Future Weather Files

IBPSA-Australasia hosted a webinar on Future Climate Files for Commercial Building Energy Modelling featuring Grace Foo from DeltaQ on Friday 13th of November. DeltaQ has been appointed by the Commonwealth Department of Industry, Science, Energy and Resources (DISER) to conduct research into the impact of using future climate files for commercial building energy modelling. The report can be accessed in this link. The report has made several recommendations including setting up an Australian-specific centralised climate files repository for easy access by modellers.

IBPSA-Australasia believes that the simulation industry will benefit from having a centralised source of trusted weather files for energy simulations including recent historic files and future files (typical and extreme). In addition to this, guidance on the use of appropriate weather files must also be provided so that the industry can adopt consistently.

While many weather files used in energy modelling are outdated, the impact of their use in NCC Section J JV3 modelling as a comparative analysis, is not too concerning as the same file is to be used in reference and proposed models. As such, we do not see the immediate need to enforce the use of future weather files in JV3 modelling or in Green Star Energy modelling where compliance is based on comparative analysis. Instead, the use of future weather files should be made mandatory for testing off-axis scenarios for NABERS Energy modelling and for Green Star Resilience related credits.

Encouraging the use of recent weather files should be the main priority to improve the stringency of JV3 modelling. The availability of weather files based on recent historic data is not well known among the energy simulators. There are sources of recent weather files such as from Climate.OneBuilding.Org where the energy simulation gurus: Dru Crawley and Lind Lawrie have volunteered to develop a repository of free climate data for building performance simulation. Data from 2004 - 2018 are incorporated into Australian files and available for many locations. The predicted results using these files show differences from those provided by the older files. However it remains the responsibility of the energy modeller to review the quality and appropriateness of the weather files for the purpose of their modelling. This is where having an appointed government body that reviews and approves a set of weather files and provides guidance and recommendation on the appropriate use of the files will be beneficial for the industry. Government would have a strong role in mandating use of the approved weather files for compliance analysis, which would encourage industry to move to using them regularly.

The more pressing issue that we see as requiring immediate intervention is the practice of adding arbitrary few degrees to the current design temperature data to oversize air conditioning equipment for future capacity requirement. This practice, in addition to the practise of combining the design Dry Bulb Temperature and the Web Bulb temperature (instead of using coincidental figures) lead to oversizing of HVAC plants. This leads to inefficient energy consumption for the majority of the year when weather conditions are more moderate. Coordination with AIRAH (and CIBSE, ASHRAE) is required to develop/select an updated set of design temperature data.

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