A growing literature demonstrates the impact of the built environment on human health and wellbeing. A wide range of factors such as daylight exposure, ambient noise and air quality may alter an individual's instantaneous state of wellbeing. Instantaneous state of wellbeing has been associated with variability in the physiological stress response. Our research goal is to capture the effect of indoor environment changes on shortterm stress response of individuals. At an early stage in this research project, we demarcate our problem by posing three questions: (a) "Which are the indoor environmental factors that correlate with heart rate variability?" (b) "Can episodic stress levels be identified using stress response patterns?" (c) "Can we optimize the overall wellbeing of individuals at workspace by controlling indoor environment?". We briefly discuss our ongoing study setup and interim results. Thereafter, we propose a Hidden Markov Model (HMM) based framework to address the second question. Addressing the first two questions provides a foundation to address the third question which is the end goal of this study.