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[Fire Smart]
Many of us watched the massive wildfires in fall, 2003 and wondered, "what can we do to protect our home from fire?" Since it is difficult to recreate a wildfire in a lab, there has been little laboratory research on what changes can be made to a house in order to eliminate any "weak points." However, many veteran firefighters, and fire officials across

the United States have singled out changes that can be made to greatly increase your house's survival success from an encroaching fire.

The problem with soffits and attic vents




Exposed soffits and eaves are potential heat traps and are at risk of catching fire. But this problem isn't the only threat. Soffit vents, which are designed to allow a roof to breath, also provide a freeway for flames and heat to enter an attic. To minimize exposure, enclose all eaves and soffits with a mold resistant gypsum underlayment. Cover it with fiber-cement sheathing. To vent attic spaces, it's safer to use ridge or gable vents. Be sure all exposed vents and chimneys are covered with 1/8-inch corrosion-resistant steel screens to keep out convection-driven embers.


Exterior Siding - Enclose your house with firewalls



Exterior walls are vulnerable to both radiant and convective heat from a wildfire. During an intense fire, vinyl and aluminum siding melts, exposing the wall's vulnerable interior. A layer of 5/8-in gypsum sheathing under either vinyl or aluminum siding can increase the level of protection significantly. However, non-combustible and fire treated wood sidings are the preferred choice of materials.


Siding materials like cement stucco, stone, pressure treated cedar siding, or other masonry materials are better choices if you live in a fire-hazard zone. But stucco and other masonry assemblies are prone to cracking and need to be maintained to be affective.

A good site plan is your first defense against wildfire



Consider fire defenses as a series of concentric spaces, or zones of managed landscape around your home. These zones act as natural breaks that can slow the spread of fire. Consult your local forest-service agency (www.fs.fed.us) for help with selecting plants that have natural fire resistance.

Long-term maintenance is also important. You should eliminate "ladder fuels" - vegetation that provides a path for fires to climb from the ground to the treetops - by removing tree branches that are within 12 feet of the ground. To eliminate potential fuel sources:
  • remove dried vines from the side of the house
  • keep gutters clean
  • sweep your roof of any build up debris
  • prune shrubs
  • remove dead leaves
Also, you should store firewood and flammable fuels at least 30 feet from the house. Any plants that can dry up and burn easily should be kept away from contact with the side of the house.  

Noncombustible materials won't make a house fireproof
While a noncombustible material like metal roofing or siding doesn't burn, metal is an excellent heat conductor. During an intense fire, enough heat can be conducted through the metal to ignite the material behind it.

When grouped with noncombustible materials, fire-rated assemblies can provide additional protection. A fire-rated assembly is a combination of materials forming a component of a building, such as a roof or a wall, which resists ignition while protecting the rest of the structure.

Fire rated assembly comes in a Class A- B- or C-rating. The best form of a fire rated assembly for a roofing material is a Class "A" assembly that uses pressure-treated cedar shakes with a fiberglass underlay. This arrangement adds an additional protective barrier for the home.

The most vulnerable component is the roof

The American Society for Testing Materials (ASTM) has a test to determine the hourly rating of an assembly. It exposes an assembly to heat and flame on one side and tests for heat transmission, burn-through, structural integrity, the ability to withstand water pressure from a fire hose, and the assembly's capability of carrying its own load.

During a fire, wind-driven embers, which have been known to travel as far as ½-mile from a wildfire, can stick to the rough surfaces or valleys of a roof. If roof materials are flammable, the structure can catch fire long before a wildfire arrives. To protect your home, consider using any of the three classes of fire retardant pressure treated cedar roofing materials available.

It's recommended that if you are going to chose an assembly, choose the highest level of protection for your home with a Class "A" rated roofing system which uses a fiberglass underlay beneath the pressure treated shingles for optimal protection.

A roof sprinkler system is, at best, a backup to a fire-resistant roof assembly (See National Fire Sprinkler Association web site at www.nfsa.org). Although a wet roof can reduce the chances of radiant and direct-flame combustion, roof sprinkler systems aren't foolproof. Water pressure tends to be low during a fire, and if sprinklers are pump driven, the electricity that powers the pump can fail. Also, fire-generated winds can redirect the spray from the roof.



Windows and skylights are vulnerable

Windows and skylights are weak points. That's because they can fail before a building ignites, allowing fire to enter a house. (Which is why an interior sprinkler system is a good idea). During a wildfire, single pane windows last only a couple of minutes before they break. Thermo-pane and double-glazed windows last twice as long.

