Mirroring an argument being played out by competing rating systems such as Energy Star and Passive House, a panel at the recent 20th Congress for the New Urbanism (CNU) in West Palm Beach, Fla., demonstrated with some squabbling the tension that exists between the proponents of mechanical and passive technologies in commercial and residential buildings. Advocates of passive systems argue that mechanical systems are unnecessary and expensive, often resulting in buildings without the resilience to withstand power interruptions. Advocates of mechanical systems argue that many passive systems are unappealing to the U.S. market in regions with even modest temperature variations, and that the lack of understanding of humidity results in both higher energy bills than expected and mold issues when occupants fail to follow technical guidelines.

At the sparring table were Bill Browning, Terrapin founder; Steve A. Mouzon, AIA, principal of the New Urban Guild and author of The Original Green: Unlocking the Mystery of True Sustainability; Ann B. Daigle, program manager for the London-based Prince’s Foundation for the Built Environment (PFBE) “Rebuilding Communities” Craftsman Apprenticeship Programme; and Elizabeth Plater-Zyberk, principal, Duany Plater-Zyberk & Co. But most of the dialogue occurred between Browning and Mouzon—staunch pugilists for their respective points of view.

Browning contended that houses have become so technological and instruction manuals so thick that more than a manual is needed to run them properly, arguing for the development of sophisticated software to drive computerized home performance systems that would adjust temperature, humidity, lighting, and ventilation systems appropriately for climate and comfort without needing any human interaction. Mouzon responded that the thickness of the instruction manual required to operate a technology was inverse to the life expectancy of the system. “The highest level of technology is self evident,” said Mouzon. He cited the example of the double-hung window to create cooling convection, “A child learns to operate this system in one evening and remembers it for life,” he said.

A lawyer on the panel (not listed in the official roster), Daniel Slone, outside counsel for the USGBC, argued that passive systems did not sell in the U.S., where the average person has a very low temperature differential tolerance range of about two degrees. Describing the problems confronted by his high-performance building clients in New Orleans, who “build a thermos” so efficient and sensitive that when a homeowner opens the window on a rare cool evening, it throws the whole house off balance for two weeks. He described a disastrous New Orleans office project that resulted in the building becoming uninhabitable due to mold stemming from improper occupant operation. In short, mechanical systems often fail when mishandled.

But it was the proponents of the passive approach who seemed to gain the upper hand, as audience reaction supported the comments of Dhiru Thadani, AIA, who spoke about his experience designing buildings in Mumbai, India. He pointed out that the climate in Mumbai is even more hot and humid than New Orleans, but that by adopting traditional architectural approaches, including strategic shading and dual-wall construction, he was able to avoid all problems related to humidity and still design energy-efficient, comfortable structures that did not have to be airtight and mechanically ventilated.

Plater-Zyberk pointed out that our inclination to use air conditioning and heating may be a cultural bias against adapting ourselves to local climates. She pointed out the difference in comfort between wearing a climate-appropriate guayabera shirt in the tropics vs. a European business suit. “You have to be an American to believe you must always be at 60 degrees,” she said. Browning then suggested that the emphasis should move away from building systems that rely on such tight building envelopes, portending a move away from the “build tight; vent right” approach, toward a combination of locally based, passive design strategies and alternative sources of energy such as photovoltaic systems, yielding a hybrid approach combining traditional passive with modern mechanical technologies as a third, and final solution.