Case study: Check out this “occupant-proof” net zero home
Willow Aliento | 10 April 2018
All homes should aim to be net zero, according to Robert McVicker, the owner and builder of a home that produces more energy and water than it uses.
His Vicker Ridge home in Logan Village, Queensland is not what most people might picture when they think of an uber-sustainable dwelling. It has four bedrooms, 2.5 bathrooms, a combined living-dining-kitchen “great room”, media room, study, kid’s retreat, library and a large outdoor entertaining area that can even be airconditioned.
However, the household comprising McVicker, his wife and two young teenagers has been producing more energy and water than they use annually, despite indifference from his family.
“My family are not enthused about net zero at all,” McVicker says.
“But the house doesn’t demand occupants do that.”
The right combination of passive design and technology can “occupant-proof” a home, he says.
The net zero status has been verified by data logging of both real-time energy production and use, and real-time water storage, water usage and discharge of A-grade treated water from the home’s water treatment plant. McVicker also posts the data regularly on a about the home’s performance.
Mobbs a major influence
When he first began the project to design and build the family’s dream home, the concepts of net zero for energy and water were “totally foreign” to him, he told The Fifth Estate.
“I just fell into it.”
Working with a building designer, he learned as the project unfolded.
Michael Mobbs’ book Sustainable House was a major influence, he says.
“It became my bible.”
A sustainability platform was put in place that ensured principles such as thermal mass, passive solar design, natural ventilation and air stacking for thermal comfort were all incorporated.
“The house has a high performance bone structure.”
Lighting was specified as LED throughout, and the best available energy efficient appliances selected.
The internal area of the home is 354 square metres, however the roof area is nearly 500 sq m. McVicker calls the style “Aussie Akubra”, as the house has eaves that are minimum of 1200mm on each side, on the western elevation extending out to an extreme overhang of 12 m.
This ensures the home is shaded from summer solar gain, while at the same time, in the north-facing “great room”, winter sun can achieve ingress of five metres or more of direct fall on the polished concrete floor, delivering passive heating.
McVicker says that on a day with a minimum temperature of 4°C, the great room can reach a temperature of 28 degrees in the middle of the day – with no heating used. By 6pm or 7pm in the evening, the room is still warm.
The majority of the home’s external walls are lightweight construction.
However there is nothing lightweight about the home’s insulation. In the roof, there is an anticondensation sheet and batts with silver backing. The ceilings have R3.0 earthwool batts – the highest R-value available.
The external walls being Villaboard on a steel frame meant there was only a narrow space for insulation. McVicker says he “researched and researched” what product would give the greatest R value in the available space, and found that a 150mm thick acoustic batt was the best solution.
“Inside the home, a lot of the internal walls also have insulation,” he says.
The home is also zoned, with evaporative airconditioning to the great room, with a damper for the system that enables it to be diverted so the outdoor entertaining area can be cooled.
The great room’s vaulted ceiling is insulated into the roof space, and where batts are shared down into the wall they have been gyprocked into place.
The hallway acts as a type of thermal chimney. A truss extending from the hallway to one of the bedrooms and then out to a parapet was deliberately left uninsulated, to give heat a pathway and utilise an air stack effect for ventilation.
In summer this heat can be vented by the operable louvres up near the ceiling. In winter, the heat can be retained.
McVicker says he was on site supervising all the insulation installations, and that the resulting installation decisions, like the pathways in the home for passive heating and cooling, are “weird and wonderful”.
He says every subcontractor used on the house was handpicked by him and rarely left to work without supervision.
“Everything needed to be executed to my level of expectations,” he says.
This also meant he had the opportunity to engage in a lot of information gathering.
“There was a lot of my asking ‘why, why, why?’ – it was a way to learn about the industry.”
When the home was first completed in late 2012, it had 16 solar panels and a 3.8kW inverter installed. McVicker says he was an early adopted with solar, and that at the time the panels were “hideously expensive”.
He also invested in an energy monitoring platform that captures data from 10 circuits and is accessible from smart phone or laptop. A display screen is also installed in the home.
The monitoring enabled him to see that in the first year, the home was not achieving net zero. That came two years after construction, he says.
The energy audit he had carried out showed that the house’s waste water treatment system, a membrane bioreactor system, was a major energy guzzler.
The system was adjusted, with more energy efficient blowers retrofitted to the plant. In addition, an extra 10 panels were added to the home solar PV system.
Energy monitoring key to net zero
McVicker says understanding where energy is being used and what is using it has been “paramount” to achieving net zero.
While in some months there is slightly more energy from the grid imported than is exported from the solar, over the year, the home is now consistently producing more energy than it draws.
McVicker says the next step will be batteries. This will come once the current feed-in tariff the household is receiving ends.
“The way the pricing is set up it is not attractive to stay on the grid,” he says.
“Once the feed-in tariff goes will be paying a hefty cost to be connected to the grid.”
He is a staunch believer that the proof of a home’s sustainability is in its performance, not just a builder putting in all the “tricks” to try and get there.
“You either make it or you don’t.”
The home is off-grid for water, as it is in a semi-rural area where there was no economical option of being connected to mains potable water or sewerage.
However, while the home’s wastewater treatment system is best practice, and the same technology used by many municipal WWT systems where chlorine is being minimised, Queensland law restricts the use of the Class-A recycled water from being re-used, even in toilets or laundry.
This means rainwater captured and stored on-site comprises 100 per cent of the home’s water supply.
McVicker is unsure if he would build a home in an urban area that had the same water systems. Part of this is due to hurdles councils put in front of sustainability, such as water service fees and sewerage service fees.
He says that if these types of fixed charges were swapped for more user-pays system based on consumption, there would be more incentive for households to put rainwater collection and storage in place and plumb captured water to toilets and laundries.
“It’s a serious impediment to sustainability,” he says.
Industry slow to change
The Vicker Ridge home won a Queensland Premiers Awards for Sustainability in 2015, after a year of operating at net zero.
McVicker says that following the win, he was optimistic about the direction the building industry might take.
However, down the track, he says the degree of change is “questionable”.
“There’s a lot of greenwashing out there.”
But given the proof that net zero can be achieved for energy and water with no behavioural sacrifices, McVicker says it should be achieved more broadly.
Evolving views of sustainability
Standards for design and construction should be “outcome-driven”.
“My version of sustainability has evolved,” he says.
It is now focused on a regenerative outcome – one where the building’s performance in terms of energy and water outputs exceeds demand.
“If consumers knew the truth of how much a high-performance home gives back, they would walk out onto those new estates and say to the builder, ‘What are you doing to keep my energy costs low?’”