The shade percentage question in a residential courtyard has a precise answer — not a feeling, not a general principle, but a number that can be calculated for any courtyard geometry, orientation, and latitude. At MÉTODO, we run this calculation at schematic design, before any shade structure is sized or specified.
What Shade Percentage Actually Means
Shade percentage is the fraction of courtyard area that falls in shadow at a specific moment: a given date, hour, and sun angle. It changes continuously through the day and through the year. The useful question is: what percentage of the courtyard seating area is in shade during the hours it will be used?
For most residential courtyards in Mexico City or CDMX highland climate, the critical window is late morning through mid-afternoon from April through October. At solar noon during the spring-summer period, a courtyard with zero shade overhead receives direct radiation at 900 to 1,000 watts per square meter. A person sitting in that space will move inside within 15 minutes regardless of how well the courtyard is designed.
For a seating or dining area to remain usable, at least 60 percent of the seating surface should be in shadow during peak sun hours. For children's play areas, we use a higher threshold of 75 percent. For purely circulatory spaces, 40 percent is sufficient.
Calculating Shade Percentage in Practice
The calculation requires four inputs:
- Courtyard geometry (plan dimensions, wall heights, orientation)
- Geographic latitude
- Target date and hour
- Shade structure geometry (pergola, roof overhang, tree canopy)
For Mexico City at 19 degrees north latitude, solar altitude at noon on June 21 reaches approximately 88 degrees — nearly vertical. This means vertical walls provide almost no shade at noon during summer. Shade must come from horizontal or near-horizontal elements: roof overhangs, pergola lattices, tree canopies.
At the winter solstice, solar altitude at noon drops to 42 degrees. Vertical elements — tall walls, a narrow courtyard section — become effective shade providers.
This is why the section drawing is more important than the plan for courtyard shade analysis. La sección como relato — the section tells you what time of year each surface is in sun or shade.
Shade Structure Options and Their Actual Coverage
Different shade structures produce different shade percentages. Common assumptions often overestimate shade coverage:
- Solid roof or polycarbonate: provides 95 to 100 percent shade below the covered area. Effective but changes the sky condition and may require artificial light during daytime.
- Pergola with 30 percent lattice coverage: typically provides 20 to 30 percent actual shade at noon.
- Pergola with 60 percent lattice coverage: typically provides 45 to 55 percent actual shade at noon.
- Mature canopy tree (deciduous): provides 50 to 80 percent shade at peak summer, zero shade in winter — useful for buildings that benefit from winter solar gain.
- Adjustable sail shade: variable coverage, typically 70 to 90 percent directly below when deployed at correct angle.
The matrix de opciones for shade structure should compare these against the target shade percentage and the courtyard program. A static pergola that delivers 45 percent shade is not adequate for a dining courtyard in CDMX without supplemental sail shades or a partial solid roof.
Thermal Comfort Beyond Shade Percentage
Shade percentage is a necessary condition for courtyard comfort, not a sufficient one. Three additional factors determine whether a shaded courtyard is thermally comfortable:
Radiant temperature of surrounding surfaces: A courtyard shaded from direct sun but surrounded by dark stone walls in full sun will still feel hot. The walls absorb radiation and re-emit it as long-wave heat. Light-colored or textured materials reduce surface temperature and radiant heat gain.
Air movement: Natural ventilation through the courtyard — openings at both high and low positions in the enclosing walls — creates convective cooling that dramatically improves comfort even at high air temperatures. A shaded courtyard with good cross-ventilation is comfortable. A shaded courtyard with stagnant air in a hot zone is not.
Evaporative cooling: Water surfaces, vegetated walls, or planted ground cover increase evaporative flux and lower ambient temperature. We design for this as a supplemental comfort strategy in high-shade-requirement courtyards.
Próximos pasos
Shade percentage calculation belongs at schematic design, not at permit or construction document stage. By the time you are detailing a pergola structure, the overall shade strategy should already be resolved.
Conoce el método de MÉTODO and how we integrate solar analysis, material selection, and ventilation design from the earliest project phases.