North Bay engineers rethink building, home design to fend off wildfire
Some homeowners who lost large structures in the October wildfires have engaged local engineers seeking fresh ideas with fire defense incorporated into design.
For one of those engineers, Kevin Zucco, executive principal of ZFA Structural Engineers, based in Santa Rosa it's personal. His father Greg, founder of ZFA, lost his own Santa Rosa home on Foothill Dr. The company has offices in Santa Rosa, Napa, Sacramento, San Francisco and San Carlos.
A home or commercial building can resist fire. “It would have non-flammable exterior cladding,” Zucco said, “stucco, plaster.” The structure itself, including roof framing, would be concrete, masonry blocks or steel.
Better window glazing is essential to survive heat and wind. Roof design has to change so windblown embers don't create a fire pit on top of the structure that ignites anything flammable.
John Cook, senior principal at Rohnert Park-based MKM & Associates Structural Engineers, spent 30 years designing office buildings, schools, industrial complexes, parking structures and homes. Hundreds of homes and businesses designed by MKM burned. “We did the majority of Coffey Park,” he said, where more than 1,000 homes burned, “and a lot of Fountaingrove.”
Cook has started discussions of fire-protective watering systems with homeowners whose places burned. “That would be a relatively inexpensive additional safety measure,” he said. “Putting sprinkler heads in is not that expensive. You need an emergency generator” in case of power failure.
Each home or commercial building could have its own koi pond or pool. If automated sensors detect heat from oncoming flames, perhaps 250 degrees, a pump draws water out of the pond and sprays it over the building. Water running down the sides of the structure would collect in concrete troughs that carry water back. A pump could have automated backup - generator or batteries in case of power failure.
Such a structure, with a watering system similar to those used for landscaping, might cost an additional $20,000 but would obviate fire insurance and nearly guarantee the home's survivability. Interior sprinklers already help quench indoor fires, but current design does not protect a building's exterior.
“I know of individuals who saved their houses by spraying them down” with garden hoses, Cook said. “A few people around the perimeter made sure embers didn't stick on the house or get under the eaves. This is very feasible,” he said.
“A lot of newer houses had interior sprinkler systems,” Cook said. “It didn't do any good” in the intense heat generated in this firestorm. “Most house fires are from the inside out. There could be a cost-effective way to install sprinklers on the roof as part of construction. Make them look like weather vanes, ornate,” he said.
“People are thinking about” ways to use on-site stored water to fight a fire, Zucco said, such as a swimming pool or pond. “They have systems where you can drop a nozzle into your pool and shoot it out” with a gas-powered pump, he said.
“I've never heard of one that's automatically piped into your house. It's pretty interesting.”
As for designing the building itself to be fire-resistant, “the issue is not, can it be done,” Cook said, but cost. “What are the architectural ramifications (ugly). Walls could be completely fireproofed. The building would still burn down because windows blew out. Unless you enclose windows, you're not going to” stop fire.
“You could design shutters” that would protect windows and doors, “impenetrable to any fire, including this fire,” he said. “What would that look like? What would it cost? Your $1 million structure now costs $1.5 million. You have a $500,000 additional cost for the chance that another event like this might happen.”
In advising property owners how to rebuild, Cook assesses the probability of another similar fire happening in the next 100 years - cost-benefit analysis. “My hunch is that it wouldn't be cost-effective to retrofit all buildings or incorporate fire-resistant construction” in rebuilding, he said.
Cook visited many burned sites. “Aluminum melts at 1,200 (degrees Fahrenheit),” he said. “Steel melts at 2,400 and will start deforming if under load at less than that (about 2,000°.)” He observed warped steel beams.
“It got very hot,” Zucco said.
Engineers look at fire-ruined building sites for clues to the fire's temperature. “We saw puddles of aluminum,” he said.
He examined custom homes that burned. “Structural steel, bent down and sagging over,” he said. “Steel turns red and loses its strength. It deforms, a nice S-shape, doesn't do any good.”