Does Double Glazing Help You Achieve a 7 Star NatHERS Rating?

Double glazing is often one of the first upgrades considered when aiming to improve a home’s energy performance.

But while it can play an important role, it is not a guaranteed path to achieving a 7-star NatHERS rating.

Understanding where glazing fits within the overall design is key to making the right decision.

What is double glazing

Double glazing consists of two panes of glass separated by a sealed air or gas-filled gap.

This gap reduces heat transfer, improving insulation compared to single glazing.

In residential buildings, double glazing can help:

• Reduce heat loss in winter
• Limit heat gain in summer
• Improve indoor comfort
• Reduce external noise

How glazing affects your NatHERS rating

In a NatHERS assessment, windows are one of the most influential elements of the building envelope.

Glazing performance affects:

• Heat gain from the sun
• Heat loss through windows
• Overall thermal balance of the home

However, glazing is only one part of the equation.

The impact of double glazing depends heavily on:

• Orientation
• Window size and placement
• Shading design
• Overall building layout

When double glazing makes a difference

Double glazing is most effective when used strategically.

It can improve performance in situations where:

• Large window areas are required
• The building has exposure to extreme temperatures
• Heat loss needs to be reduced in cooler climates

In these cases, it can help achieve compliance more efficiently.

When it may not be necessary

In some designs, strong performance can be achieved without double glazing.

For example:

• Well-oriented homes with controlled window sizes
• Designs with effective shading
• Balanced glazing across different facades

In these situations, improving layout and orientation may deliver better results than upgrading glazing alone.

Design matters more than upgrades

A common misconception is that higher NatHERS ratings come from adding more features.

In reality, performance is driven primarily by design.

This means:

• Orientation often has a greater impact than glazing upgrades
• Shading can reduce the need for high-spec glass
• Layout decisions influence thermal performance significantly

Double glazing should be seen as a supporting element — not the primary solution.

Cost considerations

Double glazing typically increases upfront construction cost.

The value depends on:

• Climate zone
• Design approach
• Extent of glazing used

While it may reduce heating and cooling demand, it is important to assess whether it is the most efficient way to improve performance for your specific project.

A balanced approach

The most effective way to achieve a 7-star NatHERS rating is through a combination of:

• Good orientation
• Thoughtful window placement
• Appropriate shading
• Suitable construction materials

Glazing decisions should support this overall strategy.

Final note

Double glazing can contribute to achieving a 7-star rating — but it is rarely the defining factor.

When integrated into a well-considered design, it can improve comfort and performance.

On its own, it is not a substitute for good design.

If you need to understand how glazing fits within overall compliance:

→ 7 Star NatHERS Certificate — what you need to know