Building Fabric

Passive Design Improvements for Existing Homes

Passive design is not only for new homes. Existing homes can often be improved by helping the building work better with its climate.

In an existing home, passive design improvements may include shading, insulation, draught sealing, ventilation, glazing upgrades, roof heat reduction, zoning and better renovation sequencing.

The goal is to reduce unwanted heat gain, reduce heat loss, improve comfort and lower the amount of mechanical heating and cooling the home needs to feel liveable.

What passive design means for an existing home

Passive design is the practice of designing or improving a home so it works with the local climate rather than fighting against it. It uses orientation, shading, insulation, ventilation, glazing and thermal behaviour to support comfort.

In a new home, passive design can be built into the layout from the start. In an existing home, the process is different. The dwelling already has its orientation, roof form, windows, materials and room layout. The task is to identify which existing features are helping performance and which are making the home harder to live in.

This makes passive design for existing homes a retrofit and upgrade strategy, not a blank-page design exercise.

Why passive design matters in existing homes

Many existing Australian homes are uncomfortable because the building fabric is doing too little work. Heat enters too easily in summer, escapes too quickly in winter, or moves through gaps and weak points before heating and cooling systems can respond effectively.

When that happens, homeowners often respond by adding more mechanical systems, larger air conditioners, extra heaters or solar panels. These can be useful, but they do not always solve the underlying comfort problem.

Passive design improvements can reduce the load on those systems by improving the way the home handles heat, sun, air and comfort in the first place.

Start with how the home performs now

The best passive design improvements start with the existing home, not with a generic product list. A home that overheats through west-facing windows needs a different strategy from a home that loses winter heat through draughty floors and weak ceiling insulation.

Useful questions include which rooms are uncomfortable, when the problem occurs, which windows receive sun, whether the home cools down overnight, whether draughts are present and whether insulation is known or uncertain.

For more detail on assessment inputs, see What Does a Home Energy Rating Actually Measure?

1. Improve shading before heat enters the home

Shading is one of the most important passive design improvements for homes that overheat. It works by reducing unwanted sun before it passes through windows and becomes heat inside the room.

Useful shading upgrades may include:

• eaves or roof overhangs
• awnings
• external blinds
• operable shutters
• screens or louvres
• verandahs or pergolas
• adjustable shading for east and west windows
• site-specific shading from neighbouring structures or landscape elements

For a deeper explanation, see Glazing and Shading in Existing Homes.

2. Review glazing where windows are a weak point

Windows can create both summer heat gain and winter heat loss. In some homes, the main issue is not only the glass itself, but the combination of window size, orientation, frame type, air leakage and lack of shading.

Glazing upgrades may be useful where existing windows perform poorly, but they should be reviewed carefully. Replacing all windows is not always the first or most cost-effective step. Sometimes shading, sealing or selective replacement may have a stronger impact.

The best glazing strategy depends on climate, orientation, comfort complaints and the renovation pathway.

3. Improve insulation where the building fabric is weak

Insulation helps slow heat movement through ceilings, roofs, walls and floors. In existing homes, insulation may be missing, compressed, damaged, inconsistent or difficult to verify.

Areas worth reviewing include:

• ceiling insulation
• roof insulation
• wall insulation
• floor insulation
• insulation around extensions or additions
• insulation disturbed by previous trades or renovations

For more detail, see Insulation in Existing Homes.

4. Reduce draughts and uncontrolled air leakage

Draught sealing helps reduce uncontrolled air movement through gaps, cracks and penetrations. This can improve comfort by helping the home hold warm or cool air more effectively.

Common leakage points include:

• external doors
• windows and sliding doors
• open fireplaces and chimneys
• wall vents
• floorboard gaps
• ceiling penetrations
• downlights and exhaust fans
• junctions between old and renovated areas

Draught sealing should always be considered with controlled ventilation. For more detail, see Draught Sealing and Air Leakage in Existing Homes.

5. Improve controlled ventilation and heat release

Ventilation can help an existing home release heat when outdoor conditions are cooler than inside. This is especially useful in the evening, overnight or early morning in climates where night purging is possible.

Some homes overheat because heat enters during the day and becomes trapped. Others have windows that do not support cross-ventilation, security concerns that limit night ventilation, or internal layouts that block air movement.

A passive design review can help identify whether ventilation needs to be improved, controlled or balanced with draught sealing and indoor air quality requirements.

6. Reduce roof and ceiling heat transfer

Roofs can absorb significant summer heat. If the roof space becomes very hot and ceiling insulation is weak, heat can move into rooms below and make the home uncomfortable late into the day.

Potential strategies may include:

• improving ceiling insulation
• reviewing roof insulation
• considering roof colour during replacement
• reviewing roof space ventilation
• reducing radiant heat transfer where appropriate
• coordinating roof works with solar, insulation and services upgrades

Roof-related upgrades are often best reviewed before major roof replacement, solar installation or ceiling works are finalised.

7. Use zoning to manage comfort more effectively

Zoning means managing different parts of the home separately. In existing homes, some rooms may be used all day, while others are only used at night or occasionally.

Passive zoning may involve doors, curtains, internal layouts, room use patterns, window operation, shading and heating or cooling strategy. It can help prevent the whole home from being conditioned when only certain areas need comfort control.

Zoning is especially useful in older homes with uneven comfort between original rooms, extensions and upper-level spaces.

8. Reduce external heat around the home

The area around the home can affect internal comfort. Dark paving, unshaded hard surfaces, heat-reflective walls and exposed outdoor areas can raise the temperature near windows and walls.

Possible improvements may include:

• reducing dark hard surfaces near windows
• adding shaded outdoor areas
• using lighter external finishes where appropriate
• reviewing heat-reflective boundary conditions
• coordinating shading with outdoor use and summer comfort

External heat control should be considered alongside glazing, shading, ventilation and roof performance.

Passive design should support both summer and winter comfort

A good passive design strategy should not only solve one season while making another worse. A home that is shaded too heavily may lose useful winter sun. A home that is sealed without ventilation may create moisture or indoor air quality risks. A home with more insulation may still need shading and ventilation to manage summer heat.

Winter-focused improvements may include insulation, draught sealing, improved window performance, controlled solar access, zoning and curtains or window coverings that reduce heat loss at night.

The best approach depends on climate zone, orientation, building fabric and the way the home is used.

Why passive design should often come before new systems

Solar, batteries, efficient appliances and modern heating or cooling systems can all be valuable. But they are more effective when the home itself is not working against them.

If a home has high heat gain, poor insulation or major air leakage, systems may need to be larger, run longer or use more energy than necessary. Passive design improvements can reduce the demand before systems are selected or upgraded.

This does not mean systems are unimportant. It means building fabric and systems should be planned together.

Renovation is the best time to plan passive design improvements

Renovation creates opportunities that may not be available later. Walls, roofs, ceilings, floors, windows and services may become accessible. This can make it easier to improve insulation, sealing, glazing, shading, ventilation and system strategy at the same time.

If passive design is considered too late, the project may lock in large unshaded windows, poor orientation responses, missed insulation opportunities or heating and cooling systems that do not match the improved building fabric.

For renovation context, see Existing Home Energy Rating vs Renovation Energy Assessment.

How a home energy rating can help

A home energy rating can help identify which passive design issues are affecting the home. The assessment may show whether comfort problems are linked to glazing, shading, insulation, draughts, roof heat, ventilation, orientation, climate or installed systems.

This can help homeowners avoid guessing. Instead of starting with the most visible or heavily marketed upgrade, the rating can support a more considered sequence of improvements.

For more detail, see What Does a Home Energy Rating Assessor Look For?

Common passive design mistakes in existing home upgrades

Common mistakes include:

• adding air conditioning before reducing heat gain
• installing solar before reviewing high heating and cooling demand
• replacing windows without reviewing shading
• insulating without considering ventilation and moisture
• sealing draughts without controlled ventilation
• using the same glazing strategy on every elevation
• blocking useful winter sun with poorly planned shading
• missing insulation opportunities during renovation
• treating each upgrade as separate rather than connected

A better approach is to assess the home as a system before choosing the upgrade sequence.

