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Ember versus flame versus radiant heat
Wind-blown embers ignite most homes lost in wildfires. Direct flame and radiant heat are different exposures. IBHS Wildfire Prepared Essential is the ember checklist. Enhanced adds flame and radiant-heat measures such as enclosed eaves and noncombustible wall covering. Mesh on a vent answers ember size. ASTM E2886 answers ember and flame through that assembly. Neither answers radiant heat on glass or siding.
You are standing in the yard after a wind-driven fire. Most houses that ignite do so from embers at openings and the five feet, not from a wall of flame a hundred feet away.
Why it matters
If you only buy finer screen, you have not enclosed the eave or cleared Zone 0. If you only buy a listed vent, you have not specified a Class A roof covering. IBHS Wildfire Prepared Essential and Enhanced score different exposures. Spec the exposure the document named.
How it works
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Embers. Burning fragments travel ahead of the fire. They land in gutters, in vents, on decks, and in the first five feet. CAL FIRE and IBHS treat this as the usual ignition path. Home-hardening work on vents, roofs, gutters, and landscaping is ember work. See gutters and debris and zone bands.
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Direct flame. Flame touches a material. Eave edges, walls, fences that hit the house, and deck undersides see this when vegetation or a neighboring structure is burning close. A test method such as ASTM E2886 asks whether flame gets through a vent assembly in a lab. That is not a whole-house flame rating. See fence as a wick.
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Radiant heat. Heat travels through air without flame touching the house. Glass can fail. Siding and eaves can ignite. Enclosed eaves, wall covering, and window rules exist because of this path. Mesh size does not measure it. See dual-pane versus tempered and ignition-resistant versus noncombustible.
Oregon R327, where adopted, writes wildfire exposure into construction rules for roofs, vents, walls, and projections. It is still not IBHS.
California CWUIC is construction code in mapped WUI areas as of 1 January 2026. People still search Chapter 7A. It is still not IBHS and not Safer from Wildfires. See Oregon R327 versus California CWUIC and IBHS does not replace adopted code.
Which document answers which exposure
| Exposure | Typical first moves | Documents that actually ask for them |
|---|---|---|
| Ember | Class A or B roof as required, 1/16–1/8 inch mesh or a listed vent, Zone 0, clean gutters, under-deck clearance | IBHS Essential. CAL FIRE home hardening. Safer from Wildfires roof, vents, five-foot zone, under-deck, six-inch wall base. R327 vents and roof, where adopted. |
| Direct flame | Listed ember- and flame-resistant vents, enclosed eaves, ignition-resistant or noncombustible walls, fence break at the wall | IBHS Enhanced. ASTM E2886 / OSFM category 8165 for vents. R327 eave, wall, and projection rules. Safer from Wildfires enclosed eaves. CWUIC construction in mapped areas. |
| Radiant heat | Enclosed eaves, noncombustible or ignition-resistant walls, dual-pane or protected glass, distance from sheds | IBHS Enhanced. Safer from Wildfires eaves and windows. R327 walls, glazing, and projections, where adopted. CWUIC glazing and wall rules in mapped areas. |
Prescriptive mesh is an ember-size recipe. The performance path for vents is a listed ASTM E2886 model. See mesh versus listed. Enclosed eaves are a soffit under the overhang. They are not an unvented attic. See eaves and unvented attic.
Example listed vent records on this site include BrandGuard gable vents, Vulcan gable vents, and Embers Out. A listing is a model record. It is not a permit. Confirm the live OSFM listing and put the model on the drawing.
Under-deck clearance is still ember work. Do not staple mesh under the walking boards and call it done. See Findings.
What people mix up
- Treating Essential and Enhanced as two names for one certificate. Enhanced builds on Essential.
- Treating IBHS as adopted code. You can pass a photo set and fail R327, or the reverse. See how to read a listing.
- Treating Safer from Wildfires as IBHS. The California credit list mixes ember items (mesh, Zone 0, Class A) with flame and radiant items (enclosed eaves, windows). It is not Oregon law. See Safer from Wildfires is not Oregon law.
- Treating CWUIC or Chapter 7A as IBHS or as Safer from Wildfires.
- Treating 1/8 inch mesh as a flame-intrusion listing.
- Treating a Class A covering as if it lived in the shingle bag. Class is an assembly result under ASTM E108 or UL 790. See Class A covering is not a bag.
- Treating perforated fiber-cement soffit as an ember-rated eave vent. See Findings.
- Skipping Zone 0 because the vents are listed. Embers still land at the wall.
How to check
- List the documents on the job. Adopted code, IBHS level if any, carrier extras, HOA.
- Walk ember paths first. Roof edge, gutters, every vent, the five feet, under the deck.
- If Essential is the ask, mesh or a listed vent can satisfy the vent line. Zone 0 still has to be noncombustible.
- If Enhanced, Safer from Wildfires eaves, or R327 eave rules apply, look under the overhang. Open-eave tails and vented soffits are the usual miss. Height under Oregon R327 is a separate rule. See the 12-foot rule.
- If the official wants a listed vent, match the model to the listing. Do not spec a brand name in the abstract.
- Do not use this page as a flame-spread rating for siding or glass. Those are separate tests.
Limits
This page does not decide which IBHS level a carrier will accept. It does not rate airflow, glass, or wall assemblies. It does not make the house fireproof. FireApproved is not the building official.
Related records
Questions
Why does IBHS split Essential and Enhanced?
Essential targets ember ignition, the usual way houses start. Enhanced adds measures against direct flame and radiant heat, such as enclosed eaves and noncombustible wall covering. Enhanced assumes Essential is already done. Neither level is adopted building code.
Does 1/8 inch mesh stop flame and radiant heat?
No. Mesh is a prescriptive ember-size rule. ASTM E2886 tests whether a vent assembly resists embers and flame in a lab. Radiant heat on glass and siding is a different path. Buy the path the document named.
If most losses start from embers, can I skip walls and windows?
No. Ember work is the usual first move. Flame and radiant heat still attack eaves, walls, and glass when the fire is close. IBHS Enhanced, Safer from Wildfires enclosed-eave and window credits, and Oregon R327 wall and projection rules exist because of those exposures.