Still no precipitation data despite NCC compliance requiring moisture management

A critical review of the CSIRO Weather and Climate Data (Part 3 of 3) 

The CSIRO weather and climate data sets discussed in our previous post are widely employed by building energy modellers, including applications to demonstrate compliance with the energy efficiency requirements of the National Construction Code (NCC). Exemplary Energy’s timely critique of the CSIRO weather and climate data sets ahead of the 2022 publication of the NCC, and highlighted three major shortcomings:

1. Reliance on weather data ending in 2015 for the characterisation of a warming climate;

2. A 30-minute error in solar data in the .epw format; and

3. A lack of coincident precipitation data despite the .epw format expressly inviting it.

Discussions of the first two issues can be accessed here and here. In this final article of our three-part series, we investigate the opportunity for incorporation of coincident precipitation.

Precipitation data is important for a wide variety of applications. The AIRAH DA07, Criteria for Moisture Control Design Analysis in Buildings, provides specifications for predicting, mitigating, or reducing moisture damage to buildings, and requires detailed consideration of precipitation. In 2019, minimum condensation requirements were incorporated into the NCC, designed to minimise impacts related to moisture on the health of the occupants in the building. Further measures for moisture management are being proposed for the NCC 2022.

One challenge is that, until recently, many sources of precipitation data are reported at inadequate temporal resolutions. For instance, the Bureau of Meteorology’s (BOM) observations network typically only reported daily totals prior to the early 2000’s.

Exemplary Energy has developed algorithms to estimate hourly precipitation from the daily historical figures reported by the BOM for over 200 Australian locations, including the 69 locations built into NatHERS. This work was recently peer reviewed and was presented by Exemplary Energy in the Asia Pacific Solar Research Conference (APSRC) in December 2021.

The issues outlined herein need to be considered by policymakers and modellers alike. We have advised our colleagues at CSIRO of these findings and will continue to work with them to avoid further propagation of the errors and offer our support to improve the data going forward. We urge policymakers to be mindful of these issues as modelling inaccuracies arising now are embedded in building operations for many years to come.

In the interests of full disclosure, we note that Exemplary Energy offers high quality climate and weather data, including ersatz future climate data, that avoid the issues of the CSIRO datasets. These are available for modellers demonstrating compliance through the JV3 pathway, along with non-regulatory applications in design and optimisation and resilience testing of buildings and energy systems.