What information helps a passive design review?

Before requesting a home energy rating or passive design review, it helps to prepare information that shows how the home behaves and what is already known.

Useful information may include:

• property address
• available floor plans or real estate plans
• photos of each side of the home
• photos of major windows and shading
• known insulation information
• renovation or extension history
• heating and cooling system details
• known comfort issues by room
• rooms that overheat or stay cold
• planned renovation or upgrade scope

For a full checklist, see What Information Do You Need for a Home Energy Rating?

FAQs

What are passive design improvements for existing homes?

Passive design improvements are upgrades that help an existing home use climate, orientation, shading, insulation, ventilation and building fabric more effectively before relying heavily on mechanical heating and cooling.

Can passive design be added to an existing home?

Yes. While passive design is easiest to include in new homes, existing homes can often be improved through shading, insulation, draught sealing, ventilation, glazing upgrades, roof colour, external heat reduction and better renovation planning.

What passive design upgrades help with summer overheating?

Summer overheating may be improved through external shading, better glazing choices, roof and ceiling insulation, controlled ventilation, night purging, draught sealing, lighter external surfaces and reducing heat around exposed windows.

What passive design upgrades help in winter?

Winter comfort may be improved through insulation, draught sealing, better window performance, controlled solar access, thermal zoning, curtains or window coverings, and reducing uncontrolled heat loss through gaps and weak building fabric.

Should passive design improvements happen before solar or new systems?

Often, yes. Passive design improvements can reduce heating and cooling demand before new systems are sized or installed. Solar, batteries and efficient appliances are valuable, but they do not automatically fix poor comfort or weak building fabric.

Can a home energy rating help identify passive design upgrades?

Yes. A home energy rating can help identify whether passive design issues such as glazing, shading, insulation, air leakage, ventilation, roof heat or orientation are affecting the home’s performance.

Home Energy Rating Review

Looking for the right passive design upgrade sequence?

A home energy rating can help identify whether shading, insulation, glazing, draught sealing, ventilation or other passive design improvements should be part of your upgrade pathway.

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Summer Comfort

Why Older Australian Homes Overheat in Summer

Older Australian homes often overheat because the building fabric was not designed or upgraded for today’s comfort expectations.

The cause is rarely one single issue. Summer overheating usually comes from a combination of direct sun on windows, poor shading, weak insulation, roof heat, air leakage, limited ventilation, orientation, climate and the way heat is stored inside the home.

A home energy rating can help separate the visible symptom from the underlying performance problem, so upgrades can be planned in a better sequence.

Why overheating is common in older Australian homes

Many older Australian homes were designed for different expectations, different materials, different appliance use and different comfort standards. Some relied on verandahs, high ceilings, lightweight construction or natural ventilation. Others were built before strong attention was given to insulation, airtightness, window performance or orientation.

Over time, renovations may also change how a home behaves. A new room may add large windows without enough shading. A garage conversion may have weak insulation. A rear extension may trap afternoon heat. A roof replacement may change heat gain without improving ceiling insulation.

This means summer overheating is often the result of many small decisions rather than one obvious failure.

Direct sun on glazing is a major cause of overheating

Windows are one of the main ways summer heat enters a home. When direct sun hits glass, heat can build quickly inside the room, especially if the glass is large, unshaded or facing east or west.

YourHome describes shading of glazing as a critical part of passive cooling because glazing is a major source of heat gain through direct radiation and conduction.

For a deeper explanation, see Glazing and Shading in Existing Homes.

West-facing rooms often become the hottest rooms

West-facing rooms can be difficult to keep cool because they receive low-angle afternoon sun when the day is already hot. This heat can enter through windows and continue affecting the room into the evening.

Simple eaves often do not shade low-angle west sun well. External screens, adjustable shading, vertical shading, planting, neighbouring built form or glazing improvements may need to be considered depending on the home.

This is why two rooms in the same house can feel completely different in summer.

Poor shading allows heat in before cooling begins

Air conditioning often deals with heat after it has entered the home. Shading helps reduce that heat before it passes through the glass.

This distinction matters. Internal blinds and curtains can help with comfort and glare, but external shading is often more effective for summer heat because it blocks or reduces sun before it reaches the glazing.

In many existing homes, improving shading may be a practical first step before replacing every window or increasing cooling capacity.

Roof heat can drive indoor discomfort

Roofs receive strong solar exposure during summer. If the roof space becomes very hot and the ceiling is poorly insulated, heat can move into the rooms below.

This is one reason bedrooms, upper-storey spaces and rooms directly under roof areas can become uncomfortable late in the day. The roof may keep transferring heat into the home after outdoor conditions begin to cool.

Ceiling insulation, roof ventilation, roof colour, radiant barriers and construction type can all affect how much heat is transferred into the dwelling.

Weak insulation can allow heat to enter too quickly

Insulation helps slow heat movement through ceilings, roofs, walls and floors. If insulation is missing, compressed, damaged or inconsistent, the home may gain heat more quickly during summer.

However, insulation is not a complete overheating solution on its own. If the home has unshaded glass or poor ventilation, insulation may slow the heat movement but not solve the main cause of summer discomfort.

For more detail, see Insulation in Existing Homes.

Air leakage can bring unwanted heat inside

In summer, uncontrolled air leakage can allow hot outdoor air to enter the home. This can make rooms harder to cool, especially during hot windy conditions or when there are leakage paths through roof spaces, wall cavities or subfloors.

Draught sealing can help reduce uncontrolled air movement, but it should be balanced with controlled ventilation. A better-performing home is not simply sealed shut. It needs to manage fresh air intentionally.

For more context, see Draught Sealing and Air Leakage in Existing Homes.

Poor ventilation can trap heat inside

Ventilation helps remove heat when outdoor air is cooler than indoor air. This can be especially useful in the evening, overnight or early morning when the home needs to release stored heat.

Some existing homes have windows that do not support good cross-ventilation, rooms that trap heat, security concerns that limit night ventilation, or layouts where air movement is blocked by doors and internal walls.

Ventilation alone cannot always solve overheating, but without a way to release heat, other upgrades may not perform as well as expected.

Thermal mass can help or hurt, depending on how it is managed

Thermal mass refers to materials that can absorb and store heat, such as concrete, brick, stone or tiles. In the right conditions, thermal mass can help moderate indoor temperature swings.

But thermal mass needs to be protected from unwanted summer sun and cooled when outdoor conditions allow. YourHome recommends protecting thermal mass from summer sun with shading and insulation, and ensuring cool night breezes and air currents can draw out stored energy.

If thermal mass absorbs heat all day and cannot release it overnight, the home may feel hot well into the evening.

Dark roofs and hard surfaces can add heat load

External materials can affect how much heat is absorbed around the home. Dark roof surfaces, dark paving, unshaded hard surfaces and heat-reflective neighbouring walls can all contribute to higher temperatures around the building.

This can be especially noticeable in dense urban areas or around homes with limited shade and large areas of concrete, tiles or paving near windows.

External heat exposure should be considered alongside internal comfort complaints.

Air conditioning may not fix the underlying problem

Air conditioning can cool a room, but it does not remove the underlying cause of overheating. If heat keeps entering through unshaded glass, a hot roof space, weak insulation or air leakage, the system may need to run harder and longer.

This can lead to higher energy use and uneven comfort. Some rooms may cool quickly, while others remain hot or reheat soon after the system turns off.

Building fabric upgrades can reduce cooling demand before mechanical systems need to respond.

How a home energy rating can help explain overheating

A home energy rating can help identify which parts of the home are contributing to summer discomfort. The issue may be glazing, shading, insulation, roof heat, air leakage, ventilation, orientation, climate or a combination of several factors.

This matters because the best solution is not always the most obvious one. A hot room may need shading before new glazing. A hot upper floor may need ceiling or roof review. A draughty home may need sealing before system replacement.

For more detail on assessment inputs, see What Does a Home Energy Rating Assessor Look For?

What should be reviewed first?

The right starting point depends on the home, but overheating reviews often begin with the rooms where discomfort is most obvious.

