Feature from Environmental Building News
May 1, 2006
Passive Survivability:
A New Design Criterion for Buildings
An Executive Summary is available for this article.
In December 2005 an editorial in
EBN introduced the concept of “passive survivability,” or a building’s ability to maintain critical life-support conditions if services such as power, heating fuel, or water are lost, and suggested that it should become a standard design criterion for houses, apartment buildings, schools, and certain other building types (
EBN Vol. 14, No. 12). Since then, the term has begun creeping into the lexicon of green building, though we have a long way to go before the mainstream building industry takes notice.
In this article we examine the concept of passive survivability in greater detail and address some specific strategies that can be employed in adopting this design criterion for buildings.
While Hurricane Katrina wasn’t the first natural disaster to affect an entire city, and it certainly won’t be the last to cause widespread power outages and damage to buildings, it may have been a turning point—both in our acceptance that global warming is real and in our awareness of the vulnerability we face in the years and decades ahead. Visionary thinker Gil Friend suggested in a recent essay that someday we will look back at 2005 as a tipping point. “The fact- and science-averse among us may still claim to not be persuaded about global warming, but I’ll wager that everyone else got the message in 2005,” he wrote in “Sustainability—At the Tipping Point?” in his online newsletter,
The New Bottom Line (
www.natlogic.com).
As the storm track images clearly convey, both the frequency and the magnitude of tropical storms affecting the Gulf Coast and coastal Atlantic states increased dramatically in the decade 1995 to 2004 compared with the previous decade. Other, longer-term, scientific studies have demonstrated that at least the
severity of tropical storms has been increasing as an effect of global warming, even if the jury is still out on the
frequency of storms.
The potential for rising sea levels has also been in the news a great deal recently. New evidence shows that the Greenland ice sheet is melting far faster than expected. This and the calving of large ice sheets in Antarctica (some as large as small states) raise the specter of significantly higher sea levels. With 53% of the U.S. population living on land defined as the coastal zone, rising sea level is a major concern. The University of Arizona Department of Geosciences Environmental Studies Laboratory website dramatically illustrates rising sea level:
www.geo.arizona.edu/dgesl/ (click on “Dynamic maps of areas susceptible to sea level rise . . . ”).
Low-lying areas prone to tropical storms and flooding are not alone in being vulnerable. An extensive ice storm in eastern Canada in 1998 left 4 million people without power for an extended period and forced 600,000 people from their homes—which could not be heated without electricity. A heat wave in Chicago killed more then 700 people in their homes or apartments in 1995; a more severe heat spell in 2003 killed 30,000 people in Europe. A widespread power outage in the eastern U.S. and Canada in 2003 left 50 million people—one-seventh of the U.S. population and one-third of the Canadian population—without power; fortunately, weather conditions were moderate.
Adding to these risks is terrorism. Following the 9/11 attacks in the U.S., Americans will forever be aware of their vulnerability to terrorism. Power and natural gas distribution systems are particularly exposed and susceptible to interruption, with large centralized trunk lines running through remote areas. The extensive power outage in 2003, caused by a circuit overload or malfunction, demonstrated this risk; well-placed explosives could even more effectively cut off power to large areas. “The blackout in the Northeast in the summer of 2003 and Katrina should be enough to make it clear that we have a serious problem,” notes David Eisenberg, of the Development Center for Appropriate Technology (DCAT) in Tucson, Arizona.
Often neglected in discussions about terrorism is the risk of
cyberterrorism. “By hacking into control systems of the utility grid,” according to Joel Gordes, of Environmental Energy Solutions in West Hartford, Connecticut, “it is possible to incapacitate the system for as long as a week with lingering effects remaining for as long as 18 months.”
Finally, we are vulnerable to energy supply shortages. The petroleum age will effectively end well within the expected lifetimes of buildings being designed and built today. Most resource experts and policy makers assume that by the time petroleum “runs out,” alternative energy sources will be available to replace that lost energy. However, during the period of transition to next-generation fuels, or if replacement fuels do not become available quickly enough to displace dwindling supplies of fossil fuel, there may be significant energy shortages. Natural gas, heating oil, and electricity derived from fossil fuels could all become scarce or prohibitively expensive.
