Understanding BAL Ratings for Windows & Doors

In February 2009, Victoria experienced devastating bushfires. On Black Saturday, February 7, over 4,500km2 of land was affected, with a shocking 173 lives lost and 78 communities destroyed. Prior to 2009, Bushfire Attack Levels (BAL) ratings for windows had four levels of bushfire attack. In response to the 2009 fires, Australian Standard 3959 was updated and republished as AS3959:2009 with six levels of bushfire attack. The Australian Window Association published a booklet as a guide for the different construction requirements for windows and doors in each level.

Bushfire Attack Level (BAL)	Description of predicted bushfire attack and levels of exposure
BAL – LOW	There is insufficient risk to warrent specific construction requiremnts
BAL – 12.5	Ember attack
BAL – 19	Increasing level of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kW m2
BAL – 29	Increasing level of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 19 and 29 kW m2
BAL – 40	Increasing level of ember attack and burning debris ignited by windborne embers together with increasing heat flux with the increased liklihood of exposure to flames.
BAL – FZ	Direct exposure to flames form fire front in addition to heat flux and ember attack

Table: A Guide to Windows and Doors in Bushfire Prone Areas, Australian Windows Association, 2012

Bal Rating

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