Sustainable home renovations
Renovating your home to suit your family, lifestyle, and environment is likely to be one of the most important financial investments you make.
Our homes need to be comfortable and efficient for today, but future-ready to respond to challenges of tomorrow. Buildings account for half of Australia’s electricity use, and almost a quarter of its emissions, but by renovating an existing house rather than demolishing for a new build, you are reducing waste and embodied energy – all while keeping its character.
The thought of renovating a house for sustainability, health, and resilience can feel overwhelming and expensive – but it doesn’t have to be. We also know that homeowners with sustainable measures in place save money from the beginning. For that reason, the Green Building Council of Australia (GBCA) alongside Allianz, developed a guide for homeowners and builders.
'A guide to sustainable home renovations’, is a practical guide filled with tips, support, and the answers you’ve been looking for. To make this information as accessible as possible, we have gathered the most important, and practical, information and easy wins to make your renovation better for today, and tomorrow.
What makes a home sustainable?
Our buildings have an enormous impact on our health and wellbeing, and our planet. It’s our belief that everyone should have access to healthy buildings that are also good for the environment.
All sustainable homes are unique, but there are a few requirements outlined in the guide that are a way for homeowners and builders to discern what sustainability targets should be met.
A sustainable home means lower impact on the environment, but it also means lower ongoing bills for you, and a healthier, more resilient life for your family.
There are three critical elements that define what a better home looks like, responding to the needs of today and tomorrow.
A positive home
A positive home is an energy efficient home. It saves you money, is more comfortable, and is designed to be powered by renewable energy.
Most of the energy used in homes is to heat and cool inadequately poorly insulated and designed homes. Water heating is the next highest consumer of energy in residential buildings, followed by appliances, lighting, cooking and stand-by power.
The following points outline approaches to guide you in targeting a positive home.
What are its features?
- Orientation: Consider the placement of windows to utilise solar energy and airflow.
- Insulation: Ensuring the building is fitted with insulation to stop the transfer of heat both in and out of the home.
- Thermal mass: Dense building elements such as concrete have a ‘thermal mass’ which allows them to absorb heat energy and release it later. This keeps homes cool in summer and warm during winter nights.
- Glazing: Windows provide light but can also be a source of heat loss during winter and heat gain during summer. Glazed windows increase resilience to the changing climate and provide a balance between comfort and amenity.
Easy wins:
- Install external shading, such as roller blinds, to problematic windows
- Install ceiling fans with multi-directional airflow
Poorly sealed homes will result in uncontrolled air movement throughout a home. This unintentional air movement is estimated to cause 25% of winter heat loss, leading to increased energy consumption from heaters. Draught-proofing a home through airtightness will improve energy efficiency, comfort, and acoustics. Some common places air leakage can be found are windows, fireplaces, and vents.
Easy win:
- Draught sealing will increase comfort and save on energy costs. This includes weather strips to doors and windows, dampers to vents and sealing gap and cracks.
It is recommended that all renovation activities make decisions that support divestment from gas. Extracting and burning gas creates greenhouse gases that contribute to climate change, and cooking with gas is estimated to be responsible for up to 12% of childhood asthma in Australia. All electric, while aiming for renewable electric, homes also benefit homeowners back pocket, by future-proofing the home against a decarbonising environment.
Did you know?
- Replace the appliance that uses the most gas first, generally hot water. While it might be more expensive upfront, it will save you the most in operational costs.
Hot water systems are the second highest use of energy in Australian homes. Old electric storage hot water systems are very inefficient and should be replaced. Options include electric heat pumps and solar electric boosted systems – which may be eligible for rebates. Aim for a heat pump with a Coefficient of Performance (COP) of 4.0, indicating high efficiency, and with refrigerants with low global warming potential (GWP), ideally below 10.
Did you know?
- Heat pump water heaters absorb warmth from the air. They are roughly 3 times more efficient than conventional water heaters.
With solar panel efficiency increasing, and prices falling by 80% since 2008, installing solar is an efficient way to reduce, and eventually remove, energy bills while future-proofing your home. Installing a Battery storage system is the best way to take advantage of solar energy and will also be there to provide uninterrupted power supply in the event of extreme weather. If this is not possible at the time of solar installation, it’s a great idea to ensure the solar system is ‘battery ready’ for when you can.
