Category Archives: Defensible Space

Reduce Embers and the Home Ignition Zone

Preventing Wildfire Destruction: Removing Embers from ‘Home Ignition Zones’

Research by the National Fire Protection Agency around home destruction vs. survival in wildfires point to embers and small flames as the most common and frequent way that the majority of homes ignite in wildfires.

What is an Ember?

Embers are burning pieces of airborne wood and/or vegetation that can be carried more than a mile through the wind. Embers can cause spot fires and ignite homes, debris and other objects. 

Experiments, models and post-fire studies have shown homes ignite due to the condition of the home and everything around it, up to 200’ from the foundation. This is called the Home Ignition Zone (source: Firewise USA).

Homeowners can prepare their homes to withstand ember ignitions and minimize the likelihood of flames or surface fire touching the home or any other structures on the property.

What are Home Ignition Zones?

The Home Ignition Zone, or HIZ, was developed by retired USDA Forest Service fire scientist Jack Cohen in the late 1990s, following breakthrough research into how homes ignite from effects of radiant heat. The HIZ is divided into three zones, Immediate, Intermediate, and Extended Zone.

 

What actions should Homeowners take to Reduce Ember Ignition in the Immediate Home Ignition Zone?

 

The home and the area 0-5’ from the furthest attached exterior point of the home; defined as a non-combustible area, is the Immediate Zone. This is the most important zone to take immediate action on, as it’s the most vulnerable to embers. The following steps will help prevent embers from igniting your home:

  • Clear leaves and debris from gutters and eaves.
  • Remove dead vegetation and other items from under decks and porches, within 10′ of the home.
  • Screen or box-in areas below patios and decks with wire mesh to prevent combustable debris from accumulating.
  • Remove flammable materials (firewood, propane tanks, gas cans) within 30′ of the home’s foundation and outbuildings – including garages and sheds.
  • Prune trees so the lowest branches are 6 to 10′ from the ground (wildfire can spread to tree tops).
  • Keep your lawn hydrated and maintained. If it is brown, cut it down! Dry grass and shrubs are fuel for fire!
  • Think about switching to some Xeriscape, or more sustainable landscape options, to cut back on the amount of lawn exposed.
  • Dispose of lawn debris and cuttings quickly. Don’t let those sit on your property!
  • Replace or repair roof tiles that are loose or missing, to prevent ember penetration.
  • Cover exterior attic vents with metal wire mesh no larger than 1/8 inch to prevent embers from entering.

 

What actions should Homeowners take in the Intermediate Home Ignition Zone?

 

5-30’ from the furthest exterior point of the home, is considered the Intermediate Zone.

  • Consider careful Landscaping and hardscaping installation, for example create breaks that can help influence and decrease fire behavior
  • Create fuel breaks with driveways, walkways/paths, patios, and decks.
  • Clear vegetation from under large stationary propane tanks.
  • Keep lawns and native grasses mowed to a height of four inches.
  • Remove vegetation under trees, sometimes called “ladder fuels” so a surface fire cannot reach the tree crowns.
  • Prune trees up to 6 to 10′ from the ground; for shorter trees do not exceed 1/3 of the overall tree height.
  • Space trees to have a minimum of 18′ between crowns with the distance increasing with the percentage of slope.
  • Tree and shrubs in this zone should be limited to small clusters of a few each to break up the continuity.

 

What actions should Homeowners take in the Extended Home Ignition zone?

 

30-100′ out to 200′ is the Extended Home Ignition zone.

  • In regards to landscaping, the goal here is to interrupt fire’s path and keep flames smaller and on the ground.
  • Trees 30 to 60′ from the home should have at least 12′ between canopy tops.
  • Trees 60 to 100′ from the home should have at least 6′ between the canopy tops.
  • Dispose of heavy accumulations of ground litter/debris.
  • Remove small conifers growing between mature trees.
  • Remove deadwood (Visit Arbortek Trees’ helpful blog on how to remove deadwood safely).

    Firewise Defensible Space

    Photo from Firewise USA

Thank you to Firewise USA for this valuable research and insight! If you have a large property and would like assistance with clean up of your defensible space and tree canopies, we are a phone call away. Now is the time to get proactive before wildfire danger arrives!