WEEDS
Facts
What is WEEDS?
WEEDS stands for Wind-Enabled Ember Dousing System. The term WEEDS describes the principle of aiming sprayers away from the structure in order to make use of the wind to disperse spray onto the structure. In this way, the windward side of the house, where firebrands will hit, obtains maximum protection. WEEDS can protect the walls, roof, under the eaves, “nooks and crannies”, and even materials within a few feet of the house.
Why are embers, or firebrands, important?
Firebrands can travel much further than the 100 feet recommended as defensible space under high-wind conditions. They’ve been observed to ignite structures up to half a mile from the fire front. Full protection of a structure requires ember-proofing.
So how does WEEDS differ from normal under-eaves sprinkling systems?
In a conventional sprinkler system, the sprayers will be directed against the side of the building, or over the roof if they are mounted on the rooftop. The spray from conventional heads may be blown downwind under high wind conditions, leaving parts of the structure unprotected. Also, conventional sprinklers use water at a high rate, whereas WEEDS uses low flow rates for extended protection time.
How much water does WEEDS use?
We’ve obtained good protection at a flow rate of less than 30 gallons per minute. For a 5000 gallon tank, this means over three hours of protection after the system is turned on.
You can’t put out a fire with a flow rate that low!
No, but you can put out a match. WEEDS is designed to douse incoming firebrands and to keep them from igniting the home. The same wind that carries burning embers will also carry spray, so firebrands will strike only pre-wetted surfaces. The amount of water needed to extinguish small firebrands is minimal. WEEDS is not a fire-suppression system, but an ember-dousing system.
What if there is no wind?
Then WEEDS will not work. However, most structure loss during wildland fires
occurs under high-wind conditions.
How do you protect against radiant heat?
WEEDS is designed to supplement the idea of defensible space. Homes need to be protected from direct flame and radiant heat by proper clearing of nearby fuel sources. WEEDS then provides the final layer of protection by ember-proofing the structure.
Are you patenting it?
Because a patent would be extraordinarily difficult to enforce, and to provide a public service, I am instead putting WEEDS into the public domain by making a full public disclosure. I am developing some related patents, but WEEDS itself as stated here is fully available for public and private study and use, without royalty or other charge.
Is “WEEDS” a trademark?
WEEDS is not a trademark. It is a term of art that describes a certain principle used for outdoor fire-sprayers.
How sure are you that it works?
Right now, WEEDS consists of a good theory and a proven prototype. Our home, with an activated WEEDS system, survived the San Diego Cedar Fire, while all adjacent homes to ours burned. We took a number of measures to protect our home, which may also have helped. Based on wind speed and observed ember damage in our yard, however, I believe that WEEDS covered the gap left by defensible space and saved our home.
What other protective measures did you take besides installing WEEDS?
We made sure that we had adequate defensible space (100 feet) so that our home was protected from radiant heat. We boxed in our soffits at the time we installed WEEDS. We covered one of our attic vents, the lowest one, with a closeable door. Our home had been sited with an adequate set-back from the ridge line (50 feet) with some ice plant on the eastern slope.
What about other methods for protecting a house against embers?
It is possible to build an ember-proof and fire-resistant home. The majority of these techniques, however, are of most use during the design and construction of the home. Our implementation of WEEDS was done as a retro-fit, and protected a wooden structure that would have otherwise been vulnerable.
Where can I find out more about WEEDS?
A website showing WEEDS details, including drawings and photos, is being set up at
My contact information is:
Joseph W. Mitchell
19412 Kimball Valley Rd.
Ramona, CA 92065
jwmitchell@mbartek.com
760-703-7521