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If you have recently opened an energy bill, you’ve probably been shocked. Electricity and gas prices have risen sharply in recent years, far outpacing wage growth, with Australian households paying some of the highest prices in the world.1 This situation has been exacerbated by the pandemic, which has seen us spend more time at home and use more household energy than ever before. Skyrocketing energy bills can be a challenge for many, but for some households they can contribute to significant financial hardship. The term “energy poverty” has many definitions but essentially describes households that have difficulty paying their energy bills, or who seek to limit their energy consumption to reduce their costs to such an extent that their comfort and health can be seriously compromised. This is no small problem in Australia. According to the Victorian Council of Social Service, 180,000 households in the state have persistent difficulty paying their energy bills and 45,000 are regularly unable to heat their homes.2

While many factors influence fuel poverty (volatility of fuel markets, insufficient support for low-income people, etc.), the poor environmental performance of our homes is a major contributor. Australia struggles with a legacy of poorly performing homes because we have been slower to act on energy efficiency improvements than many other developed countries. For example, insulation requirements were not incorporated into local building codes in Victoria until 1991,3 more than a decade after their introduction in many Western European countries. In 1993, the Nationwide House Energy Rating Scheme (NatHERS) was introduced in Australia, but it was not until 2003 that the Building Code of Australia established minimum energy efficiency standards for homes nationwide.

Existing homes in Australia also leak, meaning heat is lost in winter or gained in summer, with undesirable ease. Older homes may have an airtightness of around 30 air changes per hour, while a new single-family home is more likely to experience 10 air changes per hour. Compare that to an energy-efficient Passivhaus, which would run at a maximum of 0.6 air changes per hour, and you can see the problem.4 Add to this a reliance on single glazing, the use of dark colored roofs which contribute to overheating, and a lack of greenery and shade in many urban areas, and we are left with an abundance of environmentally vulnerable homes, ill-suited to our climates, which offer little resilience to the extreme weather conditions we are currently facing and which are sure to see more in the future.

CRC’s Guide to Low Carbon Living on Low Carbon Residential Buildings – Retrofit includes a matrix that allows users to find retrofit options that relate to their home typology and climate region .

Although exemplary low-energy homes exist in Australia, unsurprisingly significant inequalities are apparent, with energy poverty disproportionately affecting low-income people, children, people with poor mental health and the disabled. This form of poverty is felt in terms of comfort, health and financial security. Recent thermal monitoring of more than 100 low-income households in New South Wales revealed minimum indoor temperatures of 5 degrees Celsius in winter and maximum summer temperatures of 39.8 degrees Celsius.5 Such extremes have an extremely detrimental impact on households. A widely used statistic is that a higher percentage of deaths are due to cold weather in Australia than in Sweden, with our flimsy homes being a major culprit.6 Exposure to cold temperatures can contribute to respiratory diseases such as asthma, heart disease and stroke. On the opposite end of the spectrum, overheating can cause heatstroke and exacerbate symptoms of mental health disorders.

An added burden for vulnerable households is that escaping uncomfortable and dangerous temperatures is likely to be a greater challenge. If you live in an uninsulated home during a heat wave, relief can be found by visiting an air-conditioned mall or library; for those who are less able or have chronic health conditions, this option may not be possible.

The costs associated with heating and cooling a typical Australian home also vary greatly depending on performance. NatHERS provides a star rating for a home’s thermal performance – the higher the rating, the less energy needed for heating and cooling. In Victoria, the average existing home has a rating of 1.8 stars, while the minimum for new homes is 6 stars. Heating and cooling costs for a 2-star home in Melbourne could be as high as $4,624 a year, while for a new 6-star home they would be $1,373. Heating and cooling a 10-star home — the highest possible rating — could cost as little as $24 a year.7

In sum, the poor quality of our homes has a detrimental impact on both people and the planet. Upgrading our existing housing stock to improve environmental performance will have tangible benefits. But where to start ? For our existing buildings to be ‘net-zero-ready’ – that is, for homes to achieve net-zero carbon performance through on-site renewable energy or future carbon-free regional supply – it is likely that most will require what we call a “deep renovation”. This means looking holistically at layout, fabric and systems to achieve the best possible comfort and energy efficiency, rather than focusing on piecemeal interventions. For example, while parameters such as orientation and footprint are set in existing dwellings, spatial layouts can often still be reconfigured, with walls and interior spaces rearranged to provide better pathways for improved natural ventilation. through windows and openings. With regard to the structure of the building, improving the insulation of walls, roofs and floors, improving the performance of windows, sealing against drafts and increasing the airtightness of air are all essential to reduce unwanted heat flow through the envelope.

A design approach that begins with improving spatial layout and fabric can have a multitude of benefits. For starters, it reduces the cost and size of all the mechanical systems needed for comfort. (In a leaky building, energy-efficient heating and cooling equipment should be oversized to compensate for the poorly performing skin.) Improving the building structure and designing adequate ventilation reduces energy requirements, but also reduce household pollutants and mould, indoor air quality and subsequently the health of occupants. Finally, when spaces and fabric are optimized for comfort, a home’s resiliency is enhanced – for example, during a power outage during a summer heatwave, interior spaces stay cooler longer without air conditioning, which ensures the safety of the occupants.

Different design strategies and technologies are best accommodated in different climates and for different housing typologies. Several resources can provide guidance on the details. For example, the Guide to Low Carbon Residential Buildings – Retrofit, published by the CRC for Low Carbon Living,8 provides a retrofit matrix for different climates and building types in Australia (Figure 1) and breaks down the decisions considering cost, difficulty of installation, impact on comfort and energy savings. LETI Climate Emergency Renovation Guide9 focuses on the UK context, but provides a valuable range of data and decision frameworks for architects in any context.

Faced with the insalubrity of housing, there is perhaps an obvious call to raze and rebuild; to tear down what isn’t working and replace it with new, energy-efficient homes with high NatHERS ratings. However, such an approach fails to recognize that even the worst performing buildings have innate environmental value. This is an investment of labour, materials and emissions from a bygone era, and this investment can be harnessed and renewed through architectural reimagining and engineering ingenuity, rather than wasted on demolition. With each square meter of new home building construction having an embodied carbon of around 700-1200 kgCO2e/m², 10 consider the carbon emissions needed to build a new home from scratch. Building a 190 square meter house will therefore release 133 to 228 tonnes of greenhouse gases – even before a switch has been flipped. Creating 150,000 new homes a year would mean total embodied carbon in the range of 20 to 34 million tonnes – a significant portion of our national carbon budget. Refurbishment of our existing building stock, rather than building everything new, can contribute to significant carbon savings; even as part of a major renovation, the structure, foundations, walls, floors and often many finishes and services can be retained, reducing waste, costs and embodied emissions.

The recognition that renovation should be the first priority of any project is gaining momentum. In the UK, the Architects’ Journal’s ‘RetroFirst’ campaign has seen over 200 firms and organizations declare their willingness to prioritize renovation over rebuilding in response to the climate emergency.11

If the energy efficiency of our homes currently leaves something to be desired, overall, the most sustainable buildings are those that already exist. Upgrading and renovating these buildings, rather than demolishing them, will save energy, materials, waste and carbon emissions. This will not only contribute to our fight against the climate crisis, but will also improve the health, well-being and safety of millions of households across the country.

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