User-centered evaluations of multi-modal building interfaces

In the evolving landscape of building systems and human-building interaction (HBI), the complexity of building interfaces has significantly increased, posing both challenges and opportunities for enhancing energy consumption, indoor environmental quality (IEQ), and building services. This dissertation, titled "User-centered Evaluation of Multi-modal Building Interfaces," delves into the realm of HBI by focusing on the user's experience and perception of multimodal building control interfaces, particularly the various visual modalities of Connected Thermostats (CTs). This body of work aims to support CTs' ongoing adoption, expansion, and performance through a user-centered perspective. The research is motivated by the observation that the design process in the current building industry often overlooks a human-centered approach, leading to a disconnection between occupants' needs and building interface design. This misalignment not only results in user dissatisfaction but also leads to a missed opportunity in leveraging smart building technologies to enhance building performance for achieving climate change mitigation goals. This research attempts to address the main identified gaps in the literature and AEC industry concerning 1) human interaction and perception of multimodal CT interfaces,2) the scarcity of knowledge in the field of human-computer-building interaction (HCBI) regarding the user study methods, 3) the exiting highly non-standard practices in the design of building interfaces. This research highlights 1) the necessity of a multimodal interaction approach, 2) robust mixed-methods User Experience (UX) summative evaluation studies, and 3) the need for standardization in HCBI. This body of work is grounded in the Technology Acceptance Model (TAM) and Human Information Processing (HIP) theories, aiming to foster the adoption of connected building controls with a special focus on usability by suggesting best practices in design and research. The methodology comprised three-step mixed-methods summative evaluation studies designed using a funnel approach to answer the general question: "How do users interact with connected thermostats, and how do these interactions inform our understanding of human-building interaction?": 1) The first and broadest study leveraged texting mining big data of user reviews to identify the general themes and patterns that affect the UX and acceptance of CTs. 2) The second study employed mixed-methods lab experiments to further focus on usability, being recognized as the most determining factor in the adoption of CTs in the first study. This study investigated human interaction with three of the most prevalent modalities of CTs: the Fixed Visual Display (FVD), the phone app, and the web portal. 3) The third study investigated human interaction with a specific visual aspect of UI of FVD and phone app modalities, the interface icons, with the goal of providing some data-driven guidelines for their standardization. Throughout the three studies, the dissertation employed and evaluated some novel and established HCI summative user evaluation methods, including a grounded theory approach for text mining and analyzing user-generated content, eye-tracking think-aloud protocol and contextual inquiry, A/B testing and NASA TLX and SUS surveys to evaluate UX, usability and mental workload. The dissertation outlined three discrete contributions: 1) It bridged some of the well-established UX research methods into HCBI and highlighted the potential of knowledge in the HCI field, 2) Provided guidance for human-centered design of multimodal building interfaces through identifying the main strengths, weaknesses, opportunities, and threats in UX of CTs, 3) Informed the standardization of UI of multimodal building interfaces.