Concrete was the villain. Now it might be the answer, if we ask harder questions

Sustainable DesignMaterialsMulti Residential

15 June

Key insights at a glance

Cement manufacture produces roughly 8 per cent of global CO2 emissions, making concrete the single biggest material problem in construction [1]
Melbourne's most awarded sustainable apartments, including Nightingale Village in Brunswick, are predominantly concrete buildings, by deliberate choice [4][5]
Breathe has reported a concrete mix with 46 per cent cement replacement, recycled water and manufactured sand at Nightingale Skye House [4]
Low carbon concrete offering 30 to 70 per cent embodied carbon reductions is on the standard price lists of Australia's two largest suppliers right now [6][7]
Cross laminated timber cuts embodied carbon by around 40 per cent, but builder's risk insurance has run at four to ten times concrete equivalents, stalling projects [8][9]
Embodied carbon provisions were pulled from NCC 2025 and published as national guidance instead, yet NSW already requires measurement and Green Star tightens from May 2026 [11][12][13]

Glossary

Embodied carbon: The greenhouse gas emissions generated by extracting, manufacturing, transporting and installing building materials, separate from the energy a building uses in operation [11].

Cement replacement: Substituting a portion of Portland cement, the most carbon intensive ingredient in concrete, with byproducts such as fly ash or blast furnace slag [6].

Precast concrete panel: A wall or facade element cast in a factory and craned into place on site, the dominant facade system for Melbourne mid rise apartments [5].

CLT, cross laminated timber: Engineered structural timber panels made from layers of wood glued at right angles, used for walls and floors as a concrete alternative [8].

Life cycle assessment (LCA): A formal method for measuring a building's total environmental impact across materials, construction and operation [3].

The material we were taught to hate

When I was going through architecture school, concrete was taught as one of the worst materials environmentally, the embodied energy villain of the construction industry. The numbers backed it up then and still do. Cement manufacture is responsible for roughly 8 per cent of global CO2 emissions, and if the cement industry were a country it would be the third or fourth largest emitter on earth [1].

So it should be uncomfortable that the buildings leading sustainable architecture in Melbourne are concrete buildings. Nightingale Village in Brunswick, 203 homes across six buildings and arguably the most celebrated sustainable housing precinct in the country, is built largely of concrete, blockwork and brick [4]. Kennedy Nolan's Leftfield wears its ochre pigmented precast panels as its public face [5]. This is not hypocrisy. It is a story about how the conversation has matured, and it changes what homeowners and clients should be asking for.

What changed: measurement replaced moralising

The old debate treated materials as good or bad. The current one measures them. Hip V Hype's Ferrars & York in South Melbourne, 22 apartments designed with Six Degrees, underwent an independently verified life cycle assessment that put its embodied carbon at 1,380 kg of CO2 equivalent per square metre, around 3,700 tonnes for the whole building [2][3].

Regulation is moving more cautiously. The voluntary embodied carbon provisions proposed for NCC 2025 were ultimately published as separate national guidance rather than written into the Code, and new residential code changes are paused until 2029 [11]. But NSW has required developers to measure and report embodied carbon since October 2023, and from May 2026 all new Green Star registrations fall under the tighter v1.1 standard [12][13]. The direction is set even though the Code is taking its time. The practices measuring now are simply ahead of it.

Why Melbourne's greenest apartments choose concrete

Breathe Architecture's reasoning at the Nightingale projects is worth understanding properly, because it is a reduction philosophy rather than a materials preference. Leave the concrete soffit exposed and you delete the plasterboard, the suspended ceiling and the paint. The slab becomes the finish, the acoustic separation and the thermal mass in one element [4].

That thermal mass does real work in Melbourne's climate, absorbing daytime heat and releasing it across our large day to night temperature swings [14]. Pair it with a fully electric building running on 100 per cent GreenPower and operational emissions approach zero, so the embodied carbon of a durable, low maintenance structure is amortised over a very long life.

Then there is the mix itself. At Nightingale Skye House, the concrete has been reported to use 46 per cent cement replacement, recycled water and manufactured sand [4]. The deep green end of the market is not abandoning concrete. It is decarbonising it.

The reductions are already on the price list

This is the part that should provoke the industry. Holcim's ECOPact range offers a minimum 30 per cent embodied carbon reduction against conventional concrete, with some mixes exceeding 70 per cent, including mixes with the early strength needed for precast and post tensioned work [6]. Boral's Envisia achieves around 50 per cent cement replacement with equivalent performance and has already been used in precast panels on major projects [7].