In preparing for a series of charrettes on Gulf Coast reconstruction for the Greenbuild conference in November 2005, the term passive survivability emerged as an umbrella concept to convey the idea of buildings that maintain livable conditions in the event of extended power outages, interruptions of fuel supply, or loss of water and sewer services. High temperatures in the Superdome—the city’s emergency shelter—had put evacuees at risk, contributing to uproar across the country.
This made us wonder about the schools around the country that are commonly designated as shelters, as well as our houses and apartment buildings. If storms are becoming more intense and more common, and if our energy distribution systems or energy supplies are becoming more vulnerable, shouldn’t we be designing our buildings to be able to function—at least minimally to provide basic livability—in the event of power outages or interruptions in fuel or water supply? Shouldn’t passive survivability, we asked ourselves, be a basic design criterion of buildings in this day and age?
In some ways, the failure of conventional buildings to maintain survivable conditions can be thought of as a failure of design. “If they lose only electricity,” notes building researcher Terry Brennan, of Camroden Associates, Inc., in Westmoreland, New York, “few buildings in the U.S. can provide as much comfort as my backpacking tent; if the gas lines and water lines go, the situation is even worse.”
Some strategies for passive survivability can be found by looking back at our building heritage—vernacular designs that were in place before electricity and readily transportable fuels became available. The wide-open and well-ventilated “dog-trot” homes of the Deep South are examples, as are the high-mass adobe buildings of the American Southwest.
The house designs of some animals display even better examples of passive survivability. Among the best are termite mounds of Africa and Australia (see photo). “With a single ganglion for a brain, using no electricity or fossil fuels, termites construct dwellings that maintain temperature, humidity, and ventilation better than most buildings,” says Brennan.
Marc Rosenbaum, P.E., of Energysmiths in Meriden, New Hampshire, says generators are the survivability focus in large buildings, but these are really designed for short-term power outages. “It’s rare that anyone is looking for 24 hours of continuous operation.” With typical buildings, Rosenbaum hasn’t seen any planning for longer outages, which are among his arguments for incorporating daylighting and operable windows.
Fortunately, we are beginning to pay attention. “Disaster tolerance is of growing interest to many groups,” says John Straube, Ph.D., an engineer and building science expert at the University of Waterloo in Ontario. “I like the term ‘robust designs,’ since this encompasses weather, energy, extreme people, changing times, etc.” Straube argues, for example, that stairwells should be built with windows, and offices should be daylit and have the potential for natural ventilation. “High insulation and high mass with some passive solar gain and summer shading will dramatically improve survivability,” Straube told
EBN.
A 21,000 ft
2 (2,000 m
2), five-story apartment building that Straube helped design, and lives in, incorporates a wide range of passive survivability measures, including high levels of insulation, passive solar features, and natural ventilation. The design team specified the heating system to have a very low electrical draw—just 250 watts operate the pumps and fans for the entire building—so that they can use a photovoltaic-charged battery pack to operate the natural-gas heating system in the event of a power outage.
While maintaining livable thermal conditions generally gets the most attention relative to passive survivability, water is also very important. “We can live without many things,” notes New York City developer Jonathan Rose, “but water is essential.” A good start, suggests Brennan, is to install composting toilets and waterless urinals, neither of which require water to operate.
While passive survivability features can be incorporated into virtually any building, these features are most important for buildings that are lived in or likely to be used as emergency shelters: houses, apartment buildings, schools, hospitals, emergency-service buildings, and government buildings. The strategies differ somewhat by building type; the need for a high-performance building envelope, for example, is greater in smaller buildings that are skin-dominated (where heating and cooling loads are determined primarily by energy flow through the building envelope) than it is in large, load-dominated buildings.
A number of the most important design and construction strategies for achieving passive survivability in new buildings are addressed in the checklist.
David Eisenberg, whose organization, DCAT, has been working to integrate aspects of sustainability into building codes for the past ten years, points out that the purpose statement in the International Building Code states that codes should “safeguard public health, safety, and general welfare from hazards attributed to the built environment.” “When a building is unable to provide a safe and habitable environment,” says Eisenberg, “it fails to meet this standard of responsibility.” He believes that this should apply whether all of the building’s assumed utilities are functioning or not. “We should not be designing, approving, and constructing buildings that kill people when they are disconnected from their external utilities,” Eisenberg told
EBN.
