Low-carbon buildings,health and wellbeing: Current perspectives and critical challenges

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 peer-review 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.^1–6 Various communities have debated the matter, including the UK Indoor Environments Group (UKIEG), ⁷ 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. ⁸ 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 inevitably leads to the adoption of new technologies, materials and design approaches, which in turn raises the question as to whether these dramatic changes in the building stock could also result in dramatic changes in health and/or wellbeing – either positive or negative. The most obvious and commonly cited example of this potential link between low-carbon buildings and health outcomes is related to indoor air quality (IAQ), whereby the requirement for greater air-tightness (to reduce ventilation heat loss) could result in poor ventilation rates and consequently greater exposure to indoor pollutants – many of which have well-known adverse health effects, for example on the respiratory and cardio-vascular systems. The ventilation and IAQ problem is discussed extensively in this Issue, for instance by Sharpe et al. who highlight that whilst prescribed minimum air-tightness levels have been established in conjunction with requirements and strategies for background ventilation to ensure ‘healthy air’, there is a concern that such strategies are not sufficiently robust. In fact, it is unclear to what extent such background ventilation strategies have taken into account the potential for greater indoor pollution, potentially caused from new materials or changes in behaviour, as well as from a lack of proper maintenance or suitable operational strategies.

Perhaps the most distinguishing feature of the topic debated here – health/wellbeing and low-carbon buildings – is complexity. Firstly, health and especially wellbeing cannot easily be converted into a common unit (such as in the case of energy and carbon) and, secondly, it is difficult to establish universally accepted criteria for evaluating the trade-offs between health/wellbeing outcomes and energy/carbon savings. Furthermore, the pathways are intricate, with many potential positive or negative direct and indirect effects of low-carbon designs on health and wellbeing. In turn, these effects should be evaluated against the potential health risks which could arise if climate change mitigation and adaptation strategies (including low-carbon buildings) were not implemented. The complex nature of the potential health and wellbeing risks arising from climate change have been discussed elsewhere. ⁹ In this Issue, on the other hand, Shrubsole et al. highlight the complexity of the problem by discussing the unintended consequences of policies to improve the energy efficiency of the UK housing stock. The study identifies several domains which could be affected (positively, negatively or both) by such policies, including: physical and mental health, psychological wellbeing, social cohesion and inequalities. The paper highlights that a more integrated approach to decision-making is needed, also ensuring that trade-offs are dealt with explicitly. The complexity issue applies not only at the macro but also meso- and micro-scales. For example, the identification of ‘healthy’ or ‘safe’ ventilation rates can be difficult, partly because of the mix between indoor and outdoor sources, and partly because the issue of suitable ventilation is inextricably linked to the right balance between design specification, commissioning, maintenance and operation. For instance, the paper by Sharpe et al. reports poor ventilation in contemporary low-energy bedrooms in Scotland, highlighting the need for more robust and flexible strategies which also avoid the ‘one size fits all’ approach.

The paper from Chatzidiakou et al. also highlights the complexity of evaluating air quality, health and ventilation issues. The study contrasts these aspects in two London-based schools, one with a traditional design in an urban setting and another with a low-carbon design in a suburban setting. The paper reports that objectively measured aspects of IAQ were poorer in the low-carbon school. However, poorer IAQ in the low-carbon building cannot be uniquely attributed to inadequate ventilation design, as indoor concentrations are a complex result of indoor sources (highlighted by the authors as an important aspect in this case) and of ventilation rates – which in turn are not exclusively dependent on design features (e.g. impact of weather, operation/behaviour, indirect impact of noise/pollution). And of course high levels of ventilation are not always desirable, for example the study found that NO₂ concentrations (primarily an outdoor pollutant) were linked to self-reported asthma and asthma symptoms. A further paper in this Issue which highlights the complex evaluation of IAQ is the study from Fischer et al. of an unoccupied apartment of a ‘near-zero-energy’ building with a unique wooden construction in Sweden. The study aimed to examine the impact on IAQ of the interplay between outdoor air pollutants, introduced by the ventilation system, indoor air pollution caused by the building materials (as opposed to the occupants’ activities), air change rate and chemistry. The study demonstrates that indoor air chemistry could take place at conditions relevant to dwellings in Scandinavia, producing the rarely measured and potentially toxic indoor pollutant peroxyacetyl nitrate (PAN). Whilst they find that PAN concentrations are not cause for concern even when simulating outdoor episodes of outdoor pollution, the authors also highlight that their study aimed to investigate building-related IAQ only and that occupant activities could partly modify these concentrations. Furthermore, they emphasise that the potential for synergistic health effects of exposures to multiple pollutants should be further investigated.

