Peace of mind in wildfire country: Building in resilience

11/24/2020

“By 2030, unincorporated Marin must reduce greenhouse emissions to 60 percent below levels recorded in 2005 and, by 2045, achieve carbon neutrality.” You read that here. It’s part of a broader effort to end the emissions that contribute to global warming. With Joe Biden’s victory, achieving these goals will again be front and center across the United States, not just in California. 

Meeting them is especially important for West Marin households as they contend with the heightened risk of wildfire. Climate change extends our fire season and makes wildfires hotter and, thanks to arid conditions, spread faster. More wildfires also mean more smoke.

Whether you’re remodeling, renovating or building anew, a resilient home depends on three factors: achieving carbon neutrality, minimizing the added (non-renewable) energy needed to operate it, and minimizing the embedded (non-renewable) energy in materials and products. 

Here are seven common-sense steps you can take to build resiliency into your house project. 

Step one is all-electric. Switching to a solar photovoltaic system paired with a solar battery like the Tesla Powerwall or LG Chem RESU lets you electrify heating, cooling and hot water. In tandem with cutting your house’s heating and cooling load, you can quickly get to near-zero-carbon energy use. You can tap cheaper off-peak power from the grid and keep your lights and internet on even if the power goes out, as it sometimes does in wildfire country. As these systems become the norm in California, look for lower costs and higher performance. 

Step two is insulation. An “envelope” around a house is crucial to minimizing its heating and cooling loads. (It’s also crucial to the house’s wildfire resistance, so this step is a win-win.) The way we build houses here produces thermal bridges in the walls and roof; heat and cold leak through wood studs and rafters, which are often left uninsulated. Adding a two-inch layer of rigid insulation board outside of Densglass fireproofing and a weather barrier will solve this. Use non-combustible rockwool insulation board. Rockwool has zero flame spread and zero smoke production, unlike competing products. It doesn’t absorb moisture, so there’s no mold problem.

Step three is airtightness. Holes and penetrations from pipes, wiring and conduit can lead to a significant energy drain. Caulking and sealing with gaskets will solve it, but it’s also easy to miss something. The blower door test is a reliable way to check airtightness before closing in wall and roof framing with interior finish materials and pinpoint likely leaks. Airtight houses that use propane should have carbon monoxide detectors; all-electric houses don’t need them. 

Step four is air filtration. To maintain air quality, an airtight house should have a heat recovery ventilation (H.R.V.) or energy recovery ventilation (E.R.V.) system, which ducts incoming fresh air to living spaces and bedrooms, and outgoing exhaust air from the kitchen and bathrooms. (If the outdoor air inlet has a HEPA filter, the house will be smoke free.) H.R.V. and E.R.V. can be paired with a radiant or mini-split system, which both use a highly efficient heat pump.

Step five is the right siding. Incombustible Okoskin exterior siding, made from the remnants of the G.F.R.C. panels used on commercial buildings, is a win-win for West Marin. These glass-fiber reinforced concrete panels are cut into six-inch by six-foot strips that resemble traditional wood boards but are highly durable and fireproof, and have almost no embodied energy. 

Step six is the right decking. Remember to keep decks and trellises well away from the house proper. Redwood no longer meets the state fire marshal’s fire spread requirements for new construction in wildland urban interface areas like West Marin. Pakari, a recyclable, fire-resistant material, looks like redwood but has a harder, more durable surface. Originally from Finland, it’s now made in the U.S.A. from radiata pine grown in sustainable Forest Stewardship Council-certified forests. 

Step seven is a water strategy. California’s water-efficient plumbing code reflects how often we’re hit by a drought. West Marin often has a double whammy of winter rain—green as Ireland, some years—followed by all those arid months. A gray-water system recycles sink, shower and laundry drainage to water your plants (but not fruit and vegetables, because of likely chemical content). Consider a concrete—that is, fireproof—cistern for rainwater, which is fine for fruit and vegetables. If located uphill from your house, it’s a gravity-fed water source that will work even if the power’s out. That can be handy in wildfire country!

Resilient houses are an important part of slowing and potentially reversing climate change. The goals Marin County has set are an investment in our collective future—“priceless,” as the ads say, but also pragmatic in the same way that electric vehicles are quickly becoming. The future resale value of your home will likely hinge on its resilience and its fire resistance. Tackling both is a great way to save the planet and help keep your family and your neighbors safe and sound. 

 

Edward Dean of Bernheim+Dean Architects has designed and written on zero-net energy and zero-net carbon houses. Chuck Davis has designed buildings at Tassajara Hot Springs and The Sea Ranch. John Parman is a writer whose family is restoring an Inverness Ridge house. The authors have no fiscal ties to any of the systems and products mentioned.