The short answer
For a typical Mumbai flat, uPVC is the better default: it insulates better, damps sound better, needs no maintenance and costs less.
Aluminium earns its place on the openings uPVC struggles with — a full-height balcony wall, a very tall stair window, or a design where the frame is meant to disappear.
Most flats we work on end up with both, and nobody notices.
Heat
This is where the gap is widest, and it is simple physics: uPVC is a poor conductor and aluminium is a good one.
An uninterrupted aluminium section spanning from outside to inside carries the afternoon sun straight through. You can feel it — the frame itself gets warm on a west elevation.
The fix is a thermal break: an insulating strip, usually polyamide, bonded between the inner and outer halves of the profile so the metal path is interrupted. It closes most of the gap, and any aluminium window worth buying in this climate has one. Ask specifically, because unbroken sections are still sold.
Even thermally broken, aluminium does not match a multi-chambered uPVC profile. But by then the glass is doing far more work than the frame either way — see glass options.
Noise
Same direction, smaller margin. The chambers in a uPVC profile damp vibration that a hollow metal section passes along.
Worth keeping in proportion, though. At the same glass specification uPVC is quieter, but the glass build and the seal dominate the result. An asymmetric laminated unit in a well-sealed aluminium frame will beat plain double glazing in uPVC comfortably. If quiet is the goal, spend on the glass before you spend on the frame material.
Spans and sightlines
Here aluminium wins, and it is not close.
Aluminium is stronger, so for the same load it needs less material. That means:
- slimmer sightlines — more glass, less frame, per opening
- wider and taller openings before the section has to get deeper
- lighter sashes for a given pane size, which is easier on the hardware
uPVC compensates with steel reinforcement inside the chambers, and a properly reinforced profile handles most residential openings. But past a certain size the section becomes visibly chunky, and that is the point to switch.
Corrosion, on this coast
Neither is a problem, which is the main reason both have displaced timber and mild steel here.
uPVC cannot rust. Aluminium forms a thin oxide layer that re-forms when damaged, which is why it survives seafront exposure uncoated — see aluminium fabrication.
The genuine risk with aluminium is galvanic corrosion where it contacts steel or stainless in salt-laden damp. That is a detailing problem — isolating washers, correct fastener grades — not a reason to avoid the material.
Finish
uPVC: white as standard, plus woodgrain and solid-colour foils. The colour is in the foil rather than a paint film, so there is nothing to flake.
Aluminium: powder coating in any colour, or anodising for a durable metallic finish in a narrower palette.
Both are maintenance-free in the sense that matters — no repainting, ever. See colour options.
Cost
uPVC is generally lower for equivalent performance. The gap narrows as openings grow, because a large uPVC unit needs heavy reinforcement that an aluminium one does not.
Be careful comparing quotes across materials, though. The specification hidden inside each — reinforcement, hardware grade, glass build — moves the price far more than the material does. Two uPVC quotes can differ more than a uPVC quote and an aluminium one.
So, which?
Answer these and it usually decides itself:
- How wide is the opening? Past a full-height balcony wall, aluminium.
- Does the room face west or south-west? That pushes towards uPVC, or aluminium with a proper thermal break and good solar-control glass.
- Is noise the main complaint? uPVC, and spend the difference on the glass.
- Does the design depend on slim frames? Aluminium.
- Is it a standard bedroom or kitchen window? uPVC, almost always.
We make both in Bhandup West, so there is no answer here we are incentivised to give you. Tell us the opening and what it faces — window types covers how it should open, and best uPVC windows in Mumbai covers what separates a good uPVC window from a cheap one.