2018 NCC Seminars: Performance-based design - Case study

So now that we've had a brief introduction to the four step process described in our guide to the development of performance solutions, let's attempt to apply that process to a hypothetical case study. Let's consider some proposed performance solutions.

Large isolated buildings are buildings in which the size of a fire compartment may exceed the general Deemed-to-Satisfy requirements subject to the inclusion of certain fire safety measures. The scope of those fire safety measures depends on the size of the fire compartment. There are two categories. One is where a fire compartment is less than or equal to 18,000 meters squared or 108,000 meters cubed. If your build fire compartment is greater than 18,000 meters squared or 108,000 meters cubed, there is a different suite of additional fire safety requirements.

So let's look at that case study building. We have a warehouse, which is 17,225 square meters. There's an attached administrative wing, which is 525 square meters. We have an allotment boundary to the west of the building. We have an allotment boundary to the east of the building. We have a road and a road on either side to the north and the south. So the general operation of this building is that it's a building that would be capable of storing palleted goods.

Let's assume they're the same sorts of goods that you would find in a supermarket. So there'll be a variety of elements of combustibility. It'll have a high stack storage warehouse system. It'll generally comply with the Deemed-to-Satisfy provisions of the NCC. However, the designer proposes two performance solutions. One will relate to extending the Deemed-to-Satisfy travel distance to an exit, and one will relate to the omission of the Deemed-to-Satisfy smoke hazard management system. While both of these performance solutions relate to fire safety, as I mentioned before, the process that we will go through to assess these performance solutions is generic and can be used for any of the NCC requirements. So as we said before, the pathway to success to developing an acceptable performance solution is by following our guide material. That's exactly what we'll do now.

So as we discussed before, the first step in the development of a performance solution is to prepare a brief. So with regards to our particular building, we have to elect, select, nominate, volunteer, whatever the word is, a leader to guide us through the process. So let's assume that the primary designer will identify the key stakeholders and will manage the preparation of the brief.

On the basis that we require stakeholders to collaborate to develop a mutually acceptable brief, who do you think may be key stakeholders for our case study? At this point, I'll nominate some key stakeholders.

• The building designer
• The approval authority
• A warehouse manager
• A fire safety engineer
• A mechanical engineer
• A representative of the fire brigade and anyone else that you care to include.

And remembering that as the preparation of the brief progresses, other stakeholders maybe identified at a later stage can be introduced into the process at any point in time. Now just going back what we picked up before about what a brief records. We said it records the

• Characteristics of the building
• The scope of the proposal
• Agreed performance requirements, etcetera

So let's consider the first dot point of what we're gonna record in our brief and we'll look at the characteristics of the building. As I mentioned, it's predominantly a warehouse for bulk storage of what I've called supermarket goods. There's an attached two-story wing that contains office space on the upper level and staff facilities on the lower level. The warehouse is the only building on the allotment. So as we said, here is our case study building. The operation of the building will be trucks will come from Cripps Street. They will reverse under the truck bays, forklifts will then unload the goods for location in the high rack storage system. This is our high rack storage system, lots of bays, lots of areas for forklifts to move around inside. Here's a section of the building.

So what are some of the characteristics? Steel portal frame. It has sheet metal cladding on the walls, on the roof. The goods are stored on pallets and high rack system and in freezer cool rooms. Has a fire compartment greater than 18,000 meters squared or 108,000 meters cubed. And the reason that it falls into that category is because it has a ceiling height greater than 12 meters. There are six office staff and 20 warehouse staff working shifts.

So what are some of the fire safety characteristics, what are some of the issues about what may or may not burn, et cetera? What are the expected types, quantities and locations of combustible materials? The types and quantities are important, and the location of combustible materials may also be important because we might not be facing an equivalent fire load across all the floor area of the building. We'd like to know is there a storage plan for the high rack system? What are the likely sources of fire ignition in a building that has a high rack system, has forklift moving through it, has a certain number of staff, has large trucks pulling up next to external walls? How could the stakeholder group find answers to some of these questions? Would they be general knowledge? Possibly, possibly not.

I'd suggest one of the best ways is probably to ask a warehouse manager, which is the reason we included a warehouse manager in the stakeholder group. Be good to have someone with experience that has worked and operated in one of these buildings and can provide information to help us design an appropriate outcome.

Are there other characteristics? It's up to the stakeholder group. You need to document everything you think is relevant to the assessment, development and approval of your performance solutions, bearing in mind that the brief can be revised, and it possibly will be, as the project progresses. As long as the stakeholders agree. So let's move on to the next category of the content of the brief. We've crossed off characteristics of the building. The next issue to be addressed is the scope of the proposal.

