In late 2008 and early 2009 I was building a house in Mission Canyon, and the Tea Fire of 2008 and the Jesusita Fire of 2009 both came within 200 yards of the job site. Since my home was under construction and not closed in, I stayed to try and protect the structure as long as the authorities would let me, soaking the exposed wood framing with a garden hose. By luck, the house survived, but as I watched the unbelievable size and power of the approaching wall of flames, I realized that I had never known exactly what a wildfire does. From a half mile away, the heat was so intense it would hurt my eyes if I didn’t look away. The flames dwarfed 50 foot trees and ate them up in seconds. Violent gusts of wind would blast through erratically, pushing rivers of embers down the street several feet high off the ground and depositing them against walls and fences. Large glowing embers floated overhead. I left before it got really close.
Imagine a blowtorch in your hand as you walk around your current home. Is there any part of your house that you could ignite within a minute or two? That is how resistant a building material must be to survive the intense heat, gale force winds and glowing embers of a wildfire. Most homes will not be lost to a large fire that slowly approaches without a windstorm behind it. Firefighters will be able to stay and fight the fire without risking their lives and they can generally keep structures from burning. This is the type of fire they have in mind when they promote “defensible buffer” landscape clearing. But as soon as the wind starts, the firefighters leave, and the house falls under direct assault of the fire front. Very few homes, even stucco or cement board faced, will survive on their own. Why? The answer is almost always: the glass. Normal float glass, even double pane, will shatter from thermal stress as soon as the flames reach it, allowing the wind and embers inside, and it’s all over. The California Building Code Chapter 7A Fire Construction codes now address this issue, with new glazing in high fire areas required to be double pane with at least one pane of tempered glass. Tempered glass, which has been strengthened by heating and cooling, is far more resistant than ordinary glass to breakage from temperature change. However, the Code fails to foresee the strong winds and huge likelihood of flying debris ahead of a huge fire, and tempered glass will still break and fall when hit. Another critical failure is the melting of vinyl framed windows and doors. The best answer is metal framed or metal-clad windows and doors with laminated glass, which is a sandwich of two or more panes with a clear vinyl layer between them, as in a car windshield. Laminated glass will not fail in a fire situation until the frame around it fails, and it is the best insurance you can get against wildfire.Most existing homes, even in high fire environments, do not have even tempered glass windows. Laminated glass is almost unheard of in most areas (though required in Florida due to hurricanes). But retrofitting an otherwise fire-resistant home with laminated glass windows would be the single most important upgrade you could make in a high fire area. Fitting a new home or major remodel with laminated glass may be just a 20% premium added to the cost of the windows and doors, but it is one that will give you the best advantage by far.
All new homes and major remodels in California are now required to have automatic fire sprinklers installed. While these can save lives due to the slowing of fire spread or dousing accidental small fires, they will not extinguish a fully involved structure and are of no use whatsoever in a wildfire approaching from outside. In fact, the triggering of fire sprinklers in houses that are totally engulfed in flames is likely to result in the use of massive amounts of water and loss of water pressure in the neighborhoods affected, which could very well hamper the firefighting efforts.
Other important fire resistive construction concepts include minimizing door and window trim details, installing barriers to keep flame and embers from entering attics or going under decks and stairs, filling all void spaces at eaves tightly with insulation, and using only exposed lumber larger than 4x6, which is much harder to ignite than thinner boards. Completely noncombustible materials are also available but not required. Roofing is always required to be Class A fire resistant, so choosing one roof type over another is not going to make the biggest difference. Installing a garage door opener with a built-in battery backup can be helpful in getting people safely evacuated in time when the power goes out. In extremely risky or remote areas, it is often easy to build a small fireproof room or partial basement for last-chance shelter or protection of valuables, or to purchase a gas-powered firefighting pump kit for your swimming pool. There are many approaches to fire protection, and almost all of them have some merit, but as you begin to consider the combustibility of all of the elements of a house, you will realize the weakest link is always the glass. Despite this, the idea of a house with fully laminated glazing has yet to be widely recognized as the best response to the threat of wildfire. Please contact me if you would like to discuss even more advanced concepts of fireproofing your home.