Sustainable Engineering Process

Natural Ventilation

What Is It?

Natural ventilation uses natural pressure differences, rather than mechanical systems, to ventilate internal spares, moving fresh air through the building. Generally, natural ventilation depends upon passive-mode options for a ventilation system, rather than active, energy-dependent, modes. Historically, all buildings were naturally ventilated; pressure differences drew in fresh air for oxygen, alleviating odors, and adjusting internal temperatures for thermal comfort. In favorable climates, it is possible that natural ventilation can replace air conditioning, with significant energy savings as a result.

How To

Passive techniques depend significantly upon the climactic conditions of the site, as the pressure differences are caused by wind or the buoyancy effect created by temperature or humidity differences. The amount of ventilation depends upon the size and placement of openings, windows and doors, in the building. As discussed in the Whole Building Design Guideline:

"It is useful to think of a natural ventilation system as a circuit, with equal consideration given to supply and exhaust. Openings between rooms such as transom windows, louvers, grills, or open plans are techniques to complete the airflow circuit through a building."

The concept is simple, but the design execution can be complex.

"Wind can blow air through openings in the wall on the windward side of the building, and suck air out of openings on the leeward side and the roof. Temperature differences between warm air inside and cool air outside can cause the air in the room to rise and exit at the ceiling or ridge, and enter via lower openings in the wall. Similarly, buoyancy caused by differences in humidity can allow a pressurized column of dense, evaporatively cooled air to supply a space, and lighter, warmer, humid air to exhaust near the top."

Besides the difficulty of designing and modeling natural ventilation to achieve proper air exchanges and thermal comfort, there are the challenges of code requirements concerning smoke and fire transfer. Operable windows, corridors and towers are various design strategies that help direct airflow using natural ventilation principles.