Energy, both in terms of its production and its usage has occupied a prime place in research as well as politics and world economy for the past few years. This majority of nations are aiming to deliver severe carbon cuts in the next few years. However, achieving a carbon-free future needs more than infrastructure invesment and novel efficient technologies for buildings, transportation and other large consumer domains it needs a better understanding of people as consumers as well as a better understanding of energy waste across the multitude of socio -technical systems around us. With regards to the built environment and particularly residential buildings, the authors propose that dual, quantitative and qualitative. approaches to characterising, assessing and improving occupied building are necessary. Such approaches would synchronous cater for understanding i) buildings technical performance (fabric and building heating, cooling and ventilation system) and ii) occupant's motivation, ability, knowledge and efficacy for adopting low carbon lifestyles. When deployed at scale, the above will enable cost effective, targeted interventions for both building fabric and systems improvement and towards empowering their occupants to live sustainably. The paper describes such a quantitative and qualitative approach and proposes assesment tools. Futhers, the authors comment on the potential benefits from monitoring campaigns when deployed at scale.