So for our building design, the designer proposes two performance solutions: one relates to extended travel distance to the Deemed-to-Satisfy, and the other relates to our mission of the Deemed-to-Satisfy smoke hazard management system. That's what's proposed. In order to assess whether or not our performance solution will be adequate, we need to know why these Deemed-to-Satisfy provisions are in the NCC.

So in relation to our extension of travel distance, why does the Deemed-to-Satisfy provisions limit travel distance to an exit? Does anyone wanna have a go at answering that? A common answer is to facilitate safe occupant evacuation during an emergency. So in that context, specific details of the proposal should be documented to enable an assessment.

So what are some of the specific details? Well, if you're going to extend travel distance, you'd wanna know how much you're going to extend the Deemed-to-Satisfy in order to determine whether it's appropriate. You might also need to know whether the designer is going to volunteer any specific supplementary fire safety measures to those required by the Deemed-to-Satisfy so that their performance, their contribution can be considered. If the answer is yes, what are these measures?

The second proposal, the omission of the Deemed-to-Satisfy smoke hazard management system. Why does the Deemed-to-Satisfy requirements, why are they different for a smoke hazard management system in a large isolated building? Common answer, to manage potential impacts of smoke. So what are the potential impacts of smoke in a large isolated building? If you have a look at the location of requirements for smoke hazard management, they're in part E2 of the National Construction Code. Part E2 has two performance requirements. In essence, one is to provide automatic warning of the detection of fire to sleeping occupants; and the second one is to facilitate a tenable environment during evacuation of a building in the case of an emergency. But are there other potential impacts of smoke in a large isolated building? And the answer to that is yes, there are additional impacts from smoke in a large isolated building. And those impacts arise from radiant heat flux.

In a large isolated building, we're not quite sure how big the fire compartment is going to be, but we know it's big. If you have a big fire compartment, you have a large fire load, you're going to produce a large fire. A large fire will produce a large amount of smoke. That smoke will rise to the ceiling and then will start to drop down towards the floor. Bearing in mind our ceiling is 12 meters high in our large isolated building, so it might take some time for smoke to come down.

If that's the case, why is the smoke hazard management system in a large isolated building as conservative as it? An automatic smoke hazard management system. It's to reduce radiant heat flux. But you won't find the performance requirement that covers radiant heat flux in section E. It's in section C, in C2. And some of you may remember that the smoke hazard management requirements for large isolated buildings used to be in C2.3, and they were transferred to E2. So you need to be aware of why the NCC requires certain Deemed-to-Satisfy provisions in order to identify what fire safety measures and what performance requirements you're really trying to assess.

So I ask, why do the fire hazard requirements increase if the fire compartment ceiling height is greater than 12 meters? Why does it go from 12 meters for one recipe and go to a second recipe for 12.1? What are some of the options to address the impact of excessive smoke? Specific details of what you propose need to be documented to enable this performance to be addressed. Are you proposing to omit what's required under DTS and add alternatives? Or are you going to assess the building without any smoke hazard management system and evaluate with your chief compliance with the performance requirements or not? So let's move on to the next category of the content of the brief.

So we've talked about the proposal, we'll talk about agreed performance requirements. As I just mentioned, you need to be able to identify the appropriate performance requirements that need to be addressed in order to consider whether or not your performance solution is acceptable. And the performance requirements under the NCC that are relevant to a performance solution must be identified via the process described in AO7.

Now we know that performance requirement DP4 relates to travel distance, so in relation to proposal one, to increase our extended travel distance, let's nominate DP4 as one performance requirement we need to consider. We need to consider performance requirements CP2 because it relates to fire spread. And we have excessive radiant heat flux being emitted due to our very big building and our very high ceiling and our possibly very high fire load, we need to assess that, particularly when we have that with a proposal that is going to ommit the required Deemed-to-Satisfy smoke hazard management system. So performance requirement EP2.2 would also be one that we would need to address.

Now as we said, EP2.2 requires a tenable environment to be provided during evacuation. So should proposal two, which relates to our performance of our smoke hazard management system, should it be assessed against CP2 by itself, or should it be assessed against EP2.2 by itself because the Deemed-to-Satisfy solution is included in section E? Or should it be assessed against both of those performance requirements? A question to be considered by the stakeholder group. What you do need to ensure is, is that all relevant performance requirements are identified before proceeding further.

