Do Exterior Sunshades Really Cut Cooling Loads That Much?

Exterior sunshades block solar radiation before it enters the building, which makes them the most effective passive cooling strategy for glazed facades — more effective than interior blinds or high-performance glass alone. The engineering has four parts: solar geometry that sizes and angles the shade for the orientation and latitude, structural design for the significant wind loads on a projecting device, thermally broken and watertight attachments through the envelope to the building frame, and integration with daylighting so the shade cuts heat without killing natural light. Done right, sunshades shrink mechanical systems, cut energy bills, and give the facade its character. Done wrong, they are expensive sculpture that leaks at every attachment.

Solar geometry is the design driver: sun angles for the latitude, shade depth and tilt for each orientation, and the balance between blocking summer sun and admitting winter sun and daylight. I run the shading analysis before the shade profile is finalized — the architecture follows the physics, not the reverse. Wind loading is the structural reality check. A projecting shade sees full wind pressure and suction, plus local effects at the facade, and the outriggers carry it all back to the frame. Attachment detailing is the building-science crux: every outrigger breaches the air barrier, water barrier, and insulation, so thermal breaks prevent the steel from becoming a heat highway and flashing keeps water out. The shade itself needs drainage and expansion detailing — aluminum shades move with temperature, and trapped water stains everything below.

Sunshades sit at the intersection of energy, structure, and architecture. My requirements keep all three honest.

• Solar geometry analysis for the actual latitude and orientation before the shade profile is locked
• Structural design of shades and outriggers for full wind load, with attachments to the building frame
• Thermal breaks and flashing at every envelope penetration — detailed in section, not just noted
• Energy model documenting the SHGC reduction and the mechanical downsizing it enables
• Daylighting check so the shade controls heat without darkening the interior