Building Resilience – Part 2: The Role of the Building Enclosure

A video tour walks through a small accessory dwelling unit built to a passive house standard, a construction approach that uses heavy insulation and airtight sealing so a home needs very little energy to heat or cool. The building combines energy efficiency with features meant to keep people safe and comfortable through wildfires, earthquakes, and power outages. Details include mineral-fiber (Rockwool) insulation in the roof for fire resistance, blocking inside stud walls so sheathing can be nailed securely for earthquake strength, and continuous exterior insulation that prevents moisture problems and keeps the walls fire-resistant. Triple-pane windows add comfort but also buy time during a fire, since an outer pane can break without shattering the inner ones.

Outside, metal flashing and a stainless-steel screen keep embers from catching on ledges or sneaking into wall cavities, vents use small 1/8-inch openings to block sparks, and the roof is metal to resist ignition and to collect rainwater for three 5,000-gallon storage tanks. A 6.4 kilowatt solar array charges a battery, and the house also stores heating and cooling energy as hot or cold water in a tank connected to an air-to-water heat pump, letting the home stay warm or cool for a while even if the grid goes down.

The builder describes this as "passive survivability": even with no power, the insulation and airtight construction alone are enough to keep the indoor temperature from dropping below about 52°F in winter. He notes homeowners can choose how far to take these features, from bare survivability to full comfort during an outage, depending on budget and the risks where they live.