So let's move on to the next category of the content. We're gonna talk about agreed assessment methods. Which assessment methods will the stakeholder group consider are unnecessary to evaluate the performance solutions? We need to see volume one, AO5. We spoke about that before. We saw that AO5 lists four assessment methods. We have a ABCB website data sheet which will also assist this process. And importantly, the assessment methods need to be acceptable to the approval authority. The approval authority at this stage is still sitting as a member of the stakeholder group.

Remember, for the purposes of the case study, we're preparing the brief. And it's important to know what the approval authority will require or is likely to require at this point of time because if you have a performance solution and you're introducing it because of assumed conservative approach of Deemed-to-Satisfy and there's the potential to save X amount of money from the introduction of those performance solutions, but the cost of demonstrating that those performance solutions comply with the performance requirements exceeds the savings, it's unlikely the project will proceed. And the quicker you know that, the better.

So under here when we talk about agreed assessment methods, we really need to know what we're going to be required to do if you the designer in order to have your performance solutions approved. So in respect of proposal one, what assessment methods could we use? We'd need to know whether supplementary fire safety measures are necessary in order to achieve compliance with the DP4. We mentioned that before. One of the common ways of demonstrating compliance with DP4 is to do a comparison between what we call available safe evacuation time and required safe evacuation time.

As an example, if we today, in an emergency, were required to evacuate this room, and we calculated based on our travel speed, whether we had disabilities, the population, the number of people here, the location of the exits, if we calculated that it would take us six minutes 30 for us all to evacuate to a safe place, we know how long it takes us to get out. We know what evacuation time is required. If we then modeled a fire scenario that demonstrated that we only had five minutes 30 available for us to get out, we have a problem. But the process of modeling available time and comparing it to required time is a common means of assessing the efficacy of a proposal relating to extended travel distance. So that could be the answer that could be an assessment method. I'll just flick through this, I've already mentioned what available time is.

Could other assessment methods be acceptable? Certainly. That's up to the stakeholder group to determine what is and what is not acceptable, predominantly to the approval authority. So discussion of proposal two, how will the stakeholders know where the proposed smoke hazard management system will achieve compliance with the relevant performance requirements? If we look at CP2, we know that we have to avoid the spread of fire to within the building and to adjoining buildings. And in the NCC, we have an existing verification method, CV1, which enables us to quantify whether or not our radiant heat flux emitted from a building or being received on the surface of our building is acceptable. So if that's already in the NCC, then we should be able to use that as an acceptable assessment method.

We also raise the issue in regards to our proposed smoke hazard management system that we would need to demonstrate compliance with EP2.2. Now having done an ASET versus RSET analysis relating to demonstrating suitability of our extended travel distance, we know that whether or not we actually provide a tenable environment for occupant evacuation. So the same assessment method used in regards to demonstrate compliance of our extended travel distance could also be used here as a demonstration of compliance with regards to our smoke hazard management system. Here’s a copy of CV1 to give you an idea of what the verification method looks like. And it relates radiant heat flux being emitted from a building or being received by a building with respect to distance between the source of the radiant heat flux and either the allotment boundary or another building.

So let's move on to the next category of the brief. Agreed acceptance criteria. Acceptance criteria are agreed benchmarks for determining whether a performance solution is acceptable. It may be necessary to set criteria that provide safe egress in the event of an emergency and avoid the spread of fire between buildings. So with respect to our case study in which we have to provide safe egress, it may be necessary to ensure occupants are not exposed to untenable conditions for an acceptable period of time. Typically, untenable conditions are conditions that will not sustain human life. In the event of a fire in a building, we're looking at high ambient temperature. Generally, exposure, excessive exposure to 60 degree Celsius ambient temperature is considered capable of influencing a person's ability to breath. Smoke layer height. Smoke layer temperature. Limited visibility. If you have to move through smoke and you're looking for an exit, you need to have a certain length of visibility.

Potential exposure to radiant heat flux. Most of us are able to withstand some exposure to radiant heat flux. I'm sure during your time you would've stood in front of a radiator at some stage, felt the warmth on your legs. Maybe it got a bit hot and you took another step back, become more comfortable. That radiant heat flux is the same form of radiant heat that's generated in a fire and, in severe cases, is capable of igniting combustible materials. And exposure to toxic gases. These are all issues that, when humans are exposed, can create a condition where you can become incapacitated and unable to evacuate. Second thing we need to do is to avoid the spread of fire. We need to avoid direct contact with flames and we need to manage the impact of excessive radiant heat flux.

