UTS Special Series – a focus on academics and their work. In this article, Professor Leena Thomas of the UTS School of Architecture steps through research at Fairwater at Blacktown, a residential estate north-west of Sydney that uses geothermal energy.
There are many truisms in sustainable design, such as thermal mass is good, sealing the building is essential, and making a big glazed box function effectively in a hot climate is feasible if the building fabric and airconditioning is energy efficient.
As a professor in the UTS School of Architecture, Leena Thomas has dedicated her career to understanding the intersection of building design, human behaviour and the contextual elements of energy, climate and urban design.
She tells The Fifth Estate that over recent years she’s had reason to question the canon. The missing piece, she explains, is that the design of high-performance buildings alone does not dictate how people will occupy a building, nor does it have foresight of what those people will find comfortable.
In Australia, commercial building occupants expect a set-and-forget level of comfort that does not vary with the seasons. So, when it’s hot, our building services must work harder. When it’s cold, our building services need to compensate. The perennial 20-ish degrees must be maintained at all costs, even if those costs are planetary and contribute to global heating.
The emphasis in the past on thermal mass for storing heat or “coolth” has been a constant theme, but as Thomas explains, if a heat wave lasts for more than a few days, thermal mass “does what it is supposed to do” and retains and radiates the accumulated heat.
The result can be extreme discomfort and soaring energy demand as people switch on their airconditioning without pro-active management of building prior to such events.
In recent years, the heatwave experiences followed by the pandemic sending most people home have shown that many approaches have a major flaw – the behaviour of the human occupant cannot be fully predicted.
In a wide-ranging conversation, Thomas captured the journey building designers have been on, including the stage of dabbling in mixed-mode ventilation, the episodes of free-running buildings with zero energy used for cooling or heating, and the delivery of fully-sealed built boxes with a highly energy-efficient but 100 per cent mechanical ventilation, heating and cooling system.
A big issue that Thomas is interested in is the data deficit on how humans, energy, sustainable design and the general climate intersect.
A recent research project carried out by Thomas and her team on Fairwater, the 6 Star Green Star Communities estate developed by Frasers Property Australia at Blacktown, north west of Sydney, has started to close the gap.
The project has multiple partners – Climate-KIC Australia and Curtin University and it was supported by ARENA , NSW Office of Energy and Climate Change, Frasers and Wattwatchers.
Built on a former golf course, the estate features medium density housing embedded in open space with waterbodies, walking paths and green space including both grassed areas and tree covered zones.
Every dwelling was built to the prevailing standards of thermal performance, including appropriate orientation, cross ventilation and light-coloured roofs.
Geothermal and how it works at Fairwater
All homes also have an innovative geothermal ground loop installed as part of the home’s reverse cycle airconditioning system.
Thomas says that in conventional reverse cycle heating and cooling, heat exchange happens with the ambient outside air. So if it’s 40 degrees outside, it takes a significant amount of energy to moderate indoor temperatures down to around 20 degrees.
When it is very cold, similarly, it requires significant energy to raise the temperature.
The geothermal loops such as those installed at Fairwater harness the stable temperature conditions under the earth for heat exchange, thereby reducing the energy required by the reverse cycle heat pump system.
What the research did was find out was whether the promise of energy bill savings from the technology was manifested, particularly while people were at home during COVID and during intense heat event episodes.
It also examined people’s own subjective experience of comfort, and how people were using space in their homes, to give a full picture of the contextual factors.
The life experience, she says, is “really important because modelling and simulation never takes into account the variability about people and having a living lab allows you to be able to do so.”
Non-invasive sensors that measured temperature, relative humidity, mean radiant temperature and room occupancy were installed in about 40 dwellings whose occupants agreed to participate in the three-year research study. Surveys also asked people about their comfort level, and what actions they self-initiated to stay comfortable. This data was also complemented by smart meter data that showed energy use for electricity.
“ARENA were interested to understand the impacts of a large scale [geothermal] installation,” Thomas says.
“So, we conceived of an idea of having a living laboratory in which we would be monitoring not just the home to find out their energy use in the context of geothermal air conditioning, but also understanding people.”
“We said, here’s an opportunity to understand a whole bunch of strategies you’re doing at the level of the precinct.”
The data for Fairwater was also compared with energy use and ambient temperature data for an area of North Kellyville that had homes also constructed around the same time to the then-required 5 Star NatHERs standard. The Kellyville homes, however, lacked the dominance of light roofs, abundant green space or the geothermal ground loops of Fairwater.
Comparing homes across the two areas showed that the energy savings at Fairwater were of measurable benefit to the electricity network during peak demand events.
When ambient temperature and energy demand were mapped against each other, households in Kellyville dialled up the energy use much more rapidly in response to hotter weather than people in Fairwater.
Other interesting findings included the cooling effect from the light coloured roofs towards mitigating of urban heat, and the improvements to the health and wellbeing of residents from living in the Fairwater precinct. “(Geothermal) was doing what the hypothesis said it would,” Thomas notes.
Fairwater homes with geothermal had 21 per cent lower electricity consumption than Kellyville homes when normalised for house size.
However, if the compact design of the homes is factored in, compared to the larger Kellyville homes, the saving was in the order of 38 per cent over the year per household.
The surprises in the research
There were other aspects of the research findings that surprised her. For example, Thomas says she had a hunch that because people in Fairwater had airconditioning they would use it by default simply because it was hot outside.
The monitoring did show “there is still a big people dimension to energy consumption”. Some continued to use airconditioning even when outdoor and indoor conditions were reasonable without it, but not everybody chooses to use it “indiscriminately”.
Other residents the team monitored reported they were happy at 27 degrees or even 31 degrees, and would report they had put on a fan, had a cold drink and dressed appropriately.
“You can see the behavioural dimension matters, and that is independent of the star rating of the house. But it’s not about blaming star ratings – star ratings are important for one thing, and that is to ensure the building fabric works for whoever is in there.
“But the real energy story is going to be about how people understand how they use buildings and energy. And especially how we can influence the thermal comfort and airconditioning side of it as we increasingly face extreme temperatures.”
Thomas says that with climate change, as a community we may have to become better at adaptive behaviours. In addition to improving the thermal performance of our buildings, this might mean we become accustomed to embracing the weather a little more, develop some tolerance perhaps for having to dress for the season, or accept that a bit of dust might blow in when we open windows for airflow.
“We can’t just do this with a whole bunch of solar panels, and trying to keep up and keep everybody (thinking) that you can stay comfortable forever…influencing sustainable practices and rethinking adaptation alongside mitigation is going to be a 100 per cent necessary.”
This article is part of a special project between The Fifth Estate and the University of Technology Sydney focused on the education and research underway at universities on sustainability and climate related issues.