Eisenberg is not aware of any building codes that address passive survivability. He expects that the same forces that opposed energy codes and indoor air quality standards will oppose anything like this getting into the codes. “At the very least,” he argues, “the code organizations should be working to make it easier, rather than more difficult, to gain code approval for such designs.”
“Codes are very reactive and so have not been doing anything about this as far as I know,” says Straube. When codes do address survivability, they go about it the wrong way, in his opinion. “Codes prefer active systems that routinely fail and need lots of ongoing maintenance,” he says, “like back-up generators to run lights in windowless stairwells.”
A few elements of passive survivability are beginning to find their way into building codes and related regulations. The City of Chicago, for example, has passed an ordinance requiring all buildings to have reflective roofs, according to Sadhu Johnston, commissioner of the City’s Department of the Environment. “Our progress toward greener buildings continues to grow, which, by default, has passive survivability gains,” Johnston told
EBN.
Gordes notes that in general the only passive survivability measures that have been incorporated into building codes are those providing storm resilience—such as the Miami – Dade County hurricane codes. He suggests that demand for such codes may come from another major player. “I believe we may find support for some aspects of green or survivable buildings within the insurance industry, which has an interest in mitigating losses and protecting lives,” he says. “Just as they have been champions in fire-suppression sprinklers, they may support code upgrades for many green building attributes.”
When one looks through the collection of passive survivability strategies addressed in this article, it becomes immediately obvious how closely they match a general list of green building strategies. Indeed, most of the measures that make our buildings more passively survivable also make the buildings more environmentally responsible.
Passive survivability strengthens the case for green buildings. Most of us in the green building community probably don’t need another reason; we seek to create green buildings because we know that they are better for the people living in them and better for the Earth. But getting them designed and built isn’t always easy in the face of financial and regulatory obstacles and just plain inertia. To overcome these barriers, it may help to make the case that these buildings are more resilient and better able to protect the well-being of Americans in the aftermath of natural disasters or terrorist actions. Sometimes it’s useful to respond to people’s fears as well as their aspirations, and passive survivability does just that, without an antisocial survivalist agenda.
The next step in advancing the agenda of passive survivability should be a collaborative effort that involves the design community, code organizations, the insurance industry, and nonprofit social welfare organizations. The sustainability community could play a lead role in convening such an initiative. “Life safety should be the bottom line in this, and it would be gratifying to see a collaborative effort develop to address this issue,” says Eisenberg.
– Alex Wilson
Sidebar: Marc Rosenbaum on passive survivability at his own house
EBN Advisory Board member Marc Rosenbaum shared with us how he has addressed passive survivability in his New Hampshire home:
On my own house, I wanted a highly robust product. I have a drilled well and a submersible pump, but I also ran a second pipe into the basement that can be used with a hand pump. Because the static level of the well is close to the ground level, I can have water without electric power. The house is heated by a woodstove, and water is heated by either a passive solar water heater (thermosiphon) or a passive heat exchanger in the woodstove. Daylight illuminates all rooms. I use an electric range for air quality reasons, but I have a single-burner gas cooker that I can use in a power outage. A root cellar in the basement provides some level of food storage.
One challenge I haven’t solved yet is power. I have a grid-tied photovoltaic system, but when the grid goes down I can’t get power from the system. I want to set things up so I don’t have a battery bank but could use the power when the sun shines regardless of the grid being operational. This feature doesn’t need to be automated—it could be a manual changeover. I think that having power a few hours every other day would allow much of life to be fairly uninterrupted. In many places around the world, electricity is not available at all times, but provided for a known period each day. One could pump water, operate tools and computers, freeze ice, etc. during those times.
Then there is the matter of where food comes from after the first few days . . .
Checklist: Passive Survivability: A Checklist for Action
Design and construct buildings to withstand reasonably expected storm events and flooding. One should assume that storm events will become more common and more intense in the future, and that regions prone to severe storms will expand in area. More stringent design and construction standards, such as the Miami – Dade County Building Code, should be adopted widely.
