Natural Ventilation

Natural ventilation is a key component of the passive design systems embodied in the work of Architectus as part of our commitment to provide thermal comfort and a healthy indoor environment through the sustainable use of natural resources.

Along Australia’s seaboard and throughout most of New Zealand a temperate oceanic climate prevails. Warm to hot summers and mild winters generally provide favourable conditions for natural ventilation in buildings.

Natural ventilation relies on pressure differential to deliver fresh air into buildings. This differential can be wind generated or a result of 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 provides 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 warms 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 by linking a series of spaces to a vertical air path such as stair shafts, thermal chimneys or open atria, therefore allowing fresh air to be drawn deep into a building.

General guidelines recommend single sided natural ventilation for spaces of up to 6m depth or with a ratio of no more than 2.5 times depth to height. Double sided natural ventilation is typically recommended for spaces of up to 12m depth.

Natural ventilation needs to consider the following:

  • 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 will inform a buildings:

  • Orientation and relationship to the site
  • Floor plate depths
  • Organisational layout
  • Envelope design - location of supply and exhaust openings

The challenge that presents itself is to overlay project specific, functional, organisational and contextual requirements with these climatic, geographical and design considerations. On large scale and multifunctional projects this will often lead to a grouping of uses within a building based on their ‘heat loads’ and ventilation requirements. and a corresponding mix of ventilation modes including mechanical, mixed mode and natural ventilation.

Challenge to provide consistent thermal comfort throughout space, coordination with glare control such as curtains and blinds that may affect air flow, occupation of building perimeter.

Benefits of natural ventilation include:

  • Healthy and natural indoor environment
  • Reduced capital and operating costs
  • Low maintenance

At Architectus we believe that when approached in an integrated and holistic manner sustainable design initiatives including natural ventilation enrich a project and can help generate innovative, highly interactive and productive social environments with in a sustainable design framework.