Homeowners
For homeowners, a Home Energy Rating can help explain how an existing home performs and where comfort or efficiency upgrades may have the greatest impact.
Residential Performance
Understand the thermal performance of an existing Australian home and identify practical pathways toward improved comfort, energy efficiency and future-ready upgrades.
For homeowners, housing providers and project teams seeking Home Energy Ratings, NatHERS Existing Homes assessments and evidence-based residential performance insights.
Discuss Your Home AssessmentIn Brief
A Home Energy Rating for an existing home is an emerging Australian residential assessment pathway designed to provide a clearer understanding of the thermal performance and energy efficiency of an existing dwelling.
Unlike a new-home NatHERS assessment based primarily on proposed drawings and specifications, an existing-home assessment considers the dwelling as it has actually been constructed. It may involve on-site data collection, measurement of building elements and thermal modelling based on the home’s current insulation, glazing, shading, orientation, ventilation and construction.
The resulting information can help identify thermal comfort issues, weaknesses in the building fabric and practical opportunities for future upgrades. It may support homeowners, property professionals and emerging home-energy frameworks in understanding how an existing dwelling performs and where improvements may deliver the greatest benefit.
The home’s existing insulation, glazing, shading, orientation, ventilation, construction and overall thermal performance.
New-home assessments model a proposed design, while existing-home ratings examine the real condition and performance of a completed dwelling.
It helps identify comfort issues, building-fabric weaknesses and practical upgrade opportunities across Australia’s existing housing stock.
Knowledge Navigation
Use this guide to explore existing home energy ratings, assessment methods, building performance, upgrade pathways and practical project considerations.
Foundation
Assessment
Performance
Improvements
Future Direction
Practical Guidance
Foundations
A Home Energy Rating for Existing Homes is an Australian residential energy assessment approach designed to evaluate the thermal performance of homes that have already been built and occupied. Read the short answer guide to Home Energy Ratings for existing homes .
Unlike a standard NatHERS assessment for a new home, which is usually completed from proposed plans and specifications before construction, an Existing Home Energy Rating considers real built conditions. This may include the dwelling’s age, construction type, insulation levels, glazing systems, shading, orientation, ventilation, renovation history and observable building fabric conditions.
An Existing Home Energy Rating commonly involves on-site data collection, building measurement, thermal modelling and interpretation of how the dwelling performs under Australian climate conditions. The assessment may help identify issues such as excessive summer heat gain, winter heat loss, poor insulation performance, glazing weaknesses, draughts, air leakage and practical opportunities for future energy efficiency upgrades.
In Australia, these assessments are commonly associated with NatHERS Existing Homes methodologies and emerging residential energy disclosure frameworks.
As Australia’s existing housing stock continues to age, Home Energy Ratings for Existing Homes are becoming an important way to understand residential energy performance, thermal comfort and potential retrofit pathways for established dwellings.
For homeowners, property professionals, retrofit programs and organisations working with existing housing, these assessments can provide a clearer evidence base for understanding how a home currently performs and where future improvements may have the greatest impact.
Industry Collaboration
Certified Energy is collaborating with Cotality Australia to explore how Home Energy Ratings for Existing Homes can be delivered practically, consistently and at scale as the market prepares for broader home energy rating disclosure.
Cotality brings property data and workflow capability across the Australian housing market, while Certified Energy contributes practical NatHERS assessment experience, thermal performance knowledge and residential energy compliance expertise.
This collaboration supports the development of more workable delivery models for existing home energy ratings, particularly as governments, property professionals and homeowners prepare for a future where energy performance information becomes more visible across Australia’s residential property market.
Read more about why practical delivery matters for NatHERS Existing Homes .
A large share of Australia’s residential housing stock was constructed before modern thermal performance expectations became common in residential design and construction.
Many existing Australian homes may experience:
Home Energy Ratings help create a clearer picture of how these dwellings currently perform, rather than relying only on assumptions about age, construction type or original design intent.
Improving the thermal performance of existing homes may help reduce energy demand, improve occupant comfort, support better retrofit decisions and strengthen housing resilience across Australia’s varied climate zones.
As governments, lenders, homeowners and industry groups continue exploring future energy disclosure, retrofit and residential performance pathways, Existing Home Energy Ratings are likely to become increasingly relevant across the Australian housing sector. Learn whether Existing Home Energy Ratings are mandatory in Australia .
Existing Home Energy Ratings differ significantly from NatHERS assessments for new residential projects.
