The design and operation of responsive resource-efficient buildings requires high resolution data in space and time on building performance and the associated occupant response, but capturing this high quality data has traditionally been technologically challenging, costly and disruptive to building occupants. Recent developments in Internet of Things (IoT) technologies provide an opportunity to monitor holistic indoor environmental quality (IEQ) and related occupant perception and behaviour in a more cost-effective and less disruptive manner whilst providing higher granularity data in space and time. Façades have a significant and dynamic influence on IEQ and building performance, and occupants often interact with them, but there is a dearth of IoT solutions for monitoring the façade-induced effects. This paper describes the development, deployment and assessment of the Building Impulse Toolkit (BIT), a prototype IoT system for capturing the holistic and transient influence of façades on IEQ and occupants. The methodology adopted in the design and development of the BIT prototype is first explained. The results obtained from a 9-month deployment in a real-world office are then reported and discussed, in particular the capabilities and limitations of the BIT prototype in: 1) capturing the influence of the façade on IEQ in space and time; 2) monitoring occupant environmental discomfort and satisfaction and in a non-disruptive manner; 3) monitoring occupant interaction with the façade. It was found that BIT is largely successful at meeting these objectives, but occupant engagement could be improved in the next generation prototypes.