Three years ago, on Dec. 30, 2021, a wind-driven wildfire^[1] raced through two communities just outside Boulder, Colorado. In the span of about eight hours, more than 1,000 homes^[2] and businesses burned.

The fire left entire blocks in ash, but among them, pockets of houses survived^[3], seemingly untouched. The owners of these homes may have felt relief at first. But fire damage can be deceiving, as many soon discovered.

When...