Designing a house on a narrow urban plot presents distinct challenges that differ from suburban or rural projects. When the site is only 5 meters wide and 28 meters deep, with a narrow street on one side, every design decision must work harder to deliver light, ventilation, and usable floor area. The passive house architecture principles that prioritize orientation, airtightness, and controlled ventilation offer a useful starting point, but the real work lies in adapting those ideas to a tight urban footprint. In Algemesi, Valencia, the Ferragud House by Carles Faus Arquitectura demonstrates how a deep, narrow plot can be transformed through a central void that pulls light and air through the entire structure. The house covers 246.69 square meters across three floors on a plot measuring just over 5 meters by 28 meters.
Reading the Site: What a 5-Meter-Wide Plot Demands
The neighborhood surrounding the site mixes 1930s architecture with newer construction, a pattern found in many European city centers. The narrow road in front compounds the difficulty natural light reaches the ground floor at a shallow angle and the depth of the plot creates interior zones that would be dark without deliberate intervention. The same thinking about compact urban forms applies to the modern barnhouse vision that translates rural forms into tight urban packages, though the width constraints are far more extreme here.
Plots in this width range present several fixed constraints:
- Frontage is limited to one or two rooms wide at most
- The center of the house can be 10 to 15 meters from either end
- Adjacent buildings block side light entirely
- Street noise and privacy concerns limit ground-floor window size
- Building depth exceeds the reach of standard side-lit daylighting
Architects working on narrow urban infill sites typically respond with one of three strategies: a rear courtyard, a central light well, or a combination of both. The choice depends on the plot depth, local climate, and the number of floors required.
Plot Geometry and Program Distribution
With a 5-meter width, the ground floor can accommodate an open living-dining-kitchen area along its length, but the room depths exceed what windows alone can light. The solution developed for the Ferragud House was to cut a void through the center of the structure, creating an interior atrium that spans all three floors. This single decision resolves the two biggest problems of narrow plots: bringing light to the middle of the house and enabling vertical airflow.
Site Dimensions and Buildable Area Calculations
The usable buildable area on a 5-meter by 28-meter plot depends on local setback requirements. In this case, the built surface of 246.69 square meters over three floors represents roughly 82 square meters per floor, or about 58 percent site coverage. This leaves the rear portion of the plot as open courtyard, which becomes critical for the ventilation strategy.
The Central Void as an Organizing Mechanism
The central void in the Ferragud House does more than admit light. It becomes the organizing spine of the entire design. All circulation routes connect to it. The staircase threads through it. The rooms arrange themselves around it. At the top, two large skylights act as the primary light source for the whole house. This nucleus communicates from the top floor to the ground floor, linking all three levels visually and spatially.
Sizing the Void for Maximum Daylight Effect
The dimensions of a central void determine its performance. If the void is too small, it behaves like a ventilation shaft rather than a light source. If it is too large, it consumes floor area that could be used for living space. For the Ferragud project, the void spans the full usable width of the interior between the front and back walls, roughly 3 meters wide and 4 to 5 meters long. This proportion allows daylight bouncing off the void walls to reach the deepest corners of adjacent rooms.
| Void-to-Floor Ratio | Light Penetration | Floor Area Lost | Best Application |
|---|---|---|---|
| 8 to 10 percent | Moderate | Minimal | Single-aspect apartments |
| 10 to 15 percent | Good | Moderate | Two-story townhouses |
| 15 to 20 percent | Excellent | Significant | Three-story narrow houses |
| Over 20 percent | Full daylight | Major | Atrium-style houses |
For a three-story house on a 5-meter-wide plot, the 15 to 20 percent range provides the best balance between daylight performance and usable square footage.
Vertical Communication Through the Void
The staircase occupies one side of the void, allowing it to borrow light from above while functioning as a sculptural element. Every floor transition happens in a naturally lit space, which reduces the need for artificial lighting during daytime hours. This placement also means the staircase does not block light from reaching the lower floors, a common problem when stairs are positioned at the center of a narrow plan.
Motorized Skylights for Controllable Overhead Light
The two skylights at the top of the void are the primary source of natural light for the central zone of the house. Their placement aligns with the sun path so that direct light enters the void at different positions throughout the day. The skylights also play a direct role in ventilation, as their motorized controls allow the occupants to open and close them based on weather conditions and indoor temperature.
