Research now underway at the University of Florida, together with Cornell University in New York, is laying the foundation to better understand the relationship between wind and wind-driven rain and their impacts on buildings. The study could pave the way for better understanding the effects of wind-driven rain on structures in Florida and surrounding states, which will be beneficial for FGIA Southeast Region members and many others. Later phases of this research could extend that insight across the U.S.

Informing Better Design

Funded by the Florida Building Commission (FBC), the essential research is designed to analyze data and provide insight that can be used to better inform future building envelope and product design, testing, building construction, maintenance and more. The research project called, “Development of Wind-Driven Rain Climatology and Coincidental Wind Speed Return Period Maps for Florida and Surrounding Coastal Areas,” ranked first in priorities for Florida fiscal year 2021-2022 funding by the Florida Hurricane Research Advisory Committee (HRAC) and the FBC.

The HRAC, which reports to the FBC, consists of a cross-section of appointed representatives who focus on issues of importance to Florida related to hurricanes and tropical storms and their impact on structures and people. FGIA member Mark Mikkelson (Andersen Corporation), represents the fenestration industry on the HRAC.

Research Pinpoints Data in One-minute Intervals

During a virtual HRAC meeting March 15, Drs. Masters and DeGaetano provided an interim report on the study. Early research findings are fascinating. For decades, rainfall amounts have been recorded at hourly intervals. The hourly data provides a snapshot in time. Conditions can vary significantly in storms over the course of an hour.

Peak wind speeds have been clocked for years as well, but little data have been compiled to analyze the one-two punch and true impact of wind and rain together in real-life weather conditions, like hurricanes, tropical storms or thunderstorms.

As part of the study, more precise one-minute wind/precipitation data has been obtained for 243 weather stations in Florida and other coastal areas and in nearby states in the Southeastern U.S. Researchers are comparing one-minute data with hourly data from the same sites to compare and contrast differences.

Researchers have already evaluated low-to-moderate rain intensity amounts. Computing coincident rain intensity wind speed occurrence probabilities is now underway. Methods to estimate wind speed occurrence probabilities associated with more extreme rainfall conditions, like those in excess of a quarter inch in a one-minute period, will follow.

Wind-Driven Rain Maps to be Produced

One especially valuable aspect of the study will compare magnitudes of coincident extreme wind speed rainfall intensity recurrence probabilities based on hourly and one-minute observations. Then mapping software will be used to produce extreme wind speed risk maps for different rainfall intensity thresholds.

Today, people use ASCE/SEI-7 wind speed maps that provide basic wind speeds for different categories of building occupancies throughout the U.S. to determine pressures for strength design.

As part of the wind-driven rain research now in progress, wind-driven rain maps will be created to help provide greater insight on projected wind-driven rain in an area. That will help engineers, building envelope and building product design professionals, manufacturers, those who test and certify building products, building code officials, and others to gain a clearer picture of wind-driven rain in a given geography.

Final Report Expected in June

Researchers expect to complete the current wind-driven rain project in June 2022. As the pioneering study ends, a final report will be issued to the Florida Building Commission, and the Florida Hurricane Research Advisory Committee.

FGIA will continue to monitor the research results and share highlights and insights from this promising study with members. In the meantime, view the progress made to date, as reported in the interim research report.