materials and design considerations for building in...
TRANSCRIPT
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 [email protected] (813) 404-4942 (cell)
www.disastersafety.org
www.extension.org/surviving_wildfire
Where building safety research leads to real-world solutions.