NatHERS Design Process
Can NatHERS Be Improved During Design?
A NatHERS rating is not fixed until the design and specifications are fixed. In many projects, the rating can be improved by adjusting the building fabric, glazing, shading and climate response before documentation is finalised.
Improving NatHERS in brief
A NatHERS rating can often be improved during design by refining the features that affect heating and cooling demand. These may include window size and performance, shading, insulation, roof colour, floor construction, thermal mass, orientation and air leakage assumptions. The earlier the rating is reviewed, the more design options are usually available.
Why NatHERS improvement is easier earlier
NatHERS is shaped by the design of the home. It responds to the size and orientation of rooms, window placement, glazing performance, shading, insulation, roof colour, construction systems and local climate.
Many of these decisions are easiest to adjust before the design is fully documented. Once planning, costing, structural coordination and client approvals are advanced, even small changes can become harder to make.
Early NatHERS review gives the project team more room to improve performance through design intelligence rather than relying only on late specification upgrades.
What usually affects the rating?
A NatHERS rating is affected by the whole thermal behaviour of the home. One project may be limited by glazing. Another may be limited by roof heat gain, poor shading, exposed floors or insufficient insulation. Another may be affected by orientation and local climate.
This is why there is no universal upgrade that improves every home in the same way. The best improvement depends on what the model shows is driving heating and cooling demand.
A targeted improvement is usually better than simply adding higher specifications everywhere. It keeps the response more practical and better aligned with the actual design.
The practical point
Improving NatHERS is not always about adding more expensive products.
Often, the best result comes from understanding which part of the design is creating thermal pressure and adjusting that part carefully.
Improving window design
Windows are often one of the most important areas for NatHERS improvement. Window size, orientation, frame type, glazing performance and shading can all influence heating and cooling demand.
In some homes, the rating may improve through better glazing performance. In others, reducing or relocating difficult windows may be more effective. Large unshaded west facing windows, for example, can create cooling pressure in many climates.
For more detail, see our guide to how window design affects NatHERS ratings.
Improving shading and solar control
Shading can be a powerful way to improve a NatHERS result, especially where the home has strong solar exposure or large glazing areas. The right shading can reduce unwanted summer heat gain while still allowing useful winter sun where appropriate.
Good shading is orientation specific. North, east, west and south facing windows may need different strategies. A generic shading detail may not solve the actual performance issue if it does not match the sun path and room use.
For more detail, see our guide to shading and solar heat gain.
Common ways NatHERS may be improved
• Adjusting window size, placement or glazing performance
• Improving external shading for exposed glazing
• Increasing or relocating insulation where it matters most
• Reviewing roof colour and roof heat gain
• Refining floor construction, exposed floors or slab details
• Coordinating thermal mass, solar access and climate response
Improving insulation
Insulation improvements can support a stronger NatHERS rating, especially where the existing specification is weak or where heat transfer through the roof, ceiling, walls or floor is a major issue.
However, more insulation is not always the only or best answer. If the project has large unshaded glazing or poor solar control, insulation alone may not resolve the rating. The model needs to show where the problem is coming from.
For more detail, see our guides to how insulation affects NatHERS ratings and ceiling insulation and NatHERS outcomes.
Improving roof colour and roof heat gain
Roof colour can affect heat gain, especially in warmer climates or homes with large roof exposure. A darker roof generally absorbs more solar heat than a lighter roof, which can influence cooling demand and the NatHERS result.
Changing roof colour may be a relatively simple improvement in some projects, but it should still be considered in context. The benefit depends on climate, roof construction, ceiling insulation, roof ventilation and the rest of the building fabric.
Roof colour is one example of a design decision that can be easy to resolve early but more difficult once materials and approvals are locked in.
Common misunderstanding
A low NatHERS result does not always mean the whole design is wrong.
Sometimes one or two pressure points are holding the rating back, and targeted changes can make the pathway clearer.
Improving floor construction and thermal mass
Floor construction can affect NatHERS through heat transfer, exposure and thermal mass. A slab on ground, suspended timber floor, exposed floor over air or floor over a garage can each behave differently.
In some homes, floor insulation may help. In others, the key issue may be how exposed concrete, thermal mass, solar access and shading work together. A concrete slab can support performance when it receives useful winter sun and is protected from unwanted summer heat.
For more detail, see our guides to floor construction and thermal performance and thermal mass and NatHERS performance.
Improving orientation and layout
Orientation and layout can strongly influence NatHERS outcomes. The direction of living areas, bedrooms, windows and outdoor shading elements affects how the home receives sun and heat throughout the year.
Where the design is still flexible, small orientation or layout adjustments may help improve comfort and reduce heating or cooling demand. Where the site is constrained, the improvement strategy may need to focus more on glazing, shading, insulation and material choices.
For more detail, see our guide to why house orientation matters for NatHERS.
Can a rating be improved after documentation is complete?
A NatHERS rating can sometimes be improved after documentation is complete, but the options may be more limited. Product upgrades may still be possible, such as improved glazing or insulation, but design based changes may be harder to make.
Late changes may also affect cost, documentation, builder pricing, client approvals or design intent. For example, reducing a window size or adding external shading late may require drawing updates and coordination with the façade design.
This is why early review is generally more efficient. It gives the project team more flexibility and reduces the chance of late compliance pressure.
How improvement connects to compliance
For many new homes, the NatHERS rating supports the residential energy compliance pathway. If the rating is below the required level, the design may need improvement before the assessment can be finalised.
This is especially relevant for projects targeting or required to achieve a 7 Star Rating. In NSW, improvements may also need to align with BASIX documentation where NatHERS supports the thermal performance pathway.
Where broader energy requirements apply, the project may also need to consider Whole of Home, which looks beyond the thermal star rating to the home’s fixed appliances and energy systems.
Design considerations for Australian homes
Improving NatHERS should be project specific. The right improvement for a coastal home may be different from the right improvement for an inland, alpine, tropical or hot dry climate.
Australian homes need to respond to climate, orientation, shading, material choices and everyday comfort. The most effective improvements are usually those that work with the home’s actual conditions rather than applying generic upgrades.
A good NatHERS improvement process should make the home more comfortable and compliant without unnecessarily complicating the design.
Working with Certified Energy
Certified Energy provides NatHERS assessments for new homes, townhouses and multi residential projects across Australia. Our team can model the design and help identify which parts of the home are most influencing the rating.
Where a design needs improvement, we can help project teams understand whether the rating is being affected by glazing, shading, insulation, roof colour, floor construction, thermal mass, orientation or local climate. 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.
FAQ
Can a NatHERS rating be improved during design?
Yes. A NatHERS rating can often be improved during design by adjusting glazing, shading, insulation, roof colour, floor construction, thermal mass, orientation or other building fabric details.
When is the best time to improve a NatHERS rating?
The best time to improve a NatHERS rating is before the design is fully locked in, when window placement, shading, insulation, roof form and construction details can still be adjusted.
Does improving NatHERS always mean expensive upgrades?
Not always. Some NatHERS improvements come from design coordination, such as better shading, window placement or roof colour, rather than expensive product upgrades.
What is the most common way to improve NatHERS?
There is no single most common improvement for every project. Glazing, shading, insulation, roof colour and floor construction can all matter depending on the design and climate.
Can NatHERS be improved after approval drawings are complete?
Sometimes, but the options may be more limited. Product upgrades may still help, but design changes can be harder once drawings, costing and approvals are advanced.
