On 24 November 2017, the Ministry of Business Innovation and Employment changed the scope of the Building Code Verification Method C/VM2 Framework for Fire Safety Design. While previously the Framework applied to all buildings except tunnels and open air stadia, Tania says the new scope is much more explicit and has real implications for buildings that sit outside it.
“The revised scope of C/VM2 applies to all buildings except those that don’t have simultaneous evacuation schemes evacuating immediately outside the building. The scope also excludes buildings that require managed evacuation schemes or contain fire hazards that are not defined by Part 2 of Verification Method (such as hazardous substances). Owners of these excluded buildings may require a tailored solution for their fire safety design, which is where Prendos can help.”
Current compliance documents Verification Method and Acceptable Solutions are prescriptive-based regulations that provide requirements for a broad range of buildings. These requirements are generally stated in terms of fixed values, such as maximum travel distances, maximum travel speed, required fire ratings or required building safety features. They provide rules and parameters for the design scenarios but, as Tania explains, they don’t take occupants’ characteristics into consideration.
“These compliance documents don’t consider the age, gender or impairment of occupants. Similarly, movement data doesn’t take into account achievable speeds and flow/density relationship or specific behaviours and associated delays. It also doesn’t consider additional fire safety precautions that may be necessary for the intended evacuation procedures to meet the Fire Safety and Evacuation of Buildings Regulations 2006.”
So which buildings fall outside the updated scope of the compliance documents? According to the regulations, excluded buildings include hospitals, care homes, stadia, principal transport terminals, large shopping malls (greater than 10,000 m2 and containing multiple mezzanine floors), tall buildings (greater than 60 metres or 20 storeys in height) and tunnels. Tania says assessment of life safety in these buildings requires specific engineering design from first-principles.
“In the case of hospitals and aged care, based on my discussions with operators, the response time and evacuation procedures vary greatly. It’s important to select fire egress strategies that are appropriate to the facility’s size and complexity, how it’s used and the characteristics of its occupants. For these types of buildings, egress strategies need to take into account wheelchair users, occupants with mobility impairments, or those with other mobility or cognitive conditions that may hinder an independent evacuation.”
Generally, in these facilities the first approach is to move occupants to an adjacent ward, where they can remain safe during emergency conditions. However this relocation strategy needs to be aligned with and supported by the overall life safety protection provided in the building.
The ‘simultaneous full-building evacuation strategy’ is a norm for buildings up to six storeys in height. It is usually arranged via protected stairs that exit to a public place. However, for tall buildings, iconic structures (like Auckland’s Sky Tower) or large assembly buildings, a different approach is required.
“To evaluate the impact of evacuating a large number of people simultaneously from a tall building or large mall, we need to take a performance-based engineered approach,” says Tania. “The most common solution is to relocate occupants from an area of potential hazard to a protected area within a building. Usually, occupants are told to move to floors below the fire – away from the fire impact.”
Designing for ‘relocation’ or ‘protect-in-place’ strategies can be challenging. Adequate fire rating of the floors, shafts and structural fire protection are critical elements of the design, as lower floors are relied upon to provide a safe area for the duration of the fire incident.
“Designs with ‘protect-in-place’ strategies use a combination of active and passive fire protection features and management procedures to provide an appropriate level of safety,” says Tania. “The most common approach is to use automatic sprinkler protection combined with fire-rated compartmentation, stair pressurisation and smoke control to reduce fire and smoke spread throughout the building.”
“In my experience, I’ve found a combination of evacuation strategies delivers the optimal results. Staged evacuation helps to make best use of the available building fire exit components. Occupants facing imminent danger can be immediately evacuated or relocated within the building. Those who are further away from the fire can initially stay where they are, but can be evacuated later if conditions warrant a full-building evacuation.”
A performance-based evacuation design process is an important tool for situations that are not appropriately addressed by prescriptive codes, or when owner and designer needs can’t be solved with traditional solutions.
The revised scope of C/VM2 sees no changes to Building Code requirements. As Tania explains, Fire engineers must demonstrate that fire design meets the performance criteria of the code.
“The yields of combustion species given in NZBC C1-C6 are set as benchmark values. In the event of a fire, some people can be tolerant to much higher values, but the level of tolerance and time of exposure are much lower for women, children, aged people and those with respiratory disorders or heart disease. Basically, there’s no single set of tenability criteria that is universally accepted. The International Fire Engineering Guideline defines untenable conditions as ‘environmental conditions associated with a fire in which human life is not sustainable’. In other words, conditions that cause death. So it really highlights the importance of safety margins in trial designs.”
The Way Forward
So, for anyone looking at building or doing alterations to hospitals, retirement homes with care/hospital facilities, large malls or tall buildings, Tania says it’s important to get the fire safety design right.
“A performance-based fire safety design for buildings that are outside the new C/VM2 scope should be performed by Chartered Fire Engineers using the Fire Engineering Brief process as well as appropriate parts of the Verification Method. This can be considered an Alternative Solution by the Building Consent Authority (BCA).”
“For anyone who is in charge of managing existing facilities with staged evacuation, the review of existing building life safety features is very important. Under Health and Safety at Work Act 2015 a duty imposed on a person conducting a business or undertaking is to eliminate risks to health and safety, so as far as reasonably practicable. Due diligence includes taking reasonable steps to acquire knowledge of risks associated with business operations pertinent to health and safety matters.”
“Owners, managers and designers should give Prendos a call – we’re the specialists in this field and can guide them through the new requirements.”
For more information on how to optimise your building’s performance and comply with current fire safety requirements, call Prendos Fire Engineers on (09) 970-7070 or visit our Fire Engineering Services page.