Part 1: Understand fire ยท Chapter 1
How fire reaches a house
Fire reaches a house in three ways: embers, radiant heat, and flames touching it. In wildfires, embers cause most of the losses 2.
Embers
Embers are burning bits of wood and plants carried on the wind, sometimes more than a mile ahead of the fire 1. They land, pile up and smolder, often on roofs, decks and porches, until something catches 2. They also get inside through vents. NFPA recommends covering eave and attic vents with 1/8-inch metal mesh 1.
Radiant heat
Burning plants, fences or sheds next to the house heat up its walls and windows. In IBHS's tests, plants in the first five feet around a house raised the heat the house was exposed to and made the damage worse 4. Watering didn't stop it: well-watered plants still caught and burned in conditions common in a neighborhood wildfire 4.
Flames touching the house
Burning plants, mulch or a fence can bring flames right to the house or to something attached to it, like a deck 1. Plants in the first five feet make it more likely the house catches 4.
What this means for your house
NFPA says most houses lost in wildfires catch from embers and the small fires embers start 2. So the guide starts at the house and works out:
- NFPA looks at the house and everything around it, out to 200 feet 1.
- The first five feet, Zone 0, is where embers do the most harm. NFPA and IBHS both say to keep it clear of anything that burns 13.
- Sheds and other outbuildings need the same work as the house 3.
- No single fix works alone, so the later chapters treat the house as parts that work together 3.
Sources
1. NFPA, "Preparing homes for wildfire." https://www.nfpa.org/education-and-research/wildfire/preparing-homes-for-wildfire (read 2026-11-09)
2. NFPA, "Wildfire Hazards & Mitigation." https://www.nfpa.org/education-and-research/wildfire (read 2026-11-09)
3. IBHS, "Wildland Fire Embers and Flames: Home Mitigations That Matter." https://ibhs.org/wildfire/wildland-fire-embers-and-flames-home-mitigations-that-matter/ (read 2026-11-09)
4. IBHS, "Vegetation in Zone 0: Amplifying Damage to Structures." https://ibhs.org/wildfire/vegetationinzone0/ (read 2026-11-09)