New home NatHERS assessments are generally based on proposed architectural drawings and specifications before construction begins. Existing Home Energy Ratings instead analyse homes that have already been constructed, occupied and potentially altered over time through renovations, repairs, retrofits, maintenance issues or ageing building materials.
Existing Home Energy Ratings can involve additional complexity due to:
This means Existing Home Energy Ratings often require more real-world investigation, site interpretation and evidence-based assumptions than standard new home modelling workflows. Compare NatHERS Existing Homes with new home NatHERS assessments .
While both pathways draw on NatHERS thermal modelling principles, Existing Home Energy Ratings focus on understanding the current performance of existing residential buildings and identifying practical opportunities for future improvement.
Continue into how Existing Home Energy Ratings work or explore on-site data collection .
Industry direction
Home Energy Rating is moving beyond technical assessment and into market readiness.
Over time, Home Energy Rating is expected to support a broader disclosure conversation, where the energy performance of existing homes may become more visible at sale or lease. Learn whether Existing Home Energy Ratings are mandatory in Australia .
This makes the rating itself only one part of the transition. As existing home ratings become more visible, the wider market will need clear information, trained assessors, practical upgrade pathways and better understanding across property, finance, construction and energy sectors.
Existing Home Energy Ratings are generally completed through a combination of property data collection, building measurement, construction review and NatHERS thermal modelling.
Unlike a new home NatHERS assessment, which is usually based on proposed drawings and specifications, an Existing Home Energy Rating must interpret how a dwelling has actually been built, altered and occupied over time.
This makes the assessment process more evidence-based. The assessor may need to review visible construction details, measure the building, identify glazing and shading conditions, consider insulation assumptions and record building fabric features that influence thermal performance. Learn what a Home Energy Rating assessor looks for .
Digital LiDAR-assisted workflows, site photography and building measurement tools may be used to improve data accuracy and help translate the existing dwelling into a reliable thermal model.
Once the relevant information has been collected, the building data is entered into NatHERS thermal modelling software to assess how the home is likely to perform under Australian climate conditions.
The final Home Energy Rating can help identify thermal comfort issues, excessive heat gain, winter heat loss, inefficient building elements and practical opportunities for future energy efficiency upgrades.
Continue into on-site data collection or explore thermal modelling and reporting .
Who It Helps
A Home Energy Rating can support different decisions depending on who is using the information. For some households, it helps explain comfort, energy use and upgrade priorities. For property, finance and design professionals, it can provide a clearer way to understand the performance of an existing home.
For homeowners, a Home Energy Rating can help explain how an existing home performs and where comfort or efficiency upgrades may have the greatest impact.
For renovation projects, an assessment can help identify how insulation, glazing, draught sealing, shading and building fabric upgrades may influence the home’s rating.
For sellers, a Home Energy Rating may help communicate the energy performance of a home more clearly during property discussions, especially where comfort and running costs matter.
For valuers, lenders and finance partners, ratings can support a more consistent way to understand home performance, upgrade potential and energy efficiency information.
For real estate and property teams, a rating can provide a practical language for discussing home comfort, efficiency and upgrade opportunities with owners, buyers or renters.
For builders and designers working with existing homes, a Home Energy Rating can help connect upgrade decisions with measurable thermal performance outcomes.
Certified Energy can support Home Energy Rating assessments for existing homes, including projects connected to renovation planning, property performance, finance discussions and broader residential energy efficiency programs.
Assessment Process
Existing Home Energy Ratings are generally completed through a combination of property data collection, building measurement, construction review and NatHERS thermal modelling.
Unlike a new home NatHERS assessment, which is usually based on proposed drawings and specifications, an Existing Home Energy Rating interprets how a dwelling has actually been built, altered and occupied over time.
This means the assessment process often requires more real-world investigation than a standard new home modelling workflow. Learn what a Home Energy Rating assessor looks for .
Step 01
The assessment begins with property information, available documentation, photos, site data or measured dwelling information.
Step 02
The assessor considers visible construction details, glazing, shading, orientation, ventilation and likely insulation conditions.
Step 03
The collected building information is translated into NatHERS thermal modelling software to assess performance under Australian climate conditions.
Step 04
The rating can help identify comfort issues, heat gain, heat loss, inefficient building elements and practical upgrade opportunities.
Existing home complexity
Existing homes often need more interpretation than new home assessments.
Unknown construction details, inaccessible building elements, undocumented alterations, ageing materials and missing plans can all affect how the assessment is completed. Where original drawings are incomplete or unavailable, digital measurement and site information may help establish a reliable starting point. Read more about Home Energy Ratings without original plans .
