Maintaining constant thermal conditions in the offices is important. Even minor deviation from comfort may be stressful and affect performance and safety. Workers already under stress are less tolerant of uncomfortable conditions.

Because everyone reacts differently to varying levels of heat, there never will be a perfect room temperature. A generally agreed consensus based upon a wide range of studies points to an optimal temperature lying between 20 °C and 23 °C.

To have “thermal comfort” means that a person wearing a normal amount of clothing feels neither too cold nor too warm. Thermal comfort is important both for one’s well-being and for productivity.

An office which is too warm makes its occupants feel tired; on the other hand, one that is too cold causes the occupants’ attention to drift, making them restless and easily distracted.

 

Thermal comfort is determined by several factors:

  • Metabolic rate and/or activity level (of the persons in the room): varies with the number of occupants, and the amount of activity done by occupants (e.g., sitting in a restaurant versus serving the customers).
  • Clothing: varies by individual’s choices in clothing or by work requirements (e.g., chemical protective clothing or rain gear).
  • Air temperature.
  • Radiant temperature: a complex term, but generally described as how the heat transfers between the body and other objects in the area (e.g., radiation is the process by which the body gains heat from surrounding hot objects, such as hot metal, furnaces, or steam pipes, and loses heat to cold objects, such as chilled metallic surfaces, without contact with them).
  • Solar loading.
  • Airspeed (velocity): the rate of air movement.
  • Humidity: a general description of the content of the air

What temperature should an office be?

Recommendations provided