Protecting Your Buildings from a Bushfire
The 2019/2020, bushfires in Australia killed 34 people and destroyed more than 5900 buildings. That’s according to data from The Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC), which predicts such death and destruction will become commonplace due to increases in bushfire intensity and frequency. Are these deaths and destruction avoidable, or is it inevitable with the growth of cities into bushland?
The National Construction Code is the national standard for buildings on bushfire-prone land throughout Australia. (What land is deemed “bushfire prone” is defined by state and territory legislation.) It requires buildings be designed and built to reduce the risk of ignition from a bushfire, appropriate to the risk from bushfire flames, burning embers, radiant heat and intensity of the bushfire attack.
In the wake of the Black Saturday bushfires in 2009, the Victorian government commissioned a royal commission to investigate the causes and costs of those fires. The commission’s final report made several recommendations for changes to the National Construction Code. The recommendations included new provisions to:
- make protection from ember attack a performance requirement
- address the design and construction of private (underground) bushfire emergency shelters
- include design and construction requirements for non-residential buildings, such as schools and aged-care centres, in bushfire-prone areas.
All governments agreed to these first two recommendations, which were promptly implemented in the National Construction Code (in 2010).
As a result the first two recommendations were implemented through the AS 1530 – 2009 (Construction of buildings in bushfire-prone areas)
Bushfire water spray systems.
A bushfire water spray system is designed to spray or drench external elements of buildings and surrounding vegetation with water with the aim of reducing the likelihood of Ignition. The system can effectively control bushfires that have not yet ignited, but it is not effective once a fire has ignited.
The system consists of a series of fixed or portable pumps, hoses, nozzle bodies and nozzles. The pump is connected to a hose and nozzle body, which are attached to an adaptor plate at the end of a hose reel or standpipe riser. The adaptor plate allows for different types of nozzles to be used depending on the application. The hose reel or standpipe riser provides storage space for excess hoses when not in use, which reduces the risk of damage by wind or falling objects.
Sprinkler systems are designed to provide an additional layer of protection for buildings. They are not, however, a substitute for maintaining a hazard management plan or for sealing off gaps within the building’s exterior.
Sprinkler systems typically include sprinkler heads (building and/or ground-mounted), piping and fittings, a water supply, pump set and an activation mechanism. Where fitted, these systems potentially may provide buildings with some degree of protection, however there is little evidence available to demonstrate their effectiveness across a range of situations.
Spray systems may provide for partial protection from ember attack but are unlikely to protect all gaps and openings in a building’s exterior from embers. They are also unlikely to be effective if the building is exposed to direct flame contact or high levels of radiant heat.
Therefore, installing a spray system should not be considered as a substitute for maintaining a suitable hazard management area around the building, for sealing up gaps within a building’s exterior or for having a Bushfire Survival Plan.”
A bushfire water spray system should be seen as complementary to other protection measures. A bushfire water spray system should not be relied upon as a stand-alone bushfire safety solution.
A bushfire water spray system can help protect non-combustible assets, such as buildings or infrastructure, from the threat of a bushfire. It is important to consider the effectiveness of such systems in relation to the fire behaviour, fuel type and weather conditions.
The effectiveness of a bushfire water spray system will vary depending on factors such as:
• How long it takes for the fire front to reach the asset being protected;
• Whether there are gaps between existing protection measures that would allow flames to penetrate through;
• The amount of water available from a nearby source;
• The size and spacing of nozzles used in each zone; and
• The overall design and layout of the system.
If you are considering installing a bushfire water spray system, you should consider the following:
Water supply – You must consider the capacity of the static water supply and whether additional water storage or another water source will be needed. Embers may attack your site for many hours, so it may be necessary to increase your capacity by storing water from roofs (or other sources) and returning it to the tank. Tanks should be non-combustible (or shielded from the source of the hazard) and not used for any other purpose.
Pumps – If a pump is needed to achieve the required pressure and flow, it must be accessible and protected from potential exposure to radiant heat, flame and embers. An electric pump will require a backup generator in the event of a power outage. Petrol or diesel driven pumps may provide a simpler and more reliable solution but will require regular servicing to ensure performance.
Water nozzles are used in combination in firefighting and may include misting nozzles, butterfly heads, impact heads, and ridge heads. There are differences in the performance of different nozzles in terms of velocity of discharge, droplet size and density. For instance, misting nozzles can be effective for directing water onto particular areas but may not perform adequately in high winds due to a relatively low velocity of water discharge and droplet size. The selection and arrangement of nozzles needs to be designed in a way that protects points of vulnerability and possible ember ingress in windy conditions.
Piping and pipe mounting/ supports be made of metal. This is because the potential for flammable debris to be trapped against buildings during a fire is very high, and metal pipes are more likely to withstand this type of damage.
Water pressure is a significant factor in spray heads. The required pressure may vary depending on the type of spray heads being used and the area to be covered. Spray systems should be hydraulically designed to account for friction loss and to ensure that water pressure is optimised.