Useful questions include:

• Which rooms overheat first?
• Do they face west, east or north?
• Are the windows externally shaded?
• Is the ceiling or roof well insulated?
• Does the room cool down overnight?
• Is there cross-ventilation?
• Are there draughts or air leakage paths?
• Has the room been extended or renovated?
• Does heat build up again quickly after cooling?

These questions help guide the assessment toward the real cause of overheating.

Renovation is a key opportunity to solve overheating

Overheating is often easiest to address when a home is being renovated. Window changes, roof works, insulation upgrades, shading, external works and services replacement can all affect summer comfort.

If energy performance is reviewed too late, the design may already have locked in large unshaded glazing, poor ventilation or missed opportunities to improve insulation and airtightness.

For renovation context, see Existing Home Energy Rating vs Renovation Energy Assessment.

FAQs

Why do older Australian homes overheat in summer?

Older Australian homes may overheat because of unshaded glazing, poor roof or ceiling insulation, air leakage, limited ventilation, heat stored in building materials, dark roofs, west-facing windows and design features that do not respond well to the local climate.

Can poor shading make an older home overheat?

Yes. Poor shading can allow direct summer sun to enter through windows and glazed doors, increasing indoor temperatures and cooling demand. External shading is often important because it reduces heat before it passes through the glass.

Does insulation help with summer overheating?

Insulation can help slow heat entering through the roof, ceiling, walls or floors, but it is not a complete overheating solution on its own. It works best with shading, ventilation, draught sealing and appropriate glazing.

Why do west-facing rooms get so hot?

West-facing rooms often overheat because they receive low-angle afternoon sun when outdoor temperatures are already high. This sun can be difficult to shade with simple eaves and can drive significant heat gain through windows.

Can ventilation reduce overheating?

Ventilation can help reduce overheating when cooler outside air is available, especially through cross-ventilation or night purging. However, ventilation alone may not solve overheating if the home continues to gain too much heat during the day.

Can a home energy rating help explain overheating?

Yes. A home energy rating or assessment can help identify whether overheating is linked to glazing, shading, insulation, air leakage, ventilation, roof heat, orientation, climate or a combination of building fabric issues.

Home Energy Rating Review

Trying to understand why your home overheats?

A home energy rating can help identify whether overheating is caused by glazing, shading, insulation, roof heat, air leakage, ventilation or other building fabric issues.

Send property details for review

Building Fabric

Draught Sealing and Air Leakage in Existing Homes

Draughts are one of the most noticeable comfort problems in existing homes.

A home can have insulation, new appliances and even solar panels, but still feel uncomfortable if uncontrolled air leaks allow cold air in during winter or hot air in during summer.

Draught sealing is the process of reducing uncontrolled air movement through gaps, cracks and openings in the building fabric. It can improve comfort and energy performance, but it needs to be balanced with healthy, controlled ventilation.

Why draughts matter in existing homes

Many existing Australian homes were built with less attention to airtightness than modern high-performance buildings. Over time, gaps can also appear around windows, doors, floors, roof spaces, service penetrations and renovation junctions.

When uncontrolled air moves through the home, heating and cooling systems may need to work harder. Rooms can feel uncomfortable even when the thermostat suggests the home should be warm or cool.

This is why draught sealing can be one of the most practical building fabric upgrades to consider before replacing systems or adding more technology.

What is air leakage?

Air leakage is uncontrolled air movement through unintended gaps in the building fabric. It is different from intentional ventilation, which is planned and controlled.

Common air leakage paths include:

• gaps around external doors
• gaps around windows
• open fireplaces and chimneys
• old wall vents
• exhaust fans without proper backdraft control
• floorboard gaps
• skirting board gaps
• ceiling penetrations
• downlights and service penetrations
• plumbing and electrical penetrations
• junctions between old and renovated areas

These leakage paths can be small individually, but together they can significantly affect comfort and energy performance.

Draught sealing is not the same as insulation

Draught sealing and insulation both affect comfort, but they solve different problems.

Insulation slows heat transfer through ceilings, roofs, walls and floors. Draught sealing reduces uncontrolled air movement through gaps and cracks. A home can be insulated but still draughty, or sealed but still poorly insulated.

For that reason, both should be considered as part of the whole building fabric. For more context, see Insulation in Existing Homes.

How draughts affect comfort

Draughts often create discomfort before they show up clearly in energy data. A room may feel cold around the ankles, uncomfortable near windows or doors, or difficult to heat evenly.

In summer, air leakage can allow hot outside air into the home, especially during heatwaves or windy conditions. In winter, cold air can enter while heated indoor air escapes, making the home feel colder than expected.

This can lead to higher heating and cooling use because occupants keep adjusting systems to compensate for the leaky building fabric.

How air leakage affects energy performance

Air leakage can increase heating and cooling demand because conditioned air is lost and outdoor air enters the home. This can make systems run longer or work harder to maintain comfort.

The effect depends on climate, wind exposure, building type, occupant behaviour and where the leakage occurs. In some homes, a few major leakage paths may have more impact than many small gaps.

A home energy rating or assessment can help identify whether air leakage is likely to be part of the performance problem.

Common draught sources in existing homes

Common draught sources include:

• external doors without seals
• sliding doors and old window frames
• gaps around skirting boards
• old floorboards or subfloor gaps
• open fireplaces and unused chimneys
• wall vents and legacy ventilation openings
• ceiling penetrations
• recessed downlights
• exhaust fans
• rangehoods
• plumbing and electrical penetrations
• junctions around extensions or additions

A useful review looks for patterns rather than assuming every gap has the same impact.

Doors and windows are common leakage points

Older doors and windows often leak air around seals, frames, tracks and joints. Sliding doors, timber windows, poorly fitted external doors and older aluminium frames can all contribute to draughts.

This is why glazing and draught sealing should often be reviewed together. A window may have poor thermal performance because of the glass, the frame, the seal or a combination of these issues.

For more context, see Glazing and Shading in Existing Homes.

Fireplaces, vents and exhaust openings can leak air

Open fireplaces, unused chimneys, old wall vents, exhaust fans and rangehoods can allow air movement between inside and outside. In some homes, these can be major leakage paths.

The correct response depends on whether the opening is still required for safety, appliance operation, combustion air or ventilation. Some openings can be sealed or improved. Others may need to remain functional or be replaced with controlled ventilation.

This is why draught sealing should be assessed carefully rather than handled as a blanket “seal everything” exercise.

Ceiling, floor and service penetrations can matter

Air leakage is not only around doors and windows. It can also occur through ceiling penetrations, gaps around downlights, exhaust fans, plumbing pipes, electrical conduits, floorboards and subfloor openings.

These leakage paths can connect living spaces to roof spaces, wall cavities, subfloors or outside air. In windy conditions, the effect can become more noticeable.

When sealing these areas, safety and compliance matter. Electrical, exhaust, combustion and ventilation requirements should not be compromised.

Renovation junctions can create air leakage

Existing homes often contain junctions between old and new construction. Extensions, converted garages, roof additions and reconfigured rooms can create gaps or inconsistent sealing where materials meet.

These junctions can be difficult to diagnose because the problem is sometimes hidden behind finishes or located at the boundary between building stages.

Renovation is often a valuable time to address air leakage because walls, ceilings, floors and services may already be accessible.

Airtightness needs controlled ventilation

A more airtight home is not the same as a poorly ventilated home. The goal is to reduce uncontrolled air leakage while still providing healthy, intentional ventilation.

This distinction is important because sealing gaps without considering ventilation can increase moisture, condensation and indoor air quality risks. Bathrooms, kitchens, laundries and bedrooms may all need appropriate ventilation strategies.

A good retrofit approach is not simply “make the home as sealed as possible.” It is to reduce unwanted leakage and manage fresh air deliberately.

How air leakage relates to a home energy rating

A home energy rating may consider air leakage, sealing quality or draught-related features depending on the assessment pathway. In some contexts, formal airtightness testing may provide more precise information. In others, assessor observations and available evidence may guide the review.

Air leakage is part of the wider building fabric picture. It interacts with insulation, glazing, shading, ventilation, heating and cooling systems.

