Sliding and Patio Doors
by SimonPublished: September 2, 2026 | Updated: September 18, 2026Regulations & Planning7 min read
Table of Contents

Key Takeaways

  • NatHERS models glazed doors as windows, so a sliding or stacking door is assessed on its glass and frame performance.
  • Victoria’s 7-star standard has applied to new homes since 1 May 2024. It is not retrospective, so replacing a door in an existing house is not covered.
  • One 4.8 m stacking door can carry more glass than five or six standard windows combined.
  • A single glazed aluminium door sits near U6.7, while a double glazed uPVC door sits nearer U3.0.
  • Door performance data must reach the assessor before the permit, and a late substitution can undo it.

Yes. Glazed doors count towards your 7-star energy rating in Victoria, and they are assessed by the same method as windows. The NatHERS Technical Note puts it plainly: fully or partially glazed hinged and sliding doors are considered to be windows in NatHERS software tools. A sliding, stacking, bifold or French door goes into the model with a total system U-value and a solar heat gain coefficient, just as a window would.

Glazing guidance is usually written around windows, which can leave someone planning a wide rear opening assuming the detail applies elsewhere. On a modern Victorian floor plan the doors are often the largest thermal element. If you are weighing options with a Melbourne double glazing supplier, the door specification deserves as much attention as the window schedule.

The requirement applies to new homes and has been mandatory in Victoria since 1 May 2024. A home permitted before that date is not caught by it.

How NatHERS Treats Doors

NatHERS assesses the thermal shell, and every external opening is entered as a product with tested performance figures. Doors fall into three groups.

Glazed Doors

Sliding, stacking, bifold, French and fully glazed hinged doors are modelled as windows. The assessor enters the opening type, total system U-value and SHGC, drawn from Australian Fenestration Rating Council data in the NatHERS or WERS libraries. European ratings are not accepted.

Partly Glazed Doors

Only the glazed portion of a partly glazed door is modelled as a window. Where the glass makes up less than 25% of the door area, the door can be modelled as a solid door instead. That covers the usual entry door with a narrow vision panel.

Solid External Doors

A solid door is modelled as an opaque element rather than glazing. It still loses heat and its seals affect air infiltration, but it carries no solar gain calculation.

Why Door Area Matters

Doors move a rating because of area rather than count.

  • A standard 1.2 m by 1.5 m window is about 1.8 m² of opening.
  • A 4.8 m wide stacking door at 2.1 m high is close to 10 m² in one opening.
  • That single door can carry more glass than five or six of those windows put together.

Doors also carry proportionally more frame than windows, and the frame is usually the weakest part of the system. Most of Melbourne sits in NCC climate zone 6, where heating dominates, so winter heat loss through a large opening is the concern. Choosing from a published range of double glazed door systems gives the assessor real figures to model rather than software defaults.

U-Value And SHGC Explained

Two figures decide how a glazed door performs.

U-Value

U-value measures how readily heat passes through the whole door system, frame and glass together, in W/m²K. Lower means less heat lost in winter and less gained in summer. The whole-of-system figure counts, not the glass alone.

Solar Heat Gain Coefficient

SHGC is the share of solar radiation passing through the door, on a scale from zero to one. A higher SHGC on a north-facing door helps in a heating-dominated climate. The same figure facing west adds to summer overheating.

Typical Performance Figures

Published ranges show the scale of the difference.

  • Single glazed clear aluminium: around U6.7, SHGC 0.57 to 0.70
  • Double glazed clear aluminium: around U4.8, SHGC 0.51 to 0.59
  • Double glazed clear uPVC or timber: around U3.0, SHGC 0.48 to 0.56
  • Double glazed tinted uPVC or timber: around U2.9, SHGC 0.33 to 0.42

NCC 2022 also made thermal bridging a mandatory consideration, worth roughly 0.4 to 0.5 stars. Unbroken metal frames across a wide opening are where that shows up.

Door Types Compared

Door types differ in frame share and sealing, which changes the outcome even at similar glazing.

  • Sliding patio doors: two or three panels, moderate frame share, brush seals on the sliding leaf.
  • Stacking doors: the widest openings and largest glass area, with more panels across the span.
  • Bifold doors: several stiles folding across the opening, so the frame share is highest.
  • French doors: hinged leaves with compression seals, usually tighter than a slider.
  • Hinged entry doors: often mostly solid, modelled as opaque where glazing is under 25%.

Across a wide span, double glazed stacking door systems are the type most worth specifying carefully, simply because there is so much opening involved.

What Applies In Victoria

Scope causes more confusion than the technical detail, so it is worth separating out.

New Homes

The 7-star minimum applies to new Class 1 and Class 2 homes. It replaced the 6-star minimum, and a 7-star home uses roughly 20% to 25% less heating and cooling energy. A Whole of Home energy budget covering fixed appliances sits alongside the shell rating.

Renovations And Additions

Energy efficiency provisions attach to new building work, so a substantial extension or alteration can bring a rating requirement with it. Where the threshold falls on a given job is for your building surveyor and the relevant Victorian practice note, so ask at concept stage.

Existing Homes

There is no retrospective obligation. Replacing a door in a house you already own needs no NatHERS assessment and no 7-star result. Better doors still cut heat loss, draughts and noise, but that is a comfort decision rather than a compliance one.

Getting The Specification Right

Three points decide whether doors help or hinder the rating.

Timing

The assessor needs door performance data before the permit application. Leaving doors as a later selection means the model runs on default values, and defaults rarely flatter a large opening.

Product Substitution

If a specified door is swapped during construction, the replacement must match the opening type and stay within tolerance on U-value and SHGC, or the certificate stops describing the house that was built.

Orientation

Which way the opening faces changes what you should ask for. Working through a guide to home orientation first helps you decide where to chase solar gain and where to cut it back with shading or a lower SHGC figure.

FAQs

Does a sliding door count as a window in a NatHERS assessment?

Yes. NatHERS treats fully and partially glazed hinged and sliding doors as windows, using the same U-value and SHGC inputs. Only the glazed portion of a partly glazed door is modelled that way.

Do I need a 7-star rating to replace a door in my existing Melbourne home?

No. The standard applies to new homes and new building work. Swapping a door in a house that is already built does not trigger an assessment, though a larger renovation might.

Can a large stacking door still work in a 7-star home?

It can. There is no cap on glazing area. The rating depends on the system chosen, the orientation, the shading and how the rest of the shell is built.

What U-value should I aim for on a glazed door in Melbourne?

There is no single figure, because it depends on the whole design. As a guide, a double glazed uPVC system near U3.0 performs roughly twice as well as single glazed aluminium near U6.7.

Getting The Doors Right

Doors are not a footnote to the glazing schedule in a 7-star Victorian build. They are assessed as glazing, they are often the biggest single opening in the plan, and the choice of frame and glass can be worth more stars than any other product decision on that elevation.

If you are building new or planning a major renovation, get the door performance figures to your assessor early and keep the specification locked once it is modelled. If you are improving a home you already own, the standard does not apply, and the case for better doors rests on comfort, condensation, noise and energy bills.

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Simon

Simon is part of the Double Glazing Melbourne team, working with homeowners across Victoria to improve comfort, energy efficiency, and noise reduction through double glazed windows and doors. He supports clients in finding suitable uPVC window and door solutions based on their property, preferences, and local conditions. Simon focuses on practical outcomes, helping homeowners feel more confident about their choices when upgrading or replacing existing windows and doors.