Overhead Light Compared with Side Light
Side light from windows decays quickly as it moves away from the facade. A window on a 5-meter-wide facade lights a room to a depth of roughly 3 to 4 meters before light levels drop below useful thresholds. Overhead light from skylights penetrates straight down and reaches the lowest floor of a three-story void with minimal loss. The usable daylight factor from a skylight positioned directly above a void can be 300 to 500 percent higher than side light at the same distance from the source.
Motorized Control for Seasonal and Daily Adjustments
The skylights in this house are motorized, which allows adjustment based on weather, season, and time of day. In summer, they can open at night to release accumulated heat and close during peak afternoon temperatures. In winter, they remain closed to trap warm air while still transmitting light. This controllability sets them apart from fixed skylights, which offer no seasonal flexibility. The motorized system also enables the skylights to function as part of the ventilation strategy, working in tandem with the rear courtyard. The same principle of automated natural ventilation appears in the window selection for the farmhouse project, where operable windows are sized and placed to support cross-flow without mechanical assistance.
Cross-Ventilation Through Stack Effect
The void does double duty as a ventilation shaft. The two skylights at the top and the rear courtyard at ground level create a vertical pressure difference. Warm air rises and exits through the open skylights, drawing cooler air in from the courtyard below. The architect describes this as generating a natural air current that ventilates the entire space continuously when the skylights are open.
How the Stack Effect Works in a Narrow House
Natural ventilation driven by the stack effect depends on three variables:
- Height difference between inlet and outlet in meters
- Temperature difference between indoor and outdoor air in degrees Celsius
- Cross-sectional area of the flow path in square meters
In the Ferragud House, the height from the courtyard to the skylight is approximately 10 meters across three floors. The temperature differential on a typical Mediterranean summer day ranges from 5 to 10 degrees Celsius. The opening area at the skylights totals roughly 1.5 to 2 square meters. These numbers produce a natural airflow rate that changes the air in the entire house several times per hour with no mechanical input.
Night Flush Cooling Strategy
One practical application of the motorized skylight and void combination is night flush cooling. During summer, the skylights open automatically after sunset. Cool night air enters the courtyard at ground level, rises through the void, and exits through the open skylights. This cycle cools the thermal mass of the structure, reducing the following day’s cooling load by 30 to 50 percent in Mediterranean climates. The same strategy works in any climate with a diurnal temperature swing of at least 8 degrees Celsius.
Vertical Zoning of Public and Private Functions
The three-story organization follows a clear logic. The ground floor contains the day-use areas. The first floor holds the main bedroom. The second floor accommodates two additional bedrooms and a multifunctional room. The showcase homes that inspire real-world design often use similar vertical stacking principles, though the narrow width of this plot forces tighter integration of circulation and living space on each level.
Ground Floor Open Day Area
The ground floor is designed as a continuous open space running from the front entrance to the rear courtyard. The kitchen, dining, and living areas flow into each other without corridors, maximizing the usable footprint on the narrow site. The rear facade opens fully to the courtyard through a large window wall that erases the boundary between inside and out.
Upper Floor Privacy and Flexibility
The main bedroom on the first floor has a narrow window on the street side described in the project as a tear in the facade. This small opening provides enough light for the bedroom while maintaining privacy from the public road, which is a critical concern given the proximity of the house to the street. The rear of the same floor opens more generously to the void and the courtyard beyond. The second floor features a large opening for a multifunctional room that can serve as a home office, guest bedroom, or family room. Its position at the top of the void means it receives the most direct overhead light of any room in the house.
The passive house design and construction lessons from similar projects confirm that careful vertical zoning improves energy performance because each floor has different heating and cooling loads based on exposure and use. A ground floor open to a courtyard cools naturally, while an upper bedroom under a roof has higher cooling demand in summer.
Facade Design on a Narrow Street Frontage
The main 5-meter facade faces a public road, so the design must balance light access with privacy. The Ferragud House achieves this through selective opening sizes. The ground floor has a modest entry and limited glazing. The first floor has the small window tear for the bedroom. The second floor opens up with a large aperture for the multifunctional room.
This graduated approach to front facade transparency creates a composition that responds to the specific needs of each room rather than applying a uniform pattern. The rear facade, by contrast, opens fully on the ground floor because privacy is not a concern at the back of the deep plot. The upper rear floors are arranged identically, containing two more bedrooms with consistent window proportions. The passive house remodeling lessons from similar facade retrofit projects confirm that selective opening placement and high-performance glazing can maintain privacy while admitting useful daylight, even on tight urban sites facing public streets.