Window Energy Rating Scheme (WERS) Explained: How Australian Window Energy Labels Work and What They Mean for Your Project

Windows are the weakest thermal link in most Australian buildings. A typical wall might achieve an R-value of 2.5 to 4.0, while a single-glazed aluminium window can perform at the equivalent of R-0.15 to R-0.3. This means a window can lose or gain heat up to twenty times faster than the wall surrounding it. For anyone building or renovating in Australia, understanding how window energy performance is measured, labelled and compared is essential. The Window Energy Rating Scheme, commonly known as WERS, is the industry framework that makes this comparison possible.

MEICHEN Windows & Doors supplies AS2047-certified aluminium window and door systems for Australian residential and commercial projects, and provides the U-value, solar heat gain coefficient (SHGC) and air infiltration data that specifiers need to satisfy WERS, NatHERS, BASIX and NCC Section J requirements. This article explains how WERS works, how to read a window energy label, and how to use rating data to select the right window system for your climate zone.

What Is WERS and Who Runs It?

WERS is administered by the Australian Glass and Window Association (AGWA). It is a certification and labelling scheme that allows window manufacturers to publish independently verified energy performance data for their products in a standardised format. The scheme has operated in various forms since the 1990s and is widely referenced by building designers, energy assessors and building surveyors.

The core principle of WERS is simple: every rated window is tested or simulated using the same assumptions, so its performance can be compared directly with any other rated window. This removes the guesswork and marketing ambiguity from window selection. A product claiming “excellent thermal performance” means nothing without a U-value and SHGC figure calculated under a common method.

WERS ratings are based on computer simulation using the Australian Fenestration Rating Protocol (AFRP), which aligns with the international ISO 15099 standard for calculating the thermal and optical properties of fenestration. Simulation results are validated against physical testing, and participating manufacturers must have their products rated by AFRC-accredited simulation laboratories. The Australian Fenestration Rating Council (AFRC) oversees the technical protocol, mirroring the structure of the National Fenestration Rating Council (NFRC) in the United States.

It is important to understand that WERS is not a mandatory government scheme. The National Construction Code does not require a WERS label on windows. However, because NatHERS energy modelling and NCC Section J compliance both rely on the same U-value and SHGC inputs, WERS data has become the de facto currency for demonstrating window performance in Australian approvals.

The Two Numbers That Matter: U-Value and SHGC

Every window energy rating rests on two primary metrics, and understanding both is essential to reading any WERS label or datasheet.

U-value (Uw) measures heat transfer through the whole window. It is expressed in watts per square metre per kelvin (W/m²K). A lower U-value means better insulation: less heat escapes in winter and less heat enters in summer. The “w” subscript indicates the rating covers the whole window assembly, including frame, glass, spacer and seals, not just the centre-of-glass value. This distinction matters because aluminium frames without thermal breaks can add 0.5 to 1.5 W/m²K to the glass-only performance.

Typical Australian values range from around 6.0 W/m²K for a basic single-glazed aluminium window to below 1.5 W/m²K for a thermally broken frame with high-performance double or triple glazing. MEICHEN thermally broken systems achieve whole-window U-values below 1.6 W/m²K with appropriate glass make-ups, placing them among the better-performing aluminium products available to Australian specifiers.

Solar Heat Gain Coefficient (SHGC) measures how much solar radiation passes through the window. It is expressed as a number between 0 and 1. An SHGC of 0.3 means 30 percent of incoming solar heat passes through the window, either directly transmitted or absorbed and re-radiated inward. The right SHGC depends on climate and orientation, and this is where window selection becomes genuinely climate-specific:

• In cooling-dominated climates such as Darwin, Cairns and coastal Queensland, a low SHGC (below 0.3) blocks solar heat and reduces air-conditioning load.
• In heating-dominated climates such as Canberra, the southern tablelands and alpine Victoria, a higher SHGC (0.45 to 0.65) captures free winter solar gain.
• In temperate climates such as Sydney, Adelaide and Melbourne, the answer varies by facade: higher SHGC on north-facing glass, lower SHGC on east and west elevations.

Choosing the same glass for every facade is one of the most common and costly mistakes in window specification. A low-E coating tuned for a north-facing window in Melbourne may be exactly wrong for a west-facing window in Perth.

