Occupants' Wellbeing

Indoor air quality

Indoor air quality can be compromised by the build-up of humidity, particulates, and contaminants internally, which can cause severe health problems.

Indoor and outdoor humidity levels are now higher than when most traditional buildings were constructed. Modern standards of living ask for higher indoor air temperatures than in the past, which means that the air can contain more water vapour molecules. External humidity levels are rising due to climate change. Indoor humidity levels are often higher because we carry out more indoor activities that produce moisture, such as drying clothes or cooking without a pan lid.

A significant number of people now spend most of their day indoors, and their exposure to indoor pollutants has increased. Common sources of indoor contaminants are:

• Deleterious materials, such as asbestos and radon
• Finishes, furnishings and petrochemical based materials which produce particulates and volatile organic compounds
• Microorganisms, such as dust mites, fungi or mould spores, and bacteria
• Cooking appliances that contribute to particulate build-up, dependent on the type of fuel
• Building use, which can produce carbon monoxide, carbon dioxide and ozone

When planning energy efficiency interventions, it is essential that a ventilation strategy is implemented to regulate the internal moisture levels and reduce condensation risk and contaminants.

Thermal comfort

Building occupants will be satisfied with their environment if they don't feel discomfort. Many factors influence thermal comfort, such as air temperature, humidity, quality and movement of air, solar gain, and the emissivity (energy radiated from) and temperature of surfaces. The clothing and physical activities of building occupants also play a role.

Additionally, occupants' expectations and social and cultural attitudes, as well as their age and general health, will affect their perception of thermal comfort. For example, body temperature regulation is lower in older adults, and their thermal comfort will therefore be different to that of younger people in the same environment.

If they can, building occupants will adjust conditions until they feel comfortable, which will have a direct impact on energy use. Traditional buildings and furnishings provide numerous ways for them to do this. They may draw curtains to reduce heat loss or use external shutters or awnings to reduce solar gains, for example. In addition, the thermal inertia of thick walls and some solid floors can help buffer changes in external temperatures. The plan form of traditional buildings often facilitated the indoor environment of individual rooms to be controlled separately.

Surveys reveal that occupants having control over their thermal environment is beneficial to provide a sense of both agency and comfort. Where occupants have some control over conditions, most accept small seasonal variations in indoor temperature without feeling a need to act. This can have a big impact on energy use. For example, in a dwelling with central heating, 10% or more of annual heating energy consumption can be saved for each 1°C the thermostat is not turned up.

When designing energy efficiency interventions for traditional buildings, it is crucial to understand the aims and needs from the end user's point of view. It is particularly important to set objectives for space heating and cooling, using passive or active systems, that meet these. Measuring and predicting thermal comfort remains a key consideration within the design, but further work is necessary to fill current knowledge gaps.