NatHERS Design Factors
Shading and Solar Heat Gain Explained
Shading is one of the most important ways to manage solar heat gain. In NatHERS, it can influence how much heating and cooling a home is predicted to need across the year.
Shading and solar heat gain in brief
Solar heat gain is heat from the sun entering a home, usually through windows and glazed doors. Shading helps control when that heat is welcome and when it should be blocked. Good shading can reduce cooling demand, improve summer comfort and support a stronger NatHERS outcome, especially when it is matched to orientation, glazing and local climate.
What solar heat gain means in practice
Solar heat gain occurs when sunlight enters the home and becomes heat. This most often happens through windows, glazed doors and other transparent parts of the building envelope.
Solar heat gain is not always bad. In cooler weather, winter sun can help warm living areas and reduce heating demand. In hot weather, the same solar exposure can create overheating and increase cooling demand.
The design challenge is to allow useful sun when the home needs warmth and block unwanted sun when the home is already warm. This is where shading becomes central to thermal performance.
How shading affects NatHERS ratings
A NatHERS assessment estimates how much heating and cooling a home may need to remain comfortable in its local climate. Shading can affect that result because it changes how much solar heat reaches the glazing and enters the home.
If windows receive too much unshaded sun during hot periods, the home may need more cooling. If useful winter sun is blocked in a cooler climate, the home may need more heating. NatHERS modelling helps test that balance for the specific design.
This is why shading is not just an architectural detail. It can be a performance feature that affects the thermal star rating, especially where a home has large glazing areas or challenging orientations.
The practical point
Good shading is not about blocking all sun all year.
It is about controlling solar heat gain so the home receives warmth when useful and avoids overheating when conditions are already hot.
External shading vs internal blinds
External shading is usually more effective for reducing unwanted solar heat gain because it can stop sunlight before it reaches the glass. This can include eaves, awnings, balconies, pergolas, external screens, shutters and landscape shading.
Internal blinds, curtains and shutters can help with glare, privacy and some radiant comfort, but the heat has often already entered the home once sunlight has passed through the glass. They can still be useful, but they are not always a substitute for well designed external shading.
For NatHERS and practical comfort, the strongest approach often comes from combining the right glazing with external shading that suits each orientation.
Common shading elements
• Eaves and roof overhangs
• Awnings and hoods
• Balconies and upper level projections
• External screens, shutters and operable shading
• Pergolas and covered outdoor spaces
• Neighbouring buildings, fences, trees and landscape features where relevant
Why orientation changes the shading strategy
Shading needs to respond to orientation because sun angles change throughout the day. A shading element that works well on one façade may be less effective on another.
In many Australian climates, north facing windows can often be shaded effectively with horizontal overhangs because the summer sun is higher in the sky. East and west facing windows can be harder to shade because low angle morning and afternoon sun can enter beneath simple horizontal shading.
This is why house orientation and shading should be considered together. The right shading strategy depends on where the window faces, when it receives sun and how the room is used.
Shading and window performance
Shading and glazing work together. A high performance window can still create overheating if it is large, poorly oriented and unshaded. A more modest glazing specification may perform well when the window is correctly sized, placed and shaded.
Solar heat gain through windows is influenced by glass type, frame system, window size, orientation and shading. The best choice depends on whether the design needs to capture heat, reject heat or balance both across the year.
For more detail, see our guide to how window design affects NatHERS ratings.
Common shading mistakes
• Relying on internal blinds instead of external solar control
• Using the same shading detail on every façade
• Leaving west facing glazing exposed to afternoon sun
• Blocking useful winter sun in cooler climates
• Adding shading late without checking how it affects the NatHERS model
Shading and thermal mass
Shading is especially important when the home uses thermal mass. Exposed concrete floors, masonry walls or other dense internal surfaces can store solar heat. This can be helpful in winter when the heat is useful, but problematic in summer if too much sun is allowed in.
A good passive design strategy uses shading to manage when solar heat reaches thermal mass. This helps the home benefit from stored warmth when needed while reducing the risk of overheating during hotter periods.
For more detail, see our guide to thermal mass and NatHERS performance.
How shading connects to compliance
For many new residential projects, shading can affect whether the home reaches the required NatHERS star rating. This is especially relevant where the design includes large glazing areas, exposed façades or windows facing difficult orientations.
Projects targeting or required to achieve a 7 Star Rating may need shading to be resolved carefully. In NSW, shading related thermal performance may also need to align with BASIX commitments where NatHERS modelling supports the thermal pathway.
If shading is changed after assessment, the rating may need to be reviewed. Removing an eave, altering a balcony, changing an awning or adjusting a window can all affect the modelled result.
Shading details that are useful for assessment
• Eave depths and overhang dimensions
• Awning, hood and balcony projections
• External screen locations and operation where relevant
• Window sizes and sill or head heights
• Nearby overshadowing from walls, buildings or other structures
• Orientation and room layout information
Design considerations for Australian homes
Australian homes often need to balance useful sun with strong solar protection. In cooler climates, blocking too much winter sun may increase heating demand. In warmer climates, insufficient shading can increase cooling demand and reduce comfort.
The right shading strategy depends on the NatHERS climate zone, window orientation, room use, glazing type and surrounding site conditions. A simple one size fits all approach rarely gives the best result.
Shading is easiest to resolve early. Once roof forms, façades and window positions are locked in, shading changes can become more difficult to integrate without affecting architecture, cost or documentation.
Working with Certified Energy
Certified Energy provides NatHERS assessments for new homes, townhouses and multi residential projects across Australia. Our team can model the proposed design and help identify how shading and solar heat gain are influencing the rating.
Where needed, we can help project teams understand how the rating is affected by window orientation, glazing, eaves, awnings, balconies, external shading, insulation, roof colour and local climate. We can also help connect the assessment with related requirements such as NatHERS, BASIX, 7 Star Rating and Whole of Home.
For a broader explanation of the rating framework, visit our NatHERS Knowledge Hub.
FAQ
Does shading affect a NatHERS rating?
Yes. Shading can affect a NatHERS rating because it influences how much solar heat enters the home through windows and other exposed areas.
What is solar heat gain?
Solar heat gain is heat from the sun entering a home, usually through glazing. It can be useful in cooler weather but may increase cooling demand in warmer conditions.
Is external shading better than internal blinds?
External shading is often more effective for reducing unwanted solar heat gain because it can block sun before it reaches the glass. Internal blinds can help with glare and privacy, but usually do not stop heat entering as effectively.
Do all windows need the same shading?
No. Shading should respond to orientation, sun angle, climate and room use. North, east, west and south facing windows may need different shading strategies.
When should shading be considered?
Shading should be considered early, alongside orientation and window design. It can be harder to add effective shading after roof forms, façades and window positions are locked in.
