Choosing a building system is not an easy task, especially when designers are concerned about the social and environmental impacts of their choices, as in the case of a net zero energy (NZE) building. In addition, economic constraints are commonly misunderstood so that all too often decisions are based on what is cheaper upfront and do not take the life-cycle cost into account. Moreover, the interaction with increasing numbers of stakeholders makes decision-making even more complex. While decisions can be supported by decision-making methods, in practice many are made without a formal method or discussion, which often generates conflict and waste in the design process. Few designers know how to incorporate social, environmental and economical factors when making a decision. This research fills the literature gap and provides practical advice for practitioners by demonstrating the application of a method called choosing by advantages (CBA) in order to create transparent and collaborative environments in which to make decisions. This paper presents a detailed case study of choosing an HVAC system for a NZE building in California. It provides evidence that CBA supports the choosing problem by integrating multiple perspectives, creating transparency, separating "value" from cost, and clearly documenting the decision rationale. (C) 2015 Elsevier B.V. All rights reserved.