Activation of the system may therefore be difficult to achieve. Manual activation is dependent on human behaviour, which tends to change over time. There are automatic activation mechanisms available, but smoke/heat sensors may not detect ember attack until surrounding fuels have ignited. Smoke detectors may also activate prematurely, as smoke can travel large distances ahead of the fire.
Windows—if exposed to radiant heat from surrounding combustibles—should be carefully designed to protect against failure. If water is applied inconsistently to the glass surface and frame or not early enough, the water may cause the glass to fail. More reliable protection measures are available, such as bushfire shutters.
Maintenance is important to ensure that the system will function as intended when needed. It is critical that all parts of the system are routinely checked and maintained in order for the system to perform as designed.
If you are planning to install a bushfire water spray system, it is important to ensure that it is designed and installed according to the Australian Standard 5414 – 2012 “Bushfire water spray systems”
This standard provides a set of design parameters for the design, installation and maintenance of bushfire water spray systems. There are no regulations that require these systems to be designed to AS 5414, and many of the products available on the market will not conform to the standard.
When designing your system, make sure to use metal pipework and heads, as plastic hoses and fittings will likely fail during a fire.
If possible, ‘complement’ the external system with internal sprinklers.(ideally they would be separate systems). This will help suppress any internal house fires that may occur.
Use non-combustible materials.
Use the system to address specific weaknesses that can’t be remedied through siting and design.
Ensure sprinkler systems are fed by a reliable water source.
Consider using additional sprinkler heads in the roof cavity, and underfloor spaces – especially if they contain or are composed of combustible materials.
Consider using a system which can activate automatically using a combination of smoke or heat sensors. Don’t rely on someone being at home.
When you’re fighting a bushfire, you need to be prepared for anything. You should have a water spray system installed on your property that is capable of providing protection for up to four hours.
But there are some things that you shouldn’t do if you want to make sure that your system is going to work in an emergency:
Don’t rely on active water pressure to feed the system – the system should operate using a passive water supply.
Don’t use a system that requires a manual start-process which has to be switched on in an exposed location.
Don’t use sprinklers to replace sealing gaps in order to prevent ember entry.
Don’t use a system that requires refuelling in order to provide the minimum duration of water delivery (a minimum 4-hour supply is recommended).
Don’t use exposed pumps and generators – all pumps and generators should either be shielded or installed within the buildings envelope.
Don’t rely on the mains electricity grid.
Don’t rely on the mains water supply.
The cost of installing a bushfire water spray system varies depending on the size of your property, location, and type of system you choose.
If you’re building a new home or commercial building, it’s more cost effective and reliable to use passive measures such as non-combustible materials. However, if you’re retrofitting an existing building this may not be feasible, and a bushfire sprinkler system may be preferable.
The installation of a new home or commercial building can be relatively low cost for a basic sprinkler system and a lot more expensive for a complex system with alarms and sensors.
When retrofitting an existing building, the price will vary based on how much work needs to be done before the sprinkler system can be installed. It could depend on whether there is asbestos in the building or if there are other hazards that need to be removed before installing the sprinkler system.
You Need to factor in Maintenance
1. Tank water level Check that tank is full
2. Tank water level indicator Check for correct operation and reading of water level indicator
3. Float valve (where fitted) Verify correct operation of float valve by exercising the valve
4. Spray nozzles Check that blow-off caps or plugs are in place
5. Diesel-driven pumpsets Check engine start battery and enclosures for corrosion, physical damage and secure mounting
6. Fuel tank Check that tank is full
7. Pump starting Start the pumpset via the start button or switch
1. Tank inlet screen
a) Clean tank inlet screen and replace if necessary.
b) Clean piping inline and replace strainer.
c) Check accumulator air pressure and adjust as required.
Yearly, prior to each bushfire season
To ensure your fire system is ready to go when the time comes, it’s important to test it at least once a year.
a) Fit pressure gauge at test connection.
b) Start the pumpset via the start button or switch and test run the system to ensure that all spray nozzles are unobstructed and discharging correctly. Note and record end nozzle pressure _____________ kPa (or any other readings you need).
c) Restoration to operational condition
d) After completion of testing, check water and fuel tank levels, check nozzles and blow-off caps or plugs for corrosion and/or deterioration, refit all nozzle blow-off caps or plugs and return all equipment to the operational condition.
e) Replace damaged components with devices of similar performance characteristics.
f) Exposure condition Check for any changes to exposure condition which would have an adverse impact on system performance e.g. vegetation which has grown to obstruct the spray pattern or wood pile sitting up against the house or building renovation etc
It is vital to ensure that the property you own or manage is well prepared before a bushfire strikes your area. The above protective measures combined with effective fire-hazard reduction will reduce significantly the risk to your buildings and people during a bushfire.
Need Advice about the most cost effective way to protect your property this coming bushfire season? Contact the experts at Complete Fire and Pumps.
Dedicated To Your Fire Safety