Natural ventilation uses differential pressure to deliver fresh air into buildings. This differential can be caused by wind or the stack effect (buoyancy effect) of warm air rising.
Wind creates positive pressure on the windward side of buildings and negative pressure on the leeward side. Pressure equalisation between the two sides causes horizontal cross ventilation of floor plates. Wind driven natural ventilation requires a relatively direct and unobstructed route between the windward side and leeward side of a building. Extreme wind conditions need to be moderated.
The stack effect is achieved through vertical separation of supply and exhaust openings. As air heats its buoyancy increases. By purging hot air at high-level, cooler fresh air is drawn into the building at low-level. Buoyancy induced natural ventilation can be achieved through high- and low-level openings within individual spaces, or through linking a series of spaces to a vertical air path such as stair shafts, thermal chimneys or open atria, thus drawing fresh air into the building.
Natural ventilation systems consider:
- Climate – external air temperature and humidity range
- Prevailing wind direction
- Surrounding form of landscape and built environment
- Adverse impact of noise and other forms of pollution
- Building use and occupancy
- Thermal comfort temperature range
These considerations inform:
- Orientation and relationship to the site
- Floor plate depths
- Organisational layout
- Envelope design – location of supply and exhaust openings
The challenge is often realising project-specific functional, organisational and contextual requirements, along with climatic and geographical considerations. For example, large-scale, multifunctional projects that encompass varying ‘heat loads’ and ventilation requirements, often require a combination of ventilation modes including mechanical, mixed-mode and natural ventilation.
Natural ventilation must also coordinate with thermal comfort throughout a space (including in areas around the building’s perimeter), and glare control such as curtains or blinds that may affect air flow.Benefits of natural ventilation include:
- Healthy indoor environment
- Reduced capital and operating costs
At Architectus, natural ventilation is a key part of the integrated and holistic design methodology we use to create innovative, resilient and engaging environments for future generations.