What Is SHGC in Windows and What Is the Best Rating for Australian Homes?

What is SHGC in windows? SHGC stands for Solar Heat Gain Coefficient. It measures how much solar energy passes through a window and enters a building as heat.

SHGC is expressed as a number between 0 and 1.

A lower SHGC allows less solar heat into the building, while a higher SHGC allows more solar heat gain.

For Australian homeowners, architects and builders, choosing the correct SHGC can significantly influence summer comfort, winter solar heating and overall building energy performance.

However, there is no single SHGC rating that is best for every Australian home.

The ideal value depends on the climate, window orientation, shading and building design.

What Does SHGC Mean in Windows?

SHGC stands for Solar Heat Gain Coefficient.

It describes the proportion of solar radiation that enters a building through a window.

Solar heat gain includes solar energy transmitted directly through the glass and heat absorbed by the window that subsequently flows inward.

For example, a window with an SHGC of 0.30 admits approximately 30% of the incident solar energy as heat under the relevant rating conditions.

This does not mean it admits only 30% of visible daylight.

Solar heat gain and visible light transmission are different measurements.

What Is a Good SHGC Rating for Windows?

A good SHGC depends on what the building needs.

The following values illustrate the difference between solar-control characteristics.

SHGC	General solar heat gain
0.20	Low solar heat gain
0.30	Relatively low solar heat gain
0.40	Moderate solar heat gain
0.50	Greater solar heat gain
0.60	High solar heat gain
0.70	Very high solar heat gain

These are illustrative descriptions, not official Australian SHGC rating bands or universal recommendations.

A lower SHGC is not automatically better for every window.

Is a Lower SHGC Better?

A lower SHGC is generally beneficial when the objective is to reduce unwanted solar heat entering a building.

This can be particularly relevant for windows exposed to strong summer sunlight.

However, reducing solar heat gain can also reduce useful winter solar heating.

In cooler climates, some windows may benefit from a higher SHGC when appropriately shaded.

The ideal balance depends on the building.

Is a Higher SHGC Better in Winter?

It can be.

A higher SHGC allows more solar heat to enter the building.

For appropriately positioned windows, this can contribute to passive solar heating during colder months.

However, the benefit depends on orientation, shading, glazing area and the building’s thermal design.

A higher SHGC is not automatically appropriate for every winter climate or window location.

What Is the Difference Between SHGC and U-Value?

SHGC and U-value measure different aspects of window performance.

SHGC measures solar heat gain.

U-value measures heat transfer caused by temperature differences.

A lower U-value generally indicates better insulation.

A lower SHGC generally indicates less solar heat entering the building.

Both values are important when selecting energy-efficient aluminium windows.

Which Is More Important: SHGC or U-Value?

Neither is universally more important.

For winter insulation, U-value is particularly relevant.

For controlling unwanted solar heating, SHGC is particularly relevant.

The best-performing window system balances both according to the building’s climate, orientation and design.

For Melbourne homes, this balance can be especially important because of seasonal temperature variations.

What Is the Best SHGC for Melbourne Homes?

There isn’t one universal SHGC for Melbourne.

Melbourne experiences cold winters and warm to hot summer conditions.

Some north-facing windows may benefit from useful winter solar gain.

Other windows, particularly those exposed to strong afternoon sun, may require greater solar control.

The appropriate SHGC should be determined through the building’s energy assessment and glazing strategy.

What Is the Best SHGC for North-Facing Windows?

In Melbourne and other parts of southern Australia, north-facing glazing can be useful for passive solar design.

Appropriately designed north-facing windows may allow winter sunlight to enter while external shading helps limit summer solar exposure.

A higher SHGC may be beneficial where useful winter solar gain is desired.

However, the final selection depends on the building’s energy assessment and shading design.

What Is the Best SHGC for West-Facing Windows?

West-facing windows can experience substantial afternoon solar exposure.

This can contribute to overheating during warmer months.

A lower SHGC may be beneficial for reducing unwanted solar heat gain.

Other strategies can include:

• External shading
• Architectural window shrouds
• Adjustable screens
• Appropriate glazing area
• Solar-control Low-E glass

The best result often comes from combining glazing and shading strategies.

What Is the Best SHGC for East-Facing Windows?

East-facing windows receive morning sunlight.

Depending on the climate and building design, morning solar gain may be useful or unwanted.

The appropriate SHGC depends on the room’s function, window size, shading and overall energy strategy.

What Is the Best SHGC for South-Facing Windows?

In Melbourne, south-facing windows generally receive less direct sunlight than north-facing windows.

Thermal insulation may therefore be an important consideration.

However, the appropriate SHGC still depends on the building design and local conditions.

