A building must accommodate activities that will occur in and around it while supplying a healthy and comfortable indoor environment to the people using it.

The building should not cause harm to its occupants or the environment and must, for example, be structurally stable and fire safe.

Given that most people now spend a significant portion of their time indoors, the quality of an indoor environment is imperative to health and safety. Good indoor climate is an important factor in design and construction as it decreases the number of illnesses and sick building syndrome symptoms, improves comfort and increases productivity.

The quality of indoor climate is affected equally by heating, ventilation and air conditioning equipment, construction engineering, quality of construction work, building materials as well as the operation and maintenance of the building.

Working in hot or cold conditions without adequate control measures can create a number of health effects ranging from discomfort to serious illness.

Thermal comfort can be defined as a condition of mind which expresses satisfaction with the thermal environment.

The most commonly used indicator of thermal comfort is air temperature – it is easy to determine and most people can relate to it. Though it is an important indicator to take into account, however, air temperature alone is neither a valid nor an accurate indicator of thermal comfort or thermal stress. Air temperature should always be considered in relation to other environmental and personal factors.

The factors generally recognised to affect thermal comfort can be classified as environmental (air temperature, radiant temperature, humidity, air speed) or personal (the amount of physical activity and the amount and type of clothing worn). These factors may be independent of each other, but together contribute to a building occupant’s thermal comfort.

Due to large variations from person to person, it is of course difficult to satisfy everyone’s varying needs within the same thermal environment.

Typically, concerns about indoor thermal comfort occur in areas that are poorly ventilated and/or inadequately shaded from sunlight. Individual thermal comfort can also be affected by physical exertion, crowded working areas and some medical conditions. Thermal comfort is determined by subjective judgment, and even in optimal conditions some individuals may experience discomfort.

Indoor temperatures considered to be optimal for winter are 19 to 22 degrees Celsius; this temperature range is approximately one to three degrees Celsius lower than what is considered optimal in summer. A wider range of 18 to 24 degrees Celsius applies to what is considered acceptable (as opposed to optimal) for winter. These are again lower than those considered acceptable in summer. A relative humidity of between 30 and 60 per cent is also applicable to thermal conditions considered acceptable.

Even though there are no specific legislative requirements under Workplace Health and Safety laws relating to thermal comfort, the general duty to provide a safe workplace and safe systems of work represent a responsibility to employers and facilities managers to address this and related issues. There is substantial local and international guidance material on managing thermal comfort. Worth noting, however, is the importance in distinguishing between a condition which threatens health and safety, and a feeling of discomfort as the controls of management will also differ.

In an existing building a simple way of estimating the level of thermal comfort is to ask the workers or their workplace representatives. If the percentage of workers dissatisfied with the thermal environment is above a certain level, that will indicate that there is an issue which should be appropriately addressed.

There are many different methods to achieve indoor climate comfort, including passive systems, evaporative cooling systems and refrigerated systems. These may be locally controlled, occupant controlled at a building level or electronically controlled via a BMIS system.

It is important to achieve the best performance out of a building’s system, and that the occupants of a building fully understand how their system operates in order to achieve this.

Thermal comfort can be controlled or adjusted by a number of different measures:

  • Environmental monitoring and control (automated or user-controlled systems, active systems such as heating and cooling and passive systems such as shading).
  • Adapting or changing clothing. Businesses can allow people to wear different clothing depending on conditions. They can also provide things like cloak rooms or lockers so that people can change clothes or take off and store warmer clothing.
  • Allowing flexible working hours.
  • Adjusting tasks; allowing breaks or reducing the length of time people are exposed to particular conditions.
  • Providing information with regard to the conditions to expect so that they can dress and behave appropriately.
  • Providing or allowing personal equipment such as desk fans.
  • Separating people from sources of discomfort by taking steps such as putting heat generating equipment such as IT equipment in separate rooms, insulating pipes, preventing draughts and so on.
  • Providing protective clothing. This however should be an option of last resort.

To avoid unnecessary claims and to provide a safe and comfortable building to its occupants, it is important that these issues be managed and addressed at all phases of any building’s life cycle. A robust and well considered design process is equally, if not more critical, than the ongoing management of facilities, associated plant and operational strategies.

By: Andrew Angelides