GREEN LIVING

Building net-zero carbon houses is not as expensive as you think

Dr Phillip Alviano Sustainability Advisor

New research shows constructing a net-zero house may not be as expensive as you may assume. While the final costs will be dependent on the complexity of the design and access to a good, northfacing orientation, the project found the additional costs added two to three per cent to the total build costs, including land. This equated to an additional cost of approximately $20,000 for a 30-square-metre home in a growth area. But reduced or zero utility bills means the investment is paid back in around eight years. Moreover, with a number of lenders now offering reduced interest rates for “green loans”, the initial investment can be recovered within four years through a saving of $5000 per year on energy bills and repayments on interest. A typical zero-carbon home has a 100 per cent renewable energy source, usually on-site solar with or without a battery, external shading for east and west windows, insulation with a minimum R2.5 in the walls and R5 in the roof. Good-quality windows and glass doors with a U-value of at least 3.3. air tightness should also be at about 5 ACH at 50pa pressure. In addition to the savings there are health and comfort benefits. While we have been aware for some time that cold houses have a negative impact on their occupants’ health, it is increasingly evident that heat waves also lead to more frequent hospital admissions. So, having houses that are more comfortable in both summer and winter has a positive effect on public health and reduces the financial burdens on the healthcare system. The Mainstreaming Net Zero Energy Housing — Cost Analysis Report, published by the Cooperative Research Centre for Low Carbon Living (Byrne et al An example of low-carbon residences available today. Photo courtesy SJD Homes.

2019), looked at a number of case studies across Australia. The Melbourne case study used an SJD Homes typical single-storey home built in new developments. The 258sqm home had four bedrooms and two bathrooms. Upgrades included double glazing to all sliding doors, increased ceiling insulation and changes to the size and placement of some windows. This resulted in an improvement of the energy rating from 6.5 to 7.6 stars. Some of the cost increases were the result of better-quality, energy-efficient appliances such as induction cooktops and heat-pump hot water. A five kilowatt photovoltaic solar system was estimated to easily cover the energy use of a typical four-person household. The total cost of the upgrades and solar panels came in at just under $20,000. Reference: Byrne. J, Eon. C & Law. A (2019), Mainstreaming Net Zero Energy Housing – Cost Analysis Report, CRC for Low Carbon Living.

Builders’ pledge

When Master Builders Association of Victoria started the Green Living program in 2005, very few people thought builders were genuinely interested in protecting the environment. Since then, approximately 2000 people have completed sustainability training and a core group has continued as accredited Master Builders Green Living Builders. This has involved keeping themselves informed with up-to-date information on the latest building practices and materials in order to build better, healthier, more comfortable and energy-efficient housing. We were contacted recently by a number of members who told us about the ‘builder’s pledge’ to which they have committed. This pledge involves a group of builders creating a passionate community of professionals in the construction industry who are ready to face climate change and biodiversity challenges, and who want to share their knowledge and continue learning how to do things better.

Australian builders declare mission

In a world first, Australian builders have joined architects in publicly acknowledging that we are in a climate emergency, and that business as usual cannot continue if we want a prosperous future for our children and the natural environment in which we live. Builders Declare is an alliance that runs events, provides resources, shares knowledge, answers queries and links professionals passionate about building more sustainably, and creating a better future for all Australians. Australian Builders Declare seeks like-minded builders and professional tradespeople to show their support by signing up to the pledge. For more information go to https://au.buildersdeclare.com/. They can also be found on Facebook and Instagram.