SEC1 and Viability: Balancing Sustainability with Deliverability
Cornwall Council’s Sustainable Energy and Construction (SEC1) policy – part of the Climate Emergency Development Plan Document (DPD) – sets ambitious new standards for sustainable construction across the county. Introduced in 2023, it requires new residential developments to achieve net-zero carbon emissions through high levels of energy efficiency and on-site renewable generation. Under Policy SEC1, developers must demonstrate that new homes will:
· Limit space heating demand to 30 kWh/m² per year or less.
· Restrict total energy use (including heating, hot water, lighting, and appliances) to around 40 kWh/m² per year.
· Generate renewable energy on site – typically through solar PV – to match the total predicted energy use of the development, achieving a net-zero balance.
· Use a high-performance building fabric, with strong insulation, airtightness, and low U-values to reduce heat loss before relying on renewables.
· Limit water consumption to no more than 110 litres per person per day.
Developers are required to submit an Energy and Carbon Statement with their planning application to evidence compliance with these standards. The policy’s wider aim is to ensure that every new home in Cornwall contributes to the county’s goal of reaching net zero carbon by 2030.
However, achieving these standards can present challenges, particularly in relation to cost implications. From our conversations with SME developers active in the market, the cost of meeting these requirements is adding around £10,000-£15,000 to an average-sized new build dwelling. When combined with other build cost increases and a slow housing market, development margins are becoming tight.
Importantly, SEC1 can be challenged on viability grounds. Where full compliance would make a project unviable, there is scope to seek flexibility or propose alternative solutions.
Our team can assist with preparing viability assessments and supporting evidence to demonstrate where such adjustments may be justified, helping ensure your development remains both viable and deliverable.
Stephen Maycock