For a broader explanation, see What Does a Home Energy Rating Actually Measure?

How an assessor may review draughts and air leakage

An assessor may look for visible or likely air leakage paths as part of the broader home energy rating process. The level of detail depends on the assessment pathway and whether formal testing is required or available.

Useful information may include:

• rooms that feel draughty
• doors or windows that rattle in wind
• visible light around door or window gaps
• known fireplace, chimney or vent issues
• areas where curtains move even when windows are closed
• renovation junctions that feel leaky
• ceiling or floor penetrations
• rooms with moisture, condensation or ventilation concerns

For more context, see What Does a Home Energy Rating Assessor Look For?

Renovation is often the best time to address air leakage

Draught sealing is often easier when renovation works are already exposing walls, ceilings, floors, windows, doors or services. Once finishes are complete, some leakage paths become harder to reach.

This is especially relevant for extensions, roof works, window replacement, floor repairs, kitchen and bathroom renovations, services upgrades and whole-home retrofits.

For renovation context, see Existing Home Energy Rating vs Renovation Energy Assessment.

What should not be sealed without advice?

Some openings may be required for ventilation, appliance safety, combustion air or moisture management. These should not be blocked without proper advice.

Be careful with:

• gas appliance ventilation
• combustion air openings
• bathroom, kitchen and laundry exhaust systems
• subfloor ventilation
• roof space ventilation
• moisture-affected areas
• heritage building elements
• areas with mould or condensation issues

The goal is controlled performance, not unsafe sealing.

What information helps a draught and air leakage review?

Before requesting a home energy rating or upgrade review, it can help to record where draughts are felt and when they occur.

Useful information may include:

• rooms that feel draughty
• photos of doors, windows and visible gaps
• notes on fireplaces, vents or exhaust fans
• areas that feel cold near floors or skirtings
• rooms with condensation or moisture concerns
• renovation history
• known window or door replacement history
• any existing energy or comfort reports

For a full preparation checklist, see What Information Do You Need for a Home Energy Rating?

FAQs

Why does draught sealing matter in existing homes?

Draught sealing matters because uncontrolled air leakage can make an existing home feel cold, hot, draughty or difficult to condition. Sealing gaps can improve comfort and reduce heating and cooling demand when done with appropriate ventilation.

What is air leakage in a home?

Air leakage is uncontrolled air movement through gaps, cracks and penetrations in the building fabric. It can occur around doors, windows, floors, ceilings, exhaust fans, downlights, chimneys, vents, service penetrations and poorly sealed construction joints.

Does a home energy rating assess draughts or air leakage?

A home energy rating may consider air leakage, sealing quality or draught-related features depending on the assessment pathway, available information and whether formal testing or assessor observations are used.

What are common sources of draughts in existing homes?

Common draught sources include gaps around doors and windows, open fireplaces, wall vents, exhaust fans, floorboard gaps, ceiling penetrations, downlights, plumbing penetrations, poorly sealed skirtings and gaps between old and renovated areas.

Is draught sealing the same as insulation?

No. Insulation slows heat transfer through building elements, while draught sealing reduces uncontrolled air movement through gaps and cracks. Both can affect comfort and energy performance, but they solve different problems.

Can a home be sealed too tightly?

Yes. Airtightness should be balanced with controlled ventilation. If a home is sealed without adequate ventilation, moisture, condensation, indoor air quality and mould risks may increase.

Home Energy Rating Review

Unsure whether draughts are affecting your home’s performance?

A home energy rating can help identify whether draught sealing, air leakage or other building fabric issues should be part of your upgrade pathway.

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Building Fabric

Glazing and Shading in Existing Homes

Glazing and shading can strongly influence how an existing home feels throughout the year.

Windows bring light, outlook, ventilation and winter solar warmth into a home. But they can also create summer overheating, winter heat loss, glare and rooms that are difficult to heat or cool.

For existing homes, the question is not only whether the windows are single or double glazed. It is also whether the glass is facing the right direction, whether it is shaded at the right time, and how the window system works with insulation, ventilation and heating or cooling.

Why glazing and shading matter in existing homes

Windows are often one of the weakest parts of the building fabric. They usually perform differently from insulated walls, roofs and floors because glass allows light, heat and solar radiation to pass through in ways opaque building elements do not.

In winter, windows can lose heat and make nearby rooms feel cold. In summer, windows can admit unwanted solar heat and create overheating. If shading is poor, the room may become uncomfortable before the air conditioner is even switched on.

This is why glazing and shading should be reviewed together rather than treated as separate issues.

What does glazing mean?

Glazing refers to the glass in windows, doors and skylights, as well as the wider window system that affects performance. In practical assessment, window performance is influenced by the glass, frame, seals, orientation, size and exposure.

Common glazing types include single glazing, double glazing, low-e glass, tinted glass and other performance glass products. The right choice depends on the home, climate, orientation and whether the main problem is summer heat gain, winter heat loss, glare or comfort near the glass.

For a home energy rating, glazing is not only a product choice. It is part of how the building performs as a whole.

What does shading mean?

Shading refers to anything that controls direct sun on windows, glazing and sometimes walls or outdoor areas. It can be fixed, adjustable, external, internal or created by nearby structures.

Common shading elements include:

• eaves and roof overhangs
• awnings
• external blinds
• screens and shutters
• verandahs and pergolas
• balconies and upper floors
• nearby buildings or boundary structures
• internal blinds or curtains, where relevant to comfort

External shading is often especially effective because it reduces direct sun before it passes through the glass.

Two important glazing concepts: U-value and SHGC

Window performance is often described through two important concepts: U-value and Solar Heat Gain Coefficient, or SHGC.

U-value relates to how readily heat conducts through the window system. A lower U-value generally means the window is better at resisting heat transfer. SHGC relates to how much solar heat the glazing allows into the home from direct sunlight.

This matters because a window that performs well for winter heat loss may not automatically solve summer heat gain. The best window strategy depends on orientation, climate and shading.

Orientation changes how windows perform

The same window can behave differently depending on which direction it faces. In Australia, north, east, west and south-facing glazing can create very different comfort outcomes.

North-facing windows can often be shaded more predictably with well-designed horizontal shading. East and west-facing windows can be more difficult because low-angle morning and afternoon sun can penetrate deeply and create heat gain. South-facing windows may receive less direct sun in many locations but can still contribute to heat loss.

This is why a window upgrade should not simply use the same glazing and shading approach on every elevation.

Glazing, shading and summer overheating

Summer overheating is often driven by direct sun on glass. Once solar heat enters a room, it can be difficult to remove without mechanical cooling, especially if the room has poor ventilation or the home stores heat into the evening.

Good shading can reduce unwanted sun before it reaches the glass. In many existing homes, shading can be a more practical first step than replacing every window, especially where the main issue is exposed summer sun.

However, the right solution depends on which windows are causing the problem, how the home is ventilated and what other building fabric issues are present.

Glazing and winter heat loss

Windows can also be a major source of winter heat loss. Rooms near poorly performing windows may feel cold, even when the heating system is running.

Double glazing or other higher-performing glazing systems can help reduce heat loss, but the benefit depends on the whole window system, frame type, installation quality, air leakage and how the room is used.

Window upgrades should therefore be assessed alongside draught sealing, insulation and heating system strategy.

External shading usually works before heat enters the home

External shading is often powerful because it blocks or reduces direct sun before it passes through the glass. Examples include eaves, awnings, external blinds, screens, shutters and verandahs.

Internal blinds and curtains can improve comfort and privacy, and some products can help reduce heat movement. However, once sunlight has already passed through the glass, much of the heat is already inside the room.

For overheating problems, external shading is often worth reviewing before assuming the only answer is air conditioning or full window replacement.

Fixed shading and adjustable shading

Fixed shading includes elements such as eaves, roof overhangs, awnings, pergolas and verandahs. These can be durable and low-maintenance, but they need to be designed carefully for orientation and season.

Adjustable shading includes external blinds, shutters, operable louvres and some screen systems. These can provide more flexibility because they can respond to season, weather, time of day and occupant preference.