Most tall buildings, with their dependence on electrically powered elevators and their reliance on air conditioning, usually cannot be used in the event of power outages. The occupant density in tall buildings generally precludes providing a significant fraction of power requirements with onsite renewable sources, and in a development pattern with a lot of tall buildings, blocking solar access of other buildings is a significant concern. In
Adapting Buildings and Cities for Climate Change, the authors recommend six to eight stories as a reasonable height limit.
High levels of insulation, high-performance glazings (with multiple low-emissivity coatings and low-conductivity gas fill), and airtight construction are critical in achieving passive survivability in buildings. High levels of energy performance of the envelope (superinsulation) are particularly important with smaller, skin-dominated buildings.
Reduce unwanted solar heat gain by paying careful attention to building orientation (situating buildings on an east-west axis with the long façades facing south and north), minimizing east- and west-facing glazings, specifying glazings “tuned” to the orientation (using low solar-heat-gain-coefficient glazings on the east and west, for example), using overhangs and other building geometry features to shade glazings, and selecting vegetative plantings that will shade the buildings (particularly the east and west façades).
In addition to reducing unwanted solar gain, design buildings to provide for natural ventilation. Even if the building is designed to operate with conventional air conditioning, provide operable windows, natural stack-effect cooling towers, and other features that can provide passive ventilation and cooling when necessary—even if using such strategies will result in higher-than-desired humidity levels in the building.
Particularly with smaller, skin-dominated buildings, provide passive solar design features, such as direct solar gain with interior thermal mass, thermal storage walls (Trombe walls), and sunspaces or other isolated-gain solar systems.
The following strategies can optimize daylighting design while minimizing unwanted heat gain: provide windows high on exterior walls; specify glazings with high visible-light transmission and a low solar-heat-gain coefficient; install lightshelves to reflect light deep into the space; install skylights with provisions to prevent overheating; paint ceilings and walls with high-reflectance paints; consider clerestory windows and light monitors to bring light deep into buildings; utilize light wells and atria to extend daylighting to lower floors of larger buildings; in buildings with very deep floorplates, consider light-scoop and mirror systems to improve daylight distribution in the interior space.
To provide hot water during power outages or fuel supply interruptions, install solar water heating systems that can operate passively (thermosiphoning or batch/integral-collector-storage) or that operate with DC pumps powered by integrated photovoltaic (PV) modules.
Capability to power a building with PVs is invaluable during outages. To be able to rely on PV power during a power outage for nighttime electricity necessitates battery storage, which increases system cost substantially (but may be justified for the value provided). Be sure to mount PV modules in a manner that will protect them during storms. Wire the building to isolate critical loads so that they can be PV powered when the rest are cut off.
The vast majority of gas- and oil-fired heating equipment cannot operate without electricity. Providing the capability to operate that equipment during a power outage—using either a generator or a PV power system—is clearly beneficial. To simplify switching over to PV operation during an outage, equipment should be redesigned to operate on DC power; even without battery storage, some operation of heating equipment would be possible during a 24-hour period.
In more rural areas, install low-pollution-emitting wood stoves, masonry heaters, or pellet stoves (with back-up power for fan) to provide space heating in the event of an extended power outage or fuel-supply interruption.
Provide water storage to serve the building during an extended loss of water. Ideally, store this water high in the building, such as on the rooftop, to facilitate gravity delivery. In cohousing communities and planned neighborhoods, shared water systems can be developed with gravity-feed to dwellings. Cisterns can be fed with rainwater and used during normal building operation for landscape irrigation and, depending on local permitting, for toilet flushing—as long as an adequate reservoir is maintained for emergency use. Such cisterns can also serve fire suppression needs.
Composting toilets and waterless urinals can be used in the event of water loss, and composting toilets can function even if the municipal sewage treatment plant shuts down. In a large building with conventional toilets, such as an apartment building, consider installing one or two high-capacity composting toilets in a common area for use if water supply is cut off or the sewer system fails.
Whenever possible, provide for local food production in the site planning for a building or development. Consider setting aside the best land for agricultural uses and planting food-bearing trees and shrubs in the landscaping mix.
IMAGE CREDITS:
1.
Photo credit: Duane Lempke, Sisson Studios
2.
Rendering: Ethan Gibney, National Hurricane Center, NOAA
3.
Photo: Dreamstime
4.
Photo: Mark Littrell, Wilcox Group Architects
5.
Photo: Cody Andresen, Arup
