Passive Survivability

Hurricane Katrina and a long list of other natural disasters over the years—from the Northeast’s Blizzard of 1978 that killed 17 people and left tens of thousands of people without heat and water, to the Chicago heat wave that killed more than 700 people during a one-week period in 1995, to the January 1998 ice storm in Eastern Canada that killed 28 people, left 4 million people without power, and forced 600,000 residents from their homes—argue for a new mandate in building design:

passive survivability. I use this term to refer to the ability of a building to maintain critical life-support conditions for its occupants if services such as power, heating fuel, or water are lost for an extended period.

Houses, apartment buildings, and public buildings, especially schools and civic buildings that could be used as emergency shelters, should incorporate design features that will maintain livable conditions in the event of extended loss of power, heat, or water. (Even if heating fuels are available, few heating systems today can operate without electricity; the same goes for water systems.) Relative to building performance, the idea is not to maintain temperatures within the ASHRAE-defined comfort zone of 68–81°F (20–27°C)—depending on the season and humidity—but to create buildings that will not threaten the lives of their occupants if power is lost. After Hurricane Katrina, temperatures in the New Orleans Superdome rose as high as 105°F (41°C). In the Chicago heat wave, many apartments stayed above 90°F (32°C) even at night; had power been lost, even briefly, the death toll would likely have mushroomed.

With predictions of more powerful storm systems as global climate change raises water temperatures in the Gulf of Mexico and Atlantic Ocean, with a growing realization that long-term supply and availability of fossil fuels are not assured, and with the now ever-present threat of terrorism that could sever energy supply or electricity production anywhere without notice, the design and construction industry—and the regulators of that industry—must respond with buildings that provide for passive survivability.

The conventional solution to power-supply interruptions is to provide back-up generators and adequate fuel to carry a building—or at least the critical functions in that building—during outages. Indeed, generators need to be part of the answer in some situations (such as hospitals), but passive solutions are preferable in most situations for various reasons: unless very large, generators are rarely able to provide air conditioning, general or task lighting, or even heating and ventilation during outages; storing significant quantities of fuel on-site to power generators during extended outages has its own inherent environmental and safety risks, particularly during storms; and back-up generators are expensive, both to buy and to maintain.

Passive survivability can be achieved by incorporating the sustainable design features that have been so actively promoted by the green building community: cooling-load avoidance strategies, capabilities for natural ventilation, a highly efficient thermal envelope, passive solar gain, and natural daylighting. Indeed, these measures are so important that they may need to be incorporated into building codes. Buildings can go even further with features such as generating and storing photovoltaic electricity and collecting and storing rainwater, but the aforementioned passive survivability measures are most important.

Along with providing critical life-support needs in the event of loss of power and heating fuel, buildings that provide passive survivability would also have the societal benefit of dramatically reducing energy consumption—which in turn would reduce the likelihood that limited supply would cause energy service interruptions. In other words, designing buildings to provide for passive survivability may reduce the likelihood that those features would actually be needed to keep occupants safe. Such measures would also dramatically reduce operating costs.

Another ancillary benefit of designing buildings for passive survivability would be a return to the regional diversity of vernacular architecture. There was a reason why homes in the Southeast had wide porches and large roof overhangs 200 years ago, why the New England saltbox had most of its windows on the south, and why homes in the Midwest’s tornado belt were so often bermed into the ground. A design criteria of passive survivability would bring back these vernacular styles.

Most of us in the green building community don’t need another motivation to design buildings that are energy-efficient, bioclimatically appropriate, and environmentally responsible. We do it because we believe it’s the right thing to do. But for that segment of the public that doesn’t believe in global warming or doesn’t believe that pollution from energy consumption is a real concern, the notion of passive survivability just might provide such motivation—because it is a way to directly protect the public in the event of a natural disaster, terrorist action, or other event that causes an interruption in our access to critical resources.

– Alex Wilson