So our acceptance criteria for these particular issues. For proposal one, perhaps an ASET versus RSET analysis or comparison would be sufficient. For proposal two, would compliance with table CV1 with respect to radiant heat flux and ASET versus RSET with respect to providing a tenable environment during the course of evacuation, would those two criteria be sufficient as acceptable criteria for determining whether or not the performance solutions are appropriate? That's up to the stakeholder group. So let's move on to the next stop point of data that needs to be recorded in the brief, the scope of required evidence.

We discussed before that performance solutions must be assessed in accordance with AO5, and AO5 provided four alternative means, methodologies of demonstrating compliance. In essence, the scope of required evidence to support a performance solution will really depend on the needs of the respective appropriate authority for the appropriate authority to say yes I agree that the performance solutions may be able to be demonstrated to be appropriate. And in order for me to be provided with sufficient information that they are appropriate, I will need the following. And then advise the stakeholder group what is considered necessary.

At that stage, if the cost of providing the necessary evidence exceeds the benefits to be gained by implementing the performance solution, there is not a great deal of sense in moving on with perhaps that's a decision to be made by the building owner in collaboration with the stakeholder group. But in essence, the scope of required evidence will typically relate to the needs of the respective appropriate authority. So let's move on to the next category of content of the brief.

Finally, the format of the report. Under step four, stakeholders need to agree on the format and content of a final report. And all of the content that we discussed in the previous slides should be documented within the brief in order to fully justify the decisions that have been made. And then once the brief is finalized, the stakeholders should sign off. So the main purpose of implementing this process, the main purpose of step one is to document everything that is relevant to a decision to be made on the propriety of performance solution. So the completed brief will reflect an agreed approach to demonstrating that the proposed performance solutions comply with the performance requirements. And in that context, stakeholders need to commit the following, that agreed approach and process. So for our case study, that would be step one completed.

Now we will do step two, conduct an analysis of the proposal. So as I mentioned before, generically, step two is conducted by respective experts in accordance with the content of the brief. The outcomes of step two should be documented. The outcomes of the analysis, the outcomes of the testing, the outcomes of any modeling that's been undertaken to be documented and presented to the stakeholder group for review via step three. So the outcomes of step two were evaluated by the stakeholder group and compared to the acceptance criteria. So under step two, the outcomes of the testing are documented, handed to the stakeholder group. The stakeholder group considers the results of the analysis testing or modeling and says do these results comply with what we wanted as acceptance criteria? If acceptance criteria have not been achieved, then alternative performance solutions can be documented via the brief and analysed via step two. We spoke about this in our generic analysis of the four step process.

Multiple design scenarios. If you test something and you don't get the required outcome, then maybe you modify the proposal a little bit until you do get the required outcome. And all of that is documented and taken into account in step three. Proposal number one, if the acceptance criteria were not achieved, what fire safety measures could be assessed to enable extended travel distance? This would be something that would be discussed by the stakeholder group. Options could be offered, considerations would need to be evaluated by

• The building owner
• The building designer
• Fire safety engineer
• Fire brigade
• Any of the stakeholders

And then they would have to be evaluated through alternatives under step two; as would be the case with proposal number two relating to the omission of a smoke hazard management system. You would need to establish what were the points of failure and how could those points of failure be counted by additional fire safety measures.

Step four of our case study, prepare a final report. In essence, a final report should include a unique means of identification, an executive summary for those that are going to read it that don't have time to be able to consider detail or any other reason. Should include an introduction, should include a copy of the brief. It should include a description of the analysis and the results undertaken in step two. It should include a comparison of the results to the acceptance criteria undertaken by the stakeholder group in accordance with step three. It should present conclusions drawn by the stakeholder group in accordance with step three. It should include references, and it should include associated documents such as drawings. In essence, all of the information that was relied on in order to undertake steps two, three and then finally included in step four.

So that's a description of some of the issues that may arise through the application of the four steps of our guide with respect to a case study just as an example of issues to think about as a member of a stakeholder group. The exercise though was intended to demonstrate that the development of performance solutions need not be a complex process. It need not be something where a single person needs to isolate their thoughts, isolate their input and be totally responsible for an outcome. The stakeholder group is a collaboration. It's a sharing of knowledge, it's a means by which a complex problem can be resolved.

The complexity of the four step process and its application should reflect the complexity of the proposed performance solutions. Bearing in mind the respective stakeholder group determines the scope of activities necessary to demonstrate that a performance solution is compliant, that's the role of the stakeholder group. Stakeholder collaboration on the development of a comprehensive brief and adherence to that brief are critical to the successful implementation of performance solutions.

So there are some key words in that summary: stakeholder collaboration, working together with all the key people. Prepare a comprehensive brief to the satisfaction of the stakeholder group and then adhere to it in steps two, three and four. Time for questions.