Some papers in this Issue also highlight the role of confounding factors, such as outdoor conditions or occupant behaviour and lifestyle. For instance, in Chatzidiakou’s paper the low-carbon school is in a suburban setting whilst the traditional design school is in an urban context, whereby comparisons will be affected by differences in outdoor noise and pollution levels. Furthermore, despite the high levels of air-tightness and insulation of the low-carbon school, its energy performance was jeopardized by the occupants opening the doors to the playground during breaks, thus losing some of the heat in the classroom’s air. Sharpe et al. on the other hand emphasise that occupant numbers and/or lifestyles can affect the outcome of environmental conditions, despite the low-carbon design. The mismatch between building design and occupant behaviour/lifestyle is highlighted by Porteous et al. which examine aspects of domestic laundering practices, with an emphasis on passive indoor drying and air quality. The study shows how elevated moisture levels can be found as a result of the inadequacy of dwelling design with respect to indoor or outdoor provision for drying clothes, combined with poor ventilation control. This in turn results in elevated risk of exposures to moisture-related allergens such as dust mites and mould. Interestingly, the authors also emphasise a vicious circle between poor IAQ, occupant behaviour and energy use, with passive indoor drying potentially affecting energy use, primarily through an impact on heating and ventilation habits. Also, the paper highlights the importance of better understanding indoor sources, in terms of how and why they are generated – as opposed to mainly trying to understand how to disperse indoor pollutants via ventilation. The issue of confounding factors also arises in Woods et al. who aimed to better understand the relationship between indoor PM_2.5 concentrations and adverse asthma outcomes in children treated with inhaled steroid treatment. Their findings suggest that even low indoor air PM_2.5 exposures – with no reported smoking taking place – can have significant health implications for asthma outcomes in children, despite the drug treatment. The issue of child health is also addressed in the paper by D’Arcy et al. which discusses the risk of exposure to environmental bacteria in indoor locations where children spend time, i.e. hospital ward, outpatient area and classroom.

The complexity of the issues addressed here means that the identification and development of suitable methods and tools for measurement and evaluation is critical, for example of ventilation rates. For example, the measurement of ventilation rates is critical, but this can be expensive on a large scale, and the commonly used method of measuring carbon dioxide (CO₂) is not fail-safe. This is highlighted by the study from Mahyuddin et al., which examines how CO₂ is distributed within a classroom environment and how this distribution is affected by different parameters. The study finds that the spatial CO₂ distribution can vary to a greater extent than often assumed and that using only one sensor to represent CO₂ concentrations in a room can lead to inaccurate estimations. The paper also recommends that the choice of sampling locations should be evaluated on the basis of the prevailing air movement and the type of ventilation strategy. Besides measurement tools, evaluation tools are also critical. For instance, whilst natural ventilation is more common in the residential sector (with low-energy designs increasingly relying on mechanical ventilation), in sectors such as hospital environments mechanical ventilation is more prevalent, due to the need of reducing the risk for airborne transmission of infectious diseases, by diluting and extracting airborne pathogens as well as controlling airflows across spaces. Therefore, in healthcare environments, the higher potential for health risks associated with poor ventilation mean that its low energy counterpart (natural ventilation) is often discarded – although air-cleaning technologies could be combined with natural ventilation to reduce the risk of airborne infections. In this respect, tools and methods for an accurate evaluation of the trade-offs between parameters affecting IAQ, energy use, and health outcomes are essential. The paper from Gilkeson et al. is relevant to this issue: it combines computational fluid dynamics (CFD) analysis with numerical optimisation tools for evaluating the design of an upper room ultraviolet germicidal irradiation system, within a simulated multi-bed naturally ventilated hospital ward. The paper from Li et al. also addresses the question of tools, providing an actual condensation model of a radiant cooling system to characterise condensation of cold surfaces near a radiator. The findings of this research can contribute to the optimization of cold radiation systems, providing boundary conditions for CFD simulation, thermal design of enclosure structure and design of air conditioning systems terminal – thus providing a system for reducing moisture risks in cold and heating environments with a consideration of heat conservation. The paper from Girard et al. is also pertinent to the issue of assessment tools, with a focus on solar space heating and the design of low-energy buildings. The paper also reminds us that the reduction of ventilation and fabric heat loss are not the only design philosophies underpinning low-carbon buildings, whereby the use of renewables and/or low-carbon energy sources as a substitute for fossil fuel is at least as important, especially in the long term. How these aspects and associated technologies may impact upon health and wellbeing should also be evaluated, ideally considering a holistic and future-proofing approach.

