materials and design considerations for building in...

Materials and Design Considerations for

Building in Wildfire Prone Areas

Webinar October 5, 2011

WUI Webinars •  October 2011

–  Material and Design Considerations for Building in Wildfire Prone Areas

•  Steve Quarles, IBHS •  November 2011

–  Assissing Risk/FHSZ •  Dave Sapsis, Cal Fire

•  December 2011 –  No Webinar - Holidays

•  January 2012 –  Community Planning

•  Carol Rice, Wildland Resource Mgt. •  February 2012

–  Fire Response •  Dan Turner, Urban Forest Ecosystems

Institute •  March 2012

–  Ready, Set, Go! •  Bob Roper, International Assn. of Fire

Chiefs

  April 2012

- Social Motivation

  Sarah McCaffrey, USFS Research Station

  May 2012

- Fuels/Landscapting

  Ed Smith, U. Nevada Cooperative Extension

  June 2012

- Ignition-resistant buildings

  Sam Manzello, NIST

  July 2012

- FireWise Commuities/USA

  Michele Steinberg, NFPA and

Phyllis Banducci, Cal Fire

  August 2012

- Social Considerations

  Pam Jakes, USFS Research Station

  September 2012

- Evacuation Planning

  Tom Cova, Universtiy of Utah

Mission:

The Insurance Institute for Business & Home Safety’s mission is to conduct objective, scientific research to identify and promote effective actions that strengthen homes, businesses, and communities against natural disasters and other causes of loss

Buildings in wildfire prone areas must be protected from:

 Embers (also called ‘firebrands’; lofted

vegetation or construction materials that are burning)

  Flame impingement (near-by vegetation or debris,

construction material, fire wood or other woody debris)

 Radiant Heat (dense vegetation, an adjacent building/deck fire

Reducing the vulnerability of buildings to wildfires – new construction or retrofit to existing

•  Materials, Design and Details •  Vegetation Management

  three zones

Defensible Space (Vegetation Management Zones) – three zone approach (0-5’; 5-30’; 30-100’)

IBHS Research Center

Test Building

Dormer Asphalt comp roof & valley

Wood shake roof & roof edge

3 ducts at floor level (center units)

2 ducts at low level (end units)

5 ducts at mid-level

5 ducts at upper level

Five firebox / ember generators

Red circle – field of roof

Yellow square – edge of roof

“Brands” used in standard roof tests. One of three components in determining Class A, B, or C fire rating for a roof covering. Untreated wood shake roof is unrated.

Class A – 12” by 12”

B - 6” by 6”

C

Burning [12”x 12”] ‘A Brand’ placed on roof covering.

Flame penetrated to the underside (attic) of the roof sheathing. As constructed, not a Class A roof covering.

Fire rating for roof coverings

IBHS Research Center

Untreated wood shake roof

Roof edge issue?

Class A asphalt composition shingle roof covering with “woven valley”, after ember ignition of pine needle debris

Edge of Roof Vulnerability

Debris in gutters - if ignited (by embers) the fire will expose roof edge, not your Class A roof covering.

Edge of Roof

-plug openings (“bird-stops”)

Metal angle flashing at edge of roof

Embers at gap between roof sheathing and top of fascia. Photo taken inside the attic.

vinyl gutter metal gutter

Skylights

Ember ignition of debris: -  top of skylight -  roof-to-edge of skylight

Skylight on steep-slope roof: - radiant heat exposure

An open skylight or an open window is the most vulnerable – entry of embers

Gable end

Through-roof

Under Eave

Vents

Gable End Vent

Open Eave Design – significant ember entry

Soffited Eave Design – minimal ember entry

Angle flashing absent

Ember accumulation

Angle flashing present

No observable ember accumulation

Ember entry soffited eave / roof edge

Finer mesh screens can become plugged with debris, or paint, thereby having a negative impact on the ‘moisture management’ function of vents. Maintenance issue …

1/8” mesh, debris build up

Fine mesh screen, covered over with paint

“WUI” vents - specifically designed to resist the entry of embers and flames

• ASTM Standard Test Method is being developed to evaluate performance • Four “WUI vents” have been accepted for use by California OSFM.

  incorporate screening and other design features (baffle design, fused link, intumescent coating, coarse steel wool)

Blocked vent

Vent Summary

THE EAVE

Windows

Performance of windows – the glass is the most vulnerable part of the window.

Frame failure

Glass failure

Horizontal separator on single- / double-hung window.

(The horizontal separator in hung vinyl windows should be reinforced

with an aluminum cross piece.)

#1 #2

#3 #4

Inside

Outside

Dual-pane window

Frame

Radiant Heat

Exposure

Warmer, greater thermal expansion

Cooler, lower thermal expansion

Thermal stresses, resulting in crack propagation inward from the edge of glass, causes glass breakage

Broken outer pane. Inner pane in tact.

Embers collecting on fiberglass screen

Screen failure after flame contact

IBHS Research Center

Where screen remains intact, minimizes ember entry

Radiant Panel

Water-cooled radiator panel

Heat flux sensors behind window

Ignition of curtain occurred after both panes of glass in upper light fell out.

Decks

Looking down the slope from the deck

Combustible materials and debris under the deck

Water staining on bottom of (wood plastic composite) deck boards

Long term performance of wood and joist hanger?

If deck is enclosed, drainage or venting needs to be considered

WPC, not 7A compliant

‘7A’ compliant

Performance related to decking

WPC Redwood

WUI Product Handbook – CA OSFM

Siding

Flame spread up the wall …

Penetration into stud cavity

Re-entrant (interior) Corner

Avoid combustible attachments at the building.

Thanks for your attention!

Steve Quarles squarles@ibhs.org (813) 404-4942 (cell)

www.disastersafety.org

www.extension.org/surviving_wildfire

Where building safety research leads to real-world solutions.