Building on a small urban lot demands creative solutions that standard suburban construction rarely requires. When a young couple in Puebla, Mexico sought a refuge from the chaos of city living, their 150 square meter property presented a familiar challenge: rising land values drive lot sizes downward while expectations for quality living space remain high. In Puebla’s rapidly growing real estate market, where the construction sector has expanded dramatically and land prices have climbed accordingly, projects need to pack more livability into smaller footprints. The 249 square meter, three-story residence that resulted demonstrates how passive house architecture principles translate to compact urban infill sites where every square meter must earn its place.
Space Optimization Through Subtractive Design
The architects started not by adding spaces but by subtracting them. Working from the full architectural program, they removed elements until the essential core remained. The resulting floor plan forms an “I” shape that carves courtyards and light wells into the building mass rather than accepting them as leftover space. This subtractive approach, sometimes called “design by removal,” ensures that every void serves a purpose rather than being a byproduct of the building envelope.
The I-Shaped Floor Plan
The I-shaped layout creates two parallel built volumes connected by a central circulation spine. The gaps between these volumes become courtyards that deliver natural light and ventilation to the interior rooms. This configuration is especially effective on narrow lots where a solid rectangular block would leave the center permanently dark and stale. By splitting the mass, the design achieves what a solid block cannot: every room has at least two exposures, and the courtyards bring the outdoors into the heart of the house.
Programming the Voids
The courtyards serve specific functions beyond light and air delivery. One courtyard centers on an Acacia tree that provides shade in summer and, when it blossoms purple in spring, becomes a focal point visible from multiple rooms. Another patio extends the ground floor social areas outward, effectively doubling the living space during favorable weather. The design demonstrates that the spaces between buildings are as important as the buildings themselves.
Natural Lighting Strategies for Narrow Urban Lots
Urban infill sites often have neighbors on both sides, limiting window placement on the side elevations. The Casa Once design addresses this through its I-shaped plan, which creates interior-facing windows that open onto the courtyards rather than the neighboring properties. This approach provides abundant natural light without compromising privacy or dealing with setback restrictions that limit exterior wall openings.
| Lighting Strategy | Application in Casa Once | Benefit |
|---|---|---|
| Courtyard-facing glazing | All rooms open to at least one courtyard | Privacy without light loss |
| Vaulted ceiling bounce | Entry facade vault redirects light inward | Diffuse illumination, no glare |
| Open stairwell | Vertical circulation doubles as light shaft | Light reaches all three levels |
| Glass screens at ground level | Interior-exterior boundary uses full-height glass | Visual continuity with courtyard |
The Vaulting Detail
The facade includes a vaulted element that bounces light back into the studio space. This detail, common in traditional Mexican architecture, redirects incoming sunlight upward and across the ceiling rather than casting a harsh beam on the work surface below. The vault acts as a light shelf, distributing illumination evenly throughout the day. The careful joinery and precise execution of this and other architectural details relied on skilled carpentry – the kind of craftsmanship that connects modern design with traditional woodworking techniques that have shaped quality construction for generations.
Cross-Ventilation and Passive Climate Control
Puebla’s climate sits at a high elevation of roughly 2,100 meters, offering moderate temperatures year-round that make natural ventilation a viable primary cooling strategy. Daytime highs average 24°C to 27°C while nights drop to 6°C to 10°C, creating a diurnal temperature swing of 15°C or more that passive systems can exploit. The I-shaped plan creates paths for moving air across the entire width of the building. Courtyards at each end of the “I” produce pressure differentials that drive airflow through the rooms even on still days.
User-Controlled Ventilation
Each opening in the building envelope can be adjusted independently by the occupants. Windows, louvers, and courtyard gates open fully for maximum airflow on hot days or close down for privacy and temperature control on cooler evenings. This granular control allows the occupants to tune the indoor environment to their preferences without mechanical systems. The custom joinery elements that enable these adjustments – the screens, the pivoting panels, the precisely fitted windows – were crafted on site by Alberto Mares Quezada’s carpentry team. Creating these custom components required the same attention to fit and finish that specialized woodworking jigs bring to repetitive precision tasks in the workshop, ensuring every moving part operates smoothly for years of daily use.
Ventilation Performance Metrics
The cross-ventilation design achieves an estimated six to eight air changes per hour through the main living spaces during moderate breeze conditions of 8 to 15 km/h. On days with no wind, the stack effect created by the open stairwell and roof garden draws warm air upward and out, pulling cooler air in through the ground floor courtyards. This passive system maintains indoor temperatures within 2°C to 4°C of the outdoor ambient temperature without any mechanical cooling. The roof garden on the second floor contributes to this effect by absorbing solar radiation that would otherwise heat the roof slab.
Vertical Zoning for Compact Urban Living
The three-level organization separates the house into clear functional zones while maintaining visual and spatial connections between them. This vertical stacking is essential on a 150 square meter lot where a single-story layout would not provide enough space for the required program. Each level has a distinct character that responds to its position in the building.
| Level | Function | Key Spaces | Connection to Outdoors |
|---|---|---|---|
| Ground floor | Social zone | Living, dining, kitchen | Opens to courtyards via glass screens |
| First floor | Private zone | Bedrooms, bathrooms | Sky views, Acacia tree courtyard |
| Second floor | Entertainment zone | Media room, services, roof garden | Panoramic volcano views |
Ground Floor: Extending Space Through Courtyards
The ground floor social areas open onto the courtyards through full-height glass screens. When the screens slide open, the indoor floor and outdoor patio become one continuous space. The program extends into the courtyards, which function as outdoor rooms furnished with seating, planting, and dining areas. This indoor-outdoor integration effectively doubles the usable space of the ground floor during favorable weather. The kitchen, dining, and living zones flow into each other and into the courtyard, creating a 150 square meter combined space from a 70 square meter floor plan.
First Floor: Private Spaces with Sky Views
The bedrooms on the first floor occupy the arms of the I-shaped plan, each with windows overlooking the courtyards below. The design orients the bedrooms to capture views of the sky and the Acacia tree rather than the street. This inward focus creates the sense of retreat the owners requested. The separation from the street-facing facade also provides acoustic privacy from neighborhood noise.
Material Choices for Urban Infill Construction
Building on a constrained urban site requires material choices that balance performance, logistics, and aesthetics. The Casa Once project used materials from Mexican manufacturers including Cemex concrete, Helvex plumbing fixtures, and Tecnolite lighting, all selected for their availability and proven performance in local conditions. The construction team, led by Espacio 18 Arquitectura and Cueto Arquitectura, managed material delivery and staging within the tight site boundaries. Concrete was poured in sections to accommodate the narrow access lanes typical of Puebla’s single-family complex neighborhoods. The facade responds to the program directly, avoiding decorative elements on the street side and using the vaulting detail to control views and lighting from the inside out. This honesty in material expression keeps the construction straightforward and the budget manageable. For similar small-lot projects, the principles demonstrated here – subtractive design, courtyard-centered planning, user-controlled ventilation, and vertical zoning – form a reliable toolkit for creating spacious-feeling homes on tight urban sites.