Brise-Soleil Visualizer
Interactive cut-off angle calculator for horizontal louvre shading. Adjust louvre depth, spacing, and sun altitude to see exactly when direct sun is blocked from a glazed façade — critical for ECBC SHGC compliance and climate-responsive Indian envelope design.
Cut-off angle
45.0°
θ = arctan(S/D) = arctan(600/600)
Status at 60° sun
Full shading
Direct sun fully blocked from the glazing
Controls
Tropical India noon-summer ≈ 75–85°. Winter ≈ 35–45°.
Horizontal projection from the wall.
Vertical distance between louvres.
Façade orientation
Target cut-off angle
30–45°
Block summer noon sun (altitude 70°+ in tropical India) but admit low winter sun for solar gain in cold/composite zones.
Reading the cut-off angle
Above cut-off
Sun altitude exceeds the cut-off angle. Direct radiation is fully blocked from the glazing — the louvres cast long shadows across the wall. This is the design state for summer noon.
Below cut-off
Sun altitude is lower than the cut-off. Some direct sun passes between the louvres and strikes the glazing. Useful for winter passive solar gain in composite and cold zones.
Design rule
Pick D and S so the cut-off equals the lowest summer altitude you want blocked at your latitude. In tropical India, target 30–45° on south façades. Deeper / closer-spaced louvres = lower cut-off = more aggressive shading.
The geometry
For horizontal louvres of depth D and vertical spacing S, the cut-off altitude angle θ — the lowest sun angle at which direct sun is fully blocked — is:
Sun altitudes greater than θ are fully shaded; lower altitudes admit direct sun between the louvres. The same geometry underlies horizontal chajja design in vernacular Indian architecture and the brise-soleil tradition formalised by Le Corbusier at the Mill Owners’ Association building in Ahmedabad (1954) and by Charles Correa in Bombay practice.
Note: this tool models direct-beam shading geometry only. Diffuse sky radiation (which accounts for 30–50% of total in humid conditions) is unaffected by louvres and requires separate strategies — see the related guide.
Related guide
Hospital Façade & Daylight Design in India
Climate-responsive envelope strategy across India’s five climate zones, the shading device library (overhang / fin / jaali / brise-soleil / verandah / BIPV), courtyard organisation, ECBC compliance.
Read the façade guide →