Casement
Hinged sash closing onto compressed gaskets. The best air, water and acoustic performance of any opening type; inward or outward opening.
Architectural window systems
System Aluminium Windows
A system aluminium window is a complete, engineered package in which the profiles, thermal break, gaskets, glass rebate, hardware grooves and drainage were designed together and tested together as one window. That is what separates it from a window assembled from whatever profiles and fittings happen to be available. Metline supplies system window profiles in 6063 and 6060, thermal break and co-extruded sections and accessories, to window fabricators and project buyers worldwide.
- Profile alloy
- 6063-T5 / T6, 6060-T66
- Structures
- Thermal break, co-extruded, non-insulated
- Openings
- Casement, tilt-turn, sliding, fixed
- Test basis
- EN 14351-1 · NAFS
What makes a window a "system" window
The word "system" describes how the window was developed, not how it looks. A system designer starts from a performance target (an air-tightness class, a wind load, a U-value) and then designs every section, gasket, cleat and hardware groove to reach it. The finished window is tested at a laboratory, and the test report defines the sizes, glass and hardware that the performance applies to.
A conventional window is built the other way round: profiles, glass and fittings are chosen by price or availability and the result is whatever it turns out to be. Such windows can look identical on the facade, but their air and water tightness depend heavily on the skill of the fabricator and installer, and there is no test evidence to show a building inspector or energy assessor.
For a project buyer, the practical value of a system window is predictability. The same frame depth, gasket layout and drainage detail appear on every unit across hundreds of openings, the fabrication drawings already exist, and the performance claimed in the tender can be traced back to a test report. That is why most energy codes, facade consultants and main contractors now ask for a tested system rather than a generic window.
Thermal break versus co-extruded system windows
Two profile structures dominate insulated system windows. Both keep aluminium on the outside for strength and durability; they differ in how the cold outer shell is separated from the room.
| Criterion | Thermal break (polyamide strip) | Aluminium-PVC co-extruded |
|---|---|---|
| Construction | Inner and outer aluminium shells joined by glass-fibre-reinforced polyamide (PA66 GF25) strips rolled into the profile | Aluminium core with a co-extruded or clipped rigid or micro-foamed PVC layer on the room side |
| Main strength | Structural aluminium on both faces; high stiffness for large sashes and high wind loads | Warm, quiet interior surface with good insulation for its depth |
| Finishes | Powder coating, PVDF, anodising, wood-grain transfer, different colours inside and out | Aluminium face coated as usual; PVC face foiled or coloured, often wood-grain |
| Typical use | Offices, schools, hotels, apartments, high-rise and public buildings | Housing, villas, hotels and refurbishment where comfort and appearance lead |
| Points to check | Strip width and shear rating to EN 14024; foam inserts for higher insulation | Long-term bond and thermal movement between PVC and aluminium; fire and recycling requirements |
Non-insulated system windows still have a place in warm climates and for internal glazing, where condensation and heat loss are not a design issue. They are cheaper and slimmer, but a non-insulated aluminium frame conducts heat several times faster than a thermally broken one, so check local energy rules before specifying them. Our page on thermal break aluminium windows explains how the barrier works in detail.
Opening types within one system family
A good system family covers several opening types with shared outer frames, colours and sightlines, so a facade can mix them without looking patched together.
Tilt-turn
One handle gives secure tilt ventilation and full inward opening for cleaning. Standard in European housing, schools and hotels.
Sliding and lift-slide
Saves space on balconies and wide openings. Brush or lift-slide seals; lift-slide closes onto gaskets and performs much better than a plain slider.
Bi-fold
Folding sashes that clear almost the whole opening. Needs careful threshold and drainage design.
Awning and louvre
Top-hung or bladed openings for kitchens, bathrooms, plant rooms and continuous ventilation; awnings shed rain when open.
Fixed and combination
Fixed lights joined with opening sashes by mullions and transoms, for daylight and views with a controlled opening ratio.
The four subsystems that decide performance
| Subsystem | What it does | Selection points |
|---|---|---|
| Glazing | Carries most of the thermal, solar and acoustic performance; the glass usually covers 70 – 85 % of the window area | Double or triple insulating units, Low-E coatings, argon fill, warm-edge spacers, toughened or laminated safety glass, acoustic laminates; stay within the system's glass thickness range |
| Hardware | Opens, locks and carries the sash; compresses the gaskets evenly | Rated sash weight per hinge set, number of locking points, restrictors and child-safety catches, corrosion class for coastal sites |
| Sealing | Forms the air and water lines and dampens sound | EPDM gaskets with moulded or vulcanised corners; two or three sealing lines; centre gasket to separate a drained chamber from a dry inner zone |
| Drainage | Removes water that passes the outer seal | Slotted drainage with baffled covers, pressure-equalised chambers, concealed drainage for a cleaner face |
Swapping any of these components for a non-system part, for example a cheaper gasket or a different hinge, can invalidate the test report. Agree substitutions in writing before fabrication.
