Risk Factor provides a powerful way to understand wind risk in terms of the expected cost required to repair wind damage to your home’s structure.
Wind FactorTM can help you estimate current and future annual cost of wind damage, and the potential loss to a building structure over the next 30 years. These estimates are based on the likelihood and expected wind speeds to reach a building, as well as building characteristics, structure value, and type of risk.
What are wind damage estimates?
A property’s estimated cost to repair wind damage provides a powerful way to understand wind risk in terms of the financial cost to property owners. The Wind Model considers the location of a building as well as the building’s characteristics, such as its roof type, when determining the type and the subsequent cost of its wind risk.
How are damages determined?
Wind Factor uses the First Street Foundation Wind Model to determine the likelihood and speed of severe winds reaching a specific property. Given the likelihood of wind events and estimates of their severity, the probable damages that will be incurred by a structure may be estimated by engineering professionals. First Street Foundation partnered with Arup, a global engineering firm that specializes in structural engineering and damage estimates, to develop an estimate of the average annual loss (AAL) for every building impacted by extreme winds. The AAL is the average cost of damage a home could expect, in average over many years on a per-year basis based on its risk. While hurricane strength is usually categorized by the sustained 1-minute duration wind speeds within the storm, the most extreme damages to structure are usually caused by the 3-second wind gusts. These gusts impart the greatest stress on the building, and their magnitude is estimated from the sustained wind speed.
Factors affecting susceptibility to wind damage
The following factors are used to estimate a household's wind damage:
- Building height: The number of stories of the building on the property. Taller buildings can be more susceptible to damage.
- Roof material: The construction material used for the roof of the building. Different types of roofs have different levels of protection from severe winds.
- Building Face Direction: The wind damage varies based on the predominant angle between the oncoming wind and the orientation of the building and rooftop.
- Wind Gust Direction: The predominant direction that strong wind gusts typically reach the property.
Calculating the cost of wind damage
The approach simulates the impact of wind scenarios using a virtual model of the building to estimate the extent and severity of wind damage on the building. During an actual wind event, how a building is impacted depends on several factors including its location, orientation, risk from nearby manmade debris, and its wind resisting capacity. Several building “archetypes” are created in order to capture how different types of buildings sustain damages differently.
The simulation procedure developed captures the following key features:
- Building location, orientation, and the geometry effect of wind pressure
- Progressive failure behavior of buildings and interaction between buildings
- Updates to the internal pressure when wind may breach inside a building
- Wind-driven rain damage due to breach
- Uncertainty of wind pressures and wind resisting capacities
The model runs many scenarios on each building archetype to determine what level of damage occurs at each scenario and for each building type. Whether it was needing to be repaired or replaced were noted and used for the financial loss and downtime (length of repairs) calculations. Based on the level of damage, the total building financial loss was calculated for each realization as a sum across all damaged components. Downtime estimates consist of repair times for damages and impeding factors (such as time for returning from evacuation, building restoration, contractor and engineer mobilization, and equipment supply long lead times) that delay the initiation of building repairs. A construction of realistic repair sequences that mimic actual contractor logistics is aggregated to quantify the overall building downtime.
Once the downtime and financial loss had been calculated for each realization for each wind speed and wind direction, a set of loss curves (financial loss in 2022 USD vs wind speed, downtime in days vs wind speed) for all archetypes were calculated.
The wind speeds calculated per property using the 1-minute sustained wind speeds are converted to an estimated 3-second gust speed for use in the damage functions to estimate per-property losses. Losses are computed for the speeds in each of the eight compass directions, and then weighted according to the distribution of hurricane-strength wind directions as predicted in the model. Machine learning techniques impute any missing values so that estimated risk may be calculated at the property level.
Wind damage estimates vs Wind Factor™ scores
A home’s Wind Factor is based on the likelihood of its exposure to severe wind, and that exposure is used to derive the wind damage estimates. Wind Factors reflect the likelihood of severe winds reaching a building, while annual wind damage estimates capture the real-world damage that those winds are likely to cause based on the building’s unique characteristics. A home’s Wind Factor is based on its comprehensive wind risk over the next 30 years; it looks explicitly at the likelihood and speed of extreme winds reaching a property. Wind damage estimates use these projections and specific details about the building to assess the likely cost of wind damage.
While homes with high wind risks are likely to have higher annual wind damage estimates, it is still possible for a home to have a low Wind Factor and high damage estimates or a home to have a high Wind Factor and low damage estimates. The building’s orientation as well as how well it is built to protect against severe winds have a lot to do with the actual damage the home may experience.
Know your risk
Is your property expected to experience severe wind? Understanding what areas in the United States will face the largest hurricane risk or probability of severe wind speeds is important so individuals and communities can be prepared. Search your U.S address on Risk Factor to find personalized wind risk assessments for your property.
The methodology behind the model used by Wind Factor
Data sources used to determine Wind Factors