Building resilience to wildfires

Building Resilience Against Wildfires

03-24-2022

Wildfires are not solely destructive, they have an important role in forest ecosystems, but wildfires pose a risk to the lives of people who live near those ecosystems. 

Moisture is one of the primary factors that determine the frequency of wildfires. Dryer winters caused by the changing climate have resulted in a longer fire season with more devastating wildfires, at least across much of the West Coast of the U.S.

Wildfires prove to be a greater safety risk to populations bordering wildland areas, known as Wildland Urban Interface (WUI). The Federal Emergency Management Agency (FEMA) describes WUI as a zone of transition between unoccupied land and human development. It is the line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.

The U.S. Department of Agriculture (USDA) Forest Service defines “At-risk communities” as communities in proximity to WUI. These are areas where conditions are conducive to a large-scale wildland fire disturbance event, thereby posing a significant threat to human life or property. 

Although the WUI zones are considered at high risk for wildfires, urban development in these areas continues to grow. Data from FEMA shows that currently, over 46 million residences in 70,000 communities in the U.S. are at risk from WUI fires and that the WUI area continues to grow by approximately two million acres per year. Furthermore, research from 2018, states that 97% of the growth in WUI is due to new housing and that WUI growth often results in more wildfire ignitions, putting more lives and houses at risk. The research claims that one way to halt the increase in wildfire ignitions is to avoid new housing in WUI zones. 

 

Is My Home At Risk For Damage From Wildfire?

If your home is located in a WUI zone, you are at a higher risk for wildfires. The risk level is also dependent on the immediately available fuel sources on-site, the weather, the topography, and the assets at risk.

A hazard and risk assessment can help determine the level of mitigation that is needed for a building. The assessment, which can be conducted at a regional, state, or local level, needs to be both credible and professional to ensure that the analysis is accurate, comprehensive, and verifiable. 

To find whether your property is at risk from wildfires, the USDA Forest Service created an interactive map that shows the wildfire risk to your community, when submitting desired locations.

In cases of high risk, there are many ways in which you can protect yourself and your home. According to FEMA, state and local codes should include requirements for wildfire mitigation for both new construction and upgrades to existing buildings in wildfire zones.

Although the International Fire Code (IFC) is adopted by all 50 states, it focuses mainly on fire alarm systems and sprinkler protection. On the other hand, the International Wildland-Urban Interface Code (IWUIC) establishes regulations for the safety of life and property from the risk of wildfires, by focusing on fire-resistant building materials, preventing embers from penetrating into the house, and the design of the landscape around the house. This code is currently adopted in 20 states, most in the Western part of the U.S.

Building Resilience

A widely cited report from 2017 mentions that every dollar invested in the implementation of the IWUIC results in a $4 national benefit, hence, any fire-protective measure will not only protect you and your home, but it will show a return on your investment and benefit the nation.

According to FEMA, in areas where buildings are particularly vulnerable to the risk of wildfire, implementing measures that exceed the codes can improve the probability that a building will survive a wildfire. 

FEMA provides a homeowner’s checklist to help avoid wildfire damage and a more extensive guide, based on these and additional resources. 

The following strategies should be adopted if your property is at high risk for wildfire and help homeowners understand how resilience is built:

 

Location

As mentioned, it would be best to avoid new construction in WUI zones and choose a location that is not at high risk of wildfire.

Also, consider additional aspects of the location of your property. Since wildfires follow the direction of the wind, properties that are located in areas frequently exposed to strong winds, such as at the top or mid-slope of a canyon, are exposed to a higher risk for damage from a wildfire, as opposed to a property at the bottom of the valley. Saddles, which are the lowest area between two highlands, act as wind funnels and are one of the most hazardous locations for homes (in terms of wildfires). In the absence of strong winds, wildfires follow the topography and spread upslope quickly because heat rises.

Consider also the vegetation at the location site: south and west-facing slopes are generally drier. On the one hand, this means they produce less vegetation, less fuel for wildfires, but on the other, they tend to ignite more easily and burn faster. The more heavily vegetated moist slopes have a lower potential for ignition but can sustain a more intense fire for a longer duration. 

 

Defensible Space

Surrounding your property with noncombustible material can lower the risk of damage from wildfires. This is called defensible space. In this space, it is best to avoid vegetation unless it is fire-resistant, at least in a radius of 30 feet around the house. Make sure to trim yard growth, remove flammable debris often, and use non-combustible materials for landscape fences and decks. 

