External doors cannot generally be considered for the natural ventilation strategy, due to issues of controllability of ventilation.
However, where the assessor believes and can robustly justify that the requirement for ‘levels of ventilation’, referenced below, are met and that the use of the door for natural ventilation purposes would not create accessibility and/or security issues in the day-to-day use of the building, this may be acceptable.
The two levels of ventilation must be able to achieve the following:
• Higher level: higher rates of ventilation achievable to remove short term odours and/or prevent summertime overheating
• Lower level: adequate levels of draught-free fresh air to meet the need for good indoor air quality throughout the year, sufficient for the occupancy load and the internal pollution loads of the space.