Nearly 1,400 solar panels now form the outer skin of a Melbourne office tower. The engineering is impressive. The more useful story for builders is how a wall that generates electricity gets through a code written for walls that do not.

Cbus Property announced on 9 November that installation of the solar skin on 435 Bourke Street in Melbourne’s CBD is complete.

The building integrated photovoltaic system covers 2,679 square metres across the tower’s facade, crown and rooftop. It is made up of 1,391 panels with an installed peak capacity of 375 kilowatts.

Cbus Property describes it as one of the world’s first large scale solar facades on a commercial office tower. The tower was designed by Bates Smart and is being built by Multiplex, with practical completion expected in late 2026.

The facade generates power and shades the floors behind it

Unlike a rooftop array fixed to a finished roof, these panels are part of the building envelope itself.

In selected areas they also act as shading, cutting solar gain into the office floors. Bates Smart describes them as solar leaves that shade the workplace while they produce energy.

Design modelling estimates the facade will generate up to 20 per cent of the building’s forecast base building electricity once commissioned, according to Cbus Property. The balance is to come from an off site renewable energy arrangement, in line with the 6 Star Green Star rating the project is targeting.

That 20 per cent is modelled, not measured. Vertical panels in a dense city block contend with shadow from neighbouring towers and collect less direct sunlight than a tilted roof array. How the system performs in operation is the number that will matter.

What is building integrated photovoltaics?

Building integrated photovoltaics, or BIPV, are solar modules that replace a conventional building material such as facade cladding, glazing, shading or roofing, so the product is both a building element and an electricity generator. Building applied photovoltaics, the standard rooftop system, are mounted onto a finished surface and can be removed without affecting the envelope. The distinction matters because BIPV has to satisfy building regulation as a wall or roof as well as electrical standards as a solar array.

Melbourne already has a smaller precedent on Spencer Street

435 Bourke Street is not the first Australian building to make power from its walls.

550 Spencer Street in West Melbourne, an eight storey office building designed by Kennon, carries 1,182 facade panels according to its architect. Its Australian Institute of Architects awards entry describes it as the first building in Australia to produce energy from its own facade.

Cbus Property frames 435 Bourke Street as one of Australia’s first. The difference is scale. At 375 kilowatts peak, the Bourke Street system has more than double the reported capacity of the Spencer Street facade, on a 48 level tower rather than an eight storey building.

Image: Glenn Hester

The building code has no ready made pathway for a solar wall

This is where the project becomes relevant well beyond the CBD.

Under the Deemed to Satisfy Provisions of the National Construction Code, a building required to be of Type A or Type B construction must have non combustible external walls, including the components built into them. That captures apartment buildings of three storeys or more, two storey apartment buildings unless a specific concession applies, and offices of three storeys or more.

Solar modules are not non combustible. Research by RMIT University, funded through the Victorian Building Authority’s research grant program, notes that the two common encapsulants used to bond solar cells, EVA and PVB, are both combustible, and that the backsheet largely determines how a panel burns.

The researchers found that a BIPV module forming part of a Type A or B external wall would need to pass the AS 1530.1 non combustibility test or be justified through a Performance Solution. For most BIPV scenarios, a Performance Solution is the route.

They also identified gaps that land with builders and certifiers. BIPV must comply twice, as an electrical product and as a building element. The report found no explicit public information on whether current products comply with Australian building regulations, and flagged that the practices set out in the current solar installation standard may be deficient for BIPV.

Firefighting is part of the picture. The panels keep generating while there is daylight, and the report warns that the DC voltages involved are dangerous to firefighters even at low current.

The research was written against NCC 2019, but the requirement it analysed has not moved. Clause C2D10 of NCC 2025, in force in Victoria since 1 May 2026, still requires external walls of Type A and B buildings, including the facade covering, to be non combustible. The report is now published by Victoria’s Building and Plumbing Commission, which replaced the Victorian Building Authority.

Integration is a sequencing problem before it is a technology problem

Ross Snowball, Multiplex’s Regional Managing Director for Victoria and South Australia, said the solar skin was one of the most challenging aspects of delivering the project.

He said integrating nearly 1,400 panels into the envelope took extensive coordination between the facade, structural and services teams so that quality and program were not affected. In his view, early collaboration allowed the technology to be embedded in delivery “rather than bolted on at the end.”

On this kind of building, solar is no longer an add on. It is part of the wall.

That is the practical shift BIPV forces. A rooftop array is an electrical package that arrives late in the job. A solar facade sits inside the facade scope, carries electrical design through the structure, and has to be settled before the envelope is documented.

It also blurs responsibility. When the panel is the wall, a defect can be a weatherproofing problem, an electrical problem or both.

We have reported a solar installer’s view that solar is still missing from most new builds largely because of uncertainty over who carries the warranty when a system fails. A product that is cladding and generator at the same time does not make that question any simpler.

Apartments are where facade solar would matter most for residential builders

For detached housing, a CBD tower is a long way from the job site. Houses sit in Volume Two of the code and are not caught by the Type A and B non combustible wall rule.

Apartments are different. The Australian Building Codes Board states the whole of home annual energy budget for apartments is around 40 per cent more lenient than the budget for houses, to account for the practical difficulty of installing rooftop solar on apartment buildings.

A small roof shared between many dwellings is exactly the constraint facade generation is meant to solve. But apartment buildings of three storeys and up require Type A construction under the Deemed to Satisfy Provisions, and two storey apartment buildings require Type B unless a concession applies. That puts any solar wall straight into Performance Solution territory, usually with a fraction of a CBD tower’s engineering budget.

Code editions now differ by state, so the NCC edition that applies on a given project also shapes how that pathway is assessed.

The Good Builder Take

The solar skin at 435 Bourke Street shows the product can be installed at scale on an Australian tower. It does not yet show the approval pathway can be repeated affordably.

On mid rise residential and smaller commercial work, BIPV becomes realistic when there are tested products with published compliance evidence and a pathway certifiers can sign off without bespoke fire engineering on every job. Until then, it remains a solution for project teams that can afford to engineer their way through.

Measured output will settle the argument

Once complete, 435 Bourke Street will provide approximately 62,000 square metres of premium office space. Cbus Property expects around 3,500 jobs to have been created on site through construction, with up to 490 workers on site during peak periods.

The facade’s real contribution will only be known once the system is commissioned and has run through a full Melbourne year. If measured output lands near the modelled 20 per cent, that becomes a useful benchmark for every developer weighing facade generation against roof space.

For now, the more transferable lesson is the one the builder put on record. On this kind of building, solar is no longer an add on. It is part of the wall, and it has to be designed, approved and sequenced as one.

For more on how materials and methods are changing on site, our Building Better guide brings that coverage together.

Frequently asked questions

Last updated: 11 November 2026. Project figures are as reported by Cbus Property on 9 November 2026. Generation figures are design modelling estimates, not measured output.

General Information Only: This article provides general information only and does not constitute legal, financial, engineering or professional advice. It does not take into account your specific circumstances. Building code requirements vary by state, territory and code edition. Before making decisions about design, compliance or products, seek advice from a qualified building surveyor, fire engineer or other appropriately qualified professional.

Author: TGB Editorial