WERS is the recognised Australian rating scheme for window and door energy performance. Ratings are independently assessed and provide verified U-value and SHGC data for specific window and door systems and configurations.
WERS ratings are used in:
- NCC Section J energy compliance assessments for commercial buildings
- BASIX energy compliance for residential buildings in NSW
- Thermal modelling and energy simulation software
- Green Star and NABERS assessments where window performance data is required
- DBP Act regulated design documentation where energy performance is a specified building element requirement
WERS data for Hunter Windows systems is available by system and series. Ratings vary depending on frame type, glazing selection and configuration — the same frame with different glass can produce significantly different WERS outcomes.
U-value measures the rate of heat transfer through a window assembly — frame, glazing and edge seal combined. Lower U-values indicate better thermal insulation, meaning less heat transfers through the window in either direction.
U-value is the primary metric used in NCC Section J compliance calculations for commercial buildings. It directly affects the calculated heating and cooling loads of a building and influences the overall energy model outcome.
Key considerations for U-value specification:
- U-value varies by frame type, glazing type and configuration
- Double glazing consistently produces lower U-values than single glazing
- Low-e coatings reduce the radiative component of heat transfer, improving U-value
- Thermally broken frames reduce heat conduction through the aluminium frame, further lowering system U-value
- For large glazed areas, even small improvements in U-value have a significant impact on overall building energy performance
SHGC measures the fraction of solar radiation that passes through a window assembly and enters the building as heat. Values range from 0 to 1 — lower values indicate less solar heat gain.
SHGC selection depends heavily on:
- Climate zone — buildings in hot climates benefit from lower SHGC to reduce cooling loads; buildings in cold climates may benefit from higher SHGC to assist passive solar heating
- Orientation — north and west-facing windows in Australian climates typically warrant lower SHGC to manage solar exposure; south-facing windows are less critical
- Shading — external shading devices reduce effective solar exposure and may allow a higher SHGC without compromising energy performance
- NCC and BASIX requirements — minimum SHGC requirements are specified by climate zone under the NCC and BASIX
SHGC varies significantly with glazing selection. WERS ratings provide verified SHGC data for each system and glazing configuration.
Standard aluminium frames conduct heat readily through the frame section — a characteristic known as thermal bridging. Thermally broken frames address this by incorporating a low-conductivity thermal barrier within the aluminium frame section, interrupting the conductive path and reducing heat transfer.
The AWS ThermalHEART series provides thermally broken aluminium frames across window and door systems and is available through Hunter Windows for projects where elevated thermal performance is required.
ThermalHEART is relevant to:
- Projects in climate zones with significant heating or cooling loads
- NCC Section J compliance where standard aluminium frames do not achieve required U-values
- BASIX compliance where window performance targets require thermally broken frames
- Architect-designed homes and commercial buildings targeting above-minimum energy performance
- Green Star and NABERS rated projects with specific window thermal performance requirements
Glazing selection is the single most influential variable in window energy performance. Key glazing options affecting energy performance:
- Single glazing — lower cost, higher U-value and SHGC; suitable where energy performance requirements are less stringent
- Double glazing — two glass panes with an air or gas-filled cavity; significantly lower U-value than single glazing; standard specification for most commercial and multi-residential projects
- Low-e coatings — microscopically thin metallic coating applied to glass surface; reduces radiative heat transfer, improving U-value and selectively reducing SHGC
- Argon fill — inert gas replacing air in double glazing cavity; lower thermal conductivity than air, further reducing U-value
- Laminated glass — two glass panes bonded with an interlayer; primarily a safety and acoustic product but also affects U-value and SHGC depending on interlayer type
Refer to the Glass Options page for detail on available glazing types and their performance characteristics.
