Tornado-Resilient Construction with ICF: Protecting Against Nature's Fury

Explore the need to prioritize resilient construction methods in the face of extreme weather events.

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Natural disasters, especially tornadoes, pose significant threats to traditional homes, where even a well-constructed, wood-framed house can be devastated in seconds by a tornado. Traditional materials often fail to provide the necessary defense against extreme winds, putting lives and properties at risk. This vulnerability raises a crucial question: why aren’t we building safer homes with materials that can withstand these forces?

Changing Building Priorities

The NOAA National Centers for Environmental Information (NCEI) reported that in 2023 twenty-eight major weather and climate events caused damages totaling at least $92.9 billion in the United States alone. In addition, according to NOAA, every U.S. state has experienced at least one disaster with damages exceeding a billion dollars since the 1980s. These disasters are more common in central, south, and southeast regions 1.

Read more: Billion-Dollar Weather and Climate Disasters (ncei.noaa.gov)

After all the death and destruction we have experienced in recent years from tornadoes, hurricanes, and other extreme weather, it is clearly time to shift our thinking about the way we build. We have repeatedly wasted resources, time, and most importantly lives by re-building the same types of buildings that have previously blown away, fallen down, and crumbled around us. Now we must re-evaluate our priorities and strive to meet the following goals when building structures:

  • Implement measures that will reduce the risk of casualties.
  • Reduce downtime and disruption caused by damage.
  • Reduce damage repair costs.

ICF for Tornado-Resistant Construction

ICF (Insulated Concrete Forms) walls are constructed with layers of EPS foam insulation on both sides of a reinforced concrete core. The foam forms act as permanent stay-in-place molds that create a continuous insulating barrier. Steel reinforcement bars are placed within the concrete to enhance the structure’s integrity, while the dense concrete core offers unparalleled strength.

Performance Against Debris and Wind Loads

To simulate the wind speeds up to 250 MPH present in tornadoes, the Wind Engineering Research Center at Texas Tech University was the first to design an air cannon that could shoot 2x4s and other objects to duplicate flying debris conditions during high winds and tornadoes. Debris flying at over 100 MPH passed right through a standard wood framed wall leaving inhabitants at risk, while an ICF wall with 2 1/2” of Expanded Polystyrene (EPS) foam on each side of the concrete, was not damaged2.

The strength of a tornado in the United States is estimated using the Enhanced Fujita Scale (EF Scale). The scale has six categories from zero (EF-0) to five (EF-5) representing increasing degrees of damage.

An ICF wall can offer a wind resistance of 250 MPH which is equal to an EF-5 tornado. The strength is based on the wall’s composition of steel reinforcement and concrete. In addition, ICF walls are resistant to the water-damage often associated with tornadoes, hurricanes and other storms.

Despite the destruction from Hurricane Harvey, the ICF building remains intact

An important component of wind resistance is the presence of a continuous load path from roof to foundation as a means for transmitting wind uplift and shear loads safely to the ground. ICF construction addresses this requirement in two ways: Its wall-to-foundation connection is automatically strengthened by vertical reinforcing steel bars. With regard to roof and floor connections, ICF manufacturers provide specialized hardware for attachment. Roof trusses can be attached via straps to metal plates in the concrete wall or directly to the concrete itself, and ledger systems can be used to reinforce the wall-to-floor connection.

Comparison with Other Materials

Compared to traditional building materials like wood and steel, ICF outperforms in several critical areas. While steel structures offer strength, they lack the thermal insulating properties and can corrode when exposed to moisture. Wood-framed buildings, while cost-effective, are vulnerable to both fire and collapse under high wind loads. In contrast, ICF walls provide a unique combination of structural strength, insulation, fire resistance, and water resistance. ICF buildings reduce the chance of total failure in extreme weather, while wood and steel buildings are more likely to incur damage requiring expensive repairs.

The Multi-Hazard Resilience of ICF

In addition to tornado resilience, the reinforced concrete core in ICF construction also offers resilience against other natural disasters like hurricanes, wildfires, earthquakes, and floods.

Fire resistance: Since concrete won’t burn like wood and does not soften or bend like steel, it is the ideal material for resisting fires. Noncombustible concrete walls have a fire rating of 3-4 hours, protecting a building’s occupants, possessions and structural integrity far longer than highly combustible wood framing that collapses after 1 hour. The EPS insulation of an ICF is also flame-retardant, and any smoke from burning is non-toxic.

Flood protection: Since concrete actually strengthens in the presence of moisture, when it is submerged in floodwaters it suffers little to no damage. And while wood is subjected to rotting and mold, concrete’s inorganic makeup maintains its composition over time. The only post-flood cleanup needed for a concrete wall might be a good pressure washing.

Earthquake resistance: Although softwoods have a built-in advantage during seismic shifts due to their light weight, issues with structural connections and bracing prove to be the downfall of a wood-framed building. A reinforced concrete (ICF) wall provides an ideal fortress against earthquakes: the concrete works to resist the compression forces that try to push the materials together, while the reinforced steel applies tensile strength to resist the structure from being pulled apart, thereby opposing formation of large cracks. In areas of high seismic activity, double rebar curtains are often used to meet greater structural requirements.

Why Choose Amvic™ ICF for Disaster-Resilient Building?

Amvic™ ICF stands out as a superior choice for disaster-resilient construction, offering unparalleled strength and durability. Unlike traditional wood or steel-framed structures, which can be quickly compromised by extreme weather events, Amvic™ ICF combines the high-impact resistance of reinforced concrete with the insulation benefits of EPS.

ICF building under construction

Amvic™ ICF provides a resilient envelope that protects against both structural and environmental damage. Its composition achieves high fire resistance and minimizes water damage, making it especially suitable for areas prone to multiple hazards. ICF construction helps to meet the priorities stated above by providing a secure structure for occupants, reducing damage to a building’s structure, and reducing repair costs after an extreme weather event.

As we continue to face increasing threats from tornadoes and other extreme weather events, it is time to rethink how we build. ICF offers a proven, resilient solution to protect our homes, communities, and the environment from the fury of nature.

Read more: Amvic™ Insulated Concrete Forms (ICF)

1 NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2024). https://www.ncei.noaa.gov/access/billions/, DOI: 10.25921/stkw-7w73
2 The Wind Science and Engineering Research Center Texas Tech University DEBRIS IMPACT RESISTANCE OF BUILDING ASSEMBLIES (2006). https://www.depts.ttu.edu/nwi/research/DebrisImpact/Reports/TTU_Final_NIST_Report_numbered.pdf

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