The energy assessor should determine the required performance.

Does Double Glazing Reduce SHGC?

Double glazing can influence SHGC, but it doesn’t automatically produce a particular solar-control result.

The SHGC depends on the complete glass configuration.

Two double-glazed units may have significantly different SHGC values.

The glass type, coatings and other components all influence performance.

Does Low-E Glass Reduce SHGC?

Some Low-E coatings are specifically designed to reduce solar heat gain.

Other Low-E products are designed to retain useful solar heat while improving insulation.

This means not all Low-E glass has the same SHGC.

Always compare the actual product data rather than assuming every Low-E coating provides identical solar control.

What Is Solar-Control Glass?

Solar-control glass is designed to reduce unwanted solar energy entering a building.

It may incorporate specialised coatings, tints or other glass technologies.

The appropriate product depends on the building’s orientation and performance objectives.

Solar-control glass can be particularly useful for large windows exposed to strong sunlight.

Does Tinted Glass Have a Lower SHGC?

Tinted glass can reduce solar heat gain, depending on the product.

However, a darker tint doesn’t automatically mean the best thermal or solar performance.

Different tinted and coated glass products have different SHGC and visible light transmission values.

Always compare technical specifications.

What Is the Difference Between SHGC and Visible Light Transmission?

SHGC measures solar heat gain.

Visible Light Transmission (VLT) measures how much visible light passes through the glass.

These values are related but not interchangeable.

A glass product can reduce solar heat gain while still allowing substantial natural daylight into the building.

This can be particularly valuable for architectural homes with large windows.

Does Low SHGC Glass Make a Room Darker?

Not necessarily.

Some solar-control glass products can reduce heat gain while maintaining relatively high visible light transmission.

However, other products may reduce daylight more significantly.

The actual glass specification should be reviewed to understand the balance between solar control and natural light.

Can SHGC Affect Air Conditioning Costs?

Yes.

Unwanted solar heat entering through windows can increase cooling demand.

Selecting appropriate glazing and shading can help reduce this heat gain.

However, actual energy savings depend on the building’s insulation, air leakage, climate, glazing area and occupant behaviour.

A specific percentage saving should not be assumed without suitable modelling.

Does SHGC Affect Heating Costs?

Yes.

Solar heat entering a building can contribute to passive heating.

In some climates and orientations, useful winter solar gain may reduce heating demand.

However, excessive solar heat gain can increase cooling demand during warmer periods.

The ideal SHGC balances these competing effects.

What SHGC Is Required for a 7-Star NatHERS Home?

There is no single SHGC that every window must achieve for a home to receive a 7-star NatHERS rating.

NatHERS assesses the thermal performance of the complete home.

The required window specifications depend on factors including:

• Climate
• Orientation
• Window dimensions
• Glazing area
• Insulation
• External shading
• Building geometry

The project’s energy assessment should identify suitable window performance requirements.

Do Aluminium Window Frames Affect SHGC?

Yes.

Whole-window SHGC includes the influence of the complete window system, not just the glass.

Frame proportions, glazing area and frame characteristics can influence the overall result.

When comparing products, request the whole-window SHGC rather than relying solely on glass-only values.

Do Thermally Broken Aluminium Windows Have Better SHGC?

A thermal break primarily reduces heat transfer through the aluminium frame.

It does not automatically produce a lower or higher SHGC.

The solar performance of a thermally broken window still depends heavily on the glazing and complete system design.

For higher-performance projects, both whole-window U-value and SHGC should be assessed.

Can Window Shrouds Reduce Solar Heat Gain?

Yes, when correctly designed.

Architectural aluminium window shrouds can reduce direct solar radiation reaching the glass.

Their effectiveness depends on:

• Shroud depth
• Window dimensions
• Building orientation
• Sun angle
• Shading geometry

However, a window shroud does not change the intrinsic SHGC rating of the window itself.

Instead, it reduces the solar exposure reaching the window under certain conditions.

Are Aluminium Window Shrouds Good for West-Facing Windows?

They can contribute to shading, but the design matters.

West-facing sunlight often arrives at relatively low afternoon angles.

A simple horizontal hood may not provide sufficient shading on its own.

Depending on the project, vertical fins, deeper surrounds or adjustable shading may be more appropriate.

The shading strategy should be evaluated as part of the building design.

Can External Screens Improve Solar Control?

Yes.

External shading screens can reduce direct sunlight reaching glazing.

Depending on their design, screens may help manage heat gain, glare and privacy.

The actual benefit depends on material, openness, position and orientation.

External shading should be coordinated with the window and glazing specification.

Is SHGC Important for Large Sliding Doors?

Yes.

Large sliding doors often contain substantial glazing areas.

