Low SHGC vs High SHGC Windows – Which Is Better for Melbourne Homes?

Low SHGC vs high SHGC windows: which is better for Melbourne homes? The answer depends on the direction your windows face, the amount of sunlight they receive and whether your priority is reducing summer heat or capturing useful winter warmth.

Low SHGC windows reduce the amount of solar heat entering a building. High SHGC windows allow more solar heat inside.

In Melbourne’s climate, both can be useful.

For example, a north-facing living room may benefit from winter solar gain, while a west-facing bedroom may need protection from intense afternoon sunlight.

Choosing the correct Solar Heat Gain Coefficient (SHGC) can improve comfort and contribute to the overall energy performance of your home.

This guide explains the differences, how to compare glazing products and what to consider when selecting aluminium windows and doors.

What Is SHGC in Windows?

SHGC stands for Solar Heat Gain Coefficient.

It measures the proportion of incident solar energy that enters a building through a window as heat.

SHGC is expressed as a number between 0 and 1.

For example:

• SHGC 0.25 allows approximately 25% of incident solar energy to enter as heat.
• SHGC 0.40 allows approximately 40%.
• SHGC 0.60 allows approximately 60%.

These figures describe performance under standard rating conditions. Actual solar heat entering a room also depends on sunlight intensity, window area, orientation and shading.

What Is a Low SHGC Window?

A low SHGC window is designed to limit solar heat gain.

It can be particularly useful for windows exposed to strong summer sunlight.

Low SHGC glazing may incorporate:

• Solar-control Low-E coatings
• Spectrally selective coatings
• Tinted glass
• Other specialised glazing technologies

The objective is to reduce unwanted solar heating without unnecessarily sacrificing natural light.

What Is a High SHGC Window?

A high SHGC window allows a greater proportion of solar energy into the building.

This can be beneficial where passive winter solar heating is desirable.

For example, north-facing windows in Melbourne may be designed to admit winter sunlight while appropriately sized external shading reduces direct summer sun.

High SHGC glazing is not automatically less energy efficient.

Its suitability depends on how the building uses solar energy.

Low SHGC vs High SHGC Windows – Key Differences

Feature	Low SHGC	High SHGC
Solar heat entering the home	Less	More
Summer heat control	Generally better	Generally less
Passive winter solar gain	Lower	Higher
West-facing glazing	Often beneficial	May increase overheating
North-facing glazing	Depends on design	Can support passive heating
Daylight	Depends on glass product	Depends on glass product
Best application	Managing unwanted solar gain	Capturing useful solar gain

The best choice is not always the lowest SHGC. It is the SHGC that suits the building’s orientation and thermal design.

What SHGC Is Considered Low or High?

The following values provide a general comparison.

SHGC	Indicative solar gain
0.20	Very low
0.30	Low
0.40	Moderate
0.50	Moderate to high
0.60	High
0.70	Very high

These descriptions are illustrative only. They are not official Australian performance classifications or mandatory design recommendations.

The correct value should be determined for the individual project.

Is Low SHGC Better for Melbourne’s Climate?

Low SHGC glazing can be beneficial in Melbourne, particularly where windows receive unwanted summer sunlight.

However, Melbourne also experiences cold winters.

A home designed to take advantage of passive solar heating may benefit from higher SHGC glazing in selected locations.

This is why choosing one SHGC for every window isn’t necessarily the most effective approach.

Is High SHGC Better for Melbourne Winters?

It can be.

Higher SHGC glazing allows more solar energy into a room when direct sunlight reaches the window.

This may help warm living spaces during winter.

However, the window must receive useful sunlight, and the building should be designed to manage summer heat.

The benefit also depends on insulation, thermal mass and the window’s U-value.

What Is the Best SHGC for North-Facing Windows in Melbourne?

North-facing windows are often important in passive solar design in southern Australia.

They can receive useful winter sunlight when positioned appropriately.

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

External shading can help control summer sunlight.

However, there is no universal SHGC requirement for north-facing windows.

The appropriate glazing depends on the home’s energy assessment, window size and shading geometry.

What Is the Best SHGC for West-Facing Windows?

West-facing windows can experience strong afternoon sunlight.

During summer, this can increase indoor temperatures and cooling demand.

Lower SHGC glazing may help reduce unwanted solar heat gain.

Additional strategies include:

• External vertical fins
• Architectural window shrouds
• Adjustable shading screens
• External blinds
• Appropriate window sizing

West-facing glazing should be assessed carefully because afternoon sunlight often enters at relatively low angles.

What Is the Best SHGC for East-Facing Windows?

