As overheating in UK buildings becomes an increasingly urgent concern, CIBSE is launching its latest Weather Data set, a vital tool for professionals designing for future climate conditions.
Drawing on the most up-to-date observations, climate science and projections from the Met Office, the new CIBSE Weather Data set provide engineers, designers, and researchers with the data needed to assess energy use and overheating risk with far greater accuracy and geographic precision.
The launch follows a two-and-a-half-year development and testing programme, led through a Knowledge Transfer Partnership (KTP) with the University of Exeter and reviewed by experts at Loughborough University, Arup, Inkling LLP and other supporting volunteers. This robust, collaborative process ensures the 2025 release represents a major leap forward in modelling building performance in a warming climate.
What’s new in the 2025 release?
• Updated baseline data: Weather Data set now reflects Met Office observations from 1994–2023, replacing the previous 1984–2013 baseline.
• Alignment with UKCP18 projections: Data is modelled using the latest UK Climate Projections from the Met Office to create future timelines for the 2030s, 2050s and 2080s.
• Enhanced solar radiation inputs: Gaps in UK radiation data have been filled using Copernicus (CAMS) datasets, improving accuracy in energy and thermal assessments.
• More representative UK coverage: Weather data is now available for 28 climate zones across the UK, providing more localised insight than ever before.
• New digital platform: A dedicated CIBSE Weather Data Shop allows users to identify the appropriate climate zone for their project by entering a postcode or geographic coordinates.
The updated files include both Test Reference Years (TRYs) for typical annual energy modelling, and Design Summer Years (DSYs) for overheating risk assessments—offering three variants that capture different heat events.
CIBSE’s selected emissions scenarios to release is informed by detailed analysis of the weather data, prioritising those that were distinctly different from one another. The 2030s files will be based on a high emissions (RCP 8.5) scenario, which best reflects current trajectories. The 2050s will include an additional medium emissions scenario (RCP 4.5), and 2080s will provide low (RCP 2.6), medium and high emissions scenarios. Each timeline also includes a range of probability percentiles that help reflect the uncertainty in future conditions.
While the new datasets are not required for regulatory compliance at launch, they represent a significant advance in building design. Their release comes at a time when the building services sector is being called upon to mitigate overheating risk, manage rising energy demand, and deliver climate-adapted buildings that remain comfortable and affordable to run.
To access the CIBSE Weather Data set please click HERE