Brazil is set to face intense heat and irregular rains in the coming months. Despite the arrival of the La Niña phenomenon — which usually brings milder temperatures — the summer of 2025/2026 indicates averages above normal. In this scenario, architecture plays a fundamental role, and solutions such as
cross ventilation stand out for promoting
thermal comfort, reducing reliance on air conditioning, and creating healthier and more sustainable projects. Cross ventilation is a passive technique that makes use of natural winds to cool projects. It works when there are openings — such as windows and doors — on different sides of a room or building, allowing air to enter from one side and exit from another, creating a cooling airflow. One of the most advanced ways to assess the thermal comfort of buildings in Brazil is through
AQUA-HQE™ certification from the Vanzolini Foundation. Through bioclimatic charts and computational simulations, the certification establishes assessment criteria regarding the use of bioclimatic strategies — such as cross ventilation. Auditors assess natural cross ventilation from different aspects, including how it contributes directly to the building's
energy efficiency by reducing the need for
artificial cooling, and as a factor promoting health and hygiene through air renewal. According to the Vanzolini Foundation, "both natural ventilation and cross ventilation are assessed based on the AQUA-HQE™ technical reference for buildings under construction, taking into account factors such as the sizing of openings, their orientation concerning prevailing winds, and the surroundings." However, the technical team of the Foundation warns:
there is no fixed calculation for the ideal size of openings or windows. "The assessment for obtaining the seal is done through thermal energy simulations, which verify whether the design decisions have been technically justified and suitable for the climate and surroundings."
Ventilation and well-being
A architect Barbara Ferronato, a specialist in bioclimatic architecture at proActive Consulting, explains that "cross ventilation is one of the most effective strategies for the climate of Brazilian cities, being indicated during times of the day or year when temperatures range between 19 °C and 32 °C." She emphasizes, however, that "
above this range, the effect may be reversed, generating thermal gains and causing the moving air to heat up the project." Ferronato also points out that "the relative humidity of the air directly influences the performance of cross ventilation, being more favorable when it is between 15% and 75%, according to the temperature range." Ana Rocha, director of proActive Consulting, reinforces the benefits of cross ventilation: "Cross ventilation, when used correctly, can even
cool human skin." For this cooling to happen, it's important that the moving air directly reaches the occupants. "It is necessary for the openings to be at a height where the airflow directly impacts users. For this, the openings need to be located and sized according to the human occupation areas," explains Ferronato.
Strategies to apply cross ventilation
Experts recommend some practices to make the most of this technique:
- Operable frames on different faces of the building, allowing free circulation of air;
- Upper openings, such as sheds, that function as air collectors or extractors;
- Frames at different heights, especially in spaces with high ceilings;
- Possibility to close the openings in times of thermal discomfort;
- Proper shading of windows to avoid excessive solar heat gain.
