Kyoto, Japan -- Massive storms like the 2005 Hurricane Katrina, that cause over $100 billion in damage, were once considered once-in-a-lifetime events. Increasingly, however, they are becoming the norm: a direct result of climate change, which has made large storms more frequent, intense, and slower-moving, deepening their impact.
Hurricanes can damage homes through flooding and strong winds, and insurance claims target both. After the 2022 Hurricane Ian, for example, 44 percent of insurance claims were for flooding and 56 percent were for wind damage. Yet most economic research focuses on flooding because elevation data and hydrological models can predict flood extent, whereas identifying the location and severity of wind damage across a wide area has posed a particular challenge.
Unlike flooding, there is nothing like a dam or levee that can shield an entire community from wind, so the responsibility falls almost entirely on individual homeowners. To mitigate wind damage, Florida enacted the 2001 Florida Building Code -- 2001 FBC -- which required new and re-roofed homes to use stronger roof-to-wall connections, thicker roof decking, and even impact-resistant windows and doors in some areas. Many homeowners had to spend thousands of dollars to reinforce a roof or install impact-resistant features, yet whether these preventative measures proved to be worth the average cost of about $4,930 had remained unclear.
This motivated a collaborative team of researchers from Kyoto University and Kobe University to develop a new method of identifying wind damage and assessing the benefit of these measures. The team observed high-resolution drone and satellite imagery taken after a hurricane to locate homes with blue tarps -- the temporary sheeting used to cover damaged roofs -- as a proxy for wind damage.
Applying their research to Hurricane Irma, which struck Florida in September 2017, the team tested how much 2001 FBC reduced wind damage to homes. They used tarp size as a measure of damage severity and corroborated these results with building-permit records, making it possible to map wind damage across hundreds of square miles. With data on more than one million homes across eight southern Florida counties, they then applied a regression discontinuity design to compare homes built just before and after 2001 FBC took effect.
The results revealed that homes built under the new code were about 22 percent less likely to suffer wind damage, and when damage did occur its severity was roughly 27 percent lower. Additionally, damaged homes that were sold before being repaired were both harder to sell and, when they did, sold for around 13.3 percent -- or about $29,400 -- less than undamaged homes.
"This study provides large-scale evidence that stronger building codes are effective for reducing wind risk and adapting to climate change," says co-author Kenji Takeuchi. "I hope this research will provide useful insights for disaster preparedness and the development of effective climate change adaptation policies."
