Timber offsite MMC living Lab: Case study of a UK Mid-Century bungalow retrofit

The built environment, particularly ageing housing stock, significantly impacts the global energy consumption and energy related carbon dioxide (CO 2 ) emissions. Retrofitting these dwellings, particularly in the UK due to its aging housing stock, is a critical step towards reducing environmental impacts and achieving net-zero emissions. This case study adopts a “living lab” approach to investigate the phased renovation of an early 1950s bungalow in Edinburgh conducted over two phases (2011–2017 and 2021–2023). The extension and fabric upgrade measures have utilised an array of offsite and innovative Modern Methods of Construction (MMC) approaches including the 1 st retrofit and extension application of UK-grown mass timber. Phase 1, totalled in 10.8 tCO 2 e of embodied carbon emissions, while phase 2 resulted in 11.47 tCO 2 e. However, the combined offset emissions of both phases amounted -23.86 tCO 2 e when considering biogenic carbon storage. The property’s usable space area more than doubled from 91m 2 to 197m 2 and resulted in a 27% reduction in total energy consumption from 19,782 kWh/year to 15,679 kWh/year. As a result, the property’s market value has increased by 70%. The findings provide an insight into using off-site timber MMC for the retrofit of existing dwellings and offer a replicable model for net-zero transition. • This study exhibits a decade worth of research and innovation utilising offsite MMC with an emphasis on engineered and modified timber products combined with renewable technologies. • The project is one of the 1 st use cases of UK sourced mass timber products and is the 1 st use case for a retrofit and extension application. • Locally supplied and reclaimed materials have shown to lower embodied carbon emissions. • The project’s return on investment is quantified from a whole life value perspective including tax implications. • Demonstrates a transitional approach to reaching net-zero emissions and high energy performance standards. • Offset emissions totalled -23.86 tCO 2 e, while embodied carbon emissions across both phases resulted in 22.30 tCO 2 e. • The property’s footprint has increased from 91m 2 to 197m 2 while energy consumption rate decreased by 27%.