Proposed changes to the National Construction Code could alter the way energy performance is assessed, particularly for multi-residential buildings.
The changes also aim to make it easier for project proponents to innovate across all building types rather than straightforward deemed-to-satisfy solutions. This is being achieved through a change in the code language, with the “alternative” pathway potentially to be renamed a “performance” pathway.
This sounds great, but according to industry experts the proposed methodologies for proving a performance solution is compliant with energy benchmarks might still have flaws.
The Australian Building Codes Board says making DTS (the “prescriptive” pathway) and performance equally valid should encourage innovation, but the questions remains, will it encourage outcomes that are better than business as usual in terms of energy efficiency and thermal performance?
One of the changes is the inclusion of Class 2 multi-residential buildings under a similar type of energy and thermal assessment regime as Class 5 commercial office buildings. Currently, each apartment needs to be individually assessed, and each apartment needs to achieve a rating of at least five star NatHERS, with the whole building averaging six star NatHERS as a minimum.
Under the proposed changes, the whole building will need to achieve six star NatHERS, and none of the apartments will need individual assessment. It has been suggested by some experts this could lead to scenarios where some apartments are way below the benchmark for thermal comfort and energy, but the average is achieved because some of them are outstanding.
It’s a pathway – but where is it leading?
The proposed revisions include two methodologies for assessing thermal performance and energy – JV2 and JV3.
Gary Wertheimer, director of GIW Environmental Solutions, says the problem under the current version of the NCC is that when a building doesn’t comply either under DTS requirements or when assessed with the accepted energy rating software tools, it puts project proponents “between a rock and a hard place in terms of finding a compliant pathway”.
“This [proposed revision] gives a viable pathway for alternative solutions, and I think that it is a good initiative,” Wertheimer says.
“It enables you to look at other ways of offsetting the energy loads.”
The revisions state that renewable energy systems as part of a project design can be factored into energy performance assessment.
Wertheimer says that while this is what many projects do to achieve compliance, it doesn’t actually really compensate for poor thermal performance.
“Renewables are like carbon accounting. They are a way to balance things out,” he says.
“You could argue that the fundamentals of design are not being addressed.
“If you are offsetting energy use with renewable it’s not ideal, but it’s better.”
Overall, he says, it’s good the revisions are proposing a verification method that allows architects to assess and measure buildings, but doesn’t “stifle design”.
“It’s important that a prescriptive pathway offers some flexibility as well.”
And while that’s overall a positive move, Wertheimer says designers and others should keep in mind that the building code is a minimum, and should always be understood in that context.
“The emphasis on raising performance has dropped off in the last couple of years. There is room for another round of stringency measures – lifting the performance requirements slightly.”
AIRAH is looking into it
AIRAH chief executive Phil Wilkinson says his organisation has set up an industry review group to review the proposed energy verification method JV2 for NCC2016.
“This work is ongoing, and there appears to be a lot of confusion as to the intent of the proposed method and the ability of the industry and building regulators to apply it,” Wilkinson says.
“AIRAH will be making a submission on this proposal, and other new performance-based methods such as the ventilation-verification methods, as part of our response to the NCC public comment draft.”
It’s a step in the right direction – but not far enough
In terms of the revised code’s overall shift to promote performance solutions as equal to deemed-to-satisfy solutions, it is a step in the right direction, according to Studio Huss director of research and former GHD principal engineer Tai Hollingsbee.
“The amendments are about giving industry different options which are less restrictive in achieving compliance,” he says. “This, then, can encourage greater innovation in achieving compliance.”
However, it is still not much of an advance on business as usual. And Hollingsbee questions whether the fact the BCA is using BAU as a baseline, and setting benchmarks based on “should not be worse than” for building elements such as walls and windows, is going to advance the sustainable building agenda.
“It sets minimum performance requirements for elements of the building, but it is not overly ambitious,” he says.
“None of this is going to save the planet,” he says.
“What will [help] save the planet is better understanding of the metric of megajoules per square metre in the context of climate and existing energy consumption in buildings.”
Hollingsbee says there needs to be actual data based on how much energy buildings use in a particular climate – such as the metrics for energy used by NABERS – and that this data should be used as the benchmark, not BAU.
Then, by working backwards from that benchmark to the desired outcome, a better methodology and dataset can be developed.
Issues with the energy rating tools
A report by Cundall for the ABCB that forms part of the consultation documents for JV2 and JV3, Sensitivity study for the proposed changes to the verification method V 126.96.36.199, may give a false impression of the effectiveness of some of the most commonly used energy modelling software, according to Studio Huss director of research and former GHD principal engineer Tai Hollingsbee.
The study compared the results of modelling six different home designs across Australian climatic zones with FirstRate5, Integrated Environmental Solutions (IES) – Virtual Environment, v2014.2.1.0, Energy Plus (EP) Energy Simulations Software V7.2 (Energy simulation) and Autodesk Ecotect Analysis 2011 (Geometry).
Cundall’s methodology shows that the non-FirstRate5 softwares overestimated either heating or cooling loads, while underestimating the other. At the same time, Cundall expresses a cautionary note that “the [verification method] requires significant tightening, and considerable additional testing is strongly recommended before any public roll out is attempted”.
“Many significant variables and unknowns exist and the risk of unintended consequences is very high,” the report states.
Hollingsbee says that it concerns him that the report is out as part of the BCA comment process, yet its outputs are “not complete”.
“There are a number of areas of the technical approaches taken that require more analysis, and now it is out for review, perhaps it is not painting the right picture.”
Hollingsbee says that FirstRate5 is a “fundamentally old and technically restrictive way of quantifying energy consumption”.
“It should be scrapped. It’s done a lot of good, but it’s from an older period,” he says.
One of the issues is that it does not have the flexibility and data background to account for some of the new, more energy-efficient solutions for managing thermal comfort, such as low velocity ventilation systems or radiant heating systems.
“The reality is the alternative software [which the Cundall report found lacking] is far more advanced at analysis and computation of energy performance than FirstRate5.
“But because of the method [Cundall used], it suggests [FirstRate5] is a much better computational tool and that the others are worse performing, and that’s completely wrong.
“We need more research, more detailed research, into software to model performance.”
Additionally, FirstRate5, unlike the other tools Cundall analysed, does not have the ability to combine energy use with indoor environment factors, nor does it incorporate dynamic thermal modelling that can account for recent developments such as phase change materials, indirect evaporative cooling technologies, or the contribution effective ventilation can make to reducing reliance on HVAC.
“FirstRate5 has far less ability to adjust the input parameters,” Hollingsbee says.
Let’s look to Europe
He says that Australia’s building code should be looking to European building codes for guidance.
“If there’s anything worth considering it’s using a carbon intensity metric as opposed to an energy metric,” Hollingsbee says.
A carbon intensity metric that incorporates energy use and on-site energy generation is being used in countries including Germany and the UK, and in the UK from 2016, all buildings – even single detached dwellings – must achieve net zero carbon.
“It opens up the innovation window much wider,” Hollingsbee says.
“Architects and engineers have to work much harder to achieve zero carbon.
“Europe is far more advanced in evolution of the building code in general, for example, the UK and Germany’s code have more consistent calibration and methods that have been based on many years of open consultation with industry and a common agreement about reducing carbon emissions across the whole of the European Union.
“That is the level of rigour needed over here.”
Comments on the proposed revisions to the NCC are open until 3 August 2015. The finalised NCC2016 will then come into effect in May 2016.