Whilst issues surrounding IAQ and ventilation are perhaps the most obvious when considering low-carbon buildings and health/wellbeing, other aspects should not be overlooked. For instance, changes in exposures to indoor temperatures also arise from low-carbon designs. Whilst on balance such changes are likely to have a positive health impact in heated-dominated countries, the potential for comfort and health impacts from overheating should not be underestimated – especially in light of climatic changes. In fact, changes in exposure to indoor temperatures due to changes in building design could lead to a variety of potential health impacts, including impacts on energy expenditure and weight gain ¹⁰ – although this is still being debated. The paper from Virk et al. – which examines the effectiveness of retrofitted green and cool roofs at reducing overheating in current and future climates – reminds us of the importance of thinking broadly about the topic. This is not only in relation to broader questions than the ‘air-tightness debate’, but also in considering buildings as part of a wider system, rather than isolated entities. The evaluation of low-carbon designs from a health and wellbeing perspective must be done with future-proofing in mind and considering future scenarios (e.g. climate, outdoor pollution), thus adding yet another level of complexity.

In summary, the topic(s) covered in this Special Issue directly or indirectly address the question: ‘Are low-carbon buildings better or worse for the health and wellbeing of their occupants?’ Evidence from the papers presented here and found elsewhere suggests that the most likely answer is the ubiquitous ‘It depends’, which often generates frustration and disengagement in the target audience (e.g. policy makers). Firstly, the design strategies underpinning low energy or zero carbon buildings can vary, and whilst the focus of the discussion here has primarily been on the reduction of ventilation and fabric heat loss in heated-dominated climates, this is not the only low-carbon design paradigm – whereby for example renewable or alternative energy sources could be important. Furthermore, inhabitants of low-carbon buildings are not the same nor occupants necessarily maintain their behaviour unchanged over time and regardless of the building design.¹¹ Also, in order to answer the previously mentioned question, two broad approaches are possible: (1) comparing health (or exposures) in low-carbon buildings against ‘standard’ (comparable) buildings, which in itself is very difficult as ‘standard’ buildings come in a huge variety, and ‘comparability’ is not easily established; (2) measure (or model) exposures in low-carbon buildings and evaluate them against ‘safe’ thresholds – which again is complex since such thresholds are not always available (e.g. impact of new materials is under-researched) and synergistic effects could be ignored. Either way, whilst a case-study approach can be useful in highlighting some potential effects, large-scale studies are needed in order to meaningfully evaluate such effects. Based on what has been discussed so far, and in light of the current lack of joined-up-thinking in current policy approaches, the research community must address several challenges:

Communicating the value and importance of dealing with complexity, in a manner that is captivating and meaningful to those who have to translate academic thinking into policy initiatives and research programmes.

The biggest challenge by far is probably the first of the list, but we are confident that human ingenuity will prevail.