CIBSE or CFD to demonstrate compliance with natural ventilation

Gustavo, The same requirements apply internationally as in the US. There are some alternative approved standards (i.e. the EN Standards in Europe), and some alternative paths for demonstrating natural ventilation compliance using the "Engineered Natural Ventilation" approach referenced in ASHRAE 62.1 Section 6.4 (e.g. https://www.usgbc.org/resources/verification-protocol-engineered-natural-ventilation-systems-equatorial-climates).

However, with the exception of alternative approved standards, international v4 Homes projects using natural ventilation must comply with ASHRAE Standard 62.1-2010 Section 6.4.

This requires mechanical ventilation systems designed in accordance with Section 6.2 (Ventilation Rate Procedure) with the exception of:

(1) Engineered natural ventilation systems (typically CFD analysis and permanent ventilation openings or automated ventilation openings are required to demonstrate compliance using this approach). For mechanically conditioned spaces, it's unlikely that compliance could be demonstrated based solely on operable windows or doors, since the project team would need to show that the openings are likely to be open enough to assure ventilation on a daily basis. 

(2) Zones not served by heating or cooling equipment.

For projects not using engineered natural ventilation, the project must also comply with the geometric requirements for natural ventilation from Section 6.4.1, and location and size of openings requirements in Section 6.4.2. Carissa