Vents

IBHS Attic and Basement Vents and Wildfire Fact SheetIBHS Attic and Basement Vents and Wildfire Fact Sheet (1MB PDF)

 

wildfire ember resistant foundation vent chapter 7A building code compliantVents on homes create openings for flying embers.  Ember entry through vents can result in ignition of combustible materials in the attic, and result in a building burning from the inside out.  The importance of ember and flame entry into vents during wildfires has resulted in the development of commercially available vents designed to resist the intrusion of embers and flame, and recomendations for new or retrofit vents to protect existing openings.  Ember resistant vents are adrressed in Chapter 7A of the California Building Code.

eave ventIf enough embers are able to enter the building through a vent or open window, they can ignite materials inside the building. An ember that gets inside an attic or crawl space could ignite items stored in those locations, such as newspapers, cardboard boxes, or insulation. 

FIRESafe MARIN Recommends:

  • Use manufacured and CA approved vents (see below) to retrofit existing attic, soffit, basement, foundation, and gable vents where possible.
  • Alternatively, Cover all existing vent openings with 1/8-inch or 1/16-inch wire mesh.   
  • Common 1/4" screens are ineffective, and should be replaced or retrofitted*
  • Do not use fiberglass or plastic mesh because they can melt and burn.
  • Protect vents in eaves or cornices with baffles to block embers, backed by 1/16" wire mesh (mesh alone is not enough).
  • *Consult with a building contractor, architect, or engineer to ensure that adequate ventilation exists when installing ember resistant vents which may restrict airflow.

California Approved Vents

The importance of ember and flame entry into vents during wildfires has resulted in the development of vents designed to resist the intrusion of embers and flame. This development has been encouraged by language in Chapter 7A of the California Building Code.

This photograph shows the upper part of a combustible wall. Three frieze-block vent holes can be seen in one section of blocking.

Chapter 7A vent requirements:

Chapter 7A says that vents must resist the intrusion of embers and flames, or that they shall be protected by corrosion resistant noncombustible wire mesh screen with 1/4" openings. 1/8" mesh is also allowed, and is preferred based on recent research, and experience and knowledge gained in large WUI wildfires. Vent designs that incorporate plastic components would not comply with the noncombustible wire mesh screen language in Chapter 7A.

Chapter 7A language also specifies that vents cannot be used in an eave application unless that vent has been shown to resist the intrusion of 

embers and flame. Although there are a now few vents that have been accepted for use by the California OSFM, a design that incorporates two sets of through roof vents, one set for inlet air located near the roof edge, and another for outlet air located near the ridge (as shown here), has been used. Modifications to Chapter 7A that would provide for more prescriptive measures for complying are currently being considered by the California Building Standards Commission.

Several vents have been accepted for use by the Office of the State Fire Marshal - these vents can be used in applications where ember and flame intrusion resistance is required. These vents typically use a combination of screening and other design features such as baffles or intiumescent materials to resist intrusion of embers and flames. 

California Chapter 7A Listed Vents (2018)

Listing Number

Listing Information

Vulcan Technologies
8165-2192:0100 Company: Vulcan Technologies
Website: http://www.vulcantechnologies.com/
Address: 580 Irwin Street, Suite 1, San Rafel, CA 94901
Contact: John Simontacchi
Phone: (415) 459-6488 Fax: (415) 459-6055
Date Issued: 07/01/2018 Listing Expires: 06/30/2019
Description: Vulcan Technologies exterior vents. 