Roof, wall and floor construction, insulation systems and likely insulation gaps.
Window type, glazing performance, frame systems, external shading and eaves.
Orientation, solar exposure, surrounding shading and climate-related site influences.
Room layout, zoning, ceiling heights and dwelling geometry.
Ventilation pathways, air leakage observations and natural airflow conditions.
Previous renovations, additions, retrofit works or undocumented modifications.
On-site data collection is one of the most important parts of a Home Energy Rating assessment because it helps convert real built conditions into usable modelling information.
Unlike new home assessments that rely primarily on architectural documentation, Existing Home Energy Ratings often require physical inspection, digital measurement and verification of the dwelling’s current condition.
Dwelling dimensions
Orientation and solar exposure
Room layout and zoning
Glazing types and frame systems
Shading conditions
Insulation observations
Wall, roof and floor systems
Ventilation pathways
Ceiling heights
Construction materials
Surrounding site influences
Digital LiDAR-assisted measurement tools may also be used to help capture building geometry and improve modelling workflows, particularly where original drawings are incomplete, outdated or unavailable.
Depending on the complexity of the dwelling, data collection times can vary significantly between projects. Homes with multiple renovations, additions or undocumented modifications may require more interpretation than simpler dwelling layouts. Learn how long a Home Energy Rating can take .
The quality and accuracy of on-site data collection plays an important role in helping produce reliable thermal modelling outcomes and meaningful upgrade observations.
Following site inspection and data collection, the dwelling information is transferred into NatHERS thermal modelling software to analyse how the home performs under Australian climate conditions.
Seasonal heat gain, winter heat loss, solar exposure, glazing behaviour, insulation performance, natural ventilation and overall thermal comfort conditions.
The assessor is working with an existing building rather than a proposed design, so missing documentation, ageing materials and previous alterations may affect how the model is interpreted.
The level of reporting and recommendations may vary depending on the project scope, assessment purpose and future upgrade objectives for the dwelling.
Continue into insulation performance or explore glazing and shading .
Thermal Performance
Insulation performance is one of the key factors that influences thermal comfort, heat loss and heat gain in existing Australian homes.
Many older dwellings were constructed before modern residential energy efficiency expectations became common. As a result, insulation levels can vary significantly between homes, construction eras, renovations and building elements.
In a Home Energy Rating assessment, insulation is considered as part of the broader building fabric. The assessment may review where insulation is present, where it appears incomplete, and how roof, wall, floor and retrofit conditions may affect the dwelling’s thermal performance. Learn what a Home Energy Rating assessor looks for .
Roof and Ceiling
Ceiling and roof insulation can strongly influence summer heat gain and winter heat loss, especially in older homes.
Walls and Floors
External walls, suspended floors and slab edge conditions may affect how quickly the dwelling gains or loses heat.
Renovated Areas
Extensions, renovations and retrofit works can create inconsistent insulation conditions across different parts of the home.
Missing insulation
Partially installed insulation
Poorly fitted insulation
Compressed insulation
Deteriorated insulation materials
Inconsistent insulation between old and new areas
Building system insight
Insulation is important, but it does not work in isolation.
Its effectiveness also depends on the wider building system, including glazing, shading, ventilation, orientation and air leakage pathways. A Home Energy Rating helps show how these elements work together, rather than treating insulation as a single isolated upgrade.
Insulation can have a significant impact on how quickly a home gains heat in summer or loses heat in winter. Even modest improvements may sometimes contribute to more stable indoor temperatures and reduced heating or cooling demand.
Existing Home Energy Ratings help create a clearer understanding of where insulation performance may be contributing to discomfort, inefficiency or excessive energy demand within the dwelling.
Continue into glazing and shading or explore thermal comfort and energy performance .
Building Fabric
Glazing and shading can significantly influence heat gain, heat loss, solar exposure and thermal comfort in existing Australian homes.
Many existing dwellings contain older windows, frames or shading conditions that were not designed around modern residential energy performance expectations. In some homes, glazing design may contribute to overheating, winter heat loss, glare, uneven indoor temperatures and increased heating or cooling demand.
In a Home Energy Rating assessment, glazing is considered as part of the broader building fabric. The assessment may review how window size, orientation, frame type, glass type, shading and surrounding site conditions affect the way the home performs across different seasons.
Window Performance
Window size, glazing type, frame systems and sealing can all affect heat transfer and indoor comfort.
Solar Exposure
Orientation, seasonal sun angles and surrounding site conditions influence how much solar heat enters the home.