A Clean Energy Council Approved Solar Retailer can help you find a suitable system for the house and provide you with a certified contractor for installation.
Easy win:
- If solar isn't an option for you, all homes, including apartments, can switch to 'Green Power' as part of their energy contract.
Using a metering and monitoring device will allow you to take control of your energy consumption through transparency on peak times of electricity use and identifying high energy appliances.
Some options include:
- Smart plugs
- Smart meters
- Energy monitors
- Home automation
A healthy home
Our homes, where they are located and how they are built, influence every aspect of our lives – including our health and wellbeing.
Indoor air pollution is consistently ranked among the top five environmental risks to public health, with the CSIRO estimating the cost of poor indoor air quality in Australia being $12 million per year.
A well-designed, healthier home will give its occupants plenty of fresh air and natural light, while negating the buildup of moisture, which leads to mould, and harmful emissions from the materials used in its construction.
What are its features?
Your home requires constant circulation of fresh air to remove moisture, odours, and other pollutants to create a healthier environment for those inside the home.
Easy wins:
- 'Shoe-free household and regularly clean carpets
- Regularly clean A/C ducts
- Major renovations:Consider the installation of a mechanical ventilation with heat recovery to supply a constant source of fresh air.
Condensation occurs in a house when warm air meets a cooler surface, often seen on windows, or inside construction systems on walls, ceilings, and floors. This can lead to mould and mildew growth which is harmful to human health. Older homes with poor sealing will allow airflow and moisture to diffuse through the house, whereas very airtight homes will need additional ventilation to minimise risk.
Top tip:
- For any new construction it is suggested that a Weather Resistive Barrier (WRB) suitable for your climate region is installed. In colder climates, an additional internal wrap is also beneficial.
Providing your house with high quality daylight and LED light is essential for comfort and health. Dark rooms may benefit from larger windows or additional skylights to allow for increased natural light.
Easy win:
- LED lighting is affordable, energy efficient and has a long service life
Paint, materials, finishes, furnishings and other building products have a significant impact on the health of those in your household due to the off-gassing of Volatile Organic Compounds (VOCs), toxic substances which hinder indoor air quality. Impacts include lethargy, headaches, and respiratory problems. VOCs are commonly found in paints and varnishes, engineered timber, and adhesives, with kitchen and bathroom renovations being two key areas that attract VOCs.
Top tip:
- Low VOC and timber for cabinetry and benchtops with low formaldehyde content are widely available
A resilient home
Why should your house be resilient?
Global climate change is impacting all facets of life, and our homes are one of them. Australia’s climate has warmed on average by 1.4 degrees since national recordings began in 1910, which has led to increased catastrophic fire weather days. And while winter rainfall has been declining in the Southern parts of the country, the intensity of extreme rainfall events has increased.
To withstand this, and to limit additional damage to the environment, resilient homes are needed. These homes are more robust than the minimum building standard and can better withstand extreme weather events.
What are its features?
- Connect rainwater tanks to the toilets for flushing, and the laundry for the washing machine.
While a green lawn is a popular feature of many Australian homes, they need large amounts of water. In fact, 40% of the average household’s total water consumption is used for outside purposes, the majority of that due to gardens and lawns.
A sustainable garden aims to work in harmony with the natural climate. By choosing plants that are indigenous to your area, you can create a resilient garden. Not only that, but you’re also providing habitat and increasing biodiversity. Contact your local council for a list of plants native to your area.
Top tips:
- Aim to retain vegetation, particularly established trees where possible
- Install sub-surface drip irrigation to reduce water consumption
- Due to the large surface area, a roof will contribute to the heat island affect. This can be lessened by using light-coloured roofing products with a suitable Solar Reflective Index
Future proofing your home from extreme heat, bushfires and flooding are top priorities for a resilient home. To do this, there must be regular property maintenance to mitigate damage caused by the following extreme weather events.