East-facing windows receive morning sunlight.

Depending on the building, this may provide useful warmth or contribute to unwanted heat gain.

A lower SHGC may be appropriate where morning overheating is a concern.

However, the ideal value depends on the room’s use, glazing area and shading.

What Is the Best SHGC for South-Facing Windows?

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

Their performance may therefore be influenced more strongly by thermal insulation and daylight requirements.

However, summer solar exposure and surrounding reflections can still matter.

The correct SHGC should be selected as part of the overall glazing design.

Can You Use Different SHGC Glass on Different Sides of a House?

Yes.

Using different glazing specifications on different elevations can be an effective strategy.

For example, a project may use glazing that admits useful winter solar gain on one elevation and stronger solar-control glazing on another.

This approach should be coordinated with the energy assessor and window supplier.

It may improve the balance between winter comfort, summer comfort and cost.

Is Low SHGC Glass the Same as Low-E Glass?

Not exactly.

Low-E glass incorporates a coating designed to influence radiant heat transfer.

Different Low-E coatings have different properties.

Some are designed primarily to improve insulation while retaining relatively high solar heat gain.

Others provide stronger solar control.

Therefore, Low-E glass does not automatically mean low SHGC glass.

Always check the actual glazing specification.

Can Double Glazing Have High SHGC?

Yes.

Double-glazed windows can be manufactured with different solar heat gain characteristics.

A double-glazed unit designed to admit useful winter sunlight may have a relatively high SHGC.

Another double-glazed unit may use solar-control coatings to achieve a much lower SHGC.

Double glazing alone doesn’t determine the solar performance.

Can Double Glazing Have Low SHGC?

Yes.

Low SHGC double glazing can be useful for reducing solar heat entering through large windows and doors.

The exact performance depends on the glass configuration and coatings.

For Melbourne homes, the appropriate glazing should be selected according to orientation and the building’s energy assessment.

Does Low SHGC Glass Make Your Home Darker?

Not necessarily.

SHGC measures solar heat gain, while Visible Light Transmission (VLT) measures how much visible light passes through the glass.

Some advanced solar-control glazing products can reduce heat gain while retaining relatively high daylight transmission.

Other products may noticeably reduce natural light.

Compare both SHGC and VLT when selecting glazing.

What Is the Difference Between SHGC and U-Value?

SHGC and U-value describe 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 thermal insulation.

A lower SHGC generally means less solar heat enters the building.

For Melbourne homes, both values are important.

A window can have a low U-value and a relatively high SHGC, or a low U-value and a low SHGC.

Should You Choose Low U-Value and Low SHGC Windows?

Sometimes, but not universally.

A combination of low U-value and low SHGC can be useful where both strong insulation and reduced solar heat gain are priorities.

However, a window intended to capture winter sunlight may benefit from a different SHGC.

The best combination depends on the building’s design and energy requirements.

Do Thermally Broken Aluminium Windows Have Lower SHGC?

Not automatically.

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

SHGC is influenced by the glazing and the complete window system.

Thermally broken aluminium windows can be configured with different glazing products to achieve different solar heat gain characteristics.

Do Aluminium Frames Affect SHGC?

Yes.

Whole-window SHGC includes the influence of the frame and glazing together.

Frame proportions can affect the amount of glass exposed to sunlight.

Therefore, the whole-window SHGC may differ from the glass-only SHGC.

For accurate comparisons, request the performance values of the complete window system.

Are Low SHGC Windows Better for Large Sliding Doors?

They can be, especially where large glazed doors are exposed to strong sunlight.

Large sliding doors can admit substantial solar heat because of their glazing area.

Low SHGC glass may help reduce overheating.

However, north-facing sliding doors with effective summer shading may benefit from a different specification.

The correct choice depends on the project.

What SHGC Is Best for Floor-to-Ceiling Windows?

There is no universal value.

Floor-to-ceiling windows can have a significant influence on solar heat gain.

For these applications, consider:

• Window orientation
• Glazing area
• SHGC
• U-value
• External shading
• Room use
• Building energy assessment

The larger the glazing area, the more important coordinated window selection can become.

Do Window Shrouds Reduce the Need for Low SHGC Glass?

They may reduce unwanted solar exposure, depending on their design.

Architectural aluminium window shrouds can shade the glass and limit direct sunlight entering the building.

However, the effectiveness depends on orientation, depth and geometry.

A window shroud does not change the intrinsic SHGC of the glazing.

Instead, it changes the amount of sunlight reaching the window.

The energy assessor should determine whether external shading allows a different glazing specification.

