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Free-Rolling Buildings


By Vivian Loftness

Carbon-neutral buildings. The 2030 Challenge. To meet these goals, the next generation of buildings must be designed to use so little energy that on-site renewables can meet their heating, cooling, and lighting loads. More efficient technologies can help us to achieve a 30-percent reduction, but they will never get us to carbon neutrality. For that we need nature’s renewables—daylight, passive solar heating, natural ventilation, natural cooling. We need mechanical systems that are turned off as long as possible, buildings that “free-roll” through hours, days, months, and seasons.

Free-Rolling Buildings
Image courtesy Vivian Loftness
Antoni Gaudi’s Sagrada Familia in Barcelona illustrates a free-rolling building.
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Energy-efficient lamps, ballasts, and fixtures are obvious first steps for saving 30 percent on lighting energy. Daylight-responsive and occupant-responsive controls shave the next 20 percent. The giant leap, however, is in buildings designed for daylighting as the dominant light source. Good daylighting demands effective integration of new glazing technologies, introducing light redirection, and shading layers. In addition to saving energy, good daylighting contributes to greater health and the alertness of occupants. Light levels can be higher without consuming more energy and sunshine offers rich color rendition. Circadian rhythms set by daylight variations throughout the day and exterior views satisfy people’s needs.

Highly insulated building enclosures, efficient mechanical systems, and heat-recovery strategies yield significant benefits, reducing heating loads by 30 to 50 percent. The innovative step forward occurs in buildings designed for passive-solar heating as the dominant heat source. Passive-solar heating entails solar collection, absorption, storage, distribution, and controls, all rich areas for industrial innovation. Moreover, passive-solar heating can provide full-spectrum light, help reduce the risk of mold, and warm winter spaces without energy penalty. Sunnier hospital rooms speed recovery rates, reinforcing the importance of sunlight to health.

While variable-speed fans, desktop task conditioning, desiccant air handlers, and heat recovery yield significant benefits for buildings today, the giant leap can only be achieved by buildings designed for natural ventilation as the dominant ventilation strategy. Natural ventilation is not only a viable method to deliver fresh air in substantially higher quantities than forced-air systems, it can deliver cooling as well (whenever outdoor temperatures are within or below comfort levels). This means that late fall, winter, and early spring cooling loads can and should be conditioned with “free cooling” through natural ventilation. The challenge for natural ventilation is to manage drafts, humidity, condensation, noise, and pollution.

Building-enclosure insulation, shading, and energy-efficient HVAC are obvious first steps for 30 percent energy savings in air-conditioning loads. The next step, however, is achieved by designing buildings with natural cooling as the dominant cooling source—free rolling for 90 percent of the time without mechanical cooling. Cooling with nature, through night ventilation, evaporative cooling, time-lag construction, and ground-source cooling, can be advanced significantly through 21st century material and assembly innovations. Mixed-mode conditioning, the marriage of natural and mechanical cooling and ventilation strategies, is one of the most cutting-edge areas of development for the zero-energy building community.

The design of free-rolling buildings challenges architects and engineers to collaborate on regional design solutions—merging traditional and innovative materials and systems—to create or recreate buildings that are indigenous to each climate.

Vivian Loftness, FAIA, is an internationally renowned researcher, author, and educator in environmental design and sustainability, the integration of advanced building systems, climate and regionalism in architecture, as well as design for health and productivity.

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This article appeared in the November 2008 print issue of GreenSource Magazine.

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