Eave Solar Protection Brazil Calculator

Eave depth for solar shading in Brazil

How deep the eave has to be to block the summer sun while still letting the winter sun through comes down to the latitude and the solar altitude angle at noon in each season: depth = window_height / tan(α_summer). In São Paulo (-23.5°), the December noon sun sits about 90°-(23.5°-23.5°) = 90° above the horizon, so a 0.4 m overhang is enough to shade a 2 m window. Recife (-8°) gets a much higher sun, and there 0.2 m already does the job on the same window. That angle shifts across the year as the solar declination changes.

An eave only really earns its keep on the equator-facing facade, which is the north one in Brazil and the south one in the Northern Hemisphere. East and west facades are a different story: the sun comes in low at sunrise and sunset, where a horizontal eave does nothing. There you reach for vertical fins (brise-soleil), louvers or pergolas.

Applications

Bioclimatic architecture, NBR 15220 (thermal performance) and NBR 15575 (housing performance), passive cooling in tropical climates, LEED and AQUA-HQE certification, and retrofits of facades that overheat.

FAQ

Why not just install AC? A well-sized eave stops the solar gain before it ever reaches the inside, which trims the AC load by 20-40% in tropical climates.

Does the overhang block winter sun in southern Brazil? A little. The geometry tends to slip the low winter sun in under the eave on its own. At higher latitudes like Porto Alegre (-30°), check both solstices to be sure.

What about glass-only facades? Put the louvers or pergolas on the outside. Internal blinds soak up the heat and then re-radiate it right back into the room.