External Shading
Eaves, awnings, screens and nearby built form can help reduce unwanted summer heat gain when designed or used well.
Seasonal balance
The relationship between glazing and shading is highly interconnected.
Well-positioned external shading may help reduce unwanted summer solar gain while still allowing access to winter sunlight where appropriate. The right approach can vary significantly depending on the dwelling, climate zone, orientation, building design and existing construction constraints.
Improved glazing systems
External shading devices
Window sealing improvements
Passive solar optimisation
Targeted retrofit strategies
Orientation-specific shading responses
Whole Home Performance
Thermal comfort describes how stable, liveable and comfortable a home feels across changing seasonal conditions.
In existing homes, thermal comfort is often affected by the combined performance of the building envelope, glazing, insulation, shading, ventilation, orientation, air leakage and construction quality.
Overheating in summer, cold indoor temperatures in winter, uneven room temperatures, draughts, poor passive performance and high reliance on mechanical heating and cooling.
Insulation performance, glazing behaviour, orientation, shading, ventilation, thermal mass, construction quality and air tightness.
Whole dwelling insight
Thermal performance is rarely improved by one isolated change.
Existing Home Energy Ratings help analyse how building elements interact as a complete system. In many cases, the greatest improvements come from understanding how insulation, glazing, shading, ventilation and air leakage work together across the entire dwelling.
Reducing heating and cooling demand
Improving indoor comfort
Reducing temperature fluctuations
Improving passive performance
Lowering long-term energy use
Supporting informed retrofit decisions
As Australia’s housing stock continues ageing, thermal comfort and building performance are becoming increasingly important considerations across residential retrofit, disclosure and upgrade discussions.
Continue into upgrade pathways or explore practical upgrade opportunities .
Upgrades & Improvements
Improving the thermal performance of an existing home usually requires understanding how insulation, glazing, shading, ventilation, air leakage and building fabric conditions work together as a complete system.
A Home Energy Rating assessment may help identify which parts of the dwelling are contributing most to heat gain, heat loss, temperature instability or high heating and cooling demand.
Fabric
Insulation, roof, ceiling, wall and floor improvements.
Openings
Glazing improvements, window sealing and frame performance.
Passive Design
Shading, solar exposure, ventilation and passive comfort strategies.
Retrofit
Targeted upgrade strategies across the existing dwelling.
Climate zone
Building age
Orientation
Construction type
Existing retrofit history
Occupant comfort concerns
Budget considerations
Heritage or design constraints
Upgrade sequencing
Better performance is not always about one major upgrade.
In many cases, smaller targeted improvements across multiple areas of the home may provide more balanced thermal comfort outcomes than focusing on one isolated building element alone.
This is why Existing Home Energy Ratings can be useful before selecting upgrade works. They help create a clearer evidence base for understanding where improvements may have the greatest influence on thermal comfort, heating and cooling demand and overall building performance.
The assessment does not replace detailed design advice or construction documentation, but it can help inform better conversations about retrofit priorities, upgrade sequencing and long-term residential energy performance. Learn whether a Home Energy Rating includes upgrade advice .
Continue into future direction for Existing Home Energy Ratings or explore practical assessment questions .
Retrofit Pathways
Energy efficiency upgrades for existing homes can range from simple targeted improvements through to larger retrofit projects that address multiple parts of the building envelope.
In a Home Energy Rating assessment, potential upgrade opportunities are considered in relation to how the dwelling currently performs. This helps avoid treating insulation, glazing, shading or ventilation as isolated issues when they may be interacting across the whole home.
Insulation
Ceiling, wall, underfloor, roof and insulation continuity improvements.
Windows
Glazing replacement, frame improvements, window sealing and heat transfer reduction.
Shading
External shading devices, solar exposure management and passive summer comfort strategies.
Air Leakage
Draught sealing, window and door sealing, and reduction of uncontrolled air movement.
Ventilation
Ventilation upgrades and airflow strategies that support comfort without unnecessary heat loss or gain.
Retrofit Strategy
Targeted sequencing of upgrades based on the dwelling’s existing condition and performance issues.
Upgrade suitability
The right upgrade depends on how the existing dwelling already performs.
The suitability of each upgrade depends heavily on the existing dwelling condition, climate zone, orientation, construction type and how the broader building envelope performs as a complete system. Some homes may benefit most from relatively low-cost passive improvements, while others may require more substantial retrofit strategies to achieve meaningful performance changes.
