ll bets are off with regard to the extreme weather threats of the future.
That’s more or less what FEMA now says about its “best guess” tools for determining the probability of floods and other major disruptors. As an example, look at the list of exceptions they make to the inset graph predicting how likely it is that floods will exceed expectations:”FIRMS (flood insurance rate maps) do not account for the following:
- Shoreline erosion, wetland loss, subsidence and relative sea level rise
- Upland development or topographic changes
- Degradation or settlement of levees and floodwalls
- Changes in storm climatology (frequency and severity)
- The effects of multiple storm events
Thus, what was once an accurate depiction of the 100-year floodplain and flood elevations may no longer be so.” Assuming FEMA, NASA, the Pentagon and thousands of scientists worldwide are right about the side effects of impending climate change, what’s the best preemptive strategy for building and designing the homes and cities of the future?
The airline industry considers redundancy one of the best tools for preventing disasters.Hydraulic systems, for example, are often duplicated—or even triplicated—to ensure that if one fails, another takes over. Why can’t housing be designed with the same principles in mind? Some methods and systems in modern construction already rely on redundant systems. Roofing underlayment,also, plays a backup role to shingles or tiles. In well-built custom homes and factory-built modular panels, fasteners sometimes serve as backup to the adhesive that connects drywall to frame. The homes and cities of the future will take redundancy for granted, as a fail-safe against storms, wildfire, earthquakes and flooding. Simply elevating a home in a flood zone, for example, won’t be the only measure taken against flooding. It may also contain advanced systems for surviving prolonged sea level rise, tsunamis and other threats. And if living spaces are breached, lower floors will be made of materials that can be easily cleaned, perhaps with high-pressure washing equipment that’s already part of the home’s infrastructure. Future homes will be “ready for anything.” Why We Will Change A lot of the initial spending on resilient building likely will be driven by homeowners looking to retrofit their one-of-a-kind residences in at-risk areas. They’ll be looking for a stable, secure setting. They don’t want to lose that million-dollar view, nor sacrifice comfort and stability. Some of those dreams will be harder to hold onto than others, however, and owners without deep pockets may find themselves retreating from shorelines, seismic areas and parched wildfire zones sooner rather than later. Here are some of the major reasons why:
1. The End of Subsidized Risk. As we move into a more frugal future, federally backed flood insurance will face increasing scrutiny. It just makes economic sense. At present, just under 6 million homes are now protected by federal flood insurance—a protection NOT offered by most homeowner policies. When this protection ends, all of the risk will transfer to the private sector.
2. Insurance Rollback. Current flood protection policies typically cost about $600 a year for $350,000 in residential coverage ($250,000 for property, $100,000 for possessions). But what if that subsidized insurance dries up? As extreme weather events increase, private insurers will face whopping bills, which they will pass on to homeowners in higher premiums. Some owners will be unable to handle those costs. And it’s not just flood insurance that’s likely to become inaccessible—homes in earthquake-prone areas are only slightly better off. A private policy for a $300,000 single-family home in San Francisco could run about $650 annually. But what happens if frequency of quakes increases dramatically? (Source: http://www.earthquakeauthority.com)
3. Coastal Surrender. About four years ago, the U.K. began abandoning certain seaside areas to nature, because it couldn’t afford the billions necessary to keep flooding at bay (http://tinyurl.com/o5khcmm). The U.S. is feeling similar strain, as civil engineers try to contain eroding beaches and protect homes near the water, especially along the lower Atlantic coastline. Rising sea levels alone may be enough to stymie the best efforts of civil engineers to protect coastal housing. Add monster storms to that mix, and you can understand the sense of panic that some coastal residents are feeling. The city commission of South Miami, for example, just voted in favor of a resolution calling for dividing Florida into two states, one in the north, the other “South Florida,” in the low-lying southern half of the state. Their concern—and it’s a legitimate one—is that sea level rise is imminent, and the politicians on the high ground in Tallahassee show none of the political will necessary to protect the millions of residents who will be “losing ground” this century.
The Best Defense
The term “resilience” gets a bit muddied at times. It’s often used to refer to two different types of future challenges: extreme weather-related events (floods, wildfires, earthquakes, superstorms) and resource scarcity. The latter category include shortages of food, water or breathable air—basic human survival needs. In previous chapters of the Celestia Project, we’ve talked about how to avoid scarcity and achieve food and water abundance over the next century. So our resilience focus is primarily on the weather-ready aspect—ways to survive and mitigate some of the worst-case weather scenarios in the shelter we build and strengthen over coming years.
Floods: A Surge of Ideas
We begin the discussion of weather threats with flooding, because it’s one of the most destructive—and hardest to build against. It’s generally less costly to retrofit a home or multifamily structure for hurricanes and moderate earthquakes than to withstand a major flood, or repeated flooding.
The Boston Society of Architects just hosted their annual conference, with emphasis on storm-ready, resilient housing. Boston’s city officials are keenly aware of risks related climate change, according to Crystal Aiken of The Boston Harbor Association. She notes that the city has seen four recent storm surges that “have come within hours of striking Boston at high tide.” She and her panel of experts described how other countries such as the Netherlands have adopted a “Live with Water” approach to rising tides. That approach, however, involves storage of huge amounts of excess water during certain months. They have waged an aggressive PR campaign to convince the public to “make room for water” in their communities, in the form of giant seasonal lakes and reservoirs.