In existing homes, adjustable shading can sometimes be a practical retrofit option where fixed shading is difficult to add or where different seasons require different levels of solar access.

How glazing and shading affect a home energy rating

A home energy rating may consider glazing and shading because they influence heating and cooling demand. Window size, location, orientation, glass type, frame type and external shading can all affect the result.

In an existing home, some window information may be easy to identify. Other details may require documentation, product labels, site observations or reasonable assumptions under the relevant assessment pathway.

For more detail on what assessors review, see What Does a Home Energy Rating Assessor Look For?

Glazing and shading do not work alone

Window upgrades can be valuable, but they should not be treated as the only performance measure. A home with better glazing may still perform poorly if insulation is missing, air leakage is high or shading is inadequate.

Likewise, shading can reduce summer heat gain but may not solve winter heat loss, draughts, poor ventilation or inefficient heating and cooling systems.

For that reason, glazing and shading should be assessed as part of the whole-home performance pathway.

Renovation is often the best time to review glazing and shading

Window and shading decisions can be difficult to change later. If a renovation involves new openings, replacement windows, facade changes, decks, pergolas or external works, glazing and shading should be considered early.

This can help avoid situations where a room is newly renovated but still overheats, loses heat or needs more mechanical cooling than expected.

For renovation context, see Existing Home Energy Rating vs Renovation Energy Assessment.

Common mistakes in existing homes

Common glazing and shading issues include:

• large west-facing windows without effective shading
• replacing windows without reviewing orientation
• using the same glazing product on every elevation
• adding internal blinds but ignoring external summer sun
• installing shading that blocks useful winter sun
• upgrading glazing while leaving major draughts unresolved
• assuming double glazing alone will solve overheating
• ignoring nearby built form and site exposure

A good assessment can help separate the visible symptom from the underlying performance issue.

What information helps a glazing and shading review?

Before requesting a home energy rating or upgrade review, it can help to prepare simple information about the windows and shading conditions.

Useful information may include:

• photos of each side of the home
• photos of major windows and doors
• photos of eaves, awnings, pergolas or external blinds
• notes on rooms that overheat or feel cold
• known window replacement history
• glazing product information, if available
• floor plans or real estate plans showing window locations
• renovation drawings, if window changes are proposed

For a full preparation checklist, see What Information Do You Need for a Home Energy Rating?

FAQs

Why do glazing and shading matter in existing homes?

Glazing and shading matter because windows can drive heat gain, heat loss, glare and comfort problems. In existing homes, poor glazing or inadequate shading can increase heating and cooling demand.

Does a home energy rating assess glazing?

Yes. A home energy rating may consider window size, location, orientation, glazing type, frame type and related window performance information where it can be identified or assessed under the relevant pathway.

Does a home energy rating assess shading?

Yes. Shading may be considered because it affects how much direct sun reaches windows and other glazed areas. The exact shading inputs depend on the assessment pathway and available information.

What is the difference between glazing and shading?

Glazing refers to the glass and window system itself. Shading refers to elements that reduce or control direct sun on the glass, such as eaves, awnings, external blinds, verandahs or nearby built form.

Can better shading reduce overheating?

Yes. Appropriate external shading can help reduce unwanted summer sun on windows, which can reduce overheating and cooling demand. The best shading strategy depends on orientation, climate and window design.

Should glazing be upgraded before or after insulation?

Glazing and insulation should be reviewed together. The best upgrade sequence depends on the home, climate, comfort problems, budget, renovation timing and whether windows, shading or building fabric are the main performance issues.

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Building Fabric

Insulation in Existing Homes

Insulation is one of the most important building fabric elements in an existing home.

It helps slow heat transfer through ceilings, roofs, walls and floors. In practical terms, this can help a home stay warmer in winter, cooler in summer and less dependent on mechanical heating and cooling.

For existing homes, insulation is also one of the areas most likely to be uncertain. It may be missing, incomplete, compressed, damaged, hidden behind finishes or different between the original home and later renovations.

Why insulation matters in existing homes

Many existing Australian homes were built before current energy efficiency expectations were introduced. Some have little insulation. Others have insulation in one part of the home but not another. Some have had upgrades added over time without clear documentation.

This matters because insulation helps the home resist unwanted heat flow. In winter, it can help reduce heat loss. In summer, it can help slow external heat entering the building. Without adequate insulation, heating and cooling systems may need to work harder to maintain comfort.

For homeowners, insulation is often one of the first building fabric issues worth understanding before choosing appliances, solar or other energy upgrades.

How insulation affects a home energy rating

A home energy rating considers how the dwelling performs as a whole system. Insulation is one of the key building fabric inputs because it affects heating and cooling demand.

Where insulation is present and effective, the home may be better able to maintain comfort with less active heating and cooling. Where insulation is missing, incomplete or damaged, the rating may reflect higher thermal loads or poorer comfort performance.

For a broader explanation of assessment inputs, see What Does a Home Energy Rating Actually Measure?

Ceiling and roof insulation

Ceiling and roof insulation are often important because roofs can be a major pathway for heat gain and heat loss. In summer, roof spaces can become very hot. In winter, warm indoor air can be lost through poorly insulated ceilings or roof assemblies.

In existing homes, ceiling insulation may be missing, patchy, compressed, disturbed by trades or inconsistent between old and renovated areas. Roof insulation may also vary depending on the roof type, ceiling type and previous upgrades.

A rating or assessment may need to identify what is known, what is visible and what remains uncertain before insulation performance can be properly understood.

Wall insulation

Wall insulation can be harder to confirm in an existing home because it is usually hidden behind internal linings and external cladding or masonry.

Some older homes may have little or no wall insulation. Some renovations may have added insulation to new walls but left original walls unchanged. This can create uneven comfort between rooms or parts of the house.

Wall insulation is often easiest to review during renovation, when walls are already being opened or upgraded. This is why insulation should be considered early in renovation planning.

Floor insulation

Floor insulation can be relevant where the home has suspended floors, exposed subfloors, garages below living spaces or areas that feel cold underfoot in winter.

Not every home will have the same floor insulation opportunity. A concrete slab behaves differently from a suspended timber floor. Access, moisture conditions, ventilation and construction type all affect what can be assessed or upgraded.

As with other insulation types, floor insulation should be reviewed as part of the whole building fabric rather than treated as a separate product decision.

Renovations can create insulation gaps

Existing homes often contain different layers of construction. The original dwelling may have been built to one standard, while an extension or renovated area may have been built to another.

This can create insulation gaps. A rear extension may be better insulated than the original home. A converted garage may have different wall and roof performance. A renovated living area may have new glazing but no corresponding wall or ceiling upgrade.

Understanding these differences can help explain why one part of a home feels comfortable while another performs poorly.

Insulation is not the only performance issue

Insulation is important, but it does not work alone. A well-insulated home can still overheat if windows are unshaded, if glazing is poorly selected or if summer sun enters the building at the wrong times.

A home with new insulation may still feel draughty if there are air leakage issues. A home with solar panels may still need building fabric improvements if heating and cooling demand remains high.

This is why insulation should be considered alongside glazing, shading, draught sealing, ventilation and mechanical systems.

Insulation and summer overheating

Insulation can help slow heat entering the home, but it is not a complete overheating strategy on its own.

If a home has large unshaded windows, poor ventilation, dark roof surfaces or high internal heat gains, insulation alone may not prevent summer discomfort. In some cases, a home may hold heat for longer if night purging, shading and ventilation are not considered.

This is why overheating should be assessed as a whole-home performance issue, not only an insulation issue.

Insulation and draughts are different issues

Insulation slows heat transfer through building elements. Draught sealing reduces uncontrolled air movement through gaps, cracks and leakage points. Both can affect comfort, but they are not the same thing.

A home can be insulated but still draughty. It can also be relatively well sealed but poorly insulated. The best retrofit strategy often considers both thermal resistance and air leakage together.

This will be covered in more depth in the related article on draught sealing and air leakage in existing homes.

How an assessor may review insulation

In an existing home assessment, the assessor may need to determine what insulation information is available and how reliable it is.

