Redeveloping a brownfield site is a sustainability opportunity and a sustainability puzzle at once. The land is already disturbed, which the planning system rightly favours — but a sustainability statement still has to demonstrate biodiversity net gain, water efficiency, greening and, on larger schemes, BREEAM. This guide sets out how a sustainability statement handles brownfield land in 2026.
Getting it right matters more than ever: government policy is actively steering development toward brownfield and "grey belt" land, and the 2026 changes to biodiversity net gain were designed in part to remove barriers for exactly these sites.
What a sustainability statement covers on brownfield land
A sustainability statement pulls together the environmental credentials of a scheme: biodiversity, water, materials, greening and, where required, a BREEAM assessment. On brownfield land each of these has a particular slant:
- Biodiversity net gain — the baseline habitat value is often low, which can make the mandatory 10% uplift easier to achieve on site.
- Water efficiency — the 110 litres per person per day standard applies regardless of site history; see our guide to passing the water calculator.
- Urban greening — previously sealed sites offer a real chance to add green roofs, planting and permeable surfaces.
- Materials and remediation — reusing existing structures and dealing responsibly with contamination are sustainability gains in their own right.
BNG on brownfield: the low-distinctiveness advantage
Biodiversity net gain is measured with the statutory biodiversity metric, which scores habitats by distinctiveness and condition. A cleared industrial yard or hardstanding typically scores very low, so the 10% uplift required by the Environment Act 2021 can often be delivered on site through new planting, green roofs and habitat creation — see how to deliver 10% BNG on a small site.
Two cautions. First, sites left derelict for years can develop surprising ecological value — open-mosaic habitat on previously developed land is a priority habitat, and an ecologist may find the baseline is higher than the tarmac suggests. Second, the metric penalises the loss of any higher-distinctiveness habitat that has colonised the site, so an early baseline survey is essential.
The 2026 BNG changes and brownfield
In April 2026 Defra confirmed a package of BNG changes aimed at reducing complexity and removing barriers for small and brownfield sites, including a new area-based exemption for the smallest developments. The policy intent is explicit: make it easier to bring SME and brownfield schemes forward without diluting the 10% principle. If your site is small, check whether an exemption applies before commissioning metric work — but be ready to evidence it, because planners will ask.
Grey belt and the sustainability case
The NPPF's "grey belt" definition — previously developed or lower-quality Green Belt land — comes with "golden rules" that expect development to deliver genuine benefits, including improvements to green infrastructure and biodiversity. A sustainability statement is where a grey belt scheme demonstrates that it meets those expectations: net gain, greening and accessible open space rather than a bare minimum. Treating sustainability as a core part of the design, not a validation tick-box, is what turns a contested grey belt or brownfield proposal into a defensible one.
BREEAM and larger brownfield schemes
For major commercial or mixed-use redevelopment, councils frequently require a BREEAM rating — typically Very Good or Excellent. Brownfield land can score well on BREEAM's land-use and ecology credits precisely because it reuses previously developed land and can enhance a low ecological baseline. Flag the target rating early so it shapes the design rather than constraining it late.
Bringing it together at planning
A brownfield sustainability statement is strongest when it tells one coherent story: previously developed land, brought back into use, delivering measurable biodiversity gain, efficient water use, real greening and — where relevant — a credible BREEAM rating. Anchor every claim in the right metric or standard, and make sure the biodiversity baseline is surveyed, not assumed.
How Fortress Associates can help
Our sustainability statement service produces a planning-ready statement for UK schemes with the report ready in minutes and free of charge. It covers 10% biodiversity net gain under the Environment Act 2021, the 110 l/p/d water-efficiency calculator, urban greening and BREEAM where required — with the Urban Greening Factor applied on London sites via London Plan Policy G5. Explore our planning services or contact us to discuss a brownfield project.
Sources & further reading
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