Such an approach might work in parts of the U.S., but what about major coastal cities with little undeveloped land to spare? HafenCity, part of Hamburg, Germany, is preparing for storm surge flooding by raising multi-family structures on special “plinths.” The technique is described by city planners, as quoted on the previous page. If flood intensity (and depth) increases over the next century, planners will apply new tools. They’ll be looking much more closely at materials and active, as opposed to passive, flood resistance. Raising buildings above flood levels is not a new idea, of course. Even “old school” wooden pilings often outlast the structures they support. The city of Portland, Maine, for example, is debating what to do with some partially submerged piers on the waterfront that were sunk into the mud about 90 years ago. But what if sea level rise results in repeated flooding or lengthy submersion? Buildings will need to incorporate not only the usual flood-ready details, such as water inlets, pilings and structural bracing, but also materials (left) that can be cleaned instead of replaced.
Storm Wind Readiness:The Details Matter
If you have any doubt, visit the aftermath of a hurricane. The homes that suffer the most damage are usually the ones built prior to modern building codes. Modern U.S. homes, built properly to the code adopted by their local region, tend to perform extremely well in hurricanes and earthquakes. That being said, however, all it takes is one chink in a home’s armor to turn minor storm damage into a total property loss. The powerful succession of storms and tornadoes in the last decade have led to a lot better understanding of how and why homes “fail” in storm winds.A few years back, I visited the sites of both the La Plata, Maryland, tornado and Hurricane Katrina immediately following those storms, so I got a first-hand look at why things fall apart. In extreme winds, homes typically go to rack and ruin because of either wind uplift or pressure differentials as air enters the home. Oddly enough, homes from the 1920s and ’30s sometimes fare better than ones built in the 1950s. Those old homes were overbuilt, mortared to their foundations, and so on, while homes in the age of Levittown subdivisions were built light, with minimal connection to foundations and no added straps or tie-downs.
Techniques and products for storm-ready construction have advanced over the last 40 years.Lots of recent research offers clear advice on how the homes and multi-family properties of the future can weather severe winds. Here are seven rules to live by:
Modern Building Codes Have Proven Wind Performance
Simply by building to the code has had a major impact on the survival of modern homes.
Techniques and products for storm-ready construction have advanced over the last 40 years. If you have any doubt, visit the aftermath of a hurricane. The homes that suffer the most damage are usually the ones built prior to modern building codes. Modern U.S. homes, built properly to the code adopted by their local region, tend to perform extremely well in hurricanes and earthquakes. Image: FEMA
1. Remove or Reinforce Soffits. Windblown rain entering soffits has been a major cause of roof blow-offs. If you’re not a fan of vent-free attics, look for soffits that are designed to keep out storm winds.
2. Lock Down Roofing. Flying clay roof tiles caused a lot of secondary damage in some of Florida’s big hurricanes. Mortar attachment is not enough; they require metal fasteners to stay put. Use extra nails on asphalt shingles and replace any that are old and brittle. Once they lose their grip on the roof, you’re inviting trouble.
3. Follow the Code. Don’t fudge it on fasteners, tie-downs or other important details. Install impact glass or shutters as required.
4. Build Low. Single-story homes tend to suffer far less damage from wind events than two-story homes. They offer less surface area for wind pressure and a smaller target for projectiles.
5. Strengthen Wall Layers. Wind-flung projectiles have been found to penetrate vinyl siding that’s placed directly over a thin-wall sheathing. They can also smash through certain types of garage doors. Adjust accordingly.
6. Reinforce Chimneys. In the La Plata tornado, almost every unreinforced chimney we looked at had broken off and/or collapsed. Brace and repair existing chimneys to make them safer for both wind and seismic pressures. Build new chimneys with reinforcing rebar.
7. Add Sheathing Grip. By using longer fasteners at closer intervals (six inches is good) to attach sheathing to rafters (8d versus standard 6d), you gain significant fastening strength.
Wood-framed homes tend to handle seismic activity quite well, according to FEMA, due to the fact that systems in wood-framed house tend to be interdependent, not monolithic. Failure of one doesn’t automatically lead to failure of others. This might be considered an inherently redundant design feature of wood framing. And redundancy (through connectivity) is key to any strategy for earthquake-resistant housing. Essentially, what’s important is bracing. There’s no single right way. The code recognizes multiple ways to achieve the recommended resistance to sliding, overturning or racking.
Fortunately, many of the same principles that apply to hurricane-resistant construction also work for seismic loads. Build (and retrofit) to code, and you’ve probably achieved most of what is presently possible (and affordable) with regard to earthquake-proofing a home or building. An excellent training series for builder on seismic retrofit is available at http://tinyurl.com/kv3axy7. It includes some important but often overlooked details, such as how to brace a hot water heater properly so it doesn’t become a loose cannon in the basement.
Masonry Construction. The same basic rules of thumb for seismic resistance apply to homes with above-grade masonry walls. The IRC requires an engineering plan for walls more than a story high, but whatever the height, walls, ceilings and foundations have to be connected diligently. Masonry walls are heavier, so they resist more force, but they’re also more likely than wood to collapse sideways in the right conditions. A good “best practices” guide for builders is available at http://tinyurl.com/q6tc8oh.
Spurred on by record-setting droughts and migrating forest conditions, wildfire often dominates the nightly news. Home losses to fire are rising, in part because we keep pushing deeper into wilderness areas. But another, sometimes overlooked aspect of fire protection is that water is getting scarce, particularly in the Southwest and West, so water management and accessibility is likely to become a major factor in building or retrofitting a home at risk for wildfire.
A resilient, fire-ready home will have a ready supply of local water that can’t be compromised. Over the next century, as in-migration to urban living continues, we expect to see some of the threat to lives and property lessen. But weather extremes are expected to get worse, so the smart money for those who still plan to live “on the edge” will be to create homes and sites that can handle a blaze, and build with fireproof materials. FEMA publishes the extensive Home Builder’s Guide to Construction in Wildfire Zones, which is downloadable at http://tinyurl.com/n35gqa7. GB