Useful evidence may include:

• visible insulation in accessible areas
• renovation documentation
• builder or installer invoices
• product labels or specifications
• photos taken during previous works
• homeowner records
• plans or construction notes
• safe access observations

Where insulation cannot be verified, the assessment may need to treat that information carefully according to the relevant pathway. For more context, see What Does a Home Energy Rating Assessor Look For?

When should insulation be upgraded?

Insulation may be worth reviewing when a home is difficult to keep comfortable, when heating and cooling use is high, when rooms perform unevenly or when renovation work creates access to walls, ceilings, roofs or floors.

It may also be worth reviewing before replacing heating and cooling systems. If the building fabric is weak, new appliances may be forced to work harder than necessary.

The best timing depends on the property, climate, access, budget and broader upgrade pathway.

Should insulation be reviewed before solar or new systems?

Often, yes. Solar, batteries and efficient appliances can reduce energy use and emissions, but they do not automatically fix poor thermal comfort.

If a home loses or gains heat quickly, the heating and cooling demand may remain high. Reviewing insulation and other building fabric issues first can help ensure system upgrades are properly sized and better matched to the home.

A home energy rating can help identify whether insulation should be part of the upgrade sequence.

Renovation is often the best time to review insulation

Insulation upgrades can be easier and more cost-effective when they align with renovation works. If ceilings, walls, floors or roof areas are already being opened, the opportunity to improve insulation may be much stronger than after finishes are complete.

This is especially important for extensions, internal reconfigurations, roof replacements, recladding, floor works and major services upgrades.

For renovation pathway advice, see Existing Home Energy Rating vs Renovation Energy Assessment.

FAQs

Why is insulation important in existing homes?

Insulation is important in existing homes because it helps slow heat transfer through ceilings, roofs, walls and floors. This can improve comfort, reduce heating and cooling demand and support better energy performance.

Does a home energy rating assess insulation?

Yes. A home energy rating may consider insulation in ceilings, roofs, walls and floors where the information is available, visible, documented or able to be assessed under the relevant pathway.

What insulation should be checked in an existing home?

Useful areas to check include ceiling insulation, roof insulation, wall insulation, floor insulation, insulation around extensions or renovations, and areas where insulation may be missing, damaged or poorly installed.

Can insulation improve an existing home energy rating?

Insulation upgrades may improve the energy performance of an existing home, especially where insulation is missing, insufficient, damaged or poorly installed. The impact depends on the home, climate, construction and other building features.

Is ceiling insulation enough for an existing home?

Ceiling insulation is often important, but it may not be enough on its own. Walls, floors, windows, shading, draughts and heating or cooling systems can also affect comfort and energy performance.

Should insulation be reviewed before a renovation?

Yes. Renovation is often a good time to review insulation because walls, roofs, floors or ceilings may become accessible. Reviewing insulation early can help avoid missed opportunities and poorly sequenced upgrades.

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Comparison Guide

Existing Home Energy Rating vs Renovation Energy Assessment

An existing home energy rating and a renovation energy assessment can both help improve a home, but they are not the same service.

An existing home energy rating looks at the current performance of a dwelling that has already been built. A renovation energy assessment may look at proposed changes, design options, compliance requirements and upgrade sequencing for a renovation project.

The difference matters because many homeowners begin with a simple question about comfort or running costs, then realise those answers need to be translated into practical renovation decisions.

Why this comparison matters

Renovation projects often begin with a practical problem. The home is too hot, too cold, too expensive to run, difficult to ventilate or uncomfortable in certain rooms.

A home energy rating can help explain what is happening in the current dwelling. But once renovation work is being planned, the question changes. The project team may need to know how proposed works affect performance, whether the design meets approval requirements and which upgrades should be prioritised.

That is where the distinction between rating the existing home and assessing a renovation pathway becomes important.

What is an existing home energy rating?

An existing home energy rating assesses a dwelling that has already been built. It helps describe the home’s current energy performance, comfort and upgrade potential.

The assessment may look at insulation, glazing, shading, orientation, heating and cooling, hot water, solar, batteries, ventilation and comfort concerns. It is grounded in the dwelling as it currently stands.

For the broader definition, see What Is a Home Energy Rating for Existing Homes?

What is a renovation energy assessment?

A renovation energy assessment reviews energy performance in the context of proposed renovation works. It may look at how the design, construction scope, materials, glazing, insulation, shading, systems or layout changes affect the home’s performance.

Depending on the project, it may also support compliance advice, design coordination or upgrade sequencing. The assessment can help a project team understand what should be improved during the renovation rather than after the work has been completed.

In simple terms, a renovation energy assessment asks: how should the proposed renovation respond to the home’s energy performance goals and requirements?

The core difference: current performance vs proposed change

The simplest distinction is this: an existing home energy rating looks at the home as it is now. A renovation energy assessment looks at the renovation pathway and how proposed changes may affect performance.

An existing home rating asks: how does this dwelling currently perform?

A renovation energy assessment asks: how should the proposed works improve or respond to the home’s energy performance?

When might you use an existing home energy rating?

An existing home energy rating may be useful before renovation decisions are made, especially when the homeowner wants to understand current comfort, running costs and performance issues.

This may include:

• understanding why the home is hot or cold
• identifying weak points in the existing building fabric
• reviewing insulation, glazing and shading
• understanding whether heating and cooling systems are working too hard
• deciding whether upgrades should happen before or during renovation
• preparing for future sale, lease or disclosure expectations
• understanding the current dwelling before design work progresses

For more detail on what is measured, see What Does a Home Energy Rating Actually Measure?

When might you use a renovation energy assessment?

A renovation energy assessment may be useful once there is a proposed scope, concept design or set of upgrade decisions to review.

This may include:

• reviewing proposed glazing changes
• assessing insulation upgrades in the renovation scope
• checking whether shading is adequate
• reviewing heating and cooling strategy
• considering hot water and electrification options
• coordinating solar or battery decisions with renovation works
• supporting energy compliance for proposed works
• comparing upgrade scenarios before construction
• helping the design team avoid late-stage performance changes

This type of assessment is most useful before drawings, specifications and construction decisions are fully locked in.

Can a renovation project need both?

Yes. In many renovation projects, both forms of assessment can be useful at different stages.

An existing home energy rating can help establish the baseline: how the home performs before the renovation. A renovation energy assessment can then help apply that information to proposed works, design decisions, compliance questions and upgrade sequencing.

Used together, they can help avoid isolated upgrades that look useful on their own but do not fit the full performance strategy for the home.

Why assessment should happen before renovation decisions are locked in

Energy assessment is most useful when it happens early enough to influence the project. If the renovation design is already finalised, the opportunity to improve orientation, glazing, shading, insulation and system strategy may be limited.

Early review can help the project team understand whether comfort issues are caused by poor insulation, unshaded glazing, draughts, inefficient systems, layout problems or a combination of factors.

This can reduce the risk of spending money on upgrades that do not address the main performance problem.

Where compliance may fit into a renovation assessment

Some renovations are only about voluntary improvement. Others may trigger planning, building or energy compliance requirements depending on the location and project scope.

For example, a NSW alteration or addition may need BASIX if it meets the relevant threshold. Other projects may need NCC-related energy compliance support, such as DTS or another pathway.

This is why a renovation energy assessment may need to consider both performance improvement and compliance context. For NSW projects, see Existing Home Energy Rating vs BASIX.

Does a home energy rating tell you what to renovate?

A home energy rating can help identify performance issues and possible upgrade opportunities. It may show whether the building fabric, windows, insulation, systems or solar strategy should be reviewed.

However, turning a rating into a renovation scope usually requires design thinking. The right upgrade depends on the home, budget, timing, access, construction feasibility, comfort goals and whether the project has compliance requirements.

This is where a renovation energy assessment can help translate rating insights into practical project decisions.

Why upgrade sequencing matters

Renovation projects are one of the best times to improve energy performance because walls, roofs, windows, services or finishes may already be changing.

But the sequence matters. It may be better to improve insulation and draught sealing before upsizing heating and cooling systems. It may be better to review shading before replacing glazing. It may be better to coordinate solar and electrification with switchboard or hot water upgrades.

