Strategies for healthy, equitable and sustainable housing
Well-designed housing strategies can reduce energy use as well as create healthier environments for occupants and increase health equity. For instance, the transmission of airborne, waterborne and certain vector-borne diseases can be reduced through sustainable urban and housing designs that increase natural ventilation, limit vector and pest infestations, and improve access to safe drinking water and sanitation. Energy-efficient housing design can help reduce noncommunicable diseases associated with exposures to extreme heat and cold, indoor air pollution, as well as asthmas and allergies associated with chronic damp and mould.
Effective strategies for healthy, sustainable housing involve:
- insulation and thermal envelope;
- heating and cooling systems;
- improved ventilation;
- solar energy (passive and photovoltaic);
- efficient cooking and lighting technologies;
- safer building materials;
- “compact” urban planning of neighbourhoods with easy access to schools, commerce, transport and green spaces;
- healthy home behaviours.
While specific improvements are identifiable, multifaceted interventions can collectively yield significant, sustainable health gains. Strategies need to be integrated into all stages of housing design and implementation, from urban planning of neighbourhoods to construction, and retrofit or renovation of existing homes.
Insulation and thermal envelope
A thermal envelope refers to a shell serving as a barrier to unwanted heat or mass transfer between the building interior and exterior. Improvements in household thermal envelopes can yield significant health gains.
Insulation is a critical factor that determines the quality of a thermal envelope. Improvements in insulation can reduce human exposure to temperature extremes and dampness, thereby decreasing vulnerability to asthma and allergies, stroke, heart and lung diseases.
Improving the thermal envelope can be done through 3 major routes:
- insulation material;
- window modifications;
- prevention of air leakage.
While an improved thermal shell has benefits, it can reduce ventilation, also important to health. Poor air circulation can increase indoor air pollution, and concentrations of moulds and other biological contaminants. Improved insulation measures must thus be combined with adequate ventilation to ensure optimal health outcomes.
Heating systems
Energy-efficient homes and home heating systems can generate multiple health benefits directly and indirectly.
Energy efficient home construction, including the use of climate-appropriate design principles for insulation, window placement and daylighting, enables the effective use of passive solar-based home heating methods, which capture the radiant heat of the sun for improved space heating.
Passive solar design strategies not only reduce the total amount of energy required to heat a home, and associated pollution emissions, but also tend to improve indoor thermal comfort levels, and by doing so, reduce risks of respiratory illnesses as well as other health risks related to exposure to cold and damp. Thermal solar systems can also be used for hot-water heating, for better personal and kitchen hygiene, as well as for additional space heating capacity. Shifting to cleaner and more efficient household heating fuels and technologies is the other strategy for reducing reduce indoor and outdoor pollution emissions that are generated directly by heating systems. For homes using stand-alone, portable heating systems, ensuring that systems are closed and equipped with sealed chimneys or flues so that emissions are evacuated outdoors, is essential to reducing household air pollution, as well as reducing risks of burns and injuries from fuel spills. WHO guidelines discourage altogether the use of kerosene and unprocessed coal systems, due to their very high level of indoor or outdoor air pollution emissions.
Natural ventilation
Inadequate ventilation allows for the accumulation of a variety of pollutants from building materials, fuel burning, and radon gas emissions. Moulds, a risk factor for allergies and asthma, thrive in unventilated areas. Vectors, such as mosquitoes that carry dengue and malaria, pose a greater risk to those dwelling in homes with trapped air. Together, the accumulation of harmful environmental threats in unventilated homes poses a significant risk to health. Improved design for ventilation can increase air exchanges and air quality, thereby reducing these health risks. Natural ventilation also can enhance the cooling of buildings, yielding up to 25-50% in energy savings. Many traditional building styles enhance natural ventilation by providing for high ceilings, and air spaces at ceiling level or below the eaves to enhance the daytime venting of heat, and night-time cross ventilation.
Natural ventilation can provide significant health benefits, but must be examined to prevent predictable risks. For instance, natural ventilation in settings where outdoor air pollution is greater than indoor air pollution may not be beneficial. Similarly, ventilation without screening measures can allow for the entry of pests that carry diseases in certain environments. And open windows at street level can pose a security risk in neighbourhoods where crime is a serious issue.
