Overhangs and Eaves: Shading Windows from the Sun the Right Way

A guide to sizing overhangs and eaves so they block summer sun while letting winter light in.

Overhangs and Eaves: Shading Windows from the Sun the Right Way

A well-placed overhang is one of the oldest and most effective tools in climate-responsive architecture. By extending the roofline past the wall, an eave casts shade over windows during the hottest part of the day while still allowing low-angle light through in cooler months. Done well, it lowers cooling costs and improves comfort without any moving parts.

Why Overhangs Work

The sun sits high in the sky in summer and low in winter. A horizontal overhang takes advantage of that difference. When the summer sun is overhead, the eave blocks direct rays from striking the glass and heating the interior. In winter, when the sun travels a lower path, those same rays slip beneath the overhang and warm the room.

This is passive design: the building does the work through geometry alone, with no energy input.

Orientation Changes Everything

Overhangs are most effective on south-facing windows in the northern hemisphere, where the sun's vertical movement between seasons is greatest. A horizontal eave gives precise, predictable control there.

East and west windows are harder. The morning and afternoon sun strikes them at a low angle, sliding under any horizontal overhang. These openings need vertical shading instead: fins, louvers, screens, deep reveals, or planting. North-facing windows receive little direct sun and rarely need overhangs at all.

Sizing the Overhang

The right depth depends on latitude, window height, and the months you want to shade. A general approach:

- Determine the sun's altitude angle at solar noon on the summer solstice for your location. - Use that angle to calculate the overhang depth needed to fully shade the window at its hottest moment. - Check the same geometry at the winter solstice to confirm the overhang still admits low winter sun.

The goal is a balance: enough projection to block summer heat, not so much that it darkens the room year-round. In practice, an architect runs these angles for the specific site rather than relying on a single rule of thumb, since a degree of latitude shifts the numbers.

Beyond the Simple Eave

Overhangs are one part of a wider shading toolkit. Depending on the climate and facade, designers combine them with:

- Brise-soleil and fixed louvers for fine-tuned daylight control. - Pergolas and trellises that filter light and support seasonal planting. - Deep window reveals that self-shade thick walls. - Adjustable external shutters for changing conditions.

A studio such as MÉTODO Arquitectos treats shading as integral to the facade rather than an add-on, so the overhang reads as part of the architecture and not a bolt-on canopy.

Practical Benefits

A correctly sized overhang reduces solar heat gain, which means less reliance on air conditioning and lower energy bills. It also protects window frames and wall finishes from sun and rain, extending their life. And it shapes the experience inside, softening glare and giving rooms a steadier, more comfortable light.

Getting It Right

The difference between an overhang that works and one that only decorates the facade is calculation. Measure the sun angles for your exact location, size the projection to the windows it protects, and coordinate it with vertical shading where the sun strikes low. The result is a building that stays cooler in summer, warmer in winter, and uses less energy in every season.