Category: VENTS FOR WILDLAND URBAN INTERFACE (W.U.I.)
See Listing Service
Embers Out LLC
8165-2214:0100 Company: Embers Out LLC
Website: https://www.embersout.com/
Address: 21520 Yorba Linda Blvd., Suite G 530, Yorba Linda, CA 92887
Contact: George Sherry
Phone: (714) 363-3459 Fax: (714) 779-3501
Date Issued: 07/01/2018 Listing Expires: 06/30/2019
Description: Embers Out Elite exterior vents

Category: VENTS FOR WILDLAND URBAN INTERFACE (W.U.I.)
See Listing Service
Brandguard Vents
8165-2232:0500 Company: Brandguard Vents
Website: https://www.brandguardvents.com/
Address: 1001 Avenida Pico, Suite C #221, San Clemente, CA 92673
Contact: Kelly Berkompas
Phone: (949) 481-5300
Date Issued: 07/01/2018 Listing Expires: 06/30/2019
Description: BrandGuard Vents Modesl UE 3011 (22"X3.5") , UE 3021 (14"X3.5") UE 3031 (14"X3"), UE 3041 (22"X3"), UE 3051 (22"X5.5"), CS 3011 (120"X3"), CS 3021 (120"X5.5"), Undereave/Soffit Vent. 

Category: VENTS FOR WILDLAND URBAN INTERFACE (W.U.I.)
See Listing Service

The vent shown below (Vulcan) uses screening on the front and back of the honeycomb matrix. This matrix is coated with an intumescent paint that swells when contacted by flames.

The Fireguard vent uses screening and a fused-link. The fused-link device is shown in the photo inset. Activation of the fused-link causes a metal door to close.

The Brandguard vent uses a baffle design.

O'Hagins makes low profile through-roof vents.

Except for corrosion resistant metal language, Chapter 7A doesn't restrict through-roof vents. Still, O'Hagin has submitted testing information to OSFM, and has been accepted as an ember and flame resistant vent.

Vents accepted by the OSFM have provided testing information that was conducted by an accredited fire testing laboratory. Testing has evaluated the ability of a vent to resist intrusion of embers and flames. Since vents can be exposed to embers, without being exposed to flames, separate tests are run.

In addition to information regarding ember and flame intrusion resistance, you should also be looking at available air flow information. This is normally given in percent net free area and provides information on how much area the wire (or other device(s) used in the vent design) is occupying. For comparison purposes, 1/4" mesh screen has a net free area of 81%. 1/8" and 1/16" mesh screen have net free areas of 75% and 71%, respectively. Screening with smaller openings typically uses smaller diameter wire.

Vents & Ember Research

Read the report pdf"Vulnerability of Vents to Wind-Blown Embers" to learn about recent research conducted to evaluate vents for wildfire ember resistance - https://disastersafety.org/ibhs/wildfire-vulnerability-vents-wind-blown-embers/.  This reports adds to a growing body of literature on how buildings can be ignited by wind-blown embers by focusing on the vulnerability of vents to embers. 

Quarles, Stephen L.  2017.  Vulnerability of Vents to Wind-Blown Embers.  IBHS. 

Summary of Findings

  1. There are two options for inlet vents, both located in the under-eave area. These include vents in the between-rafter blocking in open-eave construction and vents in the soffit material in soffited-eave construction. Vents located in soffited-eave construction were shown to limit ember entry and should therefore be the preferred construction type.
  2.  ¼-in. (6 mm) mesh screening should not be used to cover any vent.  Finer mesh sizes of ⅛-in. (3 mm) or 1/16-in. (1.5 mm) are preferred. The finer 1/16-in. mesh screen requires more cleaning-related maintenance to remove the debris that can accumulate on the screen surface.
  3. The wildfire-resistant vents used in the gable end location performed better than the respective backing screen mesh alone.
  4. Due to the relatively large size and vertical orientation of gable end vents, they should be avoided. If alternatives are not possible, a wildfire-resistant gable vent that has passed ASTM E2886 should be used.
  5. Avoid using non-wildfire-resistant off-ridge and ridge vents. Of the ridge and offridge outlet vent options, the following performed well:
    1.  Miami-Dade wind-driven-rain-compliant ridge vent
    2. Wildfire-resistant off-ridge vent
    3. Turbine (off-ridge) vent
  6. Wind-blown vegetative debris must be removed from the inlet of all ridge and off-ridge vents, paying particular attention to vents with plastic components. Plastic components are commonly used in ridge vents.

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