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The Risks of Wildfires

How Fire Damages Roofs

If you live in an area at risk of wildfires, you need to carefully consider your choice of building materials. Wind-blown wildfire embers cause most of the fires that burn homes, which is why it’s important to build your home with fire-resistant materials—especially the roof.

While no roof is totally fireproof, the most fire-resistant roofs are made of noncombustible materials such as metal, slate, or clay tile. When looking for a roof, FEMA suggests a product with a Class A fire-resistance rating, the highest for roofing materials. Metal roofing is frequently recommended because it’s both strong and lightweight, and—unlike natural slate and clay tile—will rarely crack. Metal roofs also resist wind gusts of 120 mph or more, which is important when standing up to the high winds generated by firestorms. There are also many asphalt shingles that offer both Class A fire resistance and a high wind-resistance rating.

How Firestorms Form Infographic
How to Prepare and Recover From Fire Damage

While your roof may be noncombustible, hot debris can catch fire and create embers that can ignite dry foliage and threaten your property. When preparing your roof for wildfires, make sure that debris like twigs and dried leaves are removed from the roof. Also, be mindful of trees that are close to your home. If there are branches that hang over your home, have a tree service trim them or cut them down. 

Homes in areas at risk of wildfires should seriously consider fire-resistant products for their property. According to the Insurance Institute for Business & Home Safety (IBHS), fire is often spread by combustible fences and decks connected to houses. The IBHS recommends products like noncombustible siding, decking, playground, and roofing materials; covered vents; and fences not connected directly to the house1. Combustible structures in the yard should be at least 30 feet away from the house. Houses that are less than 15 feet apart are more likely to burn in clusters.

In general, homeowners in fire-prone areas should keep shrubbery to a minimum. Xeriscaping, the art of reducing the need for irrigation by landscaping with different types of rocks and gravel, is an ecofriendly and fire-safe option. If you have vegetation in your yard, make sure it’s 100 feet away from the home, and that you dispose of yard debris quickly. To prevent combustible materials from accumulating, or sparks from entering the home, you should screen in under-the-deck areas and cover exterior attic vents with wire mesh.

In the event of a wildfire or firestorm, shut off the gas, turn on interior and exterior lights (so your home is visible through smoke), and use a hose to wet your roof and nearby foliage. Most importantly, evacuate if you are told to do so by emergency services.

Read more: What type of maintenance does my roof require?

The Risks of Wildfires

As the conditions that create them have dramatically risen, wildfires are a growing threat to homes. According to Verisk’s 2017 Wildfire Risk Analysis2, 4.5 million U.S. homes were identified at high or extreme risk of wildfire, with more than 2 million in California alone.

Most wildfires are caused by people leaving campfires unattended, burning debris, carelessly discarded cigarettes, and arson. Longer droughts and persistently dry conditions are causing fires to burn faster and larger, making them more difficult to control. According to Mike Flannigan, director of the Western Partnership for Wildland Fire Science at the University of Alberta, the length of the fire weather season increased globally by 19 percent between 1978 and 2013. This is on account of longer seasons of warm, dry weather in one-quarter of the planet’s forests3. In the western U.S., for example, the wildfire season has grown from five months in the 1970s to seven months today.

Some of the areas at greatest risk in the U.S. are states along the West Coast, such as California, Oregon, and Washington, as well as Southwest states like Texas, Colorado, and Arizona. The Insurance Information Institute (III) reports that nearly 9 million acres burned in 2018, which is six million more than the yearly average of the 90s. The institute estimated $8.5 to $10.5 million in insurance losses just from the 2018 California Camp Fire4.

Read more : How to protect your property from wildfires

The Science Behind Firestorms

Firestorms may seem like something out of science fiction, but they are frighteningly real. They are essentially thunderstorms created from the smoke and heat of a wildfire, taking the form of anvil-shaped clouds called cumulonimbus flammagenitus, or, for short, pyrocumulonimbus. When wildfires burn hot enough to generate strong updrafts, abundant smoke particles give water droplets something to grip onto, resulting in sudden, massive cloud columns. The reaction between heat and ash particles in the cloud causes powerful lightning, triggering more fires.

When the cloud collapses, high speed winds form and can create vortexes of fire, also known as fire whirls or firenados. Wildfires pose a severe danger to property and have been on the rise in the last two decades. While around 90 percent of wildfires are caused by human activity, strong wind gusts and drought conditions contribute to their rapid spread. The Weather Channel reported that the 2018 Carr Fire in California produced a fire whirl with winds in excess of 143 miles per hour – the equivalent of an F3 tornado5.

Owing to their scale and intense conditions, these types of storms are almost impossible to fight on the ground—allowing them to grow bigger, faster, and hotter. The aftereffects of firestorms are a lingering concern that has global consequences. The U.S. Naval Research Laboratory reports that firestorms have as much energy and impact as moderately sized volcanic eruptions. Smoke and aerosols from these blazing storms can rise high into the stratosphere, where they can linger for months, obstructing sunrays and affecting our global climate.

Among all roofing types, cedar shake roofs—popular in the Northeast and Pacific Northwest—have the lowest fire rating and therefore burn the fastest. Noncombustible roofing materials such as metal or slate can help mitigate the spread of fire, allowing first responders more time to fight it and giving your loved ones more time to escape.

Understanding local climate and weather patterns greatly enhances your ability to prepare for disasters that may threaten your home. A roofing system is typically the first line of defense in protecting residential properties and commercial buildings from wind, water, ice dams, wildfires, and other forces of nature.









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