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The Nottingham Energy, Health and Housing Study: A Demonstration Project to Reduce Humidity, House Dust Mites and Asthma

Health and Housing Group National Energy Action Nottingham The Bartlett
University College London


A prevalence of dust mites and mould in domestic properties is known to aggravate the symptoms of asthma. Therefore, measures to alleviate the conditions that allow mites to thrive (e.g. high humidity) should have a beneficial impact on the health of asthmatics. Many energy efficiency interventions achieve this, although this is often an unplanned, albeit useful, side effect of work aimed at reducing energy consumption and wastage. Some interventions may even increase the problem: by reducing ventilation, for example. With better knowledge of the packages that offer the optimal combinations of energy and health benefits, interventions can increase their impact.

Key research Question

The study set out to identify what sort of energy efficiency measures and ventilation configurations would generate the most significant health benefits for asthmatics living in fuel and/or heat poverty while at the same time delivering lower fuel costs and warmer homes.

Summary of activity

The study focused on seven social housing properties in Nottingham, and the research was conducted in 1998 and 1999. It was designed to be a pilot. Interventions ranged from better insulation and humidity-controlled extraction fans to complex mechanical ventilation heat recovery systems.

A range of baseline statistical data were collected before improvements were undertaken. This included monitoring lung flow, other medical information on household members, temperatures, energy consumption, levels of humidity and dust mites and an assessment of the general condition of the property. These were remeasured 12 months after the work was completed.

Residents living in the sample households were asked to keep a record over a seven-day period of their energy behaviours (e.g. number of baths or showers, time for which windows were kept open and use of heating systems).


The authors note that the small scale of the study means that the findings should be regarded as indicative only. The literature review confirmed the importance of reducing relative humidity levels to a target of 50% or lower to control mites and the allergens they produce and the need to consider microclimates inside properties. It also established that the precise nature of measures for controlling mites is not known but that packages rather than individual procedures seem to be more effective.

Medical data collected a year after the modifications showed clear evidence of positive health benefits, including improved lung air flows and reduced use of medication. In six of the seven properties, levels of dust mites dropped significantly. This was attributed to reductions in relative humidity that averaged 8.5%. The study confirmed previous research that concluded that establishing an average relative humidity of below 50% appeared to be key for controlling mite levels. Improved health outcomes are not an inevitable consequence of energy efficiency measures; ventilation must also be factored in.

Although all the homes achieved higher National Home Energy Ratings, which predicted a considerable drop in energy costs, energy consumption actually rose after the modifications. The modifications were often not fitted properly owing to the inadequate expertise of the installers. Overall, the project showed that health improvements can be achieved cost-effectively, although it was not possible to definitively identify the optimal package.


  • Further research is needed to investigate in detail the response of dust mites to different environmental conditions. Much larger expanded trials that consider a range of ventilation options in conjunction with affordable heating are recommended. Such trials should include control groups and consider the role of microclimates.
  • Building regulations and other national standards and energy efficiency programmes should be updated to incorporate more detail and guidance on ventilation. In addition, better training for contractors is needed to ensure improvements are installed correctly.
  • Appropriate energy advice to householders must accompany the implementation of this type of scheme.

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