This Special Issue of Indoor and Built Environment addresses health and wellbeing within the context of the current drive for ‘low-carbon’ buildings – where the term ‘low-carbon’ is used here to include zero or nearly zero carbon/energy approaches. Papers are mainly from invited authors, and a few are extended versions drawn from a relevant Conference of the UK Indoor Environments Group (UKIEG) held in June 2013. All papers were subject to the journal’s peerreview process from authoritative independent experts. Whilst the focus is primarily on the United Kingdom and Europe, and especially on heating-dominated countries, many lessons/issues are also broadly applicable to other climates and regions. This introductory Editorial provides a background overview of the topic, discusses key themes emerging from the papers and argues that the lack in joined-up thinking in the climate change and health policy agendas requires researchers to urgently address one of the main challenges in this field – namely how to ‘sell’ the importance and value of addressing complexity and uncertainty. The intrinsically complex nature of the relationship between health/wellbeing and low-carbon buildings has been discussed for some time in various contexts. Various communities have debated the matter, including the UK Indoor Environments Group (UKIEG), a multidisciplinary network of academic, policy makers and industry concerned with the quality of indoor environments – especially from a health and wellbeing perspective. UKIEG members – some of whom are authors of papers in this Special Issue and have presented at our Conferences – have debated the topic(s) of this Special Issue several times since the UKIEG’s foundation in 2003. These debates have often been accompanied by a great deal of frustration amongst concerns of: (1) a disconnect between the health and the energy/carbon policies; (2) a lack of suitable evidence that current trajectories for low-carbon buildings are sufficiently robust and will provide ‘healthy’ indoor environments (or at least as healthy as current environments). Thus, this Special Issue is timely, not only as a formal contribution to those debates occurring within the UKIEG and other similar groups worldwide, but also because the implementation of the low-carbon buildings agenda is gaining momentum in several countries, both for new builds and retrofits. This means that the question of whether low-carbon buildings are more/ less conducive to health and wellbeing must be addressed urgently. Also, in the past couple of years the first mainstream low-carbon buildings (as opposed to isolated prototypes) have been constructed and inhabited, representing a fantastic opportunity to study the issue in situ. Buildings are responsible for more than 40% of global energy use and one-third of global greenhouse gas emissions both in developed and developing countries. Furthermore, the Building Sector has a large potential for delivering long-term, significant and cost-effective greenhouse gas emission reductions. Consequently, most developed countries and many developing countries have already taken steps to address emissions from the Building Sector, mainly in the form of legislation dictating minimum carbon/ energy standards – especially (but not solely) for new buildings and major renovations. For example, the European Union (EU) ‘Energy Performance of Buildings Directive’ was first published in 2002 (Directive 2002/91/EC), requiring all EU countries to enhance their building regulations and to introduce energy certification schemes for buildings, as well as inspections of boilers and air-conditioners. A further version of the Directive published in 2010 (Directive 2010/31/EU) also included, amongst other things, a move towards new and retrofitted nearly zero energy buildings. As highlighted by several authors in this Issue, the drive for new low-carbon design paradigms