A zero net carbon home combines an energy efficient building design and fixed appliances with a solar energy system to help reduce running costs, increase comfort and curb carbon emissions.
It is designed to produce enough renewable energy to off-set the annual greenhouse gas emissions of its estimated energy use.
We have been running the Zero Net Carbon Homes pilot program to develop sustainably-designed residential homes in Victoria and provide technical and marketing expertise to builders to facilitate the development, marketing and sales of such homes.
Register to get updates about our Zero Net Carbon Homes program.
Benefits of a zero net carbon home
Lower home energy bills
Our modelling indicates that compared with a new 6 star NatHERS rated home built in Melbourne, a home that meets the Zero Net Carbon Homes program standard reduces the energy bills by 60–70% depending on occupant numbers and behaviour as well as the size of the home.
Increased comfort and quality
Zero net carbon homes produce comfortable internal temperatures and are warm in winter and cool in summer.
Higher levels of insulation and draught proofing improves ‘air tightness’ resulting in lower heating and cooling requirements and less discomfort. An as-built verification test is conducted that includes insulation integrity checks and air leakage detection to ensure the home performs as designed.
Reduce carbon emissions produced by the home
Building a zero net carbon home can reduce greenhouse gas emissions by five to eight and a half tonnes per year, when compared to a home built to meet current industry standards.
Comfortable and consistent internal temperatures protect occupants from the external temperatures and can improve health outcomes, according to the World Health Organisation’s housing and health guidelines.
How to build a zero net carbon home
In order to build a zero net carbon home, home builders will need to complete zero net carbon home design modelling and an as-built verification assessment.
Zero net carbon design modelling consists of two steps:
Deliver a Nationwide House Energy Rating System (NatHERs) report that achieves a 6.5 star energy rating or above (The current National Construction Code requirement is 6 stars). This needs to be delivered using the FirstRate5® energy rating software.
Delivering a NatHERS report is a standard requirement for all new homes in Australia.
Calculate the energy use of the home’s fixed appliances using the purpose-built zero net carbon design tool.
This tool is currently being developed as part of the Zero Net Carbon Homes pilot program and will be made available to industry in early 2020.
The tool assesses the energy use of the home’s fixed appliances to calculate the specific size and orientation of a solar photovoltaic (PV) system that will off-set the home’s energy use. The modelling is based on the energy used by four people over 24 hours.
An as-built verification (ABV) assessment is a quality assurance test.
- evaluates the energy efficiency of a home after it is built
- ensures the home meets a zero net carbon standard.
It involves an independent evaluator visiting a home and rating the home’s air tightness and insulation integrity.
Evaluators perform blower door tests, using fans to simulate wind blowing against the building’s exterior to identify air leakages in the building’s envelope.
Thermal imaging is used in conjunction with blower door testing to locate missing or poorly installed insulation that may result in the movement of heat/cool into and out of the building.
Common features of a zero net carbon home
The make-up of the final features can vary as long as they contribute to meeting the zero net carbon homes standard.
Correctly installed, high-quality insulation will significantly reduce the amount of energy needed to maintain a comfortable temperature inside a home regardless of the weather outside.
The level of insulation performance is measured by the R-value. Insulation in some zero net carbon homes may have a higher R-value to meet higher NatHERS star requirements. This makes homes more resistant to heat losses and gains through ceilings and walls.
Double glazed windows
Double glazed windows can reduce winter heat loss by up to 70 per cent, according to the Energy Smart Housing Manual.
Double glazed windows have a sealed air space in between glazing layers that act like insulation and reduce the amount of heat entering or leaving the home. Double glazed windows also reduce noise pollution from outside the home.
Energy efficient fixed appliances
Heating and cooling accounts for around 60 per cent of overall household energy use, according to the Residential Baseline Study for Australia 2000–2030 (2015).
Zero net carbon homes require heating, cooling and water-heating appliances to be highly energy efficient. Induction cook-tops and solar hot water pumps are good choices as they greatly reduce energy use and remove the requirement for gas.
Building orientation determines how much free heating from the sun a home receives in winter and how much it keeps out in summer, which means the potential for lower energy usage and increased comfort. Living areas that face north benefit from winter sunshine and provide free heating, reducing reliance on mechanical systems.
Each home has solar array on the roof which has been calculated to cover the operational energy use for the home. Most homes will typically have between 3.5 to 6kW installed on the roof, so that net exports and imports of energy are equivalent to each other.
Light emitting diode (LED) lighting is the premium efficiency lighting option and the most suitable for zero net carbon homes.
Draught proofing is a very important feature of a zero net carbon home, as it helps keep the home air tight. Care should be taken around gaps between windows, walls or floors and skirting boards, between floorboards, where pipes penetrate walls and around skylights.
Visit our zero net carbon display homes
We are working with SJD Homes, Metricon Homes and Stockland as part of a funded program to design, build and market zero net carbon homes. Currently we have three zero net carbon display homes open to the public.