This can make solar heat gain an important design consideration.

For large glazed openings, the specification should consider:

• Whole-door SHGC
• U-value
• Glass type
• Orientation
• External shading
• Aluminium framing

The complete door system should be assessed.

Is SHGC Important for Bifold Doors?

Yes.

Bifold doors can create large glazed openings.

Depending on their orientation, solar heat gain can influence indoor comfort.

The appropriate glass specification should balance thermal insulation, solar control, safety and hardware requirements.

Can Two Windows With the Same U-Value Have Different SHGC Ratings?

Yes.

Two windows may provide similar insulation while allowing different amounts of solar heat into the building.

This is why comparing U-value alone is insufficient.

Both U-value and SHGC should be reviewed when selecting energy-efficient aluminium windows.

What Is WERS and How Does It Relate to SHGC?

WERS stands for the Window Energy Rating Scheme.

It provides information about the energy performance of window systems.

Relevant technical data can include whole-window U-values and SHGC values.

WERS information can help compare different aluminium window products.

However, a WERS window rating should not be confused with a NatHERS whole-home rating.

How Do You Find the SHGC of Aluminium Windows?

For new windows, request the technical performance data from the supplier.

This should identify the relevant window system and glazing configuration.

For existing windows, the original manufacturer or product documentation may provide the information.

If the exact product cannot be identified, its precise SHGC may be difficult to establish.

Can You Change the SHGC of Existing Windows?

Sometimes.

Replacing the glass with a compatible solar-control product may change the window’s solar performance.

However, existing frames may limit the glazing options available.

External shading can also help reduce solar heat gain without changing the intrinsic SHGC of the window.

The most appropriate approach depends on the existing building.

How Much Does Low SHGC Glass Cost?

There isn’t one standard price.

Costs depend on:

• Glass type
• Coatings
• Window size
• Double-glazed configuration
• Aluminium system
• Quantity
• Installation

Solar-control glass may cost more than basic clear glass, but the price difference varies between products.

Is Low SHGC Glass Worth the Extra Cost?

It can be when unwanted solar heat gain is a significant concern.

This may be particularly relevant for large windows exposed to strong sunlight.

However, lower SHGC glass isn’t automatically the best investment for every window.

The decision should consider comfort, daylight, winter solar gain and overall energy performance.

What SHGC Should Builders Specify?

Builders should refer to the project’s energy assessment and approved window schedule.

Important information includes:

1. Required whole-window SHGC
2. Required whole-window U-value
3. Window dimensions
4. Window configurations
5. Glazing specifications
6. Orientation
7. Relevant shading requirements

The final product should be checked against the approved specification before ordering.

What SHGC Should Architects Specify?

Architects should coordinate glazing performance with the building’s energy assessor.

Rather than simply requesting “solar-control glass,” the specification should identify the required performance characteristics.

This allows window suppliers to propose appropriate products and enables more meaningful quotation comparisons.

How Do You Compare Aluminium Window SHGC Ratings?

When comparing quotations, check:

• Aluminium window system
• Whole-window SHGC
• Whole-window U-value
• Glass specification
• Low-E coating
• Window configuration
• Dimensions
• Relevant performance documentation

Two windows that appear identical can have different solar and thermal characteristics.

Energy-Efficient Aluminium Windows from EZ Windows

EZ Windows provides aluminium window and door solutions for builders, architects, developers and homeowners across Melbourne and Victoria.

Depending on the project requirements and selected supplier systems, options can include:

• Fixed aluminium windows
• Awning aluminium windows
• Sliding aluminium windows
• Double glazing
• Low-E glazing
• Solar-control glass
• Thermally broken aluminium systems
• Sliding doors
• Stacking doors
• Bifold doors
• Architectural aluminium window systems

Builders and architects can provide architectural plans, window schedules and energy-assessment requirements so suitable window systems can be assessed.

Where specific U-values and SHGC values are required, the proposed products should be checked against those specifications.

The project’s designer, energy assessor and relevant building professionals remain responsible for confirming building compliance.

So, What Is the Best SHGC for Australian Windows?

There is no single SHGC that is best for every Australian home.

A lower SHGC reduces solar heat gain.

A higher SHGC allows more solar heat into the building.

For Melbourne homes, the ideal specification depends on the orientation and design of each window.

The best approach is to consider:

SHGC + U-value + glazing + aluminium frame + orientation + external shading.

For new homes, use the project’s energy assessment to determine the required performance.

For renovations, consider the balance between summer heat control, winter comfort, daylight and cost.

The best glass isn’t simply the glass that blocks the most heat. It’s the glass that delivers the right performance for the building.

Architectural precision, designed to perform.

Do It Easy @ EZ Windows.