Are Window Shrouds Better Than Solar-Control Glass?

They perform different functions.

Solar-control glass reduces the proportion of incident solar energy entering the building.

Window shrouds reduce the solar radiation reaching the glass when they provide shade.

In some applications, combining appropriately designed external shading with suitable glazing can be effective.

The best approach depends on the architectural design and solar exposure.

Can Aluminium Privacy Screens Reduce Solar Heat Gain?

Yes, when designed to provide effective shading.

Architectural aluminium privacy screens and battens may reduce direct sunlight reaching windows.

However, their performance depends on:

• Batten spacing
• Screen orientation
• Screen depth
• Distance from glazing
• Sun angle

Privacy screens should not automatically be assumed to provide a specific energy-performance benefit.

Can Low SHGC Glass Reduce Air Conditioning Costs?

It can contribute to lower cooling demand by reducing unwanted solar heat gain.

However, actual savings depend on:

• Climate
• Window orientation
• Glazing area
• Insulation
• Air leakage
• Shading
• Occupant behaviour

Specific energy savings should be established through suitable modelling rather than assumed.

Can High SHGC Glass Reduce Winter Heating Costs?

Potentially.

High SHGC glazing can admit useful solar energy during winter when sunlight reaches the window.

This may contribute to passive heating.

However, the overall result also depends on window insulation, building design and heating patterns.

High SHGC glazing isn’t automatically the best choice for every cold-weather application.

Does SHGC Affect a 7-Star NatHERS Rating?

Yes.

NatHERS considers the influence of window solar heat gain as part of the home’s overall thermal performance.

The required SHGC depends on the building’s orientation, climate, glazing area and other design characteristics.

There is no single SHGC value that guarantees a 7-star rating.

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

Is Low SHGC Glass Required Under NCC 2022?

Not universally.

NCC 2022 introduced strengthened residential energy-efficiency requirements, but it does not prescribe one low SHGC value for every residential window.

The required performance depends on the applicable compliance pathway and building design.

The designer, energy assessor or relevant building professional should confirm the project requirements.

How Do You Find the SHGC of Aluminium Windows?

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

Confirm:

1. Window system
2. Glass specification
3. Whole-window SHGC
4. Whole-window U-value
5. Window configuration
6. Relevant performance documentation

Avoid relying solely on generic descriptions such as “solar-control glass” or “energy-efficient double glazing.”

Can You Change the SHGC of Existing Aluminium Windows?

Sometimes.

Replacing existing glass with compatible solar-control glazing may change the solar performance of the window.

However, the existing aluminium frame must be assessed for compatibility.

External shading may also reduce unwanted solar gain without replacing the complete window.

The most appropriate option depends on the existing window system and building.

Is Low SHGC Glass More Expensive?

It can be.

Specialised solar-control coatings or glazing products may cost more than basic clear glass.

However, the price difference varies between products.

The overall cost also depends on window size, glass configuration and aluminium system.

A quotation should be based on the required performance rather than the assumption that lower SHGC always means a better product.

What Should Builders Look for When Comparing SHGC Window Quotes?

Builders should compare quotations against the project’s approved energy assessment.

Important details include:

• Whole-window SHGC
• Whole-window U-value
• Glazing specification
• Aluminium system
• Window configuration
• Dimensions
• Relevant performance documentation

Two aluminium window systems may look similar while having different solar and thermal characteristics.

What Should Architects Specify for SHGC?

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

Where required, the specification should identify whole-window SHGC and U-value.

Different elevations may require different glazing characteristics.

Clear specifications help window suppliers provide accurate quotations and reduce the risk of unsuitable substitutions.

Low and High SHGC Aluminium Windows from EZ Windows

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

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

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

Builders and architects can provide window schedules and energy-assessment requirements for quotation.

Where specific SHGC and U-value requirements apply, the proposed window systems should be assessed against those specifications.

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

So, Which Is Better for Melbourne Homes: Low SHGC or High SHGC?

Neither is universally better.

Low SHGC windows are useful for reducing unwanted solar heat gain.

High SHGC windows can be beneficial where useful winter solar heating is desired.

For Melbourne homes, the best approach is to assess each window according to:

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

North-facing windows may benefit from one solar-performance strategy, while west-facing windows may require another.

For new homes, follow the project’s energy assessment.

For renovations, consider summer comfort, winter heating, daylight and the cost of different glazing options.

The best window isn’t necessarily the one with the lowest SHGC. It’s the one with the right solar performance for its location.

Architectural precision, designed to perform.

Do It Easy @ EZ Windows.