The early start to this year’s bushfire season reminds us all of the importance of fire protection and prevention measures when it comes to looking after our families and homes. But threats to our homes can also come from other types of fires such as those started by accidents, faulty wiring, or incidents at neighbouring properties.
Luckily in Australia we have strict building codes which enforce minimum building standards that in turn help minimise fire risks and the impacts. While those who live in rural areas have likely heard of Bushfire Attack Levels (BAL) ratings, “fire attenuation” specifications are lesser known but just as important.
What is fire attenuation?
Fire attenuation is the ability of a product to reduce radiant heat and the spread of flames, Fire attenuation has nothing to do with flaming sources, purely radiant heat. compared to BAL ratings which are about the ability of a product to resist the fire. Products with good fire attenuation attributes will help stop heat being transferred to other areas or properties which can reduce the intensity of impacts until a fire can be brought under control. The primary purpose is to reduce the KW exposure of internal flammable items to a point that they don’t ignite.
Which buildings need it?
Fire attenuation requirements are relevant regardless of where you live or what type of building is being constructed, whereas BAL ratings are relevant to buildings in bushfire prone areas.
Fire attenuation relates to a building’s proximity to other buildings, and details of where it applies are set out in the Building Code of Australia (BCA). The Code states that any openings (i.e. doors or windows) which are within 3m of a fire source must be protected. Any openings which are within 6m of another building on the same allotment also need protection.
Just how much attenuation screening is required will depend on the nature and type of adjacent buildings, and these calculations are undertaken during the building design phase.
What types of products are used?
Window and door screening products play an important role in fire attenuation and Alspec has three key window and door security screening products designed to address this need:
- Invisi-Gard: a 316 marine grade stainless steel mesh screen, designed to provide high visibility and maximum air flow.
- Alu-Gard: 1.6mm perforated aluminium sheet screen, aimed at providing a balance of visibility and security.
- Vision-Gard: 3mm perforated aluminium sheet screen, designed to restrict those outside looking into a building.
While each three have the necessary fire attenuation properties, the right product for a project will depend on which features are of the highest priority and the required attenuation rating.
Where’s the proof they work?
The effectiveness of framing and screens to reduce fire impacts is measured by testing how much heat is blocked when exposed to radiant heat. The Australian Standard AS 1530.4:2014 Methods for Fire Tests on Building Materials, Components and Structures sets out the process and conditions for testing these products.
All three Alspec security screens have undergone testing, which involved exposing them to heat of 40kW/m2 for 130 minutes. The results were:
- Invisi-Gard: 55% or 48% reduction (depending on installation method)
- Alu-Gard: 56% reduciton
- Vision-Gard: 75% reduction
These results mean all three products can be deemed to be a satisfactory "solution" to provide fire attenuation under the National Construction Code, although final approval to use them on a building must come from a Fire Certifier or Fire Engineer. Alspec provides a range of supporting documents to assist in the certification process and you can watch a video of the screen tests here »
Pictured: This apartment block in Ascot, QLD, installed