Upcycling is the creation or modification of a product from used materials, components and products which is of equal or higher quality or value than the original. Scaling-up upcycling, in theory, contributes ultimately to reducing carbon emissions by extending lifetimes of used materials, components and products, and thereby decreasing embodied energy. This PhD focuses on the emerging household behaviour of upcycling as niche environmentally significant behaviour. It aims to understand the current upcycling behaviour and factors that influence behaviour in order to develop design and policy interventions to influence behaviour in order to\ud
upscale upcycling. Interviews, a short questionnaire study, a survey and use of a 'semi-Delphi' method (a questionnaire study followed by a workshop with experts) were employed. The interviews provided insights into current upcycling behaviour (e.g. approaches to and context for upcycling), behavioural factors influencing upcycling, and potential\ud
differences arising from demographic characteristics. The short questionnaire study showed that upcycling has potential to create high attachment leading to product\ud
longevity. The survey revealed UK-specific key behavioural factors of upcycling (intention, attitude and subjective norm) and the potential target groups for scaling up (people in art and design aged 30 years or older) based on group differences. Synthesising the data from the interviews and surveys, 15 promising design and policy interventions for upscaling upcycling were formulated. These interventions\ud
were subsequently explored and evaluated through the semi-Delphi study. The outcome pinpointed the suitable actor(s) for each intervention and sets of important\ud
and feasible interventions for short-term and long-term success in scaling-up. This research contributes further to knowledge in design for sustainable behaviour by suggesting interventions beyond product and communication design to influence behaviour, and demonstrating novel use of mixed methods consumer research based on a behaviour model and an existing framework for behaviour understanding and\ud
intervention. The research also contributes to knowledge in upcycling theory and practice by providing behavioural insights, factors influencing upcycling and promising interventions for upscaling upcycling in the UK. Finally, a contribution was made to consumer behaviour theory by suggesting and testing a new combination model to understand behaviour