What Makes a Good Retrofit?

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Six Principles for Creating More Comfortable, Healthier and Lower-Carbon Homes

Many homeowners begin thinking about retrofit because something in their home isn’t working as well as it could.

Perhaps certain rooms are difficult to heat in winter. Condensation appears on the windows each morning. Energy bills continue to rise despite upgrading the heating system. Or perhaps there is a growing desire to reduce environmental impact while creating a healthier and more comfortable place to live.

At the same time, there is increasing awareness that our existing homes have an important role to play in addressing climate change. The homes we renovate today are likely to be the homes we live in for decades to come.

Yet retrofit can be overwhelming. Homeowners are often presented with a long list of products, technologies and opinions. Should you start with insulation? New windows? Solar panels? A heat pump? Ventilation?

The reality is that a successful retrofit is rarely defined by a single product or technology.

Instead, it is the result of many decisions working together.

Increasingly, retrofit is also being recognised as one of the most effective ways to reduce both operational carbon (the emissions from running a building) and embodied carbon (the emissions associated with the materials used to create it).

The London Energy Transformation Initiative (LETI) Climate Emergency Retrofit Guide identifies six key principles for successful retrofit projects. While developed in the UK, these principles provide a useful framework for Australian homes and renovation projects.

1. Reduce Energy Demand First

When a home feels cold in winter or hot in summer, it is natural to focus on the heating and cooling system.

However, one of the most effective retrofit principles is to reduce energy demand before investing in larger or more sophisticated systems.

Many Australian homes lose significant amounts of heat through poorly insulated walls, ceilings and floors. Others suffer from uncontrolled draughts, thermal bridges or older windows that allow warmth to escape during winter and unwanted heat to enter during summer.

This often leads to a common cycle. The home feels uncomfortable, so a larger heater is installed. Energy consumption increases, but comfort improves only marginally because the underlying causes of heat loss remain unchanged.

A fabric-first approach focuses on improving the building itself.

This may include:

Improving insulation
Reducing uncontrolled draughts
Upgrading windows where appropriate
Addressing thermal weak points
Improving solar control and shading

Reducing energy demand often delivers multiple benefits at once. The home becomes more comfortable, energy bills can reduce, heating and cooling systems can be smaller, and carbon emissions are lowered.

Rather than continually adding more energy, the goal is to help the home retain comfortable conditions for longer.

For example, it’s not uncommon for older Melbourne homes to have ceiling insulation but little or no wall insulation. Homeowners sometimes replace heating systems only to find comfort improves less than expected because the home is still losing significant amounts of heat through the building envelope.

2. Prioritise Health and Comfort

While energy efficiency often dominates conversations about sustainability, comfort and health are equally important.

After all, homes exist for people.

Many older homes experience issues such as:

Condensation on windows
Damp and mould
Cold internal surfaces
Large temperature differences between rooms
Poor indoor air quality
Excessive external noise

These issues can affect wellbeing, building durability and everyday quality of life.

A successful retrofit should not simply reduce energy consumption. It should improve how the home feels to live in.

This is why increasing attention is being given to the building envelope, ventilation and moisture management. These elements work together to influence comfort, indoor air quality, energy efficiency and the long-term durability of a home.

A home with stable temperatures, fresh air and low condensation risk is often more comfortable than a home with a larger heating system but poor thermal performance.

In many cases, the most noticeable outcome of a retrofit is not lower energy bills.

A common example is condensation on bedroom windows during winter. While often dismissed as a minor inconvenience, persistent condensation can be a sign that moisture, ventilation and thermal performance need to be considered together.

It is simply that the home feels better.

The most comfortable homes are often the ones you stop noticing altogether.

You stop thinking about which room is warmest.

And you stop thinking about whether you’ll be warm enough.

3. Take a Whole-House Approach

One of the most important lessons emerging from building science is that homes are systems.

Changes made to one part of a building often affect another.

For example:

Improving airtightness influences ventilation requirements.
Additional insulation affects moisture movement through walls and roofs.
Window upgrades can alter condensation patterns.
Heating systems perform differently depending on the quality of the building envelope.

This is why piecemeal upgrades can sometimes create unintended consequences.

A homeowner may replace windows but leave significant heat loss elsewhere. Another may improve airtightness without addressing ventilation. A third may install a new heating system without understanding why the home loses so much heat in the first place.

A whole-house approach considers how different building elements interact.

