Green Ventilation Cools College Using Air Buoyancy

De Anza Community College

De Anza Community College, Cupertino, Calif., Mediated Learning Center. Image Source: American School & University Magazine

A California community college has enhanced its green building credentials by adopting a buoyancy-driven ventilation system which dispenses with the need for electric fans or air conditioning.

The new $36 million Mediated Learning Center at De Anza Community College in Cupertino, California, has introduced the energy-free ventilation system as part of efforts to shore up its green building chops and obtain LEED Platinum certification.

The system was devised by WSP Built Ecology, the sustainable design wing of San Francisco’s WSP Flack + Kurtz, and provides ventilation to over 80 per cent of the building without the need for either electronic devices or strong external winds.

Buoyancy-driven ventilation involves the use of temperature-induced disparities in air density within and outside a building to produce air flow. The warmer, lower density air is lighter than the  cooler, high density air, and thus flows above it to create an upward moving air stream.

To achieve buoyancy-driven ventilation building designers only need to place apertures at varying heights in the walls of buildings to produce movement of air where required. The greater the distance between the apertures in a wall the greater the amount of air which is displaced as a result of the interaction between cooler and warmer air masses.

According Jason Hughes, senior project engineer for Sundt Construction, the fine-tuning of the aperture locations presented the greatest challenge in the creation of the system.

Buoyancy ventilation diagram

Image Source: How to build a green house

“Because it is such a unique system, we’ve been continually fine-tuning this system based on user needs. It’s been a process to make these minor adjustments to the building control system that really optimizes building performance,” he said.

Buoyancy-driven ventilation possesses a number of advantages compared to other forms of ventilation. It relies on temperature differences instead of wind movement, and thus operates most effectively on hot, windless days when ventilation is most needed.

The air flow it produces is stable, as compared to wind-driven ventilation, and the apertures permit building occupants to control the level of air intake.

Most important of all with respect to sustainability and environmental impact, buoyancy-driven ventilation systems do not consume any power or electricity, and thus do not create any utilities expenses for users or increase their carbon footprint.

Buoyancy ventilation is just one of a raft of green measures incorporated into the design of the new college building to improve its sustainability. Other features include solar PV panels and solar hot water panels on its rooftop, water conservation and water runoff control, and radiant heating at the lobby level.

The 67,000-square-foot facility, which was completed last October and caters to anthropology, sociology and language students,  already possesses all the LEED points required for platinum certification, and was also nominated by the San Jose Business Journal for the 2012 Structure Award for Best Green Project.

By Marc Howe
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