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What size screen or mesh should go over vents?
Mesh with openings no bigger than 1/8 inch, or vents tested to the ASTM E2886 standard. The state and FAIR Plan lists both ask for ember-resistant vents. The state draft sets no vent standard.
The state Zone 0 rule is not law yet. Insurers and IBHS already use their own lists.
What to check
List every opening: attic vents, crawl space vents, eave vents, dryer vent, skylights and chimney.
Check what covers each one.
Ask your insurer whether it wants tested vents or fine mesh.
If you use tested vents, seal the joints as the maker instructs.
What each list says
The lists do not always agree. Here is what each one says about this.
- IBHS Essential
Either corrosion-resistant vents that meet ASTM E2886, or noncombustible, corrosion-resistant mesh with openings no larger than 1/8 inch. If you use tested vents, joints around them are sealed as the maker instructs. Dryer and central vacuum vents get a working louver or flap instead of mesh (section 2.1.3).
- IBHS Enhanced
The louvers or flaps on those vents must also be noncombustible. Operable skylights need noncombustible mesh with openings no larger than 1/8 inch (sections 3.1.3 and 3.1.5).
- State discount list
Ember- and fire-resistant vents.
- FAIR Plan
Ember- and fire-resistant vents, with approved wire mesh covering.
- San Diego
A voluntary step: mesh with 1/16 to 1/8 inch openings as a temporary option. Chimney and stovepipe outlets use mesh with 3/8 to 1/2 inch openings.
- State draft
Only about plants: none within 2 feet of windows, doors or vents. It sets no standard for vents or screens.
Sources
- IBHS Wildfire Prepared Home Technical Standard (2025 edition)
- Safer from Wildfires regulation: frequently asked questions, California Department of Insurance, September 2026
- Discounts for dwelling fire and commercial policies, California FAIR Plan, November 15, 2025
- Zone 0 guidelines for existing structures, City of San Diego, April 2026