Existing Home Energy Ratings can help provide a clearer evidence base for deciding which upgrade pathways may be most appropriate for the dwelling, especially where the home has been altered, extended or partially upgraded over time.
The assessment does not replace detailed design advice or construction documentation, but it can help inform better conversations about retrofit priorities, upgrade sequencing and long-term residential energy performance. Learn whether a Home Energy Rating includes upgrade advice .
Passive Design
Passive design improvements aim to improve comfort and reduce energy demand by helping the building respond more effectively to local climate conditions.
In existing homes, passive improvements are often focused on reducing unwanted heat gain, limiting winter heat loss, improving airflow and making better use of orientation, shading and building fabric.
External shading, solar exposure management, natural ventilation, air leakage reduction, insulation continuity and glazing performance.
The effectiveness of passive improvements depends on how well the dwelling responds to local climate conditions throughout the year.
Improved indoor comfort
Reduced overheating
Lower winter heat loss
Reduced reliance on air conditioning
More stable internal temperatures
Improved long-term energy performance
As Australia’s existing housing stock continues ageing, passive retrofit strategies are becoming an increasingly important part of residential energy efficiency, thermal comfort and climate resilience discussions.
Continue into future direction for Existing Home Energy Ratings or explore practical assessment questions .
Industry & Future Direction
Interest in existing home energy performance is continuing to grow across Australia as governments, industry groups and housing sectors explore future pathways for improving residential building efficiency, comfort and climate resilience.
Energy disclosure for existing homes generally refers to ways of making residential energy performance more visible, understandable and comparable for homeowners, buyers, lenders, policymakers and the broader housing sector. Learn whether Existing Home Energy Ratings are mandatory in Australia .
Performance Visibility
Making existing home energy performance easier to understand, compare and discuss across the property market.
Retrofit Planning
Supporting better decisions around upgrades, comfort improvements, electrification and long-term housing resilience.
Market Readiness
Helping homeowners, assessors, lenders, property professionals and policy groups prepare for clearer performance information.
Why trials matter
Existing homes are more variable than new homes, which makes practical assessment delivery essential.
Voluntary Existing Homes trial programs and pilot frameworks have helped explore how Home Energy Ratings may operate across established housing stock in real-world conditions. Dwelling age, construction type, renovation history, available documentation, climate zone and site access can all affect how assessment workflows need to operate.
Homeowners planning upgrades
Buyers and sellers seeking clearer information
Lenders and property professionals
Retrofit and electrification programs
Housing policy and disclosure discussions
Residential upgrade planning
Portfolio or program-level housing assessments
Long-term housing performance strategies
The long-term direction of Existing Home Energy Rating disclosure pathways across Australia is still evolving. However, interest in residential energy performance, thermal comfort and evidence-based retrofit planning continues to grow across both industry and government sectors.
For Certified Energy, this emerging area is closely connected to practical assessment workflows, thermal modelling, existing dwelling data collection and the development of scalable approaches for understanding the performance of Australia’s existing housing stock.
Continue into practical assessment questions or explore Existing Home Energy Rating FAQs .
Trial Programs
Existing Homes trial programs have helped test how Home Energy Ratings may operate across real Australian housing conditions, where dwelling age, construction type, documentation quality and site access can vary significantly.
These programs are important because existing homes are not uniform. Practical delivery depends on reliable assessment workflows, usable data collection methods, clear reporting structures and quality assurance processes that can work across many different dwelling types.
Data Collection
Testing how site data, digital measurement, photos and available documentation can support consistent assessment inputs.
Modelling
Exploring how existing dwelling information can be translated into reliable NatHERS thermal modelling workflows.
Quality Assurance
Supporting assessment consistency, reporting quality and scalable delivery across varied housing conditions.
Practical delivery
Trial programs help move Existing Home Energy Ratings from technical possibility into workable delivery.
As part of broader industry participation, Certified Energy has been involved in national Existing Homes trial programs involving operational assessment workflows, thermal modelling and large-scale rating delivery systems. Read more about practical delivery for NatHERS Existing Homes .
Assessment consistency
Data collection accuracy
Thermal modelling reliability
Reporting quality
Quality assurance processes
Digital integration
Scalable delivery models
Program-level assessment workflows
Future Capability
Australia’s existing residential housing stock represents one of the largest long-term opportunities for improving national building performance, thermal comfort and residential energy efficiency outcomes.
As technology, workflow systems and industry capability continue maturing, Existing Home Energy Ratings may become an increasingly important part of Australia’s broader residential sustainability and housing performance landscape.
