Afternoon west sun doesn't just cause glare — it transfers a large amount of heat into the wall structure, noticeably warming interior spaces even after sunset, a phenomenon known as "thermal lag".
Why the louvers need to stand off from the wall
The core principle is creating an air buffer between the louvers and the wall, typically 400-600mm apart. This air layer convects continuously, carrying heat absorbed by the louvers away before it can transfer into the main structure — very different from curtains or heat-reflective film applied directly to the glass.
Precast concrete versus other louver materials
Wood louvers look beautiful but warp and degrade quickly under harsh sun. Aluminum louvers are light and quick to install but conduct heat, and can become a secondary heat source if designed poorly. Precast concrete has high thermal mass, weathers well, and needs almost no maintenance for decades.
Calculating louver angle and spacing
Sun-blocking effectiveness depends on the tilt angle and spacing between louver blades, calculated from the sun's angle at a given latitude and season — not a fixed number that applies to every project. Louvers set at the wrong angle can still block light while letting heat through.
The upfront cost of a concrete louver system is higher than curtains or heat film, but the payback period is usually just 3-5 years thanks to significantly lower air conditioning running costs — not to mention a lifespan many times longer.
