When a project reaches the window package, the first question is often a material one: aluminium or uPVC? Both are widely used in India, both have loyal advocates, and both can perform well or badly depending on how they are designed and built. Comparing them by reputation alone usually leads to an unhelpful argument.
This article sets out how the two materials differ, where each tends to suit, and how to compare offers fairly. It does not pick a winner. The aim is to help architects, developers and homeowners ask better questions of their suppliers, so the decision is made on the needs of the building rather than habit.
Two different materials
Aluminium window frames are made from extruded aluminium profiles, cut, machined and joined into frames. The metal is strong and stiff for its weight, which allows slim profiles and large openings. On its own it conducts heat readily, so performance-focused systems use a thermal break, an insulating strip that separates the inner and outer parts of the frame.
uPVC frames are made from extruded rigid plastic profiles with several internal chambers. The material itself is a poor conductor of heat, which gives uPVC a natural insulation advantage. It is less stiff than aluminium, so larger or heavier windows usually have steel reinforcement inside the main chambers. Corners are typically welded, which forms a continuous sealed joint.
Neither description makes one material superior. They are different engineering approaches to the same problem: holding glass, keeping weather out and opening reliably for many years. Each has strengths that suit some buildings better than others, and each has quality grades ranging from basic to very good. A well-made window in either material will outperform a poorly made one in the other.
Size, weight and sightlines
Opening size is often where the decision starts. Aluminium's stiffness lets it span larger openings and carry heavier glass with narrower frames. That makes it common for tall sliding doors, wide fixed panes and window walls where slim sightlines are part of the design. Many commercial facades use aluminium for that reason.
uPVC frames are generally deeper and wider for the same opening, because the material needs more section to stay stiff. For typical residential windows this is rarely a problem and the frame proportions can look entirely appropriate. For very large panels or minimal-frame designs, a uPVC system may reach the limit of its approved sizes sooner. Each profile system publishes its own size limits, and these should be checked against the actual openings.
Heat, sound and air
For heat flow through the frame, uPVC starts with an advantage because the material insulates. Aluminium without a thermal break is a clear step behind. A well-designed thermally broken aluminium frame narrows that difference, though it adds cost and complexity. The comparison should be made between the specific systems on offer, using data the supplier can show, rather than general claims about either material.
It also helps to keep the frame in proportion. Glass usually makes up most of a window's area, so the glazing build-up, coatings and edge spacer often affect overall performance as much as the frame does. Sound insulation and air tightness depend heavily on the glass, the seals and how the opening sash closes. A casement window compresses its seals when locked, while a sliding window relies on brushes and sliding seals; that difference can matter more than the frame material. The trade-offs are explored in casement or sliding windows.
Climate, sun and expansion
Indian climates are demanding for any window: strong sun, heavy monsoons, dust and, in coastal cities, salt. Both materials can handle these conditions when the right grade of product is chosen. uPVC profiles intended for outdoor use contain stabilisers against sunlight, and the quality of that formulation differs between suppliers. Ask what the profile is designed for and request evidence that relates to the intended exposure.
Plastics expand more with heat than aluminium does. On a long frame in direct sun, particularly in darker colours, this movement needs to be allowed for in reinforcement, fixings and the perimeter joint. Aluminium also moves with temperature, just less. In either case the installer should follow the system supplier's guidance on fixing spacing and joint widths. Coastal projects should also review hardware and fixings, as described in corrosion and coastal exposure.
Finishes and appearance
Aluminium offers a wide range of finishes: powder coating in almost any colour, anodising for a metallic look, and PVDF coatings for demanding exposures. Inside and outside faces can often be finished in different colours on thermally broken frames. The options are covered in anodised, powder-coated or PVDF.
uPVC is most often supplied in white, with coloured and wood-effect foils or coatings available from many suppliers. These finishes have improved and can look convincing, but the range is narrower and the colour is usually applied to the surface rather than through the material. Ask how a coloured uPVC finish behaves in strong sun and how a scratch would be repaired.
Hardware, security and opening types
Both materials support casement, tilt-and-turn, sliding and fixed windows, though not every system offers every type. Hardware quality matters greatly in either material. Hinges, rollers, locks and handles should be matched to the sash weight and the exposure. In uPVC frames, screws for hardware typically need to reach into reinforcement or purpose-designed chambers to hold well.
Large lift-and-slide or multi-panel doors are more commonly built in aluminium because of the weights involved, though some uPVC systems offer sliding doors within defined limits. For a villa or apartment with a wide balcony opening, it is worth confirming early which material and system can meet the size. Typical considerations for homes are set out in aluminium windows for villas and low-rise homes.
Fabrication and installation quality
The material is only one part of the window. Two aluminium windows from different fabricators, or two uPVC windows from different suppliers, can perform very differently. Cutting accuracy, corner joints, drainage slots, gasket fitting and glazing all affect the result. Visiting the fabrication workshop, or inspecting a sample window, often tells a buyer more than a brochure.
Installation is equally important. Windows need to be fixed square and level, with the perimeter joint sealed according to the system's detail and drainage outlets kept clear. Many leaks blamed on a material are actually perimeter or sill problems. The window drainage article explains where water should go.
How to compare offers fairly
- Compare complete window systems, not materials in general.
- Check each system's published size limits against your largest openings.
- Ask for performance data for the specific profile and glass combination offered.
- Confirm the finish options and how each behaves in sun and, if relevant, near the coast.
- Review the hardware specification for sash weight and exposure.
- Inspect a sample window, including a corner joint and the sill drainage.
- Ask how the installer fixes and seals the perimeter, and request the detail drawing.
Price comparisons should be made on the same scope. Glass, hardware, insect screens, installation, sealing and site protection can each be included or excluded, and a lower headline figure sometimes simply leaves something out. A clear schedule of what is included makes the comparison honest.
Ask about after-sales support as well. Seals, rollers and hinges eventually need adjustment or replacement in any window. A supplier who keeps spare parts, documents the system clearly and can send a technician years later is worth more than a small saving at tender. The same question applies equally to aluminium and uPVC suppliers.
Choosing for the building
Some projects mix both materials: uPVC for standard bedroom windows and aluminium for large living-room sliding doors, for example. That can work well if the appearance is coordinated and each installer understands the interfaces. Others standardise on one material for consistency. Neither approach is wrong in principle.
The most useful starting point is a clear brief: opening sizes, the look the architect wants, climate exposure, performance targets and budget. With that in hand, suppliers of both casement windows and sliding windows and doors can propose systems, and the comparison becomes a practical one rather than a debate about materials.
General guidance for orientation, not a specification. Applicable standards, values and details are confirmed per project with the facade consultant.
