively. Any supplier who implies otherwise is promising something they do not control.
Sri Lanka has a serious domestic aluminium industry. Lanka Aluminium, for example, has publicly reported becoming the first local manufacturer to obtain international accreditation for an in-house developed window system, tested for water ingress and wind loads to ASTM standards, and it was also reported as the first in Sri Lanka to obtain SLS certification for part of its range. That is not a throwaway competitor — it is a fabricator with tested systems, a local testing relationship, and a workshop you can visit.
| Consideration | Local fabricator | Factory-direct import |
|---|---|---|
| Measurement | Surveys the actual opening, absorbs site tolerances, fixes the surprises on the day | Manufactures to your drawing. If the drawing is wrong, so is the window |
| Replacement glass | Stock glass, fitted in days | Order a spare glass pack with the original consignment. Do this and it is not a problem; forget it and it is a long wait |
| Consistency at scale | Depends on the workshop | Two hundred identical units come off the same line with the same hardware, and each one is traceable to the original order |
| Large panels | Ask for the maximum tested size and the pulley rating in writing | Engineered for it: 2.5 × 3.0 m on SL126/182, 2800 × 2600 mm at 400 kg on SL155 |
| Hardware brands | Whatever the workshop stocks unless you specify otherwise | ROTO, Winkhaus, CMECH and Wehag named as contractual line items, so what you specified is what is fitted |
| Service call | A van in Colombo this week | Written procedure, drawings, and parts matched to your batch — then someone still has to fit them |
Our actual recommendation: if the project is a house or a small block, a competent local fabricator is the better buy, and we would rather tell you that than sell you a container you do not need. Factory-direct starts to make sense when there is a written specification, a repeated unit count, and openings large enough that the engineering matters. And even then, keep a local installer. A window is not finished when it leaves the crate.
| Ask this | A good answer looks like | Red flag |
|---|---|---|
| What design pressure is this sized for, and under which standard? | A pressure, a height, an exposure category and the test report number | "Suitable for high-rise" |
| Which tested size and glass does that rating cover? | The dimensions and the full glass build-up printed on the report | A rating with no size attached |
| What is the SHGC and U value for the glass I am buying? | Two numbers, one standard, tied to a named build-up | A K value quoted with no standard and no glass |
| What coating standard and test hours, for this series? | A named standard, hours, and the pre-treatment, on the series you are ordering | A salt spray figure from a different product |
| What grade are the fasteners? | A grade, listed separately from the hardware on the quotation | "Stainless" with no grade |
| Is the insect screen part of the unit? | Mesh specification, how it opens, and its own cycle rating | "Screen available" |
| Show me the drainage path on the section drawing | A section with the chamber, the weep and the outlet marked | A rendering and the word "waterproof" |
| What frame depth do I need in the wall? | One number in millimetres, for the series, with the track count stated | "Roughly 150 mm, more if you go three-track" |
| What conformity evidence ships with the goods? | Named documents, named laboratory, accreditation stated | "All certificates provided" |
| What spares come with the order? | A written list: rollers, handles, gasket, one spare glass pack | "Spares available on request" |
No. Our published project experience is in Saudi Arabia, Dubai, the wider Middle East and Australia. We are not going to imply local references we do not have. What we can offer instead is the nearest comparable project, the test evidence behind the system you are considering, and samples you can take to your consultant.
It depends on whether the room is air conditioned. A casement closes against a compression seal and will always be the tighter, quieter unit, which is what you want for a bedroom that runs air conditioning. A sliding unit uses a brush or fin seal, which is a structural consequence of the sash having to move past the frame. If the brief says sliding but the room is conditioned, look at the side-press TS130: it slides, then presses in at the end of its travel.
Do not specify an outward-opening casement unless the building has a cradle or a cleaning plan that names one. For upper floors, an inward-opening tilt-and-turn unit lets the whole outside face be cleaned from inside the room. This is a specification decision, not a maintenance one, and it is much cheaper to make it at design stage.
In an air-conditioned building, yes. It reduces heat arriving through the frame and it keeps the interior frame face warmer, which is what stops it sweating when the air conditioning is running. In a house that is never air conditioned, it buys you very little and the money is better spent elsewhere. The honest test is whether the room will be conditioned.
Because the glass is most of the area. On a typical opening, the frame is a small fraction of the total, so the thermal and solar behaviour of the build-up dominates the result. Choose the glass first, then the frame that can carry it — the glass sash thickness on each series is what limits how thick an insulating unit you can fit.
Rollers, handles, locking parts, gasket cut to length, and at least one spare glass pack for the largest unit on the job. The glass pack is the one everybody forgets and the one with the longest lead time. Ask for it with the original consignment so that it travels in the same crate.
We will supply the material declarations, drawings, section details and test reports we hold, and we will manufacture to a specification you write. We cannot be the importer of record on your consignment, and we cannot issue a local approval or transfer a certification permit to you. Approvals are granted to an applicant by the authority that has jurisdiction, and on an import that applicant is on your side of the transaction.
If you are assembling a schedule for a Sri Lankan project, send us the opening sizes in millimetres, the elevations they face, whether each room is air conditioned, and the design pressure your structural consultant has calculated. That is enough for us to tell you which of these series fits, and — just as usefully — which ones are the wrong buy. Reach the team at ALPES contact page.
