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    BASIX #8: Understanding the "Whole of Home" Measurement


    The construction sector is witnessing a profound transformation aimed at elevating energy efficiency levels, particularly in the realm of residential buildings.

    The ambition is to enhance the thermal performance of homes, setting a new standard at seven stars, up from the current six. This evolution is indicative of a broader commitment to sustainable building practices, requiring a well-rounded awareness and strategic planning from both designers and homeowners.

    In the Spotlight: Whole Home Rating System and Energy Budget

    At the heart of this transformation lies the whole home rating system, a comprehensive methodology assessing various facets of a building's energy performance. This approach integrates the NatHERS star rating, which evaluates the building envelope's thermal performance and the home's annual energy usage budget, offering a comprehensive view of its energy efficiency.

    1. Thermal Performance:

    Thermal performance is a keystone of energy efficiency in homes. With an emphasis on upgrading to the equivalent of a NatHERS 7-star rating, significant improvements are being introduced. Here's a snapshot of these enhancements:

    • Roof, Wall, and Floor Insulation: Enhanced insulation for roofs, walls, and floors has been endorsed to foster optimal thermal comfort.

    • Reducing Thermal Bridges: Efforts are afoot to cut down on heat loss and heat gain through crucial structural elements, thereby reducing the reliance on artificial heating and cooling.

    • Lighter Coloured Exteriors: Adopting lighter hues for roofs and external walls can naturally deflect heat, reducing the internal temperature of a dwelling.

    • Climate-specific Window Requirements: To augment energy efficiency, the new standards recommend window provisions more suitable to the local climate.

    • Cooling Efficiency: In areas experiencing warmer temperatures, the introduction of new ceiling fan requirements ensures better airflow and comfort.

    • Lower Heating and Cooling Demand: Ultimately, all these measures are geared towards a significant reduction in the demand for artificial heating and cooling.

    2. Annual Energy Use Budget:

    Apart from structural thermal performance, a home's annual energy usage is now a significant point of focus. The introduction of an energy use budget aims to promote the incorporation of more efficient equipment, thereby curbing the overall energy footprint of a household. Some advancements in this area include:

    • Efficient Air Conditioners: The spotlight is on the use of energy-efficient air conditioners for both heating and cooling needs.

    • Instantaneous Gas Heating: A move towards energy-efficient instantaneous gas and electric heat pump water heaters ensures that residents get hot water without a significant energy cost.

    • Renewable Energy Integration: The inclusion of on-site renewable energy systems, especially rooftop solar installations, further contributes to reducing a home's net energy consumption.

    To understand household energy consumption better, it can be categorised into three main areas: heating and cooling, hot water, and appliances, which include lighting, cooking equipment, and pool or spa pumps. Each category roughly contributes a third to the total energy usage of an average home.

    This simplified categorisation serves as a tool to aid in comprehending where the most energy is used in a household and underscores the importance of each appliance’s specifications in the overall energy performance of the home. Optimising these aspects is key to achieving higher energy efficiency levels.

    NCC 2022 Residential Energy Efficiency Overview2

    NCC 2022 Residential Energy Efficiency Overview
    © Commonwealth of Australia and the States and Territories of Australia 2022, published by the Australian Building Codes Board. The material in this publication is licensed under a Creative Commons Attribution—4.0 International licence, with the exception of third party materials and any trade marks.  It is provided for general information only and without warranties of any kind. More information on this CC BY licence is set out at the Creative Commons Website.  For information regarding this publication, see

    Setting the Budget: The Benchmark Home

    The budget is determined from the benchmark home—a theoretical model acting as a yardstick for energy efficiency. This home is equipped with specific appliances, including a three-star ducted reverse cycle air conditioner and a five-star gas instantaneous hot water system. To outperform this standard, a home needs to demonstrate a 30% improvement in efficiency.

    The energy usage budget is a crucial element, encompassing heating, cooling, hot water, as well as the energy needs of pool and spa pumps, and lighting. It is based on the thermal envelope of the home and is balanced out by any contributions from photovoltaic installations. For a home to surpass the benchmark, it must perform at least 30% better in terms of energy efficiency.

    The budgetary approach is streamlined and is represented by the equation: Heating (A) + Hot water (B) + Lighting (C) + Pool and spa pumps (D) - On-site renewable energy (E) = Budget.

    The Assessment Process

    The assessment process ensures homes adhere to the new energy efficiency standards. Designers are required to provide details about various elements of the home, ranging from the heating and cooling systems to the hot water systems and appliances in use. Together with the details of the building envelope, this data is then utilised by energy assessors, employing specialised software to gauge the home’s energy efficiency.

    The software considers average appliance usage based on dwelling size, the number of occupants, and their energy habits. It evaluates not just the building’s thermal shell but also assesses the necessity of heating or cooling, the efficacy of the installed systems, and the total energy expended in providing these services.

    In conclusion, the new compliance standards for residential energy efficiency, both in terms of thermal performance and annual energy use, underscore the commitment to sustainable living and are integral to meeting state and national commitments to their climate targets.

    Related articles:

    BASIX #1 Orientation. Harnessing the Sun's Movement

    BASIX #2 Windows. The Importance of Window Selection in Achieving a 7-Star Home

    BASIX #3 Insulation. Unveiling the Power of Insulation and Wrapping 

    BASIX #4 Frames. The Environmental Impact of Metal Frames

    BASIX #5 Lighter Roof Colours. How Lighter Roof Colours Will Impact Homes

    BASIX #6 Ceiling Fans. How Ceiling Fans Can Enhance Your Home's Aesthetics and Energy Rating

    BASIX #7 Energy. Balancing Low Carbon Materials and Operational Technologies

    BASIX #8 Understanding Whole of Home Measurement

    BASIX #9 Process. The Impact of an Efficient Design Process in Achieving NatHERS 7-Star Rating

    BASIX #10 Let's Build a Brighter Future Together! Your Contribution

    Hall & Hart: How Energy-Efficient Homes Can Be Affordable

    Hall & Hart. Sustainability - Making a Difference to Climate Change One Home at a Time

    Hall & Hart. Starting Our Journey with Carbonhalo