Two Materials, Two Philosophies
Aluminium windows are made from extruded aluminium alloy profiles — typically 6063-T5 for architectural systems. Modern systems for air-conditioned buildings use a thermal break: polyamide strips that separate the inner and outer profiles to reduce heat transfer.
uPVC (unplasticised polyvinyl chloride) windows are made from extruded plastic profiles with several internal chambers. Because PVC itself is a poor conductor of heat, the frame insulates well, but the plastic is not stiff enough on its own, so most uPVC profiles contain galvanised steel reinforcement inside.
Both can deliver good results. The differences show up most clearly in hot climates, in large openings and over the long term.
Heat and Thermal Insulation
uPVC has a natural advantage: the frame material is a poor conductor, so even a basic profile insulates reasonably. Standard non-insulated aluminium, by contrast, conducts heat very well and is a poor choice for air-conditioned rooms.
A thermal break aluminium frame closes most of this gap. With polyamide barriers, deeper frames and good double glazing, thermally broken aluminium is well suited to Gulf villas and buildings. Remember also that glass is usually most of a window's area, so the glass specification often influences heat gain more than the frame material does.
UV Exposure and High Temperatures
This is where the Gulf climate tests uPVC hardest. Summer sun in Muscat, Dubai and Abu Dhabi is intense, and frame surfaces in direct sun become much hotter than the air around them.
- uPVC softens at temperatures far lower than aluminium, and its thermal expansion is considerably higher. Long frames and dark colours in full sun are the most exposed to movement and distortion
- Long-term UV exposure can cause some uPVC formulations to fade, yellow or become brittle; quality depends heavily on the compound and stabilisers used
- Aluminium remains dimensionally stable at any temperature a façade will reach, and the long-term appearance depends on the coating — fluorocarbon (PVDF) and quality powder coatings are designed for strong UV exposure
Strength, Sizes and Sightlines
Aluminium is much stiffer and stronger than uPVC. In practice this means:
- Larger panels: aluminium systems can carry heavy, large glass units. For example, the T127-90 thermal break lift & slide door supports panels up to 400 kg
- Slimmer sightlines: a narrower aluminium profile can do the job of a much bulkier uPVC profile, giving more glass and less frame
- Wind loads: taller buildings and exposed coastal sites need stiff frames; aluminium is the usual choice for high-rise and commercial façades
- Special systems: curtain walls, lift & slide doors, folding doors, pivot doors and slim minimal frames are predominantly aluminium
uPVC is generally best suited to small and medium window sizes in low-rise buildings.
Finishes and Colours
Aluminium accepts powder coating, fluorocarbon (PVDF), anodising and wood grain finishes in virtually any colour, and different colours can be used inside and outside. uPVC is usually white or foiled with a laminate film; darker colours on uPVC absorb more heat, which adds to the expansion issue in strong sun.
Lifespan and Maintenance
Well-specified aluminium systems with quality finishes and hardware are known for long service lives with minimal maintenance: occasional cleaning, clear drainage slots and hardware lubrication. uPVC also requires little maintenance, but its long-term behaviour in very high UV and heat depends strongly on the quality of the compound. In both cases, hardware, seals and installation quality often determine service life as much as the frame material.
Fire Behaviour
Aluminium is non-combustible. uPVC is a plastic: many formulations are self-extinguishing, but when exposed to fire it softens and can produce dense smoke and corrosive gases. For high-rise and public buildings, check the fire requirements of the local authority in Oman or the UAE with your consultant before selecting frame materials.
Recyclability
Aluminium can be recycled repeatedly without losing its properties, and aluminium scrap has a well-established recycling market. uPVC can also be recycled, but recycling of window profiles is less common and the material cannot be reprocessed indefinitely. For projects pursuing green building ratings, recycled content and end-of-life recyclability usually favour aluminium.
Cost
uPVC windows are often cheaper per square metre for standard sizes. Thermally broken aluminium generally costs more but offers larger sizes, slimmer frames, more finishes and higher structural capacity. The fair comparison is cost against required performance, size and lifespan — not price alone.
Summary Comparison
| Criterion | Thermal break aluminium | uPVC |
|---|---|---|
| Frame thermal insulation | Good, with polyamide thermal break | Good, naturally insulating |
| Stability in high heat | Very stable | Higher expansion; softens at lower temperatures |
| UV resistance | Depends on coating; PVDF and quality powder coat perform well | Depends on compound quality; may fade or yellow |
| Strength and stiffness | High | Lower; usually needs steel reinforcement |
| Maximum panel sizes | Large, including heavy lift & slide panels | Small to medium |
| Sightlines | Slim profiles possible | Bulkier profiles |
| Colour options | Very wide, inside and outside | More limited; mostly white or foiled |
| Fire | Non-combustible | Combustible plastic; smoke when burning |
| Recyclability | Highly recyclable | Recyclable but less commonly recycled |
| Typical initial cost | Higher | Lower for standard sizes |
Where Each Material Makes Sense
uPVC can be a reasonable choice for small to medium windows in low-rise, budget-sensitive residential projects, in light colours and on less exposed elevations.
Aluminium is the stronger choice for villas with large openings, contemporary designs with slim frames, dark colours, high-rise and commercial buildings, coastal sites with high wind exposure, and any project where long-term stability under intense sun is a priority.
Alminyar Recommendation
For villas and buildings in Oman and the UAE, we recommend thermal break aluminium with good double glazing — it combines the insulation that air-conditioned buildings need with the strength, stability and finishes that the Gulf sun demands. Our casement windows from the S11 to the Q35 cover everything from cost-conscious villas to premium projects. If you are comparing an aluminium quotation with a uPVC one, send us both and we will help you compare like for like.