Short answer: For a Melbourne home, choose double glazed windows by comparing the performance of the complete window system, not the glass alone. Check the whole-window U-value, solar heat gain coefficient (SHGC), frame type, glass make-up, opening style and installation detail against the home’s orientation, energy assessment, noise goals and budget.
Double glazing can improve comfort and reduce heat transfer compared with otherwise similar single glazing, but results vary by product and project. The best specification is the one that suits each elevation and room rather than applying the same glass and frame everywhere.
What is a double glazed window?
A double glazed unit uses two panes of glass separated by a sealed cavity. The cavity may contain air or an inert gas such as argon. Spacers and seals keep the unit together, while the frame, sash, gaskets, hardware and installation complete the window system.
The sealed cavity slows heat transfer through the glazing. Actual performance depends on the pane thicknesses, coatings, cavity, spacer, frame and size of the finished product.
Which performance numbers matter?
Whole-window U-value
U-value describes the rate of heat transfer through the complete window. A lower whole-window U-value generally indicates better insulation. Compare ratings for the complete product rather than relying on a centre-of-glass value.
Solar heat gain coefficient
SHGC describes how much solar heat passes through the window. A lower or higher SHGC is not automatically better: the appropriate value depends on orientation, shading, glazing area and the building’s heating and cooling strategy.
WERS ratings
The Window Energy Rating Scheme (WERS) provides independent energy performance information for rated window products in Australia. Ask which tested or rated configuration applies to the exact frame, glass and size being quoted.
Single glazing and double glazing compared
| Decision point | Single glazing | Double glazing |
|---|---|---|
| Thermal resistance | One pane provides limited resistance to heat transfer. | The sealed cavity generally improves thermal resistance. |
| Frame importance | The frame still affects whole-window performance. | Frame and spacer performance remain important and can limit the benefit of the glass. |
| Noise | Acoustic performance depends on glass thickness, seals and the complete opening. | Can improve noise control, but the best acoustic make-up may use different pane thicknesses or laminated glass. |
| Condensation | Interior glass surfaces may become colder in winter conditions. | Warmer interior surfaces can reduce condensation risk, but humidity and thermal bridging still matter. |
| Compliance | NCC and energy compliance depend on the complete building design and approved assessment, not the number of panes alone. | |
Does NCC 2022 require double glazing in Melbourne?
There is no reliable one-line rule that every Melbourne window must be double glazed. Residential energy compliance is assessed across the building, including orientation, glazing area, insulation, shading, services and the rated performance of windows and doors. A project’s energy report or approved design should identify the required window values.
The Australian Building Codes Board publishes the National Construction Code and supporting material. Builders and homeowners should confirm the applicable NCC edition, state transition arrangements and project-specific energy assessment with the relevant building professional.
When should you consider a thermally broken frame?
Aluminium conducts heat. A thermally broken aluminium frame separates the inner and outer aluminium sections with a lower-conductivity barrier. This can improve whole-window U-value and reduce interior frame surface cooling compared with an otherwise similar non-thermally-broken frame.
Thermally broken systems can be useful when the energy target, large glazing area or comfort brief calls for higher performance. They are not automatically required for every opening. Compare the rated complete systems and the project’s energy documentation.
Glass options to discuss
- Low-E glass: a low-emissivity coating changes the way heat is transferred through the glazing. The coating type and surface position should match the required U-value and SHGC.
- Argon gas: argon in the sealed cavity can improve thermal performance compared with air in a suitable insulated glass unit.
- Laminated glass: uses an interlayer that holds fragments together when broken and can also help with selected acoustic make-ups.
- Toughened safety glass: may be required in locations identified by the applicable glazing standard and design.
- Obscure glass: provides privacy while admitting daylight, commonly for bathrooms and side-facing openings.
- Tinted or solar-control glass: can help manage glare and solar gain on selected elevations.
For a broader design overview, the Australian Government-supported Your Home glazing guide explains how orientation, shading, glass and frames work together.
Which window styles can use double glazing?
- Awning windows: top-hinged opening sashes for controlled ventilation.
- Sliding windows: horizontal operation where an outward-opening sash would be inconvenient.
- Fixed windows: non-opening glazing for light and views, often combined with nearby opening sashes.
- Sliding and stacker doors: larger openings for living and outdoor connections.
- Bi-folding doors: folding panels for broad openings where the layout and structure suit the configuration.
What affects double glazed window pricing?
A useful quote needs more than a cost per square metre. Price changes with opening size, frame series, sash type, glass make-up, safety requirements, powder coat finish, fly screens, hardware, access, removal of existing windows, reveals and installation detail. Large panels and non-standard shapes can also affect engineering, handling and glass selection.
For replacement work, send interior and exterior photos plus approximate sizes. For a new home, send architectural drawings, elevations, the window schedule and available energy documentation. Iconic Windows can then quote the relevant configuration instead of using a generic price range.
Questions to ask before ordering
- Is the quoted U-value for the complete window or only the glass?
- What SHGC is specified for each orientation?
- Does the quoted frame and glass match the energy report or window schedule?
- Which safety, privacy or acoustic glass is required for each opening?
- Are fly screens, hardware, reveals, trims, removal and installation included?
- Who confirms final measurements and opening directions before manufacture?
Frequently asked questions
Is double glazing mandatory for every Melbourne home?
No. Compliance is assessed for the whole building and the required window performance should come from the project’s approved design or energy assessment.
Does double glazing reduce traffic noise?
It can help, but acoustic performance depends on the complete system. Pane thickness, different pane combinations, laminated glass, seals, frames, vents and installation gaps all affect the result.
Is a thermally broken frame always necessary?
No. It can improve whole-window performance, but the right frame depends on the energy target, glazing area, budget and project specification.
Can old timber or steel windows be replaced with double glazed aluminium?
Often yes. The existing opening, sill, wall construction, reveals and access need to be assessed so the new frame and installation method can be detailed correctly.
What should I send for a quote?
Send photos and approximate opening sizes for an early replacement discussion, or drawings and a window schedule for a new build. Include frame colour, opening style, glass goals, screens and any energy or acoustic requirements.
Request a project-specific quote
Iconic Windows supplies made-to-measure aluminium windows and doors from Mulgrave for projects across Melbourne. Call 0468 886 377 or send your photos, sizes or project drawings through the contact page.
