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By Nadav Malin

The Church of the Year 2000 in Tor Tre Teste, Italy, is the flagship project for a major initiative to build 50 new churches in the ecclesiastically bereft suburbs of Rome. In their winning proposal for the church, Richard Meier & Associates developed a dramatic design with large, upward-arching concrete shells-sections of a sphere-connected by glass walls that fill the space with soft, indirect light.

"The goal was to create a church that doesn't fight with the environment; the forms are closely related to that precept," says John Eisler, AIA, project architect. Minimizing mechanical equipment was a priority because the church, still under construction, will have no maintenance staff. "The parish priests who will maintain the church aren't trained in operating complex equipment," notes Eisler. Instead, the church will be cooled with natural ventilation.

Of course, the comfort demands of the once-a-week occupants of a village church are fewer than those of the nine-to-five tenants of modern office buildings. Within the past 50 years, engineers have made heroic efforts to meet these greater demands by creating sealed boxes with air that's conditioned by fans, motors, and refrigerants. The occupants may be able to predict, within a few degrees, the temperature of their space, but they still long for fresh, moving air and for a connection to the daily and seasonal cycles. They also yearn for greater personal control over their space, the control that comes with being able to open and close a window.

Natural ventilation provides this control and is often a cost-saving feature of energy-efficient buildings, although in most cases the energy savings are due more to an overall climate-responsive design than to the natural ventilation alone. Overall, savings are in the range of 10 to 25 percent as compared to similar buildings without natural ventilation. Achieving these energy savings, along with the other benefits of natural ventilation, requires a careful assessment of climate, occupant expectations, and occupant behavior.

Solar shading, orientation for breezes, use of materials with high thermal mass, and other measures that might be recommended to conserve energy in some mechanically conditioned buildings become more critical in naturally ventilated buildings because they directly affect occupant comfort. For example, the large, curving concrete shells that shield the Church of the Year 2000 from the Mediterranean sun would be a good idea even if the building were air conditioned, but without air conditioning they are essential to keep the interior from overheating.

Meier's church brings air from the shaded north side of the building through an underground crawl space, where it will be tempered by the cooler temperatures of the earth. "On a hot summer day, the air coming from the underground intakes will be five to nine degrees Fahrenheit cooler than the outdoor air," Eisler says. The underground chambers through which the air will flow were needed anyway to post-tension the steel cables in the curved concrete elements, so this approach proved economical as well. Because air rises as it warms, a natural convection current is created in the church as fresh, cool air is drawn through this crawl space and hot air is exhausted through operable vents in the glass between the concrete shells and at the roof level.