Energy modelling New Zealand homes at design stage is easier and more widely available, thanks to a project by Sustainable Engineering for the New Zealand Green Building Council (NZGBC). ECCHO has been accredited under ASHRAE 140, a confirmation that ECCHO’s calculations are correct. This work was carried out by SEL principal, Jason Quinn. ECCHO had to be validated in order for its results to demonstrate compliance with the new H1 standard in the New Zealand Building Code.
Jason developed the first version of ECCHO in 2021, which ran as an add-on to PHPP, the modelling software used by Passive House designers. It didn’t need to be validated, because PHPP was already proven to be accurate, both according to the ASHRAE140 standard and through real world measured heat load testing. ECCHO has its limitations but its key advantage is that anyone can learn how to use it in a few hours. PHPP is considerably more demanding, requiring full-time training for several weeks.
NZGBC’s Sam Archer subsequently created an online version of ECCHO. Drop-down forms and a simplified interface make it easier to use and therefore available to more people. It’s easier to learn, user inputs are well controlled (reducing the risk of user error) and the results can be readily checked by Homestar assessors.
“ECCHO won’t do funky stuff,” says Jason Quinn. “You can’t change settings to do unusual things, but that means the risk of making mistakes is much smaller. ECCHO allows you to build a shoebox energy model and a designer can gather all kinds of useful information from that. It can’t take into account self-shading, but the model can be rotated to test the impact of orientation on the site and the designer can experiment with different window placements and glazing percentages.
ECCHO users can only select from pre-populated lists of options. NZGBC invested considerable resources in developing the defaults, including options for slab details. Sustainable Engineering provided the data from its own window database, which it had developed in conjunction with suppliers of windows to Passive House projects and maintains as a service to the Passive House community.
“ECCHO is not accurate enough to model at a Passive House level. That’s because at that level of performance, shading is critical to delivering the Goldilocks internal temperature: not too hot, not too cold. ECCHO works in the space between Building Code minimums and the PHI Low Energy Building standard. There are some dramatic improvements to be had in that range,” says Jason Quinn.
Sustainable Engineering carried out the testing and produced a comprehensive report for NZGBC. This is not public, but the report itself is not useful to individual designers. What’s important is the process and the findings. Sustainable Engineering evaluated the online ECCHO software using ANSI/ASHRAE Standard 140, in order to provide confidence in using ECCHO as an energy model tool for building code energy performance compliance.
The three project objectives were achieved:
- Evaluate ECCHO using the ASHRAE Standard 140-2017 test cases and to record the results.
- Examine and comment on ECCHO’s predictions in comparison to benchmarks provided in Standard 140 and suggest sources of observed differences.
- Document findings in a comprehensive report, following the ASHRAE Standard 140 standard reporting method for documenting assumptions and reporting results.
The key finding:
For a total of 38 Class II test cases described by ASHRAE 140, ECCHO results were within the confidence interval of the reference software for all but one case, L155A for cooling energy. We consider this sufficient evidence for ECCHO to demonstrate that ECCHO meets the ASHRAE 140 testing standard.
This validation method does not involve real world tests. Instead, standard building assemblies are modelled in ECCHO as well as other software programmes and the results compared. ECCHO delivers almost identical results to PHPP9.
The work was done within a tight deadline. It was significantly easier due to Remi Charron generously sharing his PHPPv9.6a input files and report materials, says Jason Quinn. Remi is a leading Canadian Passive House designer, an engineer, academic and consultant and he was responsible for validating the PHPPv9.6a software to the ASHRAE Standard 140.
It’s another example of how the Sustainable Engineering team’s unique skill sets and international networks keep contributing to better outcomes for New Zealand homes. “The validation of ECCHO will see more people energy modelling more homes and apartment buildings,” says Jason Quinn. “Councils can accept ECCHO results with confidence knowing its been validated.
“I expect the next version of the NZ Building Code will require energy modelling for every building and I think a tool with ECCHO’s capabilities will be the starting point. It’s a good foundation that will introduce more people to the basics of energy modelling. Being able to easily quantify the impact of design decisions has the potential to transform a designer’s practice—and New Zealand homes badly need transformation.