What open area should I start from?

30–40% for a general facade. It shades effectively, reads as a surface rather than a mesh, and passes enough daylight to be comfortable behind. Move down for west-facing elevations needing more shading, and up where ventilation dominates.

Will a perforated screen stop solar gain?

It reduces it roughly in proportion to the solid area, so a 30% open panel blocks around 70% of direct radiation — plus the benefit of shading the wall behind it. It is not a substitute for glazing specification, but it is a substantial contributor.

Can you match a pattern on an existing building?

Usually. Send photographs with a scale reference — a known dimension in frame — and we can work back to the hole size and pitch, then confirm whether it sits within our tooling.

Open area, daylight and privacy in perforated facades

A perforated facade does four things at once — shades, screens, ventilates and is seen. Open area is the single number that trades them against each other.

5 min read · updated 30 October 2026

Specify a perforated facade by hole size alone and the result is a surprise. Specify it by open area and the behaviour is predictable, because open area is what governs how much light passes, how much solar gain is blocked, and how transparent the skin appears.

What open area does

Open area	Reads as	Typical use
10–20%	Solid surface with texture	Signage backing, feature cladding
20–30%	Dense screen, strong shading	West facades, privacy screens
30–40%	Balanced — the common choice	General rainscreen and facade
40–50%	Visibly open, light shading	Car park screening, balustrades
50–70%	Mesh-like, minimal shading	Ventilation screens, plant enclosures
Above 70%	Essentially open	Consider expanded metal instead

Why the view works in one direction

A perforated screen is far more transparent from the darker side. Standing inside during the day, you see out easily; from outside in daylight the panel reads as nearly solid. After dark, with interior lights on, that reverses entirely.

Hole size, separately from open area

Two panels can share an open area and look nothing alike. Open area sets the quantity of light; hole size sets the grain. Small holes at close pitch read as a smooth tone from a distance and resolve into texture up close. Large holes at wide pitch stay legible as a pattern from the street.

Viewing distance should drive hole size — the further away, the larger the hole needed to remain legible.
Fine patterns on tall facades tend to read as flat grey and lose the designed effect.
Hole size cannot go below sheet thickness, which sets a floor on how fine the pattern can be.

Practical constraints worth knowing early

Maximum panel size is 2200 × 4000 mm — worth checking before the facade is set out.
Above 60% open area, sheets bow during perforation and need levelling; allow for it in the programme.
Coating is applied after perforation, so cut edges are covered rather than bare.
Aluminium is about a third the weight of steel, which lightens the support structure.
In coastal Mumbai, exterior stainless should be 316 rather than 304.

Graduated and image patterns

Open area can be varied across a facade — denser where shading or privacy is needed, more open where daylight matters, or modulated to render an image at building scale. It is genuinely achievable with CNC perforation, but it needs the variation defined numerically in the drawing rather than as a rendered image, and every zone still has to obey the same minimum-ligament rule.

You do not have to do this by hand — we built the calculator that runs these numbers.

Try a pattern

Common questions

What open area should I start from?: 30–40% for a general facade. It shades effectively, reads as a surface rather than a mesh, and passes enough daylight to be comfortable behind. Move down for west-facing elevations needing more shading, and up where ventilation dominates.
Will a perforated screen stop solar gain?: It reduces it roughly in proportion to the solid area, so a 30% open panel blocks around 70% of direct radiation — plus the benefit of shading the wall behind it. It is not a substitute for glazing specification, but it is a substantial contributor.
Can you match a pattern on an existing building?: Usually. Send photographs with a scale reference — a known dimension in frame — and we can work back to the hole size and pitch, then confirm whether it sits within our tooling.