During a fire, the window's sash causes a differential in the heating and stressing of the glass, causing it to crack. On smaller windows (less that 2-feet wide), cracked glass usually stays in place and continues to offer some protection. On bigger windows, glass falls out because it's too heavy for the sash to hold.

Your best bet, especially on the windward side of the house, is to use non-combustible shutters that latch to protect your windows. Another good practice is to use low-e (low emissivity) tempered glass. The ultra-thin metallic coating on the glass dramatically reduces the fire's radiant energy from entering the house and possibly igniting drapes or other flammable material. Tempered glass, although expensive, resists high heat that weakens most glass and resists impact from wind-thrown objects.

Low-e tempered glass needs to stay in place. Vinyl frames warp, and then melt until the window fails. All aluminum frames would seem like the best choice because there are no combustible components; however, they melt at 1200 F. Pressure impregnated wood sashes will hold the glass in place best.

If replacing your existing windows isn't an option, you can use full-cover metal screens of noncombustible storm panels (www.shuttertime.com) to protect windows from heat and flying embers. These galvanized-steel storm panels aren't rated for fire but are used to protect windows from hurricane force winds and blown debris.



Decks and fences are potential fire bridges 

An attached deck, trellis, or fence should get the same attention as a roof. A deck on a sloping hill is the ultimate firetrap. Fast-moving ground forces can ignite a deck, turning it into an unwanted barbeque. If a wood deck is your choice, enclose you perimeter below you deck with 1/8" metal screening, fire retardant treated siding or non-combustible siding. The screening will stop burning embers and combustible materials from blowing under the deck.

Choosing decking material is also an important. A recent study conducted by fire marshals in Arizona showed that many of the new synthetic materials are more prone to fire than traditional cedar or redwood decks. Although more rigorous testing needs to be completed, you should choose these materials carefully.

After a wildfire rips through a forest, all that's left is the blackened tree trunks rising from the scorched earth. The thick trunks don't turn to ash because they have a low surface-to-mass ratio. They burn, but slowly, which is why heavy timber decks are considered appropriate for medium to high-risk areas.

Typically, decks are made from 2x materials. While perfect for load bearing structures, 2x materials have a low surface to mass ratio and catch fire quickly. When building a deck from wood, to give the maximum protection from fire, large 6" or thicker beams should be used for structural supports and at least 3" thick boards, with a pressure treated fire retardant, should be used for decks.


What are the chances of surviving a large-scale wildfire?  

Bill Mills, from the Colorado Springs Fire Department stated, "If you create a defensible space with all your roof and exterior home elements, in an extreme wildfire (which typically means mammoth 100 foot high flames, traveling at 100 miles per hour), your home might have a 50% chance of survival".

In the British Columbia and California wildfires of 2003, many homes simply imploded. This was due to the massive temperature differentials from the gigantic wall of flames that approached these houses.

Studies done after the 1990 Painted Cave Fire, which involved an analyses of hundreds of aspects that may influence survivability, found that homes threatened in the typical wildfire encroachment with a fire-rated roof and exterior, and a vegetation clearance of 10 meters or more had a 90% survival rate, which increased to 99% when defensive actions where also taken by civilians or firefighters.

On the flip side, it has been said, a home with no defense elements had only a 20% chance of surviving a wildfire. The majority of homes in the US are built in areas that are considered low-risk to wild fires. In these areas statistics show that less than 1% of home fires originate on roofs of any type. 98% of homes burn due to ignitions from inside the house.


Why do some districts choose to ban wood roofs?

Often it is a lack of informed decision-making that contributes to a politician's or building official's ruling to ban wood in any given area. The majority of the time officials don't even understand that Class-A wood roof is considered equal in the level of fire protection offered as other non-combustible roofing materials rated by organizations such as UL. ICBO, UBC, NFPA, and the ASTM.

In a majority of the cases, when building officials are not influenced to make quick rulings, due to such large scale disasters such as the California fire of 2003, and research is conducted into the various different fire rated roofing materials available on the market and the qualifications they hold, wood roofing is always an option used in those district's building codes.

Areas such as:
  • Pueblo, Douglas County, Co. Class "C"
  • Jefferson County (above 6400 feet), Co. Class "A"
  • Park County, Co. Class "A"
  • Castle Rock, Co. Class "A"
  • Boulder City, Co. Class "A"
  • Boulder County , Co. Class "C"
  • The entire state of California has requirements from Class "A", "B" and "C"
  • Chaparral Pines Subdivision, Arizona Class "A"
  • And many other districts around the United States
For information on ways that your state can protect against wildfires visit:

www.for.gov.bc.ca/protect
www.fire.ca.gov/FireEmergencyResponse/FirePlan/FirePlan.asp
www.nifc.gov/harvesting/index.html






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