In a larger radius of 50 feet, make sure to separate potentially flammable structures, trees, bushes, or other vegetation.

 

Fire-Resistant Materials

Combustible exterior building elements such as roof coverings, siding, and decks increase the risk of damage or total loss to a property due to their high probability to ignite during a wildfire. Consider using non-combustible or fire-resistant materials for exterior components. It is also critical to implement a fire-resistant design to reduce the risk of fire penetrating the building envelope through vents, unsealed mechanical or electrical openings, and through windows broken by heat or wind-blown firebrands. 

 

Protect Your Roof

The roof is the most vulnerable component in a wildfire due to its size and orientation, and the likelihood of a property surviving a wildfire is greatly dependent on the assembly of the roof. 

  • A class A-rated roof with noncombustible coverings is recommended. For homeowners with roof assemblies that are not Class A-rated, consider re-roofing to reduce roof vulnerability to wildfire such as removing the materials above the roof deck and replacing them with new materials.
  • Use non-combustible/fire-resistant materials for eaves, overhangs, and soffits to reduce the risk of their ignition due to a combination of windborne embers and convective and trapped radiant heat. Consider avoiding overhangs altogether or using eaves with short overhangs and flat soffits with a minimum of 1-hour fire resistance. 
  • Choose gutters constructed of noncombustible materials and consider adding noncombustible metal leaf guards over the gutters, to avoid ignition of debris such as leaves. 

 

Openings

  • Vents should be kept at a minimum of 10 feet from property lines and other buildings. They should be constructed of metal products, and have corrosive-resistant quarter-inch metal mesh screens to avoid embers and hot gases from penetrating and igniting the interior of the building. 
  • Choose fire-rated windows and doors. Consider adding weatherstripping and noncombustible or fire-resistant trim. Dual or triple-pane thermal glass windows, and fire-resistant shutters or drapes, can help prevent radiated heat from passing through and igniting combustible materials inside the house. These measures are even more significant for large windows since the larger the pane of glass, the more vulnerable it is to fire.

 

Additional Measures

  • Install interior and exterior fire sprinklers to prevent significant damage to the building, protect nearby buildings, and help prevent the fire from spreading further.
  • For fire protection, utility and equipment connections should best be installed underground. If this is not an option, try sealing small utility penetration into the building with fire-resistant materials and cover larger gaps with fire-protective sheets or pillows. Fuel such as gas should be stored underground, or 30 feet away from the house, and surrounded by a noncombustible barrier

This report specifies different costs for fire-resistant construction for different elements in the house and concludes that building a new fire-resistant house isn’t necessarily more expensive than the construction of a standard house. 

A community in Montecito, CA, proved that the investment is worthwhile. Since 1994, the community has been fighting its vulnerability to wildfires by reducing fuel sources in the community, increasing defensible spaces around homes, among other measures. Due to those efforts, in the Thomas Fire in December 2017, Montecito lost only 7 structures out of more than 1,000 and more than 280,000 acres burnt.

 

Smoke Exposure

In the wildfires that occurred in the fall of 2020, our house was not at risk of damage from the flames, but the smoke from the fire settled and covered a large region surrounding our house for days and weeks. The smoke-filled air forced us to stay inside to avoid being impacted by the smoke. For us, and many others, wildfire protection will always include thinking of indoor air quality within our homes and the potential smoke damage from wildfire.

During a wildfire, smoke can make the outdoor air unhealthy to breathe, and it can enter your home and make it unhealthy to breathe indoor air as well. Indoor air quality deserves a blog post on its own, but in short, to avoid smoke getting into the house, the structure needs to be air-sealed as much as possible. 

Try to avoid using a ventilation or central heating and air system that takes air from the outside. Instead, you should recirculate the air in the house if your HVAC system cannot do this, you can purchase a portable air cleaner, and an indoor air quality monitor to make sure your measures are beneficial.

 

Final Thoughts

To mitigate the risk and damage to people’s lives and property, new construction in WUI areas should be avoided. 

Properties that are already located in areas of high wildfire risks, can significantly reduce potential damage by implementing fire-resistant strategies that adhere to or exceed the IWUIC code. 

Such strategies focus mainly on fire-resistant materials of different elements of the exterior of the house and the landscape, their design, and layout. Health damage from smoke can also be avoided by implementing strategies such as recirculating indoor air and using air-purifying options. 

These strategies not only provide a good return on investment but they have been proven helpful in protecting from wildfire damage.

 

KEEP COOL. BUILD RESILIENCE. EAMPACT

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