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November 2007

Factors affecting thermal comfort

Thermal comfort can be defined as a condition of mind which expresses satisfaction with the thermal environment. Due to large variations from person to person, it is difficult to satisfy everyone within the same thermal environment. The most important environmental factors contributing to thermal comfort are:

  • air temperature
  • radiant temperature (ie. the temperature of the walls, floor, windows etc)
  • humidity
  • air speed
  • the amount of physical activity
  • the amount and type of clothing worn.

The recommended temperature range to optimise indoor thermal comfort for most people is 19°C to 28°C*. This temperature range is appropriate for the sedentary or near sedentary physical activity levels that are typical of general office work. This recommendation assumes that people dress appropriately to the external seasonal demands.

Possible health effects of thermal discomfort

There are no known health effects from thermal discomfort. However, extremes in air temperature may have adverse effects on productivity.

Thermal comfort versus heat/cold stress

There is a significant difference between thermal discomfort and heat/cold stress. Heat stress may occur in situations where a person's core temperature rises above 38°C and cold stress occurs when a person's core temperature falls below 35°C. Heat stress may occur in environments where there is high temperature (eg summer), radiant heat (eg foundries) or humidity (eg mines), a high level of physical activity (eg manual labour) or excessive or impervious clothing. Under these conditions, heat loss may no longer be in balance with heat production and heat-related illnesses such as heat cramps, heat exhaustion or heat stroke may occur. Cold stress may occur in environments where there are low temperatures (which will be aggravated by wind), immersion in water and working in wet clothing (which includes clothes damp from sweat). The local effects of cold stress include frostbite and immersion foot. There are very few work environments at Monash University that could give rise to heat or cold stress.

There is no legislation that specifies maximum and minimum temperatures in the workplace.

Recommendations for optimising indoor thermal comfort

The use of personal heaters in air-conditioned areas

  • The use of personal heaters in an air-conditioned area where people are experiencing discomfort may exacerbate the situation, as they can interfere with the automatic control of the heating, ventilation and air conditioning system. For example, the operation of a personal heater may cause a nearby heating or air conditioning thermostat to falsely sense that the room is too hot, consequently increasing the cool air supplied to the room.
  • If the heating or cooling is not operating within the acceptable range, report the problem to Facilities & Services or the local operational personnel at your campus/site.

Warm weather

  • Wear clothing appropriate to the external climate.
  • Drink cool water frequently, even if you are not thirsty.
  • Try to increase air movement to allow evaporation of sweat by opening windows and doors where practical and with the use of personal or ceiling fans.
  • Use blinds, curtains and solar film to decrease radiant heat from the outside environment.
  • Negotiate with local management for staff and students to take breaks in cooler and/or less humid areas or transfer some work to cooler and/or less humid areas.
  • Negotiate to alter working hours so that work can be done in the cooler parts of the day such as early morning.

Cold weather

  • Wear sufficient clothing with high thermal properties (eg wool, polar fleece).
  • Use a throw rug.
  • Move around and engage in active tasks as physical activity generates bodily warmth.
  • Shelter from external winds.
  • Drink warm fluids.
  • Use approved room heaters in un-heated or non air-conditioned areas.

*   Energy efficient panel heaters with thermostats and timers may be used and are available from suppliers listed in the Monash procurement website list of products and suppliers.

*   Floor model bar or fan radiators are prohibited in the University because of the high risk of starting fires and high energy consumption.

*   Overhead radiant heaters are not generally effective and can add to a feeling of discomfort when the head is hot, but the feet remain cold.

When a significant proportion of people in an area are experiencing thermal discomfort the head of unit should investigate the cause(s) and consider making alternative work/study arrangements for staff and students. The Procedures for OHS consultation (pdf 137kb) should be followed.

Workplace factors to be considered by the head of unit include:

  • level of physical activity in the tasks being performed by staff and students
  • temperature in the area
  • whether the work performed by staff and students involves safety-critical tasks such as operating machinery or handling chemicals
  • specific individual needs such as those arising from medical conditions
  • concerns expressed by staff and students.

Further information

Contact your local OHS consultant or Occupational Health and Safety:

* ANSI/ASHRAE Standard 55-2004: 'Thermal environmental conditions for human occupancy'