Index of Re-inventing Construction

Passive ventilation

Passive ventilation typically relies on using physical principles like the thermal updraft that naturally results from the tendency of warm air to rise and cool air to sink, and by the effect of cross ventilation, by creating unimpeded airflow through a building.

Many passive ventilation systems rely on the building users to control windows and vents as dictated by site conditions and conditions within the building. The building’s situation and relation to land forms or, for example, adjacent woods, determines the capacity for passive ventilation to be effective in cooling and ventilating a building.

Passive ventilation can occur intentionally through the control of air movement through openings such as windows or doors from wind pressure and/or indoor-outdoor temperature differences or through the unintentional or uncontrollable air flow through unintentional openings in the building envelope (infiltration) resulting from wind and temperature generated pressure differences across the building envelope.



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Source: WhatWow

Completed in July 2007, the LEED-Gold certified Library and Classroom Building at Langara College, Vancouver creates a sustainable campus that promotes environmental responsibility to the student body and wider community. Passive ventilation contributes to an energy consumption more than 70% better than the model National Energy Code. Photo: Shai Gil.

A campus to showcase sustainability
The Library and Classroom Building at Langara College in Vancouver was completed in July 2007 and is LEED-Gold certified. The project won a Holcim Awards Acknowledgement prize in 2005 for North America.

The College and design team shared a common goal: to create a sustainable campus that demonstrates environmental responsibility and stewardship for the student body and the community. LEED-Gold was achieved through a combination of factors including greening of the site, low flow bathroom fixtures, reflective and green roofs, rainwater harvesting, incorporation of fly-ash in concrete, and regional as well as low-emitting materials and furnishings.

The form of the building is generated from the environmental forces acting on it:

• wind towers drive natural displacement ventilation within the building.
• the warped roof channels wind towards the wind towers and gathers grey water for landscape irrigation.
• courtyards create voids in the building, bringing daylight into the study spaces and offices.
• air is tempered by geothermal heating and cooling, in combination with the building’s inherent thermal mass.

The annual energy consumption of the system is 24.5kWh/m2 – more than 70% better than the model National Energy Code. This energy performance is achieved through the use of natural/wind driven ventilation, geothermal energy sources, and the control of solar radiation through energy efficient glazing.

The annual electrical energy consumption for the building is 262MJ/m2. This is attributed to the electrically powered geothermal system. Natural gas usage is 38MJ/m2, which represents a savings of 94%. The drastic reduction in natural gas is particularly significant in British Columbia, where hydro-electricity is the primary energy source. Since the building is naturally heated and cooled, there is no need to rely on external energy sources to assure a high quality of air and light within the spaces.

This project exemplifies a cultural shift, one that no longer sees the world as a vast resource, but as a finite reserve, which is slowly disappearing. The building responds to these changes technically – making the most of renewable resources (wind, rain and geothermal temperatures), as well as poetically – transforming these resources into uniquely exceptional spaces.

• read Holcim Awards project submission - "Library and Classroom Building", Langara College, Vancouver, British Columbia, Canada