A renovation energy assessment can help connect these decisions so that upgrades work together rather than competing with each other.

How this differs from new-home NatHERS

A renovation energy assessment should also be separated from new-home NatHERS where the project context is different.

New-home NatHERS usually assesses a proposed residential design before construction. Existing home energy ratings assess a real dwelling that already exists. Renovation energy assessment sits between those worlds when a current home is being changed through proposed works.

For that distinction, see NatHERS Existing Homes vs New Home NatHERS Assessments.

Which pathway do you need?

The right pathway depends on the question you are trying to answer.

You may need an existing home energy rating if the question is:

• How does this home perform now?
• Why is the dwelling uncomfortable?
• Which current features are affecting energy use?
• What performance issues should be understood before design begins?

You may need a renovation energy assessment if the question is:

• How will proposed changes affect performance?
• Which upgrades should be included in the renovation scope?
• Does the renovation need energy compliance support?
• How should insulation, glazing, shading and systems be coordinated?

When both questions matter, both pathways may need to be considered together.

Practical implications

For homeowners, the distinction helps avoid jumping straight to product decisions before understanding the home’s performance.

For designers, a renovation energy assessment can help integrate energy performance into the design process before drawings and specifications are locked in.

For builders, it can help identify where upgrades need to be incorporated into the construction scope rather than treated as optional extras later.

For consultants, the key is to clarify whether the client needs a current-state rating, proposed-work assessment, compliance support or a combination of these.

FAQs

Is an existing home energy rating the same as a renovation energy assessment?

No. An existing home energy rating assesses the current performance of a dwelling that has already been built. A renovation energy assessment may review proposed changes, compliance needs, upgrade options or design decisions for a renovation project.

When would you need an existing home energy rating?

An existing home energy rating may be useful when you want to understand how the current home performs before making upgrade, sale, lease, electrification or renovation decisions.

When would you need a renovation energy assessment?

A renovation energy assessment may be useful when proposed works need energy performance advice, design review, compliance support or upgrade sequencing before the renovation is finalised.

Can a renovation project need both?

Yes. A renovation project may benefit from an existing home energy rating to understand the current dwelling and a renovation energy assessment to review proposed changes, compliance needs and upgrade options.

Does a home energy rating tell me what to renovate?

A home energy rating can help identify performance issues and possible upgrade opportunities, but a renovation energy assessment may be needed to apply those findings to design choices, construction scope and project documentation.

Should energy assessment happen before renovation design is finished?

Yes. Energy assessment is usually most useful before renovation decisions are locked in, so insulation, glazing, shading, heating, cooling, hot water, solar and ventilation choices can be considered early.

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Comparison Guide

Existing Home Energy Rating vs BASIX

An existing home energy rating and BASIX both relate to residential sustainability, but they are not the same pathway.

BASIX is a NSW planning and compliance pathway used for eligible residential development. An existing home energy rating is used to understand how an already-built dwelling performs for comfort, energy use and upgrade potential.

The difference matters because homeowners, designers, builders and property professionals can easily confuse these terms when working on renovations, alterations, sale preparation or upgrade planning.

Why this comparison matters

In NSW, BASIX is one of the most familiar residential sustainability pathways. Because of that, many people use the word BASIX when they simply mean energy efficiency, sustainability or home performance.

That creates confusion. A homeowner with an existing dwelling may not need BASIX at all. They may need a rating or assessment that explains how their current home performs and what could improve it.

On the other hand, a new residential development or qualifying alteration in NSW may need BASIX documentation even if the owner is not asking for an existing home energy rating.

What is an existing home energy rating?

An existing home energy rating assesses a dwelling that has already been built. It helps explain how the home performs for energy efficiency, comfort and likely upgrade potential.

The assessment may consider the building fabric, insulation, glazing, shading, heating and cooling systems, hot water, solar, batteries and comfort issues. It can help homeowners understand what is driving energy use and what improvements may be worth considering.

For a broader explanation, see What Is a Home Energy Rating for Existing Homes?

What is BASIX?

BASIX stands for the Building Sustainability Index. It is a NSW sustainability pathway used in the planning and approval process for eligible residential development.

BASIX addresses sustainability requirements such as water, energy and thermal performance for NSW residential projects. It is commonly associated with new homes, alterations, additions and certain pools or spas that trigger BASIX requirements.

For NSW project support, see BASIX Certificate NSW.

The core difference: current performance vs approval compliance

The simplest distinction is this: an existing home energy rating looks at how a home performs now. BASIX helps demonstrate how an eligible NSW residential project meets sustainability requirements for approval.

An existing home energy rating is usually concerned with current comfort, energy use, installed systems and upgrade potential. BASIX is concerned with whether a project meets the relevant NSW requirements for water, energy and thermal performance.

This means the two services answer different questions, even when they both involve residential energy performance.

When might you need an existing home energy rating?

An existing home energy rating may be useful when the main question is about the performance of a dwelling that has already been built.

This may include:

• understanding why a home is hot, cold or draughty
• planning energy upgrades
• reviewing insulation, windows or shading
• preparing for electrification
• deciding whether to install solar or batteries
• planning a staged retrofit
• preparing for sale or lease disclosure
• reviewing a residential property portfolio
• understanding a home before renovation decisions are made

For practical preparation, see What Information Do You Need for a Home Energy Rating?

When might you need BASIX?

BASIX is usually relevant when a NSW residential project needs approval documentation and the project falls within the BASIX requirements.

This may include:

• new houses in NSW
• new townhouses or villas
• new apartments or multi-unit residential projects
• eligible alterations and additions
• renovations that trigger BASIX requirements
• certain swimming pools or spas
• development applications requiring a BASIX certificate

BASIX is therefore tied to the NSW approval pathway. It is not simply a general existing-home energy rating.

Can a renovation need both?

Yes. A renovation or alteration project in NSW may involve both types of thinking, depending on the scope and purpose.

If the renovation triggers BASIX requirements, BASIX may be needed for planning or approval. At the same time, the homeowner or design team may want an existing home energy rating to understand how the current dwelling performs before upgrade decisions are finalised.

In that situation, BASIX supports compliance for the proposed project, while the existing home rating supports better decision-making about the current home.

BASIX does not replace an existing home energy rating

BASIX should not be used as a substitute for an existing home energy rating. It is not designed to provide a full performance rating of an established home as it currently operates.

A BASIX certificate may support a development application or approval process. An existing home energy rating may support comfort upgrades, retrofit planning, disclosure readiness or a better understanding of how the current dwelling performs.

The documents may both be useful, but they are not interchangeable.

An existing home energy rating does not replace BASIX

The reverse is also true. An existing home energy rating should not be treated as a BASIX certificate where BASIX is required for a NSW development approval pathway.

If a project needs BASIX, the project team must prepare the correct BASIX documentation. A home energy rating may help the owner understand the existing dwelling, but it does not automatically satisfy BASIX requirements.

This is why the correct pathway should be confirmed early.

How does NatHERS Existing Homes fit in?

NatHERS Existing Homes is part of the broader national shift toward rating established dwellings. It is different from BASIX because it is not simply a NSW development approval document.

The NatHERS Existing Homes pathway is focused on assessing the energy performance of homes that have already been built. This may support homeowners, buyers, sellers, landlords and project teams as existing-home ratings become more common.

For more context, see What Is NatHERS Existing Homes?

Where new-home NatHERS sits beside BASIX

In NSW, new residential projects may involve both BASIX and NatHERS, depending on the project type and approval pathway.

This can create another layer of confusion. New-home NatHERS assesses a proposed design, while NatHERS Existing Homes assesses a dwelling that has already been built. BASIX is a NSW approval pathway that may use or interact with energy assessment inputs depending on the project.

For that distinction, see NatHERS Existing Homes vs New Home NatHERS Assessments.

Which pathway do you need?

The right pathway depends on the project question.

You may need an existing home energy rating if the question is:

• How does this existing home perform now?
• Why is the home uncomfortable?
• Which upgrades should be considered first?
• How can the dwelling be improved before renovation, sale or lease?