Typical technical parameters
The ranges below are typical of mid- to high-performance thermally broken systems on the market. Each specific system has its own tested limits, and those limits, not this table, are what must appear in a project specification.
| Parameter | Typical range | Comment |
|---|---|---|
| Frame depth | 55 – 100 mm | Deeper frames allow wider thermal breaks, thicker glass and stiffer sections |
| Main wall thickness | 1.4 – 2.0 mm | Thicker walls for large sashes and high wind loads |
| Glass thickness accepted | about 20 – 60 mm | Double glazing at the low end, triple at the high end |
| Sash size | up to about 1.7 m wide × 2.5 m high (casement) | Limited by hardware load and system test |
| Sash weight | about 80 – 150 kg per sash | Depends on hinge set; concealed hinges usually carry less |
| Whole-window U-value (Uw) | about 1.0 – 2.0 W/m²·K | Calculated to EN ISO 10077 or NFRC 100 at a reference size |
| Air permeability | EN 12207 class 3 – 4 | Casements and lift-slides reach class 4; plain sliders lower |
| Watertightness | EN 12208 class 7A – 9A and above | Higher classes for exposed and high-rise sites |
| Wind resistance | EN 12210 class C3 – C5 | North American equivalents expressed as performance class and grade (e.g. CW-PG50) |
| Sound reduction | about Rw 32 – 45 dB | Mainly set by the glass build-up and number of seals |
Profile alloys and surface finishes
System window profiles are extruded from 6xxx alloys because they flow through intricate dies, harden by ageing and give a smooth surface for coating. 6063-T5 is the standard frame and sash material; 6063-T6 or 6060-T66 is used where higher strength is needed, and 6005A-T6 for heavily loaded mullions. Tight architectural tolerances to EN 12020-2 keep gasket grooves and corner joints consistent from one extrusion batch to the next. See our 6063 aluminium guide for the alloy data.
Polyester powder coating
Wide RAL colour range and good weathering; specify Qualicoat class 1 or AAMA 2603/2604 for standard exposure.
Super-durable powder and PVDF
Better gloss and colour retention for coastal, high-UV and high-rise facades; AAMA 2605 or Qualicoat class 2/3.
Anodising
Hard, metallic oxide surface; use 20 µm or thicker (Qualanod class 20 or 25) for exterior exposure.
Wood-grain transfer
Sublimated wood pattern on a powder base, popular for villas and hotels.
Dual colour
Thermal break profiles allow a different colour inside and outside at no loss of performance.
Black and dark colours
Absorb more heat; check expansion allowances and use dark-colour-rated thermal strips on large frames.
Choosing a system by building type
- Housing and apartments: thermally broken casements or tilt-turns with Low-E double glazing; focus on condensation resistance, insect screens and consistent colour across many floors.
- Hotels: acoustic laminated glass, triple sealing and restrictors; consistent appearance across hundreds of identical rooms.
- Schools and public buildings: robust hinges, restrictors, safety glazing and tilt ventilation for occupied classrooms.
- Offices and commercial buildings: fixed lights with top-hung vents, matched to a curtain wall or ribbon window sightline.
- Plant rooms and service areas: louvre and awning windows for continuous ventilation with drainage.
- Renovation: systems that fit existing openings, colours and opening types, often with flush or slim sashes.
A typical mid-rise residential tender might ask for a 70 mm thermally broken system, Uw ≤ 1.4 W/m²·K with 6-16-6 Low-E argon glass, air class 4, water class 7A, wind class C4 and a super-durable grey finish, all evidenced by test reports for the chosen system and size.
How Metline supplies system window profiles
- ReviewWe check the window schedule, drawings and performance targets against the tested limits of suitable systems.
- ProposeSystem depth, opening types, profile series, gaskets, hardware and finish are proposed, with section drawings for approval.
- ProduceProfiles are extruded, thermally broken or co-extruded as specified and finished to the approved colour.
- ProcessOn request, profiles are cut and machined to the schedule; orders ship as lengths or cut-to-size profiles with matching accessories.
- Inspect and shipDimensions, wall thickness and finish are checked; bundles are labelled by schedule reference and export packed.
Every profile shipment carries a mill test certificate for the alloy, and the finish is documented against the agreed specification.
References and standards
- EN 14351-1 – Windows and doors: product standard, performance characteristics
- EN 12207, EN 12208 and EN 12210 – Air permeability, watertightness and wind resistance classification
- EN ISO 10077-1/-2 – Thermal performance of windows, doors and shutters
- AAMA/WDMA/CSA 101/I.S.2/A440 – North American Fenestration Standard
- EN 14024 – Metal profiles with thermal barrier: mechanical performance
- EN 755-2 – Extruded rod, bar, tube and profiles: mechanical properties
System aluminium (aluminum) windows: frequently asked questions
What is a system aluminium window?
A window built from a matched family of profiles, thermal breaks, gaskets, hardware and drainage parts that were designed and laboratory-tested together. The test report states the air, water, wind and thermal performance for defined sizes and glass, so the result is predictable on site.
How is a system window different from a standard aluminium window?
A standard window combines profiles and fittings chosen by price or stock, with no test evidence for the combination. A system window has fixed components, fabrication rules and test reports, so every unit performs the same and the performance can be proven to inspectors and consultants.
Thermal break or co-extruded: which should I choose?
Thermal break profiles suit commercial, high-rise and high-wind projects because both faces are structural aluminium. Co-extruded aluminium-PVC profiles suit housing, hotels and refurbishment where a warm, decorative interior surface and acoustic comfort are priorities.
Are system aluminium windows energy efficient and quiet?
Yes, when correctly specified. A thermally broken system with Low-E double glazing typically reaches Uw values around 1.2 – 1.6 W/m²·K, and with laminated acoustic glass and triple seals sound reduction of 40 dB or more is achievable.
Can system windows include insect screens and restrictors?
Yes. Most systems have matching screen frames, opening restrictors and child-safety catches designed to fit the profiles without affecting the seals.
What information do you need for a quotation?
The window schedule or drawings with sizes and quantities, opening types, performance targets, glass and hardware preferences, colour and finish, whether you need profile lengths or cut-to-size profiles, and the delivery destination.
Specifying system windows for a project?
Send the window schedule, performance targets, finish and destination. Our team will propose a profile series and quote profiles and accessories.
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