STRONG CONTINUOUS LOAD PATH
IBHS High-Wind Test Demonstration
Built in 2010, the IBHS Research Center is a state-of-the-art research facility located on a 90 acre parcel of land in Chester County, South Carolina (approximately 45 minutes south of the Charlotte airport). This unique facility will significantly advance building science by enabling researchers to more fully and accurately evaluate various residential and commercial construction materials and systems.
IBHS’ scientific research already has influenced residential and commercial structural design and construction, and will continue to do so for decades to come. The U.S. experienced $24 billion in insured catastrophe losses in 2016, which included 15 individual events with losses exceeding $1 billion each. Given the staggering losses expected from Hurricanes Harvey and Irma in 2017, there is an urgent need for the applied science solutions being developed by IBHS – the savings realized as a result of these solutions will “pay for” the lab many times over.
Top 10 Facts
- Stronger, more durable homes can be achieved through precise, objective engineering solutions, which IBHS generates through rigorous research and testing.
- IBHS launched its FORTIFIED HomeTM—High Wind program last year during the National Tornado Summit to help homeowners located in inland areas build safer, stronger new homes, and retrofit or repair existing homes to make them more resistant to high winds.
- During the past five years, claims related to wind and hail damage on a national basis have accounted for almost 40 percent of all insured losses, averaging approximately $15 billion annually—and growing each year; just last year (2016), the top five most costly catastrophes for insurers were all high wind, hail storms and thunderstorms, according to ISO’s Property Claims Service.
- Billion dollar wind storms are not unusual any more. On May 8 this year, Denver had its most expensive high wind and hail storm ever with estimated insured losses of $1.4 billion. Minnesota, Wisconsin, and Michigan had high wind and hail storms June 11, with insured losses likely to reach $1 billion.
- The highest designation IBHS offers, FORTIFIED Home—High Wind Gold, recognizes (among other things) a sealed roof deck, porches, carports, and garage doors, as well as a strong continuous load path, which ties a home together from the roof to the foundation so that it can withstand the significant stress of high winds.
- During summer 2017, IBHS conducted a series of groundbreaking tests on a 1,400 square foot home built with a strong continuous load path that meets IBHS’ FORTIFIED Home–High Wind Gold standard.
- Known as the science house, this home had a two-car garage and is typical of homes in the middle of the country, with one critical difference – it had a FORTIFIED Home–High Wind Gold strong continuous load path.
- The science house was fully instrumented with sensors to monitor forces (wind pressures and loads) being carried through critical elements and connections, as well as to measure the stresses and any deformation of the building as it responded to those forces.
- The science house was subjected to wind testing from: 1) different directions, 2) different wind speeds, 3) at different stages of construction, 4) with different levels of wall anchorage, and 5) with various exterior wall openings (as though individual windows and doors were damaged/breached).
New Research Finding
- Closing interior doors helps compartmentalize the pressure inside a home into smaller areas reducing the overall force on the roof structure, which gives the roof a better chance of staying intact.
- High winds place homes under intense pressure; wind entering a home through an open or broken window, for example, can create strong upward pressure on the roof.
- The roof is a home’s first line of defense against Mother Nature. In addition to external pressures on a house during a storm, such as wind, rain and flying debris, the roof must withstand internal pressure if winds get inside.
- Pressure in a home can build like air in a balloon, eventually causing the roof to fail and blow apart.
- Closing interior doors during a high wind event in areas not prone to storm surge can reduce the risk of significant roof damage.
Additional Science House Research Testing Outcomes
- This series of tests also:
- Validated the benefits of a strong continuous load path – a key component of a FORTIFIED Home—High Wind Gold designation.
- Determined the least amount of structural reinforcements needed to affordably and reasonably achieve significantly greater durability.
- Tested how a continuous load path safely transfers/carries the forces that wind inflicts on a home and disperses those forces through the strongest parts of the home and safely into the ground.
- Generated a new, much-needed benchmark data set for home designers and builders; to date, architects and engineers have had to make estimates based on much less precise data.
- This new data will provide important scientific guidance for all stakeholders in the building and construction industry, including informing technical standards and building codes.
- The new data will provide further proof of the value of FORTIFIED construction standards and the critical importance of IBHS’ continuous load path recommendations.
- The new data set will include wind speeds and wind gusts over time, along with measurements of the wind pressure being exerted throughout the test house, and the complete wind loads placed on the house, all the way from the roof to individual trusses and walls, right down to foundation anchor bolts.
- Once testing on the science house was completed, the FORTIFIED components related to the continuous load path were removed, including straps that tie together the roof, walls and floors, as well as anchor bolts that tie the house to the foundation. IBHS scientists then subjected the house to the kind of high winds typical of severe thunderstorms in the middle of the country – and, as expected, the house will came apart once wind speeds reached 100+ mph.
- A second identical house, known as the demonstration house was constructed to typical building code requirements for a home located in the middle of the country. This house is being used to demonstrate existing homes’ vulnerability to wind damage.
- Like the science house, the demonstration house also has a two-car garage and is typical of homes in the middle of the country.
- There are three primary differences between the two test houses:
- The demonstration house does not have a FORTIFIED Home–High Wind Gold strong continuous load path.
- Unlike the science house, the demonstration house is not instrumented for gathering precise scientific data.
- The demonstration house is fully furnished like a typical family home.
- The demonstration house will be subjected to the same high winds placed on the science house which had a FORTIFIED Home–High Wind Gold strong continuous load path.
- IBHS engineers expect the demonstration house to fail, demonstrating what – sadly – too often happens to homes in the middle of country when thunderstorms occur, or when they are on the peripheral edges of tornadoes (EF-0 to EF-1). These relatively common events, including straight line wind storms, cause billions of dollars in insured property damage each year. That damage and associated costs to homeowners and communities, can be greatly reduced.