Incorporate Passive Survivability into Building Codes
March 31, 2008
In December 2005, when we first argued for incorporating
passive survivability into buildings (see
), I thought of it as a smart design criterion that could provide another motivation for creating energy-efficient and environmentally responsible buildings. In a future of more intense storms that could cause extended power outages, with an ever-present risk of terrorism that could target energy distribution networks, and with higher energy costs and the prospect of fuel and water shortages, it makes sense to design homes and apartment buildings—along with certain other public-use buildings, such as schools and community centers—so that they will maintain livable conditions in the event of extended power outages or loss of heating fuel or water. Passive survivability can be achieved with such features as a highly insulating building envelope, passive-solar design, cooling-load avoidance, and natural ventilation (see
I now believe that instead of pursuing a voluntary approach for incorporating passive survivability into these buildings, we should mandate it. Passive survivability is a life-safety issue and should be incorporated into residential building codes (similar arguments also apply to commercial building codes). Passively survivable houses and apartments will protect the lives and well-being of residents. With loss of electricity or heating fuel, such a home in the winter will never drop below a temperature deemed adequate to keep the house livable—perhaps 55°F (13°C); the residents will remain safe and pipes won’t freeze. Furthermore, when such an energy-efficient home is without power or heating fuel, it could be maintained at more comfortable conditions—temperatures of 68°F to 75°F, for example—with just a very small amount of heat that could be provided with a kerosene heater or woodstove.
Similarly, in the summer months, a passively survivable house or apartment won’t get so hot that residents are at risk of heat stroke or hyperthermia. Overhangs will block the hottest sunlight, and windows will provide natural ventilation—as our vernacular designs did before the advent of air conditioning. With multi-family buildings and apartment complexes, the design challenges in achieving passive survivability are greater, but so too is the investment in architectural design. If we mandated such performance, design firms would gain the expertise needed to achieve it.
Widespread adoption of passive survivability would, as a major side benefit, reduce greenhouse-gas emissions. Under normal operating conditions, a passively survivable building will use very little energy for heating and cooling—which will go a long way toward reducing carbon emissions.
We need a multi-pronged effort to incorporate passive survivability into building codes. We need to determine what constitutes “livable conditions” and how that varies regionally; we need to agree on the assumed duration of outages for the purposes of survivability; we need to identify a building-performance metric, such as a score close to zero on the Home Energy Rating System (HERS) scale, that could serve as a proxy for passive survivability; and we need to convince code authorities and government leaders that risks of interruptions in electricity and heating fuel supply present a significant enough life-safety risk that we should incorporate passive survivability into all new houses.
Voluntary green builder programs go a long way toward encouraging passive survivability, but these programs are not proliferating fast enough to protect the public. We may need to mandate minimum levels of energy performance. Global climate change is already making our homes more vulnerable, and fuel shortages are likely to become a reality well within the lifespan of houses we are building today. We have a responsibility to ensure that houses keep their occupants safe and protected from the elements—just as we have a responsibility to ensure that they are resistant to fires and earthquakes. Let’s take that responsibility seriously and mandate, through building codes, that our houses will keep us safe, even without power or supplemental heat. Let’s not wait for the tragedy of a major summertime heat wave or wintertime cold spell that coincides with an extended power outage or fuel shortage before we act.