It looks at:

Building fabric
Ventilation
Moisture management
Heating and cooling systems
Occupancy patterns
Existing constraints
Future renovation plans

This broader perspective can help identify priorities, avoid costly mistakes and create a clearer pathway for future improvements.

A whole-house approach doesn’t necessarily mean doing everything at once. It means understanding how the different parts of your home work together, so each improvement supports the next rather than creating unintended consequences.

4. Measure Performance Where Possible

Many building performance issues are difficult to see.

A room that feels cold may not have the problem we expect. Condensation may be caused by several factors working together. Areas of heat loss are often hidden within the building fabric.

Assessment and testing can help move decision-making from assumptions to evidence.

Depending on the project, this may include:

Thermal imaging
Airtightness testing (blower door testing)
Energy modelling
Utility bill analysis
Moisture assessments

For example, thermal imaging can reveal areas of heat loss that are not visible during a standard inspection, while blower door testing can help identify unwanted air leakage that contributes to discomfort and increased energy use.

The goal is not testing for the sake of testing.

The goal is to better understand how a home performs and where investment is likely to have the greatest impact.

Measurement also provides a valuable benchmark. It allows improvements to be assessed and helps homeowners understand whether retrofit measures are delivering the outcomes they expected.

5. Think Long-Term

If you’re planning a major renovation, it’s often preferable to consider the home as a whole rather than treating each upgrade as a separate project.

This creates opportunities to coordinate upgrades, reduce disruption and ensure different parts of the project work together effectively.

However, not every homeowner has the budget to undertake a comprehensive retrofit all at once.

In these situations, having a long-term plan becomes even more valuable.

A staged retrofit strategy can help identify which improvements should be prioritised now, which can wait until later, and how today’s decisions can support future upgrades rather than create unnecessary rework.

For example, improving insulation during a renovation may influence future heating and cooling requirements. Replacing windows may affect future airtightness and ventilation strategies. Opening walls for one project may provide an opportunity to complete work that would be much more disruptive and expensive later.

Whether undertaken in a single renovation or over a number of years, the most successful retrofit projects are guided by a clear long-term vision rather than a series of disconnected upgrades.

6. Consider Embodied Carbon

When sustainability is discussed, most people think about operational energy, the energy required to heat, cool and run a home.

Embodied carbon looks at a different part of the equation.

It refers to the greenhouse gas emissions associated with extracting raw materials, manufacturing products, transporting them, constructing the building and, eventually, its demolition and disposal. Unlike operational carbon, much of embodied carbon is released before a building is even occupied.

Reducing operational energy has long been a central focus of sustainable building design, and for good reason. Improving insulation, reducing draughts and designing more efficient buildings has significantly reduced the energy needed to heat and cool our homes.

As homes become more energy efficient, the carbon associated with building materials becomes increasingly important. This is why embodied carbon is receiving growing attention within the building industry.

One of the greatest advantages of retrofit is that it allows us to retain and improve existing buildings rather than replacing them entirely. Every wall, floor, roof and foundation already contains invested resources, energy and carbon.

Rather than automatically replacing everything, retrofit encourages us to ask:

Can this be repaired?
Can it be adapted?
Can it be upgraded?
Can we retain more of what already exists?

Embodied carbon also encourages us to think more carefully about material choices. Every product we specify has an environmental footprint, from concrete and steel to timber, insulation and finishes. Considering these impacts alongside comfort, durability and building performance helps create more informed design decisions.

This doesn’t mean every building should be preserved exactly as it is, nor does it mean new materials should never be used. Rather, it encourages a more thoughtful approach to demolition, material selection and long term environmental impact.

For homeowners considering a renovation or retrofit, embodied carbon is another reminder that some of the most sustainable decisions are often made before construction begins.

Taking the Next Step

If you’re planning a renovation and wondering how these principles apply to your own home, Fluit Studio’s Retrofit Advisory service provides an architect-led assessment to help identify opportunities to improve comfort, health, energy performance and long-term sustainability. It takes a whole-house approach, helping you prioritise improvements and develop a staged strategy that reflects your home, your goals and your budget.

Learn more about the Retrofit Advisory service.

Acknowledgement

This article was inspired by the London Energy Transformation Initiative (LETI) Climate Emergency Retrofit Guide and has been adapted for an Australian residential context. Additional insights were drawn from Mariana Moreira’s article, The Relevance of Embodied Carbon in the Passive House World – 475 HQ Retrofit Case Study (Passive House Accelerator, 2026). Readers interested in learning more are encouraged to explore these excellent resources.