This report describes several strands of research examining the connection between winter- and cold-related mortality/morbidity, and the energy efficiency (thermal insulation) properties of the housing stock in England. Our purpose was to address current knowledge gaps and to strengthen the evidence base for appraisal of policy options in the housing sector, which could see large investments over the coming decades that are partly motivated by climate change goals.
It has long been recognised that the UK has a large and unacceptable burden of excess winter mortality and morbidity1–3 (around 25,000 excess winter deaths each year depending on the definition used), which is greater than that of many comparable northern European countries with colder climates. Although part of the winter excess is attributable to influenza and other seasonal infections, time-series studies suggest that the major part of the seasonal burden is related to exposure to cold.1,4,5 Theoretical considerations and some direct evidence from the UK, New Zealand and elsewhere suggest that housing may play an important role in determining vulnerability,6–11 although it is recognised that exposure to cold through outdoor excursions may also be important. Therefore, there has been much interest in, and debate about, the contribution that interventions on housing quality may make to winter- and cold-related mortality and morbidity, especially in the context of fuel poverty (FP).8,9
Over the next few decades, there are likely to be major investments in the housing sector driven by (1) policies aimed at reducing household energy use and greenhouse gas (GHG) emissions to meet the legally binding obligations of the Climate Change Act 2008,12 and (2) considerations of health, in particular the assumed benefits of improved insulation and energy efficiency for winter- and cold-related deaths and illness. However, these investments may be very costly and have potential for adverse as well as positive effects on health,13 especially if achieved in part through reduced ventilation. Therefore, it is important that policies are informed by quantitative evidence on the impacts of home energy efficiency (HEE) investments on health and that decision-makers have tools needed to assess likely health and other costs and benefits. We have attempted to contribute such evidence both by exploiting opportunities for using national data on HEE interventions [specifically the Homes Energy Efficiency Database (HEED)14] and by the development and application of models and tools.
Energy efficiency and health
The energy efficiency of dwellings relates to four main parameters: the insulation properties of the building fabric (its walls, roof, floor and windows); the control of ventilation; the efficiency of the heating, cooking, lighting and other power-consuming devices within the home; and the sources of energy.
Figure 1 summarises the principal pathways by which energy efficiency affects health. There are four main sets of pathways. The first is the thermal control of the indoor environment, especially protection against cold in winter months but also, potentially, against heat exposure during warmer weather. Cold is important not only because of its physical effects but also because of its bearing on mental well-being and social interactions within families and with friends and neighbours. Second, energy efficiency typically entails a tighter control of ventilation to avoid heat loss through the poorly controlled escape of heated air. The consequences of such reduced permeability may be positive or negative. Greater airtightness protects against the ingress of harmful pollutants from the external environment but acts to increase pollutants generated inside the home, including second-hand tobacco smoke (STS), volatile organic compounds from materials inside the home, and radon. Third, there are emissions to the external environment that can contribute to ambient pollution but other emissions to the external environment include GHGs which are an increasingly important factor in global environmental change and, thus, in future planetary and human health, even if they are not directly toxic. Finally, there are consequences relating to the cost of meeting energy needs that may be especially important for families on low incomes.
FIGURE 1 Diagrammatic representation of the main direct and indirect pathways by which energy efficiency measures affect health. (Figure not reproduced here; see the original article.)
These four sets of pathways give rise to potentially innumerable forms of health impact, many of which are not sufficiently well understood to attempt quantification, such as those relating to more distant climate change effects or to cost savings. Figure 2 also schematically shows that the timing of these impacts varies. The effects of cold or heat are fairly immediate in terms of both physical and mental well-being. However, changes to indoor air quality have effects that may take years or even decades to evolve even if the change in pollution concentrations is immediate. This means that the assessment of the health effects depends not only on which pathways are considered but also on the time window.
FIGURE 2 Diagrammatic representation of the evolution of the main categories of health impact consequent to changes in the energy efficiency properties of a dwelling. AQ, air quality; CC, climate change. (Figure not reproduced here; see the original article.)
Although it should be an aspiration to be as inclusive as possible with regard to the spectrum of exposures and outcomes and the time horizon, all studies are necessarily restricted. The study that we report here is no exception. However, as we have a partial focus on the development of modelling methods, we have begun to consider the medium- to long-term effects of energy efficiency measures in more depth than originally intended. This has been useful because of the insight that it has given into HEE interventions, which should not be viewed as dominated by issues relating to the effects of cold. As we will show, other forms of health impact may be of equal, if not greater, importance, and when assessing practical choices it may often be instructive to consider multiple consequences of actions.