There are so many tools for measuring a building’s energy efficiency and sustainability that choosing the most appropriate one for a project can be confusing.
The Australian Institute of Architects recently sought to clear up the confusion with a rating systems speed dating night at its Melbourne office.
Experts on five rating systems had 10 minutes each to explain the basics of each system.
Here’s a brief summary:
- NatHERS is a nationwide rating scale for thermal performance of homes. Ratings are conducted with software such as FirstRate5, and range from zero to 10, with 10 meaning little or no energy is being used to heat or cool a house in a given year. The tool is not a measure of sustainability but focuses on how much energy is needed to heat or cool a certain space.
- NABERS compares energy performance of a building against other buildings with similar characteristics, to ascertain a benchmark. NABERS looks at a building’s energy consumption data across 12 months and considers building size, how many people use it, what time of day they use it, what the local climate is like and then benchmarks the data against other buildings in the same situation. The tool is widely used, particularly for office buildings.
- The Built Environment Sustainability Scorecard or BESS has been developed by a group of councils in metropolitan Melbourne as an aid to planning applicants and to complement sustainable design assessment. Due to launch next week on May 15, it’s the newest rating system on the block. The tool is designed to rate the sustainability and efficiency features of residential and non-residential buildings. The BESS tool is free to users and is paid for by councils. An overall score of 50 per cent is considered best practice and BESS creators hope developers and other will aim higher.
- Green Star rates building design and performance on a scale of 1 to 6 stars. Performance ratings have to be re-certified every three years to make sure the building’s operations are up to date and to encourage improvement over time. The Green Star rating has lifted the profile of sustainability measurements in the built environment.
- The Living Building Challenge is the most demanding rating system. In fact, participants do not receive a rating – you either meet the requirements or you don’t. Buildings must behave like plants in that they are “net positive” on energy, water and waste. The criteria for building materials are the hardest to meet. There are 777 materials and chemicals not allowed. Only 12 buildings in Australia are currently being assessed for the Living Building Challenge.
Shifting the goal posts
A common attribute of rating systems is that the definitions for each rating have to keep being changed.
As renewable technology improves and sustainability standards increase, the definition of “five stars” has to be modified.
Sustainability consultant Ania Hampton explained that the NABERS tool went from a maximum five stars to six.
“A lot of the buildings were getting five stars and it wasn’t really that much of a challenge anymore,” Ms Hampton said.
“And the market was saying, I’m doing much better than five stars, but I’m still getting compared to these guys who are just getting five stars.”
Ms Hampton said there was talk of a seventh star but NABERS assessors decided against it because that extra star would have been “such a huge leap that nobody would get it”.
“It’s nice for people to be able to achieve full stars, to six out of six,” she said.
“They can say, ‘I’m really at the top of performance for the current marketplace.’”
The concept of “rating” sustainability is being challenged
University of Melbourne senior architecture lecturer Dr Dominque Hes introduced a new paradigm with her brief presentation on the Living Building Challenge.
Buildings have to be “net positive”, she said.
“All of the energy needs to be brought by renewable sources.
“At the end of the day a plant doesn’t get its energy from elsewhere.”
“Is that doable? Is that real?” architect and event MC Scott Willey said.
“It is real,” Dr Hes replied.
The Living Building Challenge has discarded the idea of “rating” sustainability.
“Can I half get a Living Building Challenge rating?” Mr Willey asked.
“No. You can be attempting to get Living Building Challenge [certification] but if you don’t meet all of the [criteria] you won’t get the full certification,” Dr Hes said.
“There’s no scale. You either survive as a plant, or you don’t.”
Buildings can actually be good, not just less bad
Dr Hes remembers when she was first introduced to the idea that buildings could be regenerative like plants.
“Back in 2005 when somebody said to me, ‘Efficiency is not enough, Green Star is not enough,’ I was like, ‘What? No, really? Oh shit, you’re right.’”
She first became aware of the Living Building Challenge in 2010 when its American creators visited Melbourne.
“Everyone was excited to see that there was a way that buildings could be good, rather than less bad,” Dr Hes said.
“A lot of people are very frustrated with tools that are about ticking boxes, that are limiting their innovation.
“Whereas all that Living Building Challenge says is “be net positive”, don’t care how you get net positive.
“It’s got to be renewable; there can’t be any fossil fuels involved.
“You’ve got to offset all your embodied energy, just be like a plant.”
Inspiring the industry
Dr Hes said many of her architecture students had been put off sustainability because filling out Green Star scores sapped their creativity.
She used the analogy of a “sustainable marriage” to illustrate her point.
“If I said I had a sustainable marriage, you’d be like, ‘Are you sure? Are you okay?’”
“You don’t want a sustainable marriage, you want an exciting, invigorating marriage where you’re dealing with problems together and growing and learning.”
Dr Hes does not begrudge the other rating systems and believes they have played a vital role in creating a language for the industry to understand sustainability.
“We’ve got that language going, now let’s move forward to the inspirational side of things,” she said.
“We can actually create more ecological capital but we’ve never thought of ourselves as being able to do that.
“We’ve always thought the earth would kind of be better off without us. And that’s not true.”
- See our story Behind the Living Building Challenge process: the SBRC