Daylighting and Floor Plan Design for Author Residences in CDMX

A floor plan drawn without a daylighting analysis is a guess. In Mexico City, where urban lots are bounded by neighboring structures and the sun travels from a southern arc at this latitude, the quality of light in every room is a consequence of decisions made in the first diagrams — decisions that cannot be corrected cheaply after construction begins.

In MÉTODO, the floor plan for a casa de autor begins with the sun. Everything else follows.

Mexico City's Solar Geometry

At 19 degrees north latitude, Mexico City's sun is consistently in the southern sky throughout the year. The sun never crosses north of the zenith — it always has a southerly component. This means:

• South-facing rooms receive direct sunlight for the largest portion of the day
• North-facing rooms receive only diffuse sky light — cooler, consistent, and glare-free
• East-facing rooms receive morning sun that rakes across surfaces at low angles
• West-facing rooms receive afternoon sun — warm but potentially overheating in the dry season

The seasonal variation matters less than in northern latitudes. CDMX has a mild climate with no extreme winter cold, so solar gain is a comfort benefit in December mornings but not a survival necessity. The design problem is predominantly about light quality, not heating.

The Urban Lot Problem

Most authored residential projects in Mexico City occupy infill urban lots — narrow, deep, bounded on two or three sides by existing structures. The floor plan cannot simply open windows on all sides. It must solve the daylighting problem vertically.

The tools for vertical daylighting on urban lots:

• Central patios that bring light to rooms facing the interior, not the street
• Narrow courtyards between the building and the property line — even 90 cm of clear space between two walls allows diffuse sky light to enter rooms below clerestory height
• Skylights and light wells that introduce overhead light to central rooms
• Clerestory windows above the roofline of neighboring structures, receiving unobstructed sky light

The section is more important than the plan on these sites. The section drawing shows which rooms can receive direct light and at what time of year, and it shows where the shadows from neighboring buildings fall across the facade.

The Floor Plan Emerges from the Section

In our process, the floor plan for a residence in CDMX follows this sequence:

1. Sun path diagram for the lot — where is south? What is the altitude of the sun at 9 am in December, 3 pm in June?
2. Shadow study — where do neighboring buildings cast shade, and at what hours?
3. Section diagram — what roof profile allows light to enter primary spaces over the neighboring structure's roofline?
4. Program allocation — primary living, dining, and sleeping spaces placed where light quality is best
5. Service allocation — kitchen (which has its own heat), bathrooms, utility, and storage placed in the darker zones
6. Floor plan development — the plan is the projection of decisions already made in section

This sequence is the opposite of the conventional approach, which draws the floor plan first and asks about windows second. In an authored residence, the sequence matters: process before style.

Light as Spatial Structure

In a casa de autor, natural light is not a background condition — it is a spatial event. A specific room receives specific light at a specific time of day. A south-facing living room on the second floor, raised above the height of the street wall, receives low winter morning sun that sweeps across a stone floor and reaches the north wall by 10 am. This is designed, not discovered.

The design tools for creating spatial light events in CDMX residences:

• Patio as light distributor: a central patio at first floor level receives direct midday sun from above; rooms on all four sides receive reflected light from the patio walls
• Light shelf: a horizontal projection at window head height reflects light deeper into the room while blocking direct sun from entering below the shelf
• Double-height space: a tall space connected to a high-level window brings light down to the lower floor level without a direct window at that level
• Rooftop terrace with translucent floor panels: in single-story buildings over a lower floor, translucent glass or polycarbonate panels allow diffuse light to reach spaces below

The Authored Floor Plan as Document

A floor plan for a casa de autor is not a layout — it is a document of decisions. Each room carries information: what light it receives, at what time, with what quality. The section carries the same information in elevation.

When we present a floor plan at design development stage, every spatial decision can be traced back to a sun angle, a shadow line, or a material behavior. This traceability is what makes the design authored rather than generic.

Próximos pasos

If you are planning a residence in Mexico City and want the floor plan to be a response to your specific lot and its light conditions — rather than a template adapted to your program — the daylighting analysis must happen first.

Conoce el método de MÉTODO to understand how we develop the floor plan as a consequence of sun, section, and program — in that order.