- Bushfires: Dangerous fire weather days have significantly increased in Australia. Properties are classified by a Bushfire Attack Level (BAL) as a way of measuring the risk of a house being impacted by a bushfire. Your BAL rating will determine requirements for construction, including fire shutters.
- Ember attack: Embers enter the home through gaps to ignite the building’s interior or debris on roofs. In high-risk zones, create a clear protection zone around the house with no overhanging trees.
- Storms: Secure roof coverings, keep gutters and drains clear of debris, and trim damaged branches regularly.
- Extreme heat: Mitigating effects of extreme heat and increasing temperatures, can be achieved through shading strategies and improvements to your home’s thermal performance. Ensure outdoor services such as hot water and cooling systems are positioned in the shade to reduce the risk of failure due to heat exposure - which will also increase system efficiency.
- Flooding: With an increase in storms and cyclone activity in recent years comes an increase in flash flooding. Homes at risk should consider mitigation strategies such as flood barriers, increasing stormwater pipe sizing, and elevating new structures above flood risk level.
- Electric vehicles: EV’s are predicted to be the same price as their petrol counterparts by 2026, and 30% cheaper by 2030. When using grid electricity, the cost of charging an EV is about half the cost of petrol, and that number falls even more when charging from rooftop solar panels and a home battery.
Top tips:
Contact your local council or rural fire service to determine the BAL rating for your property.
Quick resilience win:
To reduce water consumption, replace lawn area with native plants, and install new fixtures and appliances with high WELS ratings.
Major resilience renovation:
Install light coloured metal roof sheeting to increase reflectivity and minimise heat gain
Renovating an existing house rather than demolishing the entire building will reduce waste and embodied energy. Second-hand building materials can be used, such as windows, bricks, metal sheeting, doors, and timber. Discuss you waste management plan with all parties, particularly subcontractors, to achieve the targeted waste reduction.
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Green Specs
For an interactive look at sustainable renovation options across your home, please visit Allianz and Green Building Council of Australia’s website: Green Specs, making blueprints green, and breaks down the technical information available in the guide.
Explore the interactive website
Case studies
Tropical living
Located within tropical South-East Queensland, ‘Yagoi 100’ is a house designed to incorporate the best of thea currently available environmentally sustainable design principles and products.
1950s house renovation
Mylor home in Adelaide Hills, experiences hot summers and cold, wet winters. The owners chose to enhance the interior, expanding the north side while shielding from harsh winter sun instead of demolishing the home.
The little loft house
The Little Loft House is a rejection of the 'disposable’ mindset by breathing new life into a home that many would consider ripe for a ‘knock-down/rebuild’.
Planning a sustainable renovation
Collaboration is key in achieving a successful sustainable renovation.
Local Council
Can advise you on local environmental hazards, such as flooding and bushfires.
Homeowner
Select building professionals that align with, and understand, your project’s goals. Remember to keep an open mind, the sustainable choice may not be the preferred option for several reasons - find a balance.
Architect/designer
Uphold client’s goals for achieving an energy efficient and sustainable home. Ensure quality construction with careful attention to building sealing at all junctions and ensure there are no gaps in insulation for airtightness and thermal performance.
Builder
Encourage minimalist designs and sustainable alternatives, including incorporating passive design strategies into all projects, reuse of materials from existing house and engage with a NatHERS Assessor early on for feedback.
Resources
Government incentives
Several financial incentive schemes and grant programs exist to support sustainable homes, particularly focusing on energy and water efficiency, and these opportunities will vary depending on your location. Current schemes (as of May 2023) can be found here.
Financing
Financial institutions may also offer low, or no interest loan schemes for sustainable building and energy efficiency upgrades.
Bank Australia
Commonwealth Bank
NAB
Gateway Bank
Insurances
Renovating the home, whether through size or added technology, is likely to increase the overall value of the home, and the replacement cost in the event something happens to the property. With climate change increasing the occurrence of extreme weather events that may impact the home, re-evaluating is important.
Cost vs benefit
To assist in decision making, strategies and initiatives for sustainable renovations discussed on this page have been summarised into three tiers, identifying simple solutions for improving sustainability, through to considerations for major renovations. This summary can be found on page 49 of sustainable renovation guide.