Home Performance
Energy bills matter, but they are not the whole story. A home can use less energy because it performs well, or because the people inside are simply putting up with discomfort.
Thermal comfort describes how comfortable a home feels in hot, cold and changing weather. NatHERS focuses on the heating and cooling energy a home may need to stay comfortable, not on household bills. This matters because a good home should not only reduce energy demand. It should also feel more stable, liveable and comfortable throughout the year.
Energy bills are influenced by many things: household behaviour, appliance use, solar generation, tariffs, heating and cooling habits, occupancy patterns and personal tolerance for discomfort. They do not always show whether the building itself is performing well.
A household may have low heating and cooling bills because the home is comfortable with little mechanical conditioning. But another household may have low bills because they avoid using heating and cooling, even when the home feels too hot or too cold.
This is why thermal comfort is such an important measure of home performance. It looks at the lived experience of the home, not just the cost of running equipment.
Thermal comfort is the difference between a home that feels calm and stable and a home that needs constant correction. It is felt in bedrooms that do not overheat at night, living areas that receive winter sun without becoming uncomfortable in summer and rooms that do not swing sharply between hot and cold.
It is also felt in quieter ways: fewer draughts, less radiant heat from windows, better protection from afternoon sun, more even temperatures between rooms and less reliance on heaters or air conditioning to make the home usable.
A comfortable home is not just cheaper to operate. It is easier to live in.
A low bill is not always the same as a comfortable home.
The better question is whether the home can stay comfortable with less heating and cooling in the first place.
NatHERS assesses how much heating and cooling energy a home may need to maintain comfortable indoor conditions in its local climate. The star rating is not a prediction of the household’s energy bill. It is a measure of the home’s thermal performance.
A higher NatHERS rating generally means the home is predicted to need less heating and cooling to stay comfortable. That can support lower energy demand, but the comfort benefit is just as important.
For a broader explanation, see our guide to what a NatHERS star rating means.
Thermal comfort is strongly shaped by the building fabric. This includes the roof, ceiling, walls, windows, doors, floors, insulation, shading and construction details that separate indoor and outdoor conditions.
When the fabric performs well, the home is less exposed to extreme outdoor conditions. Heat gain, heat loss, draughts and temperature swings are reduced. The home does not have to fight the weather as hard.
This is why NatHERS focuses heavily on the physical design of the home. Comfort begins with the building itself.
• Window size, orientation and glazing performance
• External shading and solar heat gain
• Ceiling, roof, wall and floor insulation
• Roof colour and roof heat gain
• Floor construction and thermal mass
• Air leakage, draught control and ventilation strategy
Windows have a strong effect on comfort because they influence daylight, views, heat gain and heat loss. Poorly placed or poorly performing glazing can make rooms too hot, too cold or uncomfortable near the glass.
Good window design is not only about choosing better glass. It is about the relationship between window size, orientation, frame type, glazing performance, shading and the climate zone.
For more detail, see our guide to how window design affects NatHERS ratings.
External shading can reduce unwanted solar heat gain before it enters the home. This can make a significant difference to summer comfort, especially for windows exposed to strong afternoon or low angle sun.
Good shading is climate and orientation specific. A home may need to allow useful winter sun while blocking unwanted summer sun. The balance depends on where the home is, how it is oriented and which rooms are affected.
For more detail, see our guide to shading and solar heat gain.
Energy efficiency is sometimes described only as saving money.
But in homes, the deeper value is often comfort: rooms that feel better, require less correction and respond more calmly to weather.
Insulation helps slow heat transfer through the building fabric. In winter, it can help reduce heat loss. In summer, it can help reduce heat entering through the roof, ceiling, walls or floors.
The comfort benefit is often felt as more stable indoor conditions. Rooms are less likely to become cold quickly after heating turns off or heat up rapidly during the day.
For more detail, see our guide to how insulation affects NatHERS ratings.
Air leakage can make a home feel draughty, uneven and harder to condition. Gaps around doors, windows, floors, ceilings and service penetrations can allow unwanted air movement between indoors and outdoors.
A home still needs healthy ventilation, but uncontrolled draughts are different from planned air movement. Comfort improves when air movement is intentional rather than accidental.
For more detail, see our guide to air leakage and home performance.
A comfortable home in a cool climate may need a different design response from a comfortable home in a hot humid, hot dry, coastal, inland or alpine climate. Thermal comfort is always connected to place.
This is why NatHERS uses local climate data when assessing a home. The rating reflects how the design is expected to perform in that specific climate, not as a generic national average.
For more detail, see our guide to building for different Australian climates.
NatHERS supports residential energy compliance by assessing the thermal performance of the home. The compliance outcome is important, but the underlying purpose is closely connected to comfort: reducing the heating and cooling needed to keep the home liveable.
For many new homes, this may connect with 7 Star Rating, Whole of Home and state based pathways such as BASIX in NSW.
The best outcome is not simply a certificate. It is a home where the compliance pathway supports a more comfortable building.
Designing for comfort means thinking about the whole home. A strong result rarely comes from one product alone. It comes from the relationship between climate, orientation, glazing, shading, insulation, air movement, thermal mass and construction details.
Australian homes need to manage hot days, cold nights, seasonal shifts, humidity, coastal conditions and inland temperature swings. Comfort is created when the home is designed for those conditions rather than relying only on mechanical correction.
The aim is a home that feels calm, stable and liveable, with less pressure on heating and cooling systems.
Certified Energy provides NatHERS assessments for new homes, townhouses and multi residential projects across Australia. Our team can model the home and help identify how the design is likely to perform in relation to thermal comfort and heating and cooling demand.
Where needed, we can help project teams understand the effect of glazing, shading, insulation, roof colour, floor construction, thermal mass, air leakage assumptions and climate zone. We can also help connect NatHERS with related requirements such as NatHERS, BASIX, 7 Star Rating and Whole of Home.
For the broader assessment framework, visit our NatHERS Knowledge Hub.
Thermal comfort matters because it affects how a home feels every day. Energy bills show part of the outcome, but comfort depends on the building fabric, climate response, glazing, shading, insulation and air movement.
Does NatHERS measure energy bills?NatHERS does not predict a household energy bill. It estimates the heating and cooling energy a home may need to stay comfortable in its local climate.
Can a home have low bills but still feel uncomfortable?Yes. A home may have low bills because occupants avoid using heating or cooling, but it can still feel too hot, too cold, draughty or unevenly conditioned.
What parts of a home affect thermal comfort?Thermal comfort is affected by windows, shading, insulation, air leakage, roof colour, floor construction, thermal mass, orientation, climate and the overall building fabric.
Does a higher NatHERS rating mean better comfort?A higher NatHERS rating generally means the home is predicted to need less heating and cooling to maintain comfort, but the lived outcome still depends on construction quality, use, climate and final specifications.