This Fire-Fighting "Mist" Is How Some Homeowners Protect Their High-End Properties
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After the 2017 wildfires in Napa Valley, California architect Katherine Schwertner helped some clients of the firm she worked for at the time rebuild their fire-ravaged home exactly as it had been—only with added layers of fire protection. She researched all manner of fire protection, and came up with some innovative solutions.
Chief among them was a perimeter sprinkler system installed about 200 feet from the home that creates what Schwertner calls "a ring, or a belt, or a moat around the home that is the first line of defense."
When the system's heat sensors are activated, it goes off, spewing a combination of fire retardant and water into the air. "It creates a fire break," Schwertner explains, allowing for the second line of defense to be activated: an exterior sprinkler system built into the eaves and above the windows of the home.
A Moat, A Mist, A Cloud
Branden McDonald, director of development for Centric General Contractors, who worked with Schwertner on the project, explains that while it is a ring of defense around the home, the perimeter sprinkler system doesn't really create a moat but more of a protective cloud. When activated, "the interior mixing valve combines the fire retardant with water, and sprays out about 100 feet in every direction around the house, soaking the ground. When and if the fire comes up the hill, it reacts with the moisture in the ground and creates kind of a cloud system, so any embers would be flying through a mist and cooling off before they actually landed on the home."
While the exterior sprinkler system on the house coats the home with water, the perimeter system "continues to spray, creating that kind of mist," explains McDonald. "It's a tropical feel rather than the arid, dry windy climate that the fire is approaching with."
Think of these perimeter systems as superpowered lawn sprinklers; instead of spraying water about 10 feet in every direction, they cover 100 feet in every direction, with a mix of water—which evaporates quickly in a fire situation—and fire retardant, which lasts longer. "The heat begins to evaporate all of the water that's now soaked into the ground, and that evaporation turns into a mist or a cloud creating more of a tropical non-burnable area," explains McDonald.
Different types of retardant are available in a variety of price points, but the high-end kind used in this particular home, says McDonald, is biodegradable and nontoxic—"you could drink it straight out of the sprinkler head if you wanted to. It’s similar to what they use in airports to put out an aeronautics fire. It lasts for about two weeks and then washes away into the soil and ground and and actually acts like a fertilizer—although it does leave a film on the window that needs to be washed off for aesthetics."
How Do I Create a Fire-Fighting Cloud System for My Home?
While sprinkler companies have been experimenting with similar perimeter systems in a more rudimentary way for 10 to 15 years, says McDonald, it was after the 2017 Napa fires that this kind of fire protection became a go-to option for the types of properties Centric works with—luxury homes, resorts, and wineries. (For the rebuild that McDonald and Schwertner collaborated on, they worked with a company called WaveGuard.) If you're considering a system, you'll want to have it installed by a company that specializes in fire-retardant sprinklers. "They're typically a certified system because, as you can imagine, there's some liability to this not working," says McDonald. "Most of these fire sprinkler professionals would be installing it themselves or contracting it directly, much like you would have for a home builder. They take on all of the scope of work and make sure that the system works and would then carry on with the maintenance."
That being said, McDonald muses, "there are ways you could go down to the Home Depot and buy a bunch of pipe and set up valves and do it yourself, but it's a very different system. It would be like a soapbox derby car versus something that comes off of the Ferrari line."
While you hope your perimeter fire-fighting sprinkler system will never have to go off, you will want to have it tested it yearly to make sure that it will if and when it needs to. "A couple of times annually, we will go through, deploy the system, make sure the valves are clean, make sure that they open and close, make sure that a woodpecker hasn't pecked off a piece of the sprinkler systems," McDonald says. "The systems have valves that switch off the retardant deployment so you can run it with just water, because the retardant is more expensive. It's not ideal to practice with that."
McDonald's parents' perimeter system underwent an unexpected test recently when a rogue hot air balloon from the Napa Valley had to do an emergency landing on their property, and the heat set off the sprinklers. "At least we know it works," says McDonald, whose family has lost three ranches to wildfires over the past decade and a half. "We've been very fortunate to not lose any primary residences, and some of that is based on the sprinkler systems, many of us were out on bulldozers and fire trucks and pump trailers, making sure that we could help out the fire department in any way possible."
In the end, it doesn't matter if you think of your perimeter sprinkler system as a moat, a cloud, or a mist—as long as it works when you need it to.
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