New quantified Performance Requirements

One of our initiatives is to increase the competent use of performance, with a focus on building industry’s capability in developing Performance Solutions. 

With this in mind, we’ve introduced more quantified Performance Requirements in NCC 2022.

This article explores the new quantified Performance Requirements across the 3 volumes.

In this section, we discuss the quantification in Volumes One and Two of the NCC. These are grouped together as many of methods of quantification carry across both volumes.

We’ve quantified the sound transmission and insulation requirements, Volume One F7P1, F7P2, F7P3, F7P4 and Volume Two H4P6 (2019: FP5.1, FP5.2, FP5.4, FP5.5 and P2.4.6). To do this, the impact pressure level and spectrum adaption terms are elevated from the Verification Methods (2019) to the Performance Requirements. The Verification Methods (F7V1 to F7V4) (2019: FV5.1 to FV5.4) still contain suitable pathways to use these metrics.

Quantification of bushfire resistance, G5P1, H7P5 and H7P6 (2019: GP5.1, P2.7.5 and P2.7.6) is included in NCC 2022. These now include a design bushfire, using annual probability of exceedance. This means the approach to bushfire design now aligns with other catastrophic events such as cyclones and earthquakes.

The rainwater requirements, F1P1, F1P2, F1P3, and H2P1 (2019: FP1.1, FP1.2 FP1.3 and P2.2.1) have also changed in NCC 2022. We adjusted the metric for quantification from annual recurrence interval to annual probability of exceedance. This shift aligns with current terminology used by other agencies and standards. The performance level of these requirements remains the same.

Fire safety in Volume Two is now fully quantified. Fire spread, H3P1 (2019: P2.3.1) is quantified with the inclusion of a design heat flux and applicable duration. Automatic warning includes efficacy and reliability terms for smoke detection devices.

Lots of Volume Three is now quantified. We’ve quantified the following topics:

• velocity (B1P2, B2P3, B3P3,B6P2) (2019: BP1.2, BP2.3, BP3.3, BP6.2)
• water efficiency (B1P4, B2P11, B3P2, B6P3, C1P3) (2019: BP1.2, new, BP3.2, BP6.2, CP1.1)
• pressure (B1P5, B2P9, B3P5, B6P1) (2019: BP1.2, BP2.3, BP3.3, BP6.2)
• pressure relief and temperature limitation (B2P5) (2019: BP2.4)
• legionella control (B2P6) (2019: BP2.5)
• fire-fighting flow rate and pressure (B4P1) (2019: BP4.1)
• ventilation (C1P5, C2P4) (2019: CP1.1, CP2.1)
• contamination (C1P6) (2019: CP1.1).

While this may seem like a lot of quantification, they are typically applying a common approach to the same metric across the different types of plumbing systems. For instance, velocity is generally quantified as a maximum water speed of “3 m/s for 1% of the time water is required during the annual peak hour”. The main exception to this is for heated water where some additional requirements are needed as temperature effects the flow of water in pipes.

Water efficiency uses maximum outlet flow rates or flush volumes for cisterns. Pressure specifies static and working pressures for different systems. Pressure relief sets a maximum pressure that relief devices must maintain, and also ensures systems maintain hot water to a maximum of 99 °C.

We’ve set a maximum bacteria count to minimise the chance of Legionella growth. For fire-fighting flow rate and pressure, a minimum fire-fighting system performance that water services must deliver is defined.

For contamination, performance is set by minimum water trap seal depths. And, for ventilation a maximum pressure differential (375Pa) is set for the discharge of air.

Some Performance Requirements are qualitative in nature, which discourages practitioners from using them for Performance Solutions. Quantifying them provides objective levels of performance for practitioners to target. This encourages increased and competent use of performance when using Performance Solutions. It also helps ensure a level playing field and reduce the risk of misinterpretation.

If you’re new to performance-based design, or just wish to increase your knowledge and understanding, we have several supporting resources to help you.

• Performance Solutions process guidance document
• Handbook: Performance Solution Process
• The NCC: Meeting the Performance Requirements video
• The NCC: A performance-based code video
• The NCC: Developing Performance Solutions video

This article was updated on 19/06/2023