Which material blocks more sunlight while keeping airflow: expanded metal grating or perforated sunshades?
Every architect has fought this battle: the client wants a bright, naturally ventilated building — but not the glare, heat gain, and UV damage that come with it. Sunshading is the obvious answer, yet the material choice is rarely obvious. Two options dominate the conversation: expanded metal grating and perforated sunshades. Both filter light. Both let air move. But they behave very differently under the Australian sun, and choosing wrong means either a building that overheats or a façade that underperforms. Let’s put them head to head.
Why the Sunlight–Airflow Trade-Off Matters
Sunlight is not the enemy — uncontrolled sunlight is. Left unchecked, solar radiation through glass drives cooling costs up, fades interiors, and turns west-facing rooms into greenhouses. The temptation is to block it all with solid screens, but that creates a second problem: stagnant air, trapped heat, and a façade that fights the building instead of serving it. The best sunshading strategy blocks the harsh rays while letting breezes do their cooling work — which is exactly where these two materials split.
How Each Material Works
Expanded Metal Grating
Expanded metal grating begins as a solid sheet that is slit and stretched into a lattice of interlocking diamond-shaped strands. No material is removed, so the sheet gains rigidity as it gains openness. As a sunshade, it delivers:
- Serious UV blocking — the dense strand pattern can intercept up to 99% of UV radiation, making it one of the most effective open sunscreens available
- Outstanding airflow — the open structure lets wind pass almost freely, preventing heat from banking up against the façade
- Serious longevity — corrosion-resistant finishes and a weld-free structure mean decades of service with minimal upkeep
The trade-offs: views through it are filtered rather than open, and in exposed locations the strands can sing or rattle in high wind.
Perforated Sunshades
Perforated sunshades are flat sheets — usually aluminium or steel — punched with regular patterns of small holes. They function differently:
- Moderate UV blocking — typically topping out around 80%, since light passes through the perforations directly
- Restricted airflow — the small holes let some air through, but far less than an open grating
- Design flexibility — hole size, spacing, and arrangement can be customised to tune light transmission, and the flat surface takes almost any colour beautifully
- Quiet operation — the flat profile generates far less wind noise, which matters in residential or hospital settings
Side-by-Side Comparison
| Factor | Expanded Metal Grating | Perforated Sunshades |
|---|---|---|
| UV radiation blockage | Up to 99% | Up to ~80% |
| Airflow | Excellent | Limited |
| Visual transparency | Filtered views | More transparent at eye level |
| Wind noise | Can rattle in exposed sites | Very quiet |
| Design flexibility | Gauge and pattern options | Fully customisable hole patterns |
| Maintenance | Very low | Low (holes can trap dirt) |
| Best suited to | Harsh sun, hot climates, industrial sites | Design-led façades, noise-sensitive areas |
Which One Should Your Project Choose?
There’s no universal winner — only a best fit. In practice, the decision resolves quickly once you know which priority is non-negotiable: maximum solar protection, or aesthetics and acoustics. Work through the priorities in order and the material usually selects itself:
Practical Tips for Getting the Best of Either Material
Whichever way you lean, a few details separate a good installation from a great one:
- Angle matters more than material — horizontal louvres or angled screens block high summer sun while admitting low winter light, multiplying the effectiveness of either product
- Stand off the glass — leave an air gap between the screen and the window so heated air can escape upward
- Match the gauge to the span — oversized panels on undersized supports will flex and buzz; get the engineering checked
- Specify the finish for the site — coastal and industrial locations demand marine-grade coatings on either material
Frequently Asked Questions
Can perforated sunshades block enough sun for west-facing façades? They can, but typically as part of a system — combined with fritted glass or deeper reveals — rather than on their own, given their ~80% UV ceiling.
Does expanded metal grating make rooms dark? It filters rather than blocks visible light. Interior daylight levels stay comfortable while glare and UV drop sharply — most occupants notice the softer light, not less of it.
Which material is cheaper? Expanded metal grating is generally more economical per square metre, since the stretching process adds no material cost, while perforating adds a manufacturing step.
The Final Word
If the brief is maximum sunlight blocking with genuine airflow — think west-facing façades in hot climates, industrial facilities, sun-blasted school buildings — expanded metal grating is the stronger performer, and it isn’t close. If the brief leans on clean aesthetics, design customisation, and acoustic comfort in sensitive settings, perforated sunshades earn their place, accepting a modest sacrifice in UV performance and ventilation. Decide which priority your building can’t compromise on, and the material question answers itself.