The barrier is no longer technology or availability. It is specification habit. Every conventional apartment building poured with a full Portland cement mix today is leaving a 30 to 50 per cent carbon saving on the table because nobody asked.

The honest comparison with timber and steel

Cross laminated timber deserves its reputation. Australian research shows mass timber construction cuts embodied carbon by roughly 40 per cent against conventional concrete and steel [8]. Melbourne proved it could work at scale back in 2012 with Forte in Docklands, then the world's tallest timber apartment building [10].

The problem is commercial, not technical. Builder's risk insurance for mass timber projects has run at four to ten times concrete equivalents, and many development budgets simply cannot absorb that, so projects stall before they start [9]. Most CLT is still imported, adding cost, transport emissions and programme risk. Insurers expect parity closer to 2030 as fire performance data accumulates [9].

Steel is the counterintuitive one. A steel structure weighs 50 to 60 per cent less than concrete at the same form and height, yet carries roughly 25 to 30 per cent more embodied carbon, because steel is far more carbon intensive per kilogram [10]. Recycled steel from electric arc furnaces, made locally at Laverton, narrows that gap and belongs in the conversation, but steel alone is rarely the low carbon answer for apartments today [13].

The facade question nobody is asking

Here is where I part ways with the default. I understand why floors, columns and party walls are concrete. Structure, acoustics and fire all argue for it, and the thermal mass earns its keep. I am far less convinced that the facade needs to be a precast concrete panel.

A facade panel is not primary structure. Its jobs are weather, fire, durability and insulation, and concrete is mediocre at the last one. Concrete conducts heat readily, so a precast facade still needs an insulation layer behind it, and the panel's mass is doing little that the slabs are not already doing. Developers choose precast facades for speed, cost certainty, a mature local supply chain and, since the cladding crisis, the comfort of a non combustible wall in a single trade package [5]. Those are real advantages. They are not laws of physics.

The honest question for the industry is this: where is the prefabricated facade panel that matches precast on fire, acoustics, speed and cost, but beats it on embodied carbon and thermal conductivity? Timber framed cassettes, panels using low carbon binders and bio based insulation cores all point in that direction, but none has yet displaced precast at scale in Melbourne. Until one does, the minimum standard should be precast poured from a verified low carbon mix, not the default blend.

What this means for sustainable architecture in Melbourne homes

The same logic scales down to houses, extensions and townhouses. Concrete used deliberately, in slabs where thermal mass works hardest, specified with high cement replacement, and left exposed where it can replace finishes, is a defensible sustainable choice. Concrete used by habit, everywhere, in a standard mix, is not. We cover how this fits into a broader palette in our guide to sustainable building materials for Melbourne homes.

Five questions to ask before the concrete pours

Has anyone calculated the embodied carbon of this design, even roughly, before documentation is finished?
What cement replacement percentage is specified in the structural mix, and why not higher?
Is a low carbon range such as ECOPact or Envisia available from the supplier for this application?
Where is concrete doing real work, thermal mass, acoustics, structure, and where is it just habit?
Could the facade achieve fire, weather and acoustic performance in a lighter, lower carbon panel system?

FAQs

1) Is concrete bad for the environment? Conventional concrete carries a heavy embodied carbon cost because of its cement content, and cement produces around 8 per cent of global CO2 emissions [1]. But low carbon mixes can cut that by 30 to 70 per cent, and concrete's durability and thermal mass offset some of its impact over a building's life [6][14].

2) What is low carbon concrete and does it perform the same? It replaces a large share of Portland cement with byproducts such as slag and fly ash. Current commercial ranges achieve equivalent strength, including for precast and post tensioned work [6][7].

3) Why don't more apartments use timber instead? Mass timber cuts embodied carbon by roughly 40 per cent, but insurance premiums, import supply chains and fire engineering complexity have made it commercially difficult in Australia. That is expected to ease towards 2030 [8][9].

4) Does low carbon concrete cost more? Premiums vary by mix and supplier, and high replacement mixes can need longer curing allowances. On most projects the cost difference is modest against the structure budget, but confirm pricing with your builder and engineer early.

5) Is thermal mass actually useful in Melbourne's climate? Yes. Melbourne's significant day to night temperature swings are well suited to exposed concrete mass, provided the design includes night ventilation and the mass is not buried behind plasterboard [14].

6) Can I ask for low carbon concrete on a house project? Yes, and you should. It is a specification line, not a special order. An architect can nominate cement replacement targets in the structural documentation and confirm availability with the supplier.

References