Reading a WERS Label and Datasheet

A WERS-compliant product listing or label presents performance data in a standard structure. The key fields to look for are:

• U-value (Uw) in W/m²K for the whole window, in both heating and cooling conditions where reported
• SHGC for the whole window, again differentiated by condition
• Air infiltration rating, expressed in litres per second per square metre (L/s·m²) at a standard pressure difference
• Visible light transmittance (VLT), showing how much daylight passes through the glass
• Frame and glass description, so the rating can be matched to the actual product being quoted

Star ratings are also used in some WERS presentations, with heating and cooling star bands running from one to ten stars. More stars mean better performance in that condition. Because a window can perform differently for heating and cooling, the two star ratings should be read separately. A window with ten heating stars may have only modest cooling performance if its SHGC is high.

A critical point for buyers: ratings apply to specific combinations of frame, glass and size. Changing the glass, the frame finish or the dimensions changes the performance. When comparing quotations, insist that each supplier provides the U-value and SHGC for the exact window configuration offered, calculated for the whole window, not a generic glass catalogue figure.

How WERS Connects to NatHERS, BASIX and the NCC

WERS does not exist in isolation. It feeds directly into the compliance pathways that every Australian building must navigate.

NatHERS (Nationwide House Energy Rating Scheme) rates the thermal performance of residential buildings on a star scale from zero to ten. Accredited software such as AccuRate, BERS and FirstRate5 models the whole building, and the windows are among the most influential inputs. Assessors enter the U-value and SHGC of each window; if actual product data is unavailable, the software defaults to conservative assumptions that usually drag the score down. Supplying real WERS-based data to the assessor can lift a star rating by one or two points, which is often the difference between passing and failing.

BASIX (Building Sustainability Index) applies to new residential development in New South Wales. It sets mandatory thermal comfort and water and energy targets. Like NatHERS, the thermal comfort section is sensitive to window performance, and BASIX reports list the required U-value and SHGC for each orientation.

NCC Section J governs commercial buildings and uses the glazing calculator, which compares the actual U-value and SHGC of the proposed glazing against maximum allowable values based on climate zone, facade orientation and window-to-wall ratio. Under the 2022 and later editions of the NCC, Section J has become markedly stricter, effectively requiring double glazing on most new commercial work and pushing residential volumes towards thermally improved frames.

The practical consequence for builders and developers is that window energy data is no longer optional paperwork. It is compliance evidence, and suppliers who cannot produce credible, whole-window, climate-appropriate ratings create risk for the project.

U-Value and SHGC Benchmarks by Climate Zone

Australia spans eight NCC climate zones, and sensible window targets differ substantially across them. The table below provides indicative whole-window targets used by energy assessors and specifiers. These are guidance values rather than legal limits; the actual requirement depends on the building’s design, orientation and window-to-wall ratio.

These figures show why a one-size-fits-all “double glazing” claim is inadequate. Double glazing with the wrong coating can still fail a Section J calculation in Zone 1, while single glazing in a warm zone may technically pass yet deliver uncomfortable summer temperatures. Specifying by climate zone, orientation and performance data is the only reliable approach.

How Frame Design Changes the Rating

Many buyers assume the glass does all the thermal work. In reality, the frame can account for 20 to 40 percent of the window area, and aluminium conducts heat roughly 1,700 times faster than air. Frame design therefore has an outsized effect on whole-window performance.

The main frame categories and their typical impact are:

• Standard (non-thermally-broken) aluminium. Conductive bridges run from outer to inner surface. Whole-window U-values typically 0.4 to 1.0 W/m²K worse than the glass alone.
• Thermally improved aluminium. A partial polyamide or poured-in-place break reduces conduction but does not eliminate it. Suitable for warm zones and moderate performance targets.
• Fully thermally broken aluminium. A continuous polyamide (PA66) strut of 20 to 34 mm separates the outer and inner frame. Enables whole-window U-values below 1.6 W/m²K with quality double glazing, and below 1.2 W/m²K with triple glazing.
• Composite and timber-aluminium systems. Lower frame conductivity but higher cost and different maintenance profiles.

Spacer technology inside the insulating glass unit matters as well. Conventional aluminium spacers create a thermal bridge around the glass perimeter; warm-edge spacers in stainless steel or polymer composite can improve the U-value by 0.05 to 0.15 W/m²K and reduce perimeter condensation risk.

MEICHEN systems use PA66 thermal breaks of up to 34 mm in the high-performance ranges, warm-edge spacers, and low-E coated double glazing with argon fill as standard options. When the project requires documentation, MEICHEN provides the U-value, SHGC and air infiltration data for the specified configuration so assessors and building surveyors can complete NatHERS, BASIX or Section J calculations without assumptions.

