By NFPA's Michele Steinberg
From NFPA's Fire Break blog
A recent article in the Colorado Springs Gazette has some Colorado property owners extremely upset about wildfire mitigation. An insurance spokesperson is quoted as saying, “We recommend cutting all trees within 100 feet of a house,” and then referencing changes in NFPA’s recommendations about wildfire safety and defensible space.
So what does NFPA’s Firewise Communities program actually recommend? And have we changed our recommendations?
For more than 15 years, NFPA’s wildfire safety recommendations have been shaped by fire science research on how homes ignite. Our Firewise Landscaping and Construction Guide, one of our primary information resources, has stated, for some time now, “The primary goal for Firewise landscaping is fuel reduction — limiting the level of flammable vegetation and materials surrounding the home and increasing the moisture content of remaining vegetation. This includes the entire ‘home ignition zone’ which extends up to 200 feet in high hazard areas.” The document then breaks out the home ignition zone concept into intermediary zones, starting with a 30-foot perimeter around the house and attachments. This information is not new…and it hasn’t changed in years and years.
Safety in the "home ignition zone": The concept of the home ignition zone was developed by USDA Forest Service fire scientist Jack Cohen in the late 1990s, following some breakthrough experimental research into how homes ignite due to the effects of radiant heat. The 30-foot number comes from the very minimum distance, on flat ground, that a wood wall can be separated from the radiant heat of large flames without igniting. Because of other factors such as topography, the recommended distances to mitigate for radiant heat exposure actually extend between 100 to 200 feet from the home – on a site-specific basis.
Property owners need to address the "little things" first: We advise property owners to start with the house and work their way out. Having a nonflammable roof covering and assembly adds an enormous safety measure. Keeping roofs and gutters clean and clear of leaves or needles is critical to minimizing ignition from embers. Flammable attachments (e.g., untreated wooden decks) are very vulnerable to ignition and can carry fire to the main structure. Keep flat surfaces clear of debris. Clean out any leaves, needles or stored material that could burn from under decks or porches. During this high fire danger season, remove large potential heat sources such as piles of firewood, spare building materials, vehicles - anything that could catch embers or ignite by flames in the grass needs to be as far away from dwellings as possible.
Remove fuel sources close to the house: The perimeter of the home and attachments out to about 5 feet is vulnerable if there is anything there - organic mulch, woody shrubs and plants, juniper bushes - that could ignite and thus allow flames to touch the house. Wind-driven fire will create a blizzard of embers that will pile up in corners where you might normally find accumulations of leaves or needles around your home. These corners, nooks and crannies should be clear of any flammables. If there are any limbs or branches overhanging the roof, or any branches close to/touching the house, trim back to at least 10 feet from the house. Keep grass mowed low and well watered if possible.
Larger projects to reduce potential fuel: Our tips for homeowners also cover projects they can undertake when fire is not imminent - landscaping to create space between trees, removing heavy accumulations of brush or trees out to 100-200 feet depending on slope and topography (because radiant heat ALSO causes homes to burn), creating a low-water (xeriscape) landscape, adding hardscape (rock or concrete patios, walkways, etc.) to break up the path of flames, screening vents or openings with fine metal mesh, replacing windows with double- or triple-paned alternatives or tempered glass - the list goes on.
There are things you can do to protect your home: While this article has generated a lot of controversy and conversation on the problem of homes burning down during wildfires, the important thing to know is that residents are able to take effective action to protect their homes. That’s why NFPA focuses on the science behind how homes ignite and provides actionable guidance for homeowners. The bottom line is, there are very effective things that homeowners can do to protect their properties from wildfire ignition – and thus from being destroyed. Chopping down every tree in sight doesn’t appear anywhere on the Firewise list of recommendations.