Cooling and air conditioning
Cooling methods for buildings can promote reduced energy use and improve health outcomes.
According to the Intergovernmental Panel on Climate Change, principles of design that can be used to cool buildings include:
clustering buildings to promote shading; using highly reflective material to reflect light; orienting a building to minimize wall area facing direct sunlight; window shading and window placement; double walls or lattice work, or vegetation, particularly along the southern exposures; design for cross-ventilation and natural ventilation to promote night-time cooling; selective use of insulating building materials that deflect, rather than absorbing heat (e.g. stone).Air conditioning is increasing in use worldwide, and offers immediate protection from heat waves. Its use has also been associated with vector control and protection from the impacts of heavy outdoor air pollution hotspots.
However, the benefits of air conditioning are not without consequences. Cooling units often utilize hydrofluorocarbons (HFCs) that can leak into the environment and contribute to climate warming. Furthermore, many air conditioning systems are highly energy-intensive, with significant demands for electricity and fossil fuel use which can undermine energy security and exacerbate climate change. These units can also provide a breeding ground for microorganisms such as Legionella which can cause lung disease. Noise for neighbours, inequitable access and excessive heat production are other undesirable effects of cooling technology.
Lighting and daylighting
The provision of adequate light, both natural and artificial, is a determinant of health. Sufficient natural light exposure is a factor in biophysical performance, mental health and injury prevention. Exposure to natural light is important for vitamin D production, sleep cycle regulation and mood. Lighting is also important for the prevention of falls and injuries among the elderly.
Cleaner cookstoves
More efficient stoves and cleaner fuels that meet WHO indoor air quality guidelines have the potential to avert millions of deaths each year caused by household air pollution, while also reducing emissions that impact climate change.
Among the available technologies, cleaner fuels such as biogas, ethanol, LPG, and natural gas along with electricity are the best alternatives to solid fuels for reaching WHO air quality guideline levels for household air pollution.
Other benefits of more efficient cooking appliances include fuel cost or collection savings, injury reduction, and better temperature and indoor environment control. Cleaner cookstoves and fuels have the potential to achieve gains in health, gender equity, and sustainability across the developing world.
Improved building materials
Building materials such as asbestos and lead have the potential to damage human health. Insulation, paint and dust derived from harmful materials can result in cancer, lung disease and impaired growth and development.
Thus, measures must be taken to improve existing dwellings by replacing hazardous substances in rooftops, walls, floors, pipes, or other household components with less harmful materials. In addition, improved regulations in developing countries can ensure that new housing developments assess all materials for potential environmental and health risks. This will reduce the risks of building-related toxic substances having negative impacts on ecosystems and human well-being.
While dwellers may suffer from exposure to these materials in existing structures, workers may also suffer from exposure during the building and renovation process. Focused measures need to be in place to reduce both residential and occupational exposures to prevent adverse health outcomes.
Urban planning and residential environments
Urban design impacts powerfully on residential environments and finally on health outcomes. Medium housing density, with easy pedestrian access to local businesses, schools, and green spaces, is associated with safe, accessible pedestrian environments, more access to healthy physical activity, greater access to basic services for women, children, elderly and those without cars – as well as significant carbon efficiencies.
Clustered housing also can lower heating costs with shared walls, and medium-building heights can also facilitate natural ventilation and cooling – avoiding the energy and health costs of air conditioning. Connectivity to public transport, walking and cycling in neighbourhoods provides opportunities for physical activity while lowering pollution and traffic noise. Urban landscaping of trees, green spaces and water sources promote cooling, thermal comfort, sanitation and mental health. Collectively, these aspects of healthy urban planning are also key to healthier housing environments.
Healthy home behaviours
Behavioural factors can either promote or confound housing’s impacts on health and climate emissions. Behaviours and preferences related to ventilation, protective clothing, temperature and pest control result in actions that may or may not be healthy or environmentally friendly.
For instance, overuse of heating or air conditioning systems for temperature changes is often behaviourally driven, even though adequate hydration, clothing, and bedding can mitigate extreme temperatures with less climate and pollution impacts. These measures also can benefit health more directly in settings where forced air heating or air conditioning systems recirculate bacteria and other pathogens. While behaviours are important factors that contribute to healthy home environments, they must be addressed by staged and multi-faceted educational and promotion strategies for long-term change.