You may need BASIX if the question is:

• Does this NSW residential project need sustainability compliance documentation?
• Is this new home, alteration, addition, pool or spa subject to BASIX?
• What documentation is required for the development application or approval pathway?

When in doubt, the project scope and location should be reviewed before selecting the pathway.

Practical implications

For homeowners, the distinction helps prevent requesting the wrong service. A person trying to improve an established home may need performance advice, not BASIX.

For designers and builders, the distinction matters because BASIX may be required for approval, while existing-home rating may support better renovation or retrofit decisions.

For property professionals, the distinction becomes more important as existing home rating disclosure pathways develop separately from new-build planning compliance.

For consultants, the key is to clarify the project scope before recommending BASIX, NatHERS Existing Homes or another assessment pathway.

FAQs

Is an existing home energy rating the same as BASIX?

No. An existing home energy rating assesses the performance of a dwelling that has already been built. BASIX is a NSW planning and sustainability pathway used for new residential development and certain alterations, additions, pools and spas.

When do you need BASIX?

BASIX is generally relevant to NSW residential development applications, including new homes and certain renovation, alteration, addition, pool or spa projects. The exact requirement depends on the project type and approval pathway.

When do you need an existing home energy rating?

An existing home energy rating may be useful when assessing the current performance of an established dwelling, planning upgrades, preparing for future disclosure, reviewing comfort issues or understanding energy efficiency before renovation decisions.

Can BASIX be used as an existing home energy rating?

No. BASIX is not a general rating of an existing home as it currently performs. It is a NSW compliance pathway connected to development approval and sustainability requirements for eligible residential projects.

Can a renovation need both BASIX and an existing home energy rating?

Yes. A renovation or alteration project in NSW may need BASIX for approval while also benefiting from an existing home energy rating to understand the current performance of the dwelling and guide upgrade decisions.

Does BASIX replace NatHERS Existing Homes?

No. BASIX and NatHERS Existing Homes serve different purposes. BASIX relates to NSW development compliance, while NatHERS Existing Homes is an emerging pathway for rating the performance of dwellings that already exist.

Pathway Review

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Home Energy Rating Timing

How Long Does a Home Energy Rating Take?

The time required for a home energy rating depends on the property, the available information and the assessment pathway.

A straightforward existing home with clear access, available documents and simple systems may be faster to review than a larger home with multiple renovations, missing plans, complex systems or uncertain construction details.

The process usually involves more than one step: initial property review, information gathering, site data collection, modelling or rating input, assessor review, follow-up questions and reporting.

Why timing varies between homes

Existing homes are rarely identical from an assessment perspective. Two houses may look similar from the street but have very different construction, insulation, renovations, system upgrades, access conditions and documentation.

A home with clear plans, easy access and simple building systems may move through the review process more easily. A home with missing plans, several extensions, hidden insulation details or complex services may require more time for data collection and clarification.

This is why it is better to think of the rating as a process rather than a single appointment.

Stage 1: Initial property review

The first timing factor is the initial review. Before an assessor can confirm the likely pathway, they need to understand the property and why the rating is being requested.

Useful starting details include:

• property address
• dwelling type
• approximate age of the home
• number of storeys
• whether plans or photos are available
• reason for requesting the rating
• preferred timing or access constraints

Providing this information early can help Certified Energy review whether the NatHERS Existing Homes assessment pathway is likely to be suitable.

Stage 2: Information gathering

Before the assessment can proceed efficiently, it helps to gather any information already available for the home. This does not need to be perfect, but it should give the assessor a clearer starting point.

Helpful information may include:

• available floor plans or drawings
• renovation or extension history
• photos of the home
• known insulation information
• heating and cooling system details
• hot water system details
• solar PV or battery information
• known comfort issues

For a full checklist, see What Information Do You Need for a Home Energy Rating?

Stage 3: Site data collection

For many existing home assessments, site data collection is an important part of the process. NatHERS has described existing home ratings as requiring assessors to enter homes, collect on-site data, input the data into an energy rating tool and generate a Home Energy Rating Certificate.

Site data collection may include reviewing:

• dwelling layout
• orientation
• windows and glazing
• shading
• visible construction details
• insulation information where available
• heating and cooling systems
• hot water systems
• solar PV and batteries
• comfort or performance issues

The time required for this stage depends on the size, layout and complexity of the home, as well as access to relevant areas.

Stage 4: Assessment input and modelling

After the information has been collected, it needs to be entered into the relevant assessment pathway. This is where property information becomes structured enough to support modelling and rating.

This stage may take longer if there are missing plans, unclear construction details, uncertain insulation, complex renovation history or system information that needs to be checked.

For a fuller process explanation, see How Does a NatHERS Existing Home Assessment Work?

Stage 5: Review and clarification

Existing home assessments often require some review after the first round of information is collected. The assessor may need to clarify details about renovations, insulation, window changes, systems or access limitations.

Follow-up questions can add time, but they can also improve the quality of the assessment by reducing uncertainty where possible.

This stage is especially important for homes without original plans or homes that have been altered over time.

Stage 6: Rating and reporting

After the home’s energy performance is assessed, the final output may include a Home Energy Rating Certificate and supporting information that helps guide decisions about comfort, running costs, emissions and upgrades.

NatHERS explains that Whole of Home can complement the thermal star rating and includes major energy use and generation within the home, such as hot water, heating and cooling systems, pool and spa equipment, lighting, plug-in appliances, solar energy and battery storage.

Reporting time depends on the assessment pathway, review requirements and whether additional clarification is needed before the rating is finalised.

What can delay a home energy rating?

Most delays come from missing or uncertain information, access difficulties or properties that are more complex than expected.

Common timing issues include:

• no available plans
• unclear renovation history
• uncertain insulation details
• large or complex dwellings
• multiple additions or extensions
• limited access to rooms or relevant areas
• missing system information
• unclear solar or battery details
• follow-up questions after review

If original plans are not available, see Can You Get a Home Energy Rating Without Original Plans?

How to help the process move more smoothly

You can help the process by preparing the information that is already available before requesting a quote.

Helpful preparation includes:

• sending the property address
• providing available plans or floor plans
• including photos of the home
• summarising renovation history
• noting known insulation details
• providing heating and cooling system information
• providing hot water system information
• including solar or battery details
• explaining known comfort issues
• confirming access availability

This does not mean you need to solve every information gap yourself. It simply gives the assessor a clearer starting point.

When should you request a home energy rating?

It is best to request a rating before major decisions are locked in. Waiting until after upgrades are purchased or renovation documentation is complete can reduce the value of the assessment.

A home energy rating may be useful before:

• planning a renovation
• replacing heating or cooling systems
• upgrading insulation
• installing solar or batteries
• planning electrification
• listing a property for sale
• preparing a rental property
• reviewing a residential property portfolio
• trying to solve comfort problems

Early assessment can help avoid rushed or poorly sequenced energy upgrade decisions.

FAQs

How long does a home energy rating take?

The time required for a home energy rating depends on the property, available documentation, access, site data collection, modelling, review and reporting. A straightforward home with clear information may be faster than a larger, altered or poorly documented dwelling.

What affects the timing of a home energy rating?

Timing can be affected by dwelling size, property complexity, access arrangements, missing plans, renovation history, insulation uncertainty, system information, photos, site data collection and whether follow-up questions are needed.

Does a home energy rating require a site visit?

For many existing home assessment pathways, on-site data collection is required so the dwelling’s layout, construction, systems, appliances and visible performance features can be recorded.

Can missing plans delay a home energy rating?

Missing plans can affect timing because the assessor may need to rely more on site data, photos, observations, available records and permitted assumptions. They do not always prevent a rating, but they can add review time.

How can I speed up a home energy rating?

You can help the process by preparing the property address, available plans, photos, renovation history, insulation details, heating and cooling information, hot water details, solar or battery information and known comfort issues.

When should I request a home energy rating?

It is best to request a home energy rating before major upgrade decisions, renovation documentation, sale preparation, lease preparation or electrification planning move too far forward.

Assessment Timing Review

Need a clearer assessment timeframe?

Send property details, available plans and photos so Certified Energy can review the likely home energy rating pathway and timing.

Send property details for review