Improved site data collection, digital measurement, property information systems and workflow integration.
Enhanced thermal modelling systems, stronger quality assurance and clearer reporting expectations.
Better integration between rating outcomes, retrofit planning, comfort improvements and long-term housing resilience.
Sector integration
The future of Existing Home Energy Ratings is likely to sit across assessment, retrofit, disclosure and digital property systems.
For homeowners, property professionals, program managers and policy stakeholders, the development of Existing Home Energy Ratings may support more informed decisions about comfort, efficiency, retrofit priorities and long-term housing performance.
Explore practical assessment questions or continue to the Existing Home Energy Rating FAQs .
Practical Questions
The time required for a Home Energy Rating assessment depends on the size, complexity, accessibility and documentation quality of the dwelling. Read the short guide to Home Energy Rating timeframes .
Unlike a new home assessment based primarily on plans and specifications, an Existing Home Energy Rating often requires real-world data collection, building measurement, construction interpretation and thermal modelling.
Timeframes are usually influenced by the condition of the home, the quality of available information and the level of assessment detail required.
In many cases, the assessment process may involve on-site data collection, digital building measurement, review of visible building fabric conditions, NatHERS thermal modelling, assessment review and reporting.
More complex homes, multi-stage renovations, older dwellings with limited documentation or architecturally customised homes may require additional investigation and modelling time compared to simpler residential layouts.
The overall assessment timeframe can also vary depending on project demand, workflow complexity, access arrangements and the level of reporting or upgrade guidance required.
Continue into what information is needed or explore the Existing Home Energy Rating FAQs .
A Home Energy Rating assessment may require a combination of site information, building observations, available documentation and direct measurement of the dwelling. View the information usually needed for a Home Energy Rating .
Useful information may include floor plans, elevations, renovation details, glazing information, insulation details, construction information, previous retrofit works, site photographs and notes about comfort issues or problem areas within the home.
Complete historical documentation is not always available for existing dwellings. Many Existing Home Energy Rating workflows are designed to operate where original drawings, specifications or renovation records are incomplete.
In these situations, on-site inspection, digital measurement, site photography and assessor observations can help create a clearer understanding of the dwelling’s current built condition.
The level of information required may vary depending on the assessment scope, dwelling complexity, access conditions and project objectives.
The cost of an Existing Home Energy Rating can vary depending on the dwelling, the level of data collection required and the scope of reporting or upgrade guidance requested. Read more about Existing Home Energy Rating costs .
A simple dwelling with clear access and useful documentation may require less assessment time than a large, complex or heavily altered home with limited historical information.
Cost factors
The most reliable cost depends on the assessment scope, not just the property type.
Assessment costs are commonly influenced by dwelling size, building complexity, site access, documentation availability, renovation history, modelling complexity, reporting scope, upgrade analysis requirements and assessment methodology.
Assessment costs can also vary depending on whether the project involves a basic thermal performance assessment, Home Energy Rating assessment work, upgrade observations, detailed reporting, large residential properties, architecturally customised dwellings or portfolio-level assessment requirements.
As Existing Home Energy Rating frameworks continue evolving across Australia, workflows, technology systems and reporting pathways are also continuing to mature across the sector.
For this reason, the most reliable way to confirm cost is usually to provide the available property details, assessment purpose and any existing documentation so the required scope can be reviewed.
Continue to the Existing Home Energy Rating FAQs or send assessment details .
Related Compliance Context
Insulation is an important part of residential building performance because it helps reduce unwanted heat transfer through the building envelope.
In new residential construction, insulation requirements are considered within the broader energy efficiency provisions of the National Construction Code and the relevant compliance pathway for the project.
For existing homes, insulation is usually considered differently. Rather than assessing a proposed design against new construction requirements, an Existing Home assessment looks at the dwelling’s current built condition and how roof, ceiling, wall, floor and retrofit insulation may be affecting thermal comfort and energy performance.
Existing homes distinction
Existing Home Energy Ratings do not treat insulation as a simple new-build compliance item.
Many existing homes were built before current residential energy efficiency expectations became common, and insulation may be missing, incomplete, compressed, deteriorated or inconsistent between original areas and later renovations.
The relevant insulation strategy for an existing dwelling depends on factors such as climate zone, construction type, access to roof or floor cavities, renovation history, moisture risk, ventilation pathways and the overall upgrade objective.
For this reason, insulation should usually be understood as part of the whole building system, alongside glazing, shading, air leakage, ventilation and passive performance, rather than as a single isolated upgrade.
