Editor’s Note: Design for Impact is a series spotlighting architectural solutions for communities displaced by the climate crisis, natural disasters and other humanitarian emergencies.
CNN
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Flood insurance in hurricane-prone Crystal River, Florida would have cost Gene Tener $12,000 a year. But the retired engineer has taken matters into his own hands.
Sat on stilts anchored deep into the bedrock, his 3,200 square-foot house is designed to withstand storm surges and category 5 hurricanes. In the five years since Tener moved into his prefabricated home, it has survived a succession of major storms, including Idalia, Debby and Helene.
“We had one of the hurricanes, I forget the name, come right up straight over the top of the house… And we were fine,” Tener said as he toured CNN around his home, which he shares with wife Tammy, via Zoom.
The 66-year-old, whose previous insurer had refused to underwrite the three-story property, said several of his neighbors now “self-insure.” Beneath two elevated floors of living space, he has equipped a ground-level garage with flood vents (which let water in to equalize the pressure) and breakaway walls, not part of the building’s structural support, that are designed to cleanly break off in the event of severe flooding.
Elsewhere, high-impact windows protect the home from powerful winds — as does its distinctive shape.
Tener’s property is among more than 5,500 circular houses produced by Deltec, a US company that says its “hurricane-resistant” designs can withstand winds of up to 190 miles an hour. (A category 5 hurricane, the highest classification, is defined as having wind speeds of at least 157 miles per hour.)
The firm claims a “99.9% success rate against extreme weather,” and its factory-built homes, most of which are found in the US, have survived some of the Atlantic’s most destructive hurricanes, including Michael, Katrina and, most recently, Milton.
Stronger by design
Much of Deltec’s success is down to an aerodynamic circular design that redirects winds around its houses, reducing the pressure exerted on them by some 30%, according to the company’s president, Steve Linton. Inside, roof and floor trusses radiate from the buildings’ center, like spokes on a bicycle wheel, dispersing energy evenly around the structure, regardless of which direction extreme winds are blowing.
“The Deltec is designed to work with nature, rather than against it,” Linton told CNN in a phone interview.
Structural collapse is not the only risk during a hurricane. Roofs are the most common point of failure, he said, while poorly fitted windows and doors can also cause breaches that expose the insides of homes to destructive winds.
“How do we keep the roof on the home at all costs?” asked Linton, who is a structural engineer by training. “How do we keep the entire building envelope from (sustaining) any damage? These are the two biggest things.”
Deltec’s answers to these questions, beyond the circular design, include plywood sheathing that shields from flying debris and a roof angle that deflects wind and reduces lift. The firm says the connections it forges between roofs, walls and floors are far tighter than is required by most building codes. Deltec also claims that its frames are constructed from lumber that is twice as strong as in a “typical” home.
This reinforcement comes at a cost, however. The exact price of installing a Deltec home depends on numerous factors, including the finishes and geography of the site, but Tener’s Crystal River property cost him around $750,000 (the median house price in Crystal River is less than $293,000, according to Zillow). The prefabricated shell only accounted for a third of that figure, with installation costs and various additions, including an elevator and a boat dock, making up the rest of his investment. The estimated total cost for the homes featured on Deltec’s website varies from $600,000 to $2.2 million.
Deltec’s off-the-shelf homes come in various sizes and can be customized to different floor plans and room configurations, or to accommodate extensions like decks and porches. The homes typically take eight months to a year to design and build at the firm’s manufacturing facility in Asheville, North Carolina. They are then transported to the homeowner’s plot for assembly and installation, which in Tener’s case took a year and a half, due to the complexity of the foundations.
“It is more expensive, upfront — there’s really no two ways around that,” Linton said, adding that he believes maintenance and energy-efficiency savings nonetheless make owning a Deltec cheaper than a conventional home “over time” — even before taking extreme weather into account.
Earlier this year, the company launched a new, slightly cheaper range, the 360 Signature Collection, which varies in size from about 500 to 2,000 square feet. The homes are only resistant to winds of 130 miles per hour (with options to upgrade up to 190 miles per hour), but can be built and designed in just four months.
Growing need
More than 32 million residential properties across the Gulf and East Coasts, with a combined reconstruction cost value of $10.8 trillion, are at “moderate or greater” risk of hurricane wind damage, according to real estate analytics firm CoreLogic.
Insurance premiums are rising as a result. Comparison website Insurify’s latest figures show that the four of the five US states with the highest home insurance prices were hurricane-prone ones: Florida, Louisiana, Texas, and Mississippi. Some insurers have pulled back or completely ceased operations in high-risk areas, reducing competition and inflating prices further still.
An increasing number of homeowners like Tener appear to be — whether by choice or not — finding alternatives to flood insurance. Deltec says sales are growing, and while Linton believes people buy its homes for a variety reasons, not just storm protection, he estimates that around half of the company’s business comes from hurricane-prone areas, with southeastern states proving to be its biggest market.
The climate crisis may be accelerating the trend. Experts say human-caused global warming is increasing the likelihood of more intense storms. Not only are they generating more rainfall and flattening the coasts with higher storm surges, they have stronger winds and are intensifying faster.
While Linton could not definitively attribute increased demand for Deltec’s houses to growing fears over climate change, anecdotal evidence suggests they are linked. “From the stories we’re hearing from our homeowners, and seeing what people are doing with these homes, I think it’s hard to say that it’s not (a factor),” he said.
Learning lessons
Founded by two brothers in the late 1960s, as interest in prefabs exploded in the US, Deltec initially made its houses circular to provide occupants with panoramic views. The structures’ wind-proof properties only emerged later, and the company began explicitly focusing on weather-resistant design from the mid-1990s.
But even Deltec’s houses are not entirely failsafe. The company previously claimed to have “never lost a house to high winds” in its history, though it has since revised this success rate to 99.9% for homes built in the last 30 years. Linton also acknowledged that the loss of roof shingles and siding — or, more rarely, window failure — does occur from time to time, but these are not factored into the figure: “We are basing our success rate on structural damage.”
He also said two older Deltec homes have sustained significant damage, including a Bahamas property whose owner told the Washington Post that he considered the house a “total loss” after it was hit by Hurricane Dorian in 2019. This year, the company also received a report of damaged foundations in a group of Florida condos built in the 1980s. But Linton believes only one of the approximately 3,000 Deltec homes built after the mid-1990s has ever suffered structural damage — during Hurricane Irma in 2017.
“That 99.9% survival rate… looks at what we think of as the modern era, when we began focusing on designing these homes for hurricanes. Before (then), there wasn’t a particular emphasis on it until we started to see the results of Hurricane Hugo and Andrew (in 1989 and 1992, respectively), which were kind of the epoch moments, where it was like, ‘Huh, look at how much better a Deltec is doing than a neighboring home’,” Linton said, adding that “the track record, before the modern era is still very impressive.”
The company says it contacts homeowners after every major hurricane, and is always looking to improve its designs. Deltec’s long-term goal is to produce a house that can withstand winds of 225 miles per hour — just short of the strongest wind ever recorded in the northern hemisphere.
“We started to ask ourselves the question: What would we have to do to design the home of the future?” Linton said, explaining that wind tunnels are only able to accommodate scale models, not full houses. “Because whatever we’re building today, we obviously want it to be around for hundreds of years.”