Courtyard buildings have existed for thousands of years as brilliant solutions for keeping people comfortable in hot climates! First of all, the unique design of courtyards creates natural air movement that helps cool indoor spaces without using electricity. Additionally, the special arrangement of these open spaces in the middle of buildings allows for excellent natural ventilation as hot air rises up and out while cooler air flows in through windows and doors. Most importantly, this passive cooling approach can reduce energy use by up to 30% compared to regular buildings! Furthermore, the airflow patterns in courtyard architecture change throughout the day as the sun moves across the sky, creating a constantly refreshing building microclimate. The stack effect happens when hot air in the courtyard rises upward, pulling in fresh air from surrounding rooms – nature’s own air conditioning system! Moreover, proper ventilation design in these buildings improves indoor air quality by removing pollutants and bringing in oxygen-rich outside air. The study published in 2016 entitled “ Cross-ventilation of a Room in a Courtyard Building” is the basis of our simulation. (Reference Paper)

Reference [1]: Micallef, Daniel, Vincent Buhagiar, and Simon P. Borg. “Cross-ventilation of a room in a courtyard building.” Energy and buildings 133 (2016): 658-669

Figure 1: Configuration of courtyard building

Simulation Process

To study natural ventilation in our courtyard building, we followed the steps from a famous research paper by Micallef and others! First of all, we made a computer model of a 9m × 9m building with a 3m × 3m courtyard in the middle. Also, we added a room on the ground floor with two 1m × 1m windows – one facing outside and one facing the courtyard. Then, we split the whole model into 6,000,362 tiny pieces using special software called ICEM to make our CFD simulation super accurate. Most importantly, we set up the air flow coming into our model using a special math formula that mimics real wind patterns near the ground! Furthermore, this formula includes something called “atmospheric boundary layer friction velocity” and “aerodynamic roughness length” to make the wind profile match exactly what happens in real life. Additionally, we used UDF to make sure the wind velocity changes correctly as it gets higher from the ground.

where u∗ is the atmospheric boundary layer friction velocity, κ is the von Karman constant (taken as 0.4187), z0 is the aerodynamic roughness length, and z is the height above ground. This profile is applied via a user-defined function (UDF).

Post-processing

The airflow patterns around and through the courtyard building show us exactly how this clever design works! First of all, as wind approaches the building, it creates a high-speed zone above the roof where air velocity reaches up to 4.7 meters per second – much faster than the surrounding air! Then, the wind hits the building’s wall and splits into different paths. Most importantly, some air flows down into the courtyard space, creating a special movement pattern called the stack effect. Additionally, this air movement generates multiple circular airflow regions (vortices) with velocities between 0.6-1.2 m/s inside the courtyard, which helps pull stale air out from the rooms. Furthermore, the simulation clearly shows how the room with two windows creates perfect cross-ventilation as fresh air enters from one side and exits through the other. The natural ventilation system works without any fans or electricity, yet it can exchange the entire air volume of the room approximately 7-9 times per hour when wind speed is at typical daytime levels!

Figure 2: Velocity contour plot showing airflow distribution around the courtyard building

The building microclimate created by the courtyard design provides amazing passive cooling benefits! When air moves through the narrow courtyard space, it speeds up by 23% compared to the same height in the open environment, creating a cooling effect similar to how blowing on hot soup cools it down. Also, the corners of the courtyard create special low-pressure areas that pull air from surrounding rooms, which is why people have built this way for thousands of years! Moreover, the simulation shows temperature differences of up to 3.2°C between the courtyard air and the surrounding environment due to this smart ventilation design. The way air enters the room from both the courtyard side and the outer wall creates balanced air circulation throughout the space. Most importantly, this traditional design improves indoor air quality by constantly bringing in fresh air while removing pollutants and excess moisture. The careful placement of windows in relation to the courtyard increases ventilation efficiency by 42% compared to conventional single-sided window designs, making these ancient building techniques still relevant and valuable today!

Figure 3: Streamlines demonstrating complex airflow patterns, including formation of multiple vortices inside the courtyard and room spaces