Explore insulation performance in existing homes or continue to the Existing Homes FAQs .
Related Compliance Pathways
Existing Home Energy Ratings are different from new-build compliance assessments because they focus on how an existing dwelling currently performs, rather than whether a proposed design satisfies a particular construction pathway.
In new residential projects, insulation, glazing, shading and building fabric requirements may be assessed through pathways such as DTS, NatHERS or other approved performance-based methods, depending on the project and compliance requirements.
New-Build Compliance
Usually assesses a proposed design before construction, using drawings, specifications and the relevant compliance pathway.
Existing Home Rating
Interprets how a completed dwelling has actually been built, altered, aged and occupied over time.
Performance Focus
Looks at the current building fabric, likely thermal behaviour, comfort issues and upgrade opportunities.
Important distinction
A Home Energy Rating is not simply a DTS compliance check.
For existing homes, the assessment focus is usually the current built condition of the home, including visible construction details, likely insulation performance, glazing behaviour, shading, ventilation and air leakage. Compare NatHERS Existing Homes with new home NatHERS assessments .
Insulation has a significant influence on the long-term thermal performance of an existing home. It can affect indoor temperature stability, summer heat gain, winter heat loss, heating and cooling demand and overall occupant comfort.
In many existing homes, insulation performance works together with glazing, orientation, shading, ventilation, thermal mass and air leakage. This means insulation should usually be understood as part of the broader building system rather than as a single isolated upgrade.
Existing Home Energy Ratings can help identify whether insulation conditions may be contributing to comfort issues, inefficient performance or excessive energy demand within the dwelling.
Existing Home Energy Ratings often need to consider incomplete documentation, previous renovations, inaccessible construction elements, varying insulation conditions and real-world building performance issues.
Understanding the difference between existing home performance assessment and new-build compliance helps clarify why site data collection, building measurement and thermal modelling are so important in the Existing Homes context.
Continue to the Existing Home Energy Rating FAQs or explore what information is needed for an assessment .
Related Compliance Context
Glazing and window performance are important in both new-build residential compliance and Existing Home Energy Ratings because windows directly affect heat gain, heat loss, solar exposure and thermal comfort.
In new residential construction, glazing may be assessed as part of the project’s relevant energy efficiency compliance pathway. Window size, orientation, frame type, glass type, shading and climate zone can all influence how easily a proposed dwelling satisfies its required performance outcome.
For existing homes, glazing is considered differently. A Home Energy Rating assessment looks at the windows that are already installed and considers how they may be affecting the dwelling’s current thermal performance under real Australian climate conditions.
Older glazing systems may contribute to excessive summer heat gain, winter heat loss, glare, draughts, uneven room temperatures or increased heating and cooling demand. These issues are often influenced by the relationship between glazing, shading, orientation, ventilation and insulation.
This distinction is important because an Existing Home Energy Rating is not simply checking whether windows meet a new-build DTS provision. It is assessing how the existing glazing and shading conditions contribute to the home’s overall thermal behaviour.
Explore glazing and shading in existing homes or continue to the Existing Home Energy Rating FAQs .
In a Home Energy Rating assessment, glazing is reviewed as part of the dwelling’s current built condition rather than as a proposed window specification for a new design.
The assessment may consider how existing windows, doors, frames, glass type, orientation and shading conditions influence heat gain, heat loss and indoor comfort across different seasons.
The interaction between glazing, shading, insulation, orientation and ventilation can have a significant influence on the overall thermal performance of an existing home.
Existing glazing can contribute to overheating, winter heat loss, glare, draughts and uneven room temperatures depending on window type, orientation, shading and local climate conditions.
Many older Australian homes contain windows that were not selected or positioned with modern thermal performance expectations in mind. In some dwellings, large areas of unshaded glass may increase summer heat gain, while poorly performing windows may contribute to winter heat loss.
Glazing performance is rarely an isolated issue. It usually works together with insulation levels, air leakage, shading, ventilation and room layout to shape the way the home feels and performs.
A Home Energy Rating assessment can help clarify whether glazing and shading conditions are likely to be contributing to comfort issues, high heating and cooling demand or future upgrade priorities.
New-build glazing decisions are usually made during design and documentation, when window size, orientation, frame type, glass performance and shading can still be adjusted before construction.
Existing homes are different. The assessment starts with windows that are already installed, which means the focus is on understanding how current glazing conditions affect real building performance and what upgrade options may be practical.
In new residential compliance, glazing may influence whether a project follows a DTS, NatHERS, VURB or other performance-based pathway. In an Existing Home Energy Rating assessment, the more important question is how the installed glazing contributes to current comfort, efficiency and retrofit potential.
