Wildland Fires: A Growing Threat

News reports about wildfires frequently feature people fleeing under evacuation orders and firefighters defending suburban subdivisions from encroaching flames. Meanwhile, the wildland–urban interface — areas near fire-prone forests and grasslands — continues to expand. Land development experts estimate that since 1990, 60% of new housing in the United States is in WUI areas¹.

More local and state governments need to develop WUI building codes to protect lives and property due to shifting development patterns. Changes in the intensity, size and duration of wildfires also demand new thinking and solutions.

Municipalities and states adapt existing WUI codes developed by national and international building code and fire safety organizations to meet local needs.

These are examples of WUI codes currently available:

International Code Council (ICC) – International Wildland Urban Interface Code (I-WUI)
National Fire Protection Association (NFPA) – 1144 - Standard for Reducing Ignition Hazards from Wildland Fire
National Research Council of Canada (NRC) – National Guide for WUI Fires
California Building Code – Title 24, Chapter 7A

WUI Building Codes: Designing Buildings to Prevent Loss

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Most local and state WUI codes mirror the International Wildland–Urban Interface Code with modifications made to reflect the specific needs of a community and its surrounding landscape. In California, for example, Chapter 7A, the WUI code, is part of Title 24, the California Building Standards Code. The state creates a map of fire hazard safety zones ranked by risk severity and designates state, federal or local responsibility. Municipalities may update their maps based on input from the county fire marshal and local legislative bodies.

In addition to requiring “defensible space” cleared of vegetation around the building, WUI codes also prescribe the use of noncombustible materials on the exterior and construction methods to prevent flame and ember intrusion into vents.

A WUI code typically includes the following components of the home:

Roofs
Eaves
Vents
Windows and exterior doors
Exterior decking and stairs
Exterior walls and cladding

The California Office of the State Fire Marshal Building Materials Listing provides architects, designers and builders with a convenient list of independently tested products that can be used reliably to meet WUI code. ROCKWOOL has four stone wool insulation products on the listing.

Check out the listings

Dive into the history of WUI codes and examples of requirements governing WUI-compliant components on a home. You’ll also find more information about the complex demands of meeting WUI and energy codes.

Learn more

WUI map of the United States

2010 Mapping

WUI map of Canada

2016 Mapping

Energy Efficiency vs. Fire Safety

Increasingly stringent energy code requirements in places such as California have made meeting fire code more difficult, and only with new thinking can we solve this challenging puzzle.

ROCKWOOL worked with Sagan Design Group to solve the challenge of complying with WUI and energy codes, which often compete against one another. Sagan engineers developed an exterior wall assembly using ROCKWOOL Comfortboard® 80 rigid continuous stone wool insulation.

To meet the energy code requirements that call for tighter building envelopes to combat air leakage and lower U-values to address thermal bridging, architects often rely on foam plastic continuous exterior insulation.

Adding extra Type X gypsum increases the material and labor costs of the wall assembly.

Added fuel load – Foam plastic insulation adds to the home’s fuel load because it is combustible.
Increased cost – Wall assemblies made with foam plastic insulation often require an additional layer of Type X gypsum to achieve the required fire resistance.

Stone wool continuous exterior insulation offers fire resistance, budget savings

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Sagan engineers showed local code officials that ROCKWOOL Comfortboard® 80 continuous exterior stone wool sheathing board provided the same fire resistance performance benefits as Type X gypsum while also helping the wall assembly reach required R-values and the strict U-value rating. Stone wool brought a variety of additional benefits to the new wall assembly.

Naturally noncombustible – Stone wool is fire resistant and can withstand heat above 2,100℉.
Time and labor savings – Using ROCKWOOL Comfortboard 80 continuous exterior stone wool sheathing board eliminates a layer in the assembly to potentially reduce installation time and labor cost.
Increased cladding options – Stone wool opens up a world of cladding options that can be used in the wall assembly.
Improved moisture management – Stone wool is breathable and hydrophobic and guards against moisture issues

Read the California House Case Study

Choosing Products for WUI Projects

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The California Office of the State Fire Marshal building materials listing includes products tested by OSFM-accredited laboratories to help building professionals source reliable products for projects in the increasing number of fire-prone areas. ROCKWOOL has four fire-resistant stone wool products — the only insulation products in the listing — that provide WUI design solutions.