James (Josh) McCosh is Principal at van Heyningen and Haward Architects, with over 25 years’ experience delivering complex education, cultural and heritage projects across the UK and internationally.

He leads the practice’s work in retrofit and the creative adaptation of existing buildings, with a particular focus on heritage contexts and challenging sites. His approach combines design leadership with technical expertise in Passivhaus, whole-life carbon assessment and evidence-based sustainability, supporting clients to future-proof their buildings while reducing environmental impact.

James has led a number of award-winning projects, including the transformation of listed buildings at Houlton School, and is currently working on the retrofit of significant historic assets such as the Grade I Commissioner’s House at Chatham Historic Dockyard.

Alongside practice, he contributes to industry knowledge and policy, including work on the LETI Non-Domestic Retrofit Guide and advisory roles with organisations such as the Society for the Protection of Ancient Buildings and York Minster.

His work is driven by a commitment to reuse as a fundamental design principle—unlocking the social, environmental and economic value of existing buildings.