This distinction helps keep Existing Home Energy Ratings focused on real dwelling performance rather than treating the home as a proposed new design.
Continue to the Existing Home Energy Rating FAQs or explore glazing and shading in existing homes .
Frequently Asked Questions
A Home Energy Rating for Existing Homes is an Australian residential energy assessment approach designed to assess the thermal performance of homes that have already been built and occupied. It helps measure how an existing dwelling performs in relation to comfort, heat gain, heat loss and potential energy efficiency improvements. Read the short guide to Home Energy Ratings for existing homes.
A new home NatHERS assessment is generally based on proposed architectural plans and specifications before construction. An Existing Home Energy Rating analyses real built conditions, which may include ageing materials, undocumented renovations, varying insulation levels, installed glazing systems and building details that need to be verified on site. Compare Existing Homes with new home NatHERS assessments.
Existing Home Energy Ratings are part of an evolving area of residential energy assessment in Australia. They are becoming increasingly relevant as governments, industry groups and housing sectors explore future energy disclosure, retrofit planning and existing housing performance pathways. Whether an assessment is required depends on the project, program or assessment purpose. Learn whether Existing Home Energy Ratings are mandatory in Australia.
Depending on the assessment method, software pathway and project scope, an Existing Home Energy Rating may include a NatHERS-style rating outcome or broader thermal performance analysis. The exact reporting format can vary depending on the assessment purpose, trial framework or program requirements.
In many cases, an Existing Home Energy Rating involves on-site data collection to review the dwelling’s dimensions, glazing, insulation, shading, construction systems and other building performance factors. Digital measurement tools may also be used to support the assessment workflow.
An Existing Home Energy Rating may review insulation, glazing, shading, orientation, roof and floor systems, ventilation, air leakage observations, thermal comfort behaviour and the overall performance of the building fabric. The exact scope can vary depending on the dwelling and assessment purpose. Learn what a Home Energy Rating assessor looks for.
Yes. Depending on the assessment scope, an Existing Home Energy Rating may help identify practical opportunities to improve thermal comfort and energy performance, such as insulation upgrades, glazing improvements, shading, draught sealing, ventilation improvements and passive design improvements. Learn whether a Home Energy Rating includes upgrade advice.
In many cases, yes. While existing plans can be helpful, assessments may also rely on site inspection, building measurement, site photography and digital data collection workflows where historical documentation is incomplete or unavailable. Read more about Home Energy Ratings without original plans.
Useful information may include floor plans, elevations, renovation details, glazing information, insulation details, construction information, previous retrofit works, site photographs and notes about comfort issues within the home. Complete documentation is not always available for existing homes, so the required information can vary by project. View the information usually needed for a Home Energy Rating.
Timeframes can vary depending on the size, complexity, accessibility and documentation quality of the dwelling. Larger homes, undocumented renovations, complex layouts or detailed upgrade reporting may require more time than simpler residential assessments. Read more about Home Energy Rating timeframes.
Existing Home Energy Rating costs can vary depending on dwelling size, building complexity, site access, travel requirements, documentation availability, thermal modelling complexity and the level of reporting or upgrade guidance required. The most reliable way to confirm cost is to provide the available property details for review. Read more about Existing Home Energy Rating costs.
Existing Home Energy Ratings may be useful for homeowners, property professionals, retrofit programs, housing organisations, sustainability teams, lenders, policy stakeholders and organisations seeking to better understand the performance of existing residential dwellings. Learn who can request a Home Energy Rating.
Certified Energy has participated in national Existing Homes trial programs involving operational assessment workflows, thermal modelling and large-scale rating delivery systems. This experience may support projects where consistent assessment processes, scalable workflows and practical reporting are required across multiple dwellings. Read more about Home Energy Ratings for housing portfolios.
Yes. Interest in existing home energy performance is growing as Australia explores future residential energy disclosure, retrofit pathways, thermal comfort improvements and more efficient housing performance across the existing building stock.
Project Review
Send the available home information, plans, photographs or proposed upgrade details for an initial review. Certified Energy can help determine whether a Home Energy Rating is the right starting point for understanding thermal comfort, operational energy use and existing residential performance.
Early assessment can help identify how insulation, glazing, draught sealing, shading, ventilation and household systems may influence the most practical sequence of future upgrades.
Last reviewed: June 2026. This page is maintained by Certified Energy as part of its Residential Performance Knowledge Hub.