Air Infiltration: The Overlooked Third Metric

U-value and SHGC describe heat crossing the window materials, but air leakage bypasses them entirely. A poorly sealed window with a good U-value can still bleed conditioned air through gaps between sash and frame, causing draughts, dust and energy losses that no glazing upgrade can fix.

AS 2047 sets air infiltration test requirements for windows, and WERS datasheets report infiltration in L/s·m². High-performance systems achieve values below 1.0 L/s·m² at the standard test pressure, while cheap sliding windows can exceed 4.0 L/s·m². The difference is felt directly: fewer draughts in winter, less dust ingress in dry summers, and better acoustic performance because air paths are also noise paths.

Design details that drive air tightness include twin compression seals at meeting stiles, continuous perimeter gaskets, multi-point locking that pulls the sash evenly against the seals, and factory-assembled corner joints that stay airtight over years of movement. Casement, awning and tilt-and-turn windows are inherently more airtight than sliders because compression seals work better than brush seals. When maximum air tightness is the goal, hardware selection is as important as glass selection.

Practical Steps for Specifiers and Homeowners

Using WERS data effectively comes down to disciplined comparison. The following process works for projects of any size:

• Start from the energy assessment. Obtain the NatHERS or BASIX report, or the Section J glazing calculation, and extract the required U-value and SHGC per window orientation before approaching suppliers.
• Request whole-window data. Ask each supplier for Uw and SHGC for the exact frame and glass combination quoted, in writing. Reject centre-of-glass figures and vague performance claims.
• Check the size basis. Ratings shift with window dimensions. For large slider stacks and doors, ask for the rating of a representative panel size, not a small casement.
• Match frames to climate. In Zones 6 to 8, insist on fully thermally broken frames. In Zones 1 to 3, prioritise SHGC control and sealing over extreme U-values.
• Verify air infiltration data. Especially for sliding doors and operable louvres, where leakage is highest.
• Keep the documentation. WERS datasheets, test reports and glazing schedules form the compliance trail for certification and future resale.

Buyers comparing MEICHEN systems can request configuration-specific performance data covering U-value, SHGC, air infiltration, water penetration and wind load, aligned with the AS2047 and AS4284 testing behind each certified series.

Frequently Asked Questions

Is WERS mandatory for windows sold in Australia?

No. WERS is a voluntary industry scheme administered by AGWA. However, the underlying U-value and SHGC data it standardises are required inputs for NatHERS, BASIX and NCC Section J compliance, so reputable manufacturers publish comparable data whether or not a WERS label is displayed.

What is a good U-value for windows in Australia?

For most southern Australian homes, a whole-window U-value of 2.0 W/m²K or lower is a sensible target, and 1.6 W/m²K or lower is appropriate for cooler zones such as Canberra and Melbourne. In tropical zones, SHGC control matters more than U-value, so 3.0 to 3.5 W/m²K with an SHGC below 0.25 is often the better investment.

Does double glazing automatically mean good energy performance?

No. A double-glazed unit in a non-thermally-broken aluminium frame can perform worse overall than a well-sealed single-glazed window with a good frame in a warm climate. The whole-window U-value and SHGC, including the frame, are the figures that matter.

Can I use WERS data for my BASIX or NatHERS report?

Yes. Energy assessors use manufacturer U-value and SHGC data as inputs to the rating software. Provide the data for the specific frame, glass and configuration quoted, and the assessor can model the real performance rather than applying conservative defaults.

How much can high-performance windows improve a star rating?

In practice, upgrading from default single glazing to thermally broken frames with low-E double glazing can improve a NatHERS rating by one to two stars in most climate zones, and more in cool zones with large north-facing glazing. The exact gain depends on the building design, orientation and window-to-wall ratio.

Conclusion

WERS exists to replace marketing language with numbers. For Australian projects, the two numbers that matter most are the whole-window U-value and SHGC, supported by air infiltration data, all matched to the climate zone and facade orientation of the building. Specifiers who work from energy assessment requirements, demand configuration-specific data, and choose frames engineered for the local climate will achieve compliance with fewer surprises and buildings that are genuinely comfortable. MEICHEN Windows & Doors supplies certified aluminium systems with complete performance documentation, giving assessors, surveyors and builders the evidence they need from design through to certification.