By SASHA PAULSEN – Napa Valley Register

When we met for the second time to survey the progress of the house David Horobin is building in the Montecito area of Napa, the sky was murky with smoke from wildfires burning in California, as Horobin was describing the steps he’s taking to make his house “as fireproof as possible.”

For Horobin, a British architect and longtime proponent of living sensibly and sensitively with the earth, fireproofing is an essential part of building a sustainable house. In part, it’s personal: He and his wife Lynn lost a house in a 1986 Los Gatos wildfire. “I know how it feels,” he said.
That feeling he added is compounded when he hears reports of rebuilding the same kind of structure in the same place after a fire. “I watched a report about people who lost homes in San Diego fires in 2003 and 2007 and are rebuilding with stick frames — one definition of insanity is doing the same thing again and again and expecting different results.”

Not so for Horobin, who has incorporated a highly resistant shell, steel interior frame, insulated shutters, no ventilation and defensible space landscaping into the house he began building in June.
The result is what Napa County Fire Marshal Darren Drake calls “a poster project for fire-hardening,” in a potentially dangerous area for wildfires, the Alta Heights-Montecito area.

The choices he’s making will add about $3,000 to his costs, Horobin estimates, but every step not only insures that his house has the best possible chance of withstanding a wildfire, but will reap benefits in insurance rates.

Inside houses, the city now requires sprinklers, he said, an idea he fully supports for fires that start inside; but living in an area where there is a wildfire threat, sprinkles won’t be of much use when the outside of a house is gone. Horobin’s first step to help avert this is in his choice of building materials — ICF foam building blocks manufactured by Arxx — which snap together and then are filled with concrete. The resulting walls, about 11 and 1/2 inches thick, Horobin said, will yield about four hours protection if a wildfire moved through the area. “The foam may melt,” he said, “but you’re left with the frame.

“The evidence of this,” he added, “is when the Oakland fires hit, we had foam block houses standing amid the ashes.”

Inside the house he’s using steel rather than wood framing, but he noted it’s a choice he made more for quality than fireproofing. It’s hard today, he said, to find quality wood for interior frames. Wood, he said, is often “defective and warped — with steel each piece is consistent.”

“Fire seeks out the weakest links,” Horobin said. In this case, he said, it’s doors and windows.

To compensate for this, Horobin will be installing fireproof shutters that can be closed over both doors and windows. When they’re open, you’ll see an attractive wood laminate, on the inside of the shutters is a fireproof material called Densdeck, manufactured by Georgia Pacific, which will be the exposed surface when the shutters are closed.

Horobin’s design also takes into consideration another threat that’s emerging as a significant one, according to Drake: attic vents that can draw in embers from fires that in turn, smoulder and erupt into flames, long after firefighters have moved on. “Burning embers attack the smallest openings. What we’re finding from a lot of post-damage inspection is that houses are burning from the inside out.”

Ventilation is necessary for attics; without it an attic has unhealthy air with potential for mold and rot, Horobin said. “Vents do what they’re supposed to do,” Horobin said, “they draw in air — but when a fire is burning outside they can also draw in embers.”

Horobin’s solution is to build a house without attics. “With cathedral ceilings, there’s no need to ventilate,” he said.

“And I get wonderful cathedral ceilings,” Lynn Horobin said.

“He’s restricting the opportunity for embers,” Drake said, noting that new materials on the market make it possible to retrofit vents on existing houses .

To top it all off, literally, Horobin’s roof will be constructed using a “structural insulated panel system,” called SIPS, which Horobin said is “double the standard” for fire resistance. He’ll also be using the SIPS system on the roof overhangs, another place that can draw in and trap embers.

“If there’s nothing for it to burn, the fire moves on,” Horobin said.

The final element in a fire-wise house, Horobin said, is the landscaping — removing burnable debris, sticking to trees and plants less likely to burn, and creating the defensible space around the house. For this he’s turning to Tara Burns of Inside & Out Landscaping.

“If you look at all the ingredients, he’s really adding to the pot,” Drake said of Horobin’s design.

And the payoff for Horobin’s plan is already evident, Horobin noted in a recent e-mail to the Register.

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