麻豆原创

A granular look at the most expensive hurricane in Florida’s history, written by respected catastrophe-modeling firm Karen Clark & Co., highlights building practices that had a major impact on the scale of insured losses:

• Contrary to what may seem like common sense, low-sloped and flat roofs fared much worse than more steeply pitched roofs. With low roofs, the air pressure above decreases compared to the pressure below, creating suction that ripped a number of roofs completely off of buildings when Hurricane Ian hit southwest Florida in September 2022, the report found.
• But even flat and low roofs that were made of metal, reinforced concrete or built-up wood-deck systems sustained less damage than other types of roofs. “These built-up roof systems perform better because the multiple layers add redundancy,” KCC’s engineers and data analysts found.
• Exterior insulation and finishing systems, a popular siding material for commercial buildings and multifamily residential structures, proved to be especially vulnerable even in lower-than-peak winds during Ian. The sheets of insulation boards are lightweight and can detach easily. “Wind can exploit small cracks and cause significant siding damage, which can then lead to extensive interior damage due to water infiltration,” the report said. (Update: The CEO of the EIFS industry association took issue with that point, noting that newer building codes have made the cladding more resistant to hurricane winds.)
• Soffits on site-built homes also were damaged in and around the hard-hit Fort Myers area, but the damage is usually visible only from below and not from aerial surveys. Soffit damage can happen when high winds pull the fascia board off the edge of the roofline and exposes the soffit, the underside of the eaves or roof overhang. And soffits on corners of homes are especially vulnerable to wind that’s directed upward by exterior walls. “Soffit damage can necessitate complete replacement of a building’s siding because wind-driven rain gets under the siding and into the walls. Rainwater can also be driven over the exterior wall into wall breaches and attic spaces. Water infiltration can then lead to significant interior damage, increasing the ultimate loss,” the report noted.
• Garage doors were a common failure point in the areas that saw only Category 3 winds during the storm. The winds can cause the doors to bulge and buckle, increasing wind pressure on the overall structure of the property and raising the chance that the roof and walls will fail.

Karen Clark, whose engineers and scientists surveyed Ian damage shortly after the storm, then again in March, found that newer homes and buildings survived Ian in much better shape than older structures. Other studies have said that’s due to newer building codes and construction techniques. Older, low-rise structures, especially those made of wood frame or masonry, suffered severe damage, while concrete and steel buildings saw less of an impact from wind and water.

Many older homes that were elevated were not elevated enough to overcome Ian’s storm surge, which reached 12 feet at Fort Myers Beach. About 20% of the buildings on that beach were total losses and the majority of those were not elevated. Those structures that sustained severe damage or total losses saw the failure of foundation connections or the failure of the foundations themselves, the report found.

“Anchor bolts create a much stronger connection than clips or nails because anchor bolts are often cast in place and connect to a concrete surface, which creates a higher load capacity,” the analysts noted. The report included many photographs of damage, including one home that had shifted completely off its foundation, while others were wiped away altogether by the surge.

“Because coastal areas experience a combination of the highest wind speeds and storm surge inundation, it can be challenging to separate the cause of loss, but assigning the damage to the correct sub-peril is necessary to assess the insured loss,” KCC wrote. “Wind-related damage typically initiates at the roof and progresses downward, while coastal flood damage initiates at the ground and progresses to other parts of the building.”

Overall, Hurricane Ian, with winds as high as 160 miles per hour as it made landfall, caused more than $100 billion in economic damage. One number in the report shows just how destructive Ian was in Florida: Total privately insured losses from all 2022 storm events in the U.S. are expected to be about $64 billion. Almost $63 billion of that was from Ian, and most of that was in Florida. The Florida loss estimate assumes a large number of litigated claims, typical for recent storms in Florida’s litigious atmosphere, before some of the 2022 and 2023 legislative litigation reforms were enacted.

Forecasts on the impact of future hurricane seasons do not look rosier. A hurricane needs three main ingredients to rapidly intensify, as Ian did twice as it churned across the Caribbean and the Gulf of Mexico: low vertical wind shear; high ocean heat content, and high sea surface temperatures.

Climate change is driving an increase in surface temperatures and rapid intensification of storms is likely to become even more frequent, the report predicted.

U.S. meteorologists last week reported that the weather phenomenon known as “El Nino” will likely form off the west coast of South America. Historically, El Nino patterns have been linked to a lower-than-average number of hurricanes in the Atlantic basin. The U.S. National Oceanic and Atmospheric Administration will post its outlook for the 2023 Atlantic hurricane season on Thursday, May 25. Researchers at two universities have predicted six to eight hurricanes for the season, which begins June 1. That’s slightly fewer than what last year saw.

But as Karen Clark and other reports have noted, it takes just one rapidly-intensifying storm to produce record losses.

The firm was founded in 1987 by Karen Clark and Vivek Basrur, producing one of the country’s first catastrophe modeling companies, the firm has said. An updated report on the 2022 Atlantic hurricane season can be found here.

Topics Florida Windstorm