Sunita SomvanshiA roof coated in native plants and solar panels at Sydney’s First Building is outperforming conventional rooftops by as much as 23 percent during summer heat waves. According to the UTS research team, the biosolar roof kept temperatures significantly lower than a standard aluminium roof — up to 28 degrees Celsius cooler during extreme heat events. UTS published the full study results on August 10, confirming the 28°C cooling and 23.25% energy gain.
The 1,300 square-metre biosolar roof at Bradfield City in Sydney’s West holds 319 solar panels embedded within more than 14,000 native plants, including flowering groundcovers like lilies and wild geraniums. The design, created by architecture firm Hassell and green roof specialist Three Owls Landscaping, generates a simple mutual benefit: plants cool the solar panels so they work better, while the panels above also provide shade for the vegetation below. For Australia’s climate, where heat is a major drag on solar performance, this matters. Other cutting-edge solar technology has claimed 200 times the efficiency of traditional panels — though the Bradfield biosolar roof’s passive cooling approach is far more practical for widespread urban deployment.
Solar panels lose roughly 2 percent of efficiency for every degree Celsius above 25 degrees. On a 40-degree Australian summer day, that loss compounds. University of Technology Sydney researchers led by Associate Professor Dr Peter Irga spent four months over summer 2025 monitoring the First Building’s roof across five areas: panel efficiency, biodiversity, stormwater filtration, air quality, and heat.
The biosolar roof was maintained at cooler temperatures through plant transpiration — the evaporation of water from leaves. “The cooling effect of the vegetation was highly dynamic and became more effective as the ambient temperature rose,” Dr Irga said.
The biosolar roof was large-scale environmental infrastructure. It retained an average of 73 percent of stormwater runoff and filtered out 99.9 percent of manganese, 98.7 percent of arsenic, and 99.8 percent of nickel from rainfall. “The roof acts as a giant natural filter, substantially reducing the volume of toxic metals entering urban stormwater networks,” Dr Irga noted.
Air quality monitoring recorded the vegetation capturing approximately 65 grams of air pollutants daily, preventing nearly 24 kilograms of pollutants annually from entering the local atmosphere. Field surveys and environmental DNA analysis identified 39 bird, insect, mammal, and gastropod species on the roof within a year—including 13 pollinator species and a rare blue-banded bee. “Seeing a complete multi-trophic food web establish itself within about a year, from pollinators and spiders through to kookaburras, was remarkable,” Dr Irga said.
The First Building itself, a 3,000 square-metre structure clad in low-carbon timber with rammed earth walls, has already won multiple architecture and sustainability awards. It represents the flagship project for Bradfield City, Australia’s first new city in a century. The master plan requires 80 percent of suitable roof space on new buildings to incorporate green or biosolar roofs.
Bradfield Development Authority CEO Ken Morrison described the installation as part of a broader approach: “Bradfield City presents a once-in-a-generation opportunity to embed sustainable solutions from the outset.”
The research, published by UTS, will inform future biosolar installations, including a pilot program on prefabricated modular cabins by Future Property Group. Eco-focused residential design is a growing trend, with properties like the Omaze Surrey Hills eco-home incorporating Tesla Powerwalls and rooftop solar as standard features.
