Explainer: is your new home net zero?

Mahmudul Hasan

living room

A new home with operational net zero means to make it zero in terms of both energy and carbon emissions. 

Otherwise, it means net zero energy or net zero carbon home depending on which initiatives or options (either energy or carbon) were adopted for the home. 

Building a new home and want to make sure it’s operationally net zero?

Here’s how.

Building fabric

Unfortunately, many homes in Australia would not pass an air tightness test or leakage test.

Fabric specifications vary greatly according to the climate – for example, the fabric specification of a house in Sydney or Melbourne will be different from that in Brisbane. When building a new home, it is important to check with your designer and builder to ensure that the fabric specifications are appropriate. 

The external walls should be made with optimum insulation and the glazing should be energy efficient. This will assist in removing mold, reduce worn out walls internally and lower air conditioning energy consumption. Running energy costs will also be greatly reduced. 

Things to look out for: 

  • An Energy Efficiency Report or Certificate, plus who provided it and what their qualifications are 
  • The exterior colour of the building (I still can’t believe how many roofs of Brissy homes are dark, with occupants crying out that the upper storeys are too hot to stay in summer)

Daylight (adequate sunlight) and ventilation

Does a buyer or owner notice the daylight and ventilation at all? 

If not, they definitely should.

It is important to ask an architect to do a daylight analysis when you are designing, and to ask a sustainability consultant to verify it. This will reduce use of internal lights in your house during the day, and air-conditioner use – and you will benefit from improved thermal comfort during the winter. 

Many times, problems arise when homes are built between two houses, resulting in limited daylight inside the home.

Also, many existing homes in Sydney and Brisbane do not have ceiling fans, which results in poor air flow and warmer temperatures inside. 

Ceiling fans should be installed without attached or inbuilt lights, ensuring there are sliding windows and sunset awnings to provide ventilation and shade. In warmer climates, ensure ceiling fans and insulation are installed in the outdoor area or patio. 

Services and appliances

When it comes to services and appliances, there are so many aspects to consider that generalists may not think of. That’s why it is so important to consult with a designer, and not just rely on the trade. 

There are some basics that you should keep in mind when you have this chat: 

  • cooling and heating equipment should have at least Co-efficient of Performance (COP) or Energy Efficiency Ration (EER) of 5.0 or 6.0 standard or at least 4 Stars
  • heat pumps are becoming increasingly popular (EER/COP>3.0), and mechanical design plays a key role
  • LED lights should be selected with a design criterion of 2.5 watts per square meter, and large homes can have daylight sensors installed
  • do not buy or install any household appliances (fridge, washing machine, dryer) below 4 Energy Star
  • Similarly, dishwashers should be installed with at least 5 Star WELS
  • keep an electric oven for cooking, do not install any gas appliances
  • if there is a swimming pool, let it run on the heat pump and try to keep the temperature at 24-28 degrees Celsius (having a pool cover will also reduce energy costs)

Solar panels

Here’s another contributor to a net zero home that should be installed in consultation with an electrical designer. Simply buying and installing 5 kilowatt solar panels is not the right thing to do. If you do manage to install it on the correct location of the roof, you may get decent output. However, the solar output may be reduced due to neighbouring shades, and you do need to think about what capacity of solar you can install. 10 kilowatt capacity is now a much better option than 5 kilowatts in a new home. But PV systems can be designed to be battery ready for future application.

Carbon offsetting

To mitigate any remaining carbon footprint that cannot easily be brought down, carbon offsetting may be the right way to go – but keep in mind that that is always the last resort.

A carbon offset – the reduction or removal of greenhouse gas emissions made in order to compensate for emissions made elsewhere – should never be relied upon to reach net zero. 

But once you’ve done a combination of all these tactics to reach a net zero home, carbon offsets can be the way to get over the line. 

For example, say your home consumes 40 kilowatt hours of energy per year. 35 kilowatt hours can be covered by solar. But the remaining 5 kilowatt hours of energy can be offset by 2 cents a kilogram ($125 a year) for tree planting or any other carbon offset project.

How much does it cost to build a net zero home?

It will cost a bit more to build a net zero home than a house without net zero.

My research and the research of others highlighted that the cost will be 1-10 per cent higher than the usual capital cost.

You must be extra careful after creating your building specification document, and quotes should be taken from several builders. It is recommended to review the building contract very well with the opinion of an experienced builder who already has experience building net zero or Green Star homes, along with the opinion of the designer.

Why should I build a net zero home?

If you can build a net zero home, it will have less operational energy cost, less carbon emission, and less carbon offset compared to a standard home. A net zero home will have excellent market value and you will be able to sell it at a right price in the market.

To build a Green Star home, you will have to achieve Green Building Certification from the Green Building Council of Australia (GBCA). You will have to achieve the Zero Energy Certification for energy under the Living Building Challenge (LBC) to be net zero. For zero carbon certification under LBC, both the energy and carbon requirements need to be met, involving a comprehensive Life Cycle Analysis (LCA). 

If you are planning to build a net zero home on your own, have patience and consider the project for 12-18 months. Consult with an experienced and qualified sustainability consultant for net zero options. 

Are you on the right track for making your home healthy, resilient and net zero?

– Mahmudul Hasan, sustainability professional for the built environment

The views presented in this article are the author’s own.