Inspired by the question of the Club of Rome as to Design could help to translate the ubiquitous knowledge on sustainability into daily practise and Peter Senge's belief on mental models as a limiting factor to implementation of systemic insight (Senge 2006), we explored working with mental models as a sustainable design tool. We propose a definition for design uses. At the 7th Sustainable Summer School we collected general unsustainable mental models and "designed" sustainable ones. These mental models were tested as a part of the briefing to student projects and evaluated by the students. Analysing an existing product portfolio, we tested the ability of mental models to aid the creation of strategic design advice. We argue that mental models in the form of associative thinking and cognitive metaphors have been part of designing all along and overlap in nature with design methodologies to such an extent that they are sublimely suited to be used as a design tool. We summarize our prototyping exercises with the proposal of a design process using mental models to root sustainability in design practise and thinking beyond present-day eco-design (Liedtke et al 2013, Luttropp and Lagerstedt 2006, Pigosso and McAloone 2015).

Inspired by the question of the Club of Rome as to Design could help to translate the ubiquitous knowledge on sustainability into daily practise and Peter Senge's belief on mental models as a limiting factor to implementation of systemic insight (Senge 2006), we explored working with mental models as a sustainable design tool. We propose a definition for design uses. At the 7th Sustainable Summer School we collected general unsustainable mental models and "designed" sustainable ones. These mental models were tested as a part of the briefing to student projects and evaluated by the students. Analysing an existing product portfolio, we tested the ability of mental models to aid the creation of strategic design advice. We argue that mental models in the form of associative thinking and cognitive metaphors have been part of designing all along and overlap in nature with design methodologies to such an extent that they are sublimely suited to be used as a design tool. We summarize our prototyping exercises with the proposal of a design process using mental models to root sustainability in design practise and thinking beyond present-day eco-design (Liedtke et al 2013, Luttropp and Lagerstedt 2006, Pigosso and McAloone 2015).