Brief description

Passive ventilation is the process of supplying and extracting air from an interior space without using mechanical systems (like fans or air conditioning). It harnesses natural forces, such as wind and temperature differences, to renew air and cool spaces.

Use / Function

Its main purpose is to maintain indoor air quality and thermal comfort without consuming electrical energy or fuel.

• Primary Use: Cooling and air renewal in homes and warehouses.
• Secondary Use: Humidity control to prevent mold and material deterioration.
• Scale: From small individual homes to large public buildings.

Operating Principle

It relies fundamentally on two physical phenomena:

1. Wind Ventilation (Pressure): Wind hitting one side of the building creates positive pressure (push), while negative pressure (suction) is created on the opposite side or roof. If there are openings on both sides, air crosses the building (cross ventilation).
2. Buoyancy Ventilation (Stack Effect): Hot air is less dense than cold air and tends to rise. If high openings are created for hot air exit and low ones for fresh air entry, a natural upward current is generated, even without wind.

How to Create It

It is not “built” like a machine, but “designed” into the building structure.

Minimum Functional Version

• Operable Windows: Place windows on opposite walls to allow cross-airflow.
• High Outlets: Openings near the ceiling or on the roof to let accumulated hot air escape.

Advanced Elements

• Windcatchers: Structures protruding from the roof to catch wind and direct it inside.
• Solar Chimneys: Ducts painted black or glazed that heat up with the sun to boost the stack effect and extract air more forcefully.
• Internal Courtyards: Act as fresh air reservoirs and facilitate ventilation to surrounding rooms.

Technical Level Required

• Basic: Opening strategic holes in the structure.
• Intermediate: Building solar chimneys or simple windcatchers.
• Advanced: Integral bioclimatic design calculated for the local climate.

Materials Needed

• Structural Building Materials: Brick, stone, concrete, or wood for walls and ducts.
• Closing Elements: Wood or metal for shutters, lattices, or windows to regulate flow.
• Thermal Mass: Dense materials (stone, brick, water) that absorb heat during the day and release it slowly, stabilizing temperature.

Variants and Improvements

• Cross Ventilation: The simplest and most effective way if the building design is narrow.
• Evaporative Cooling: Combining ventilation with water (fountains, wet cloths) at the air inlet to reduce its temperature (very useful in dry climates).
• Earth Tubes (Canadian Well): Pipes buried underground through which air circulates before entering the house, cooling in summer and warming in winter thanks to stable subsoil temperature.

Limits and Risks

• Weather Dependence: If there is no wind and the outside temperature is equal to the inside, wind ventilation does not work (though the stack effect might still work).
• Noise and Pollution: Openings allow outside noise, dust, or smoke to enter.
• Security: Large openings can be entry points for intruders or animals if not protected with grilles or screens.
• Condensation: In very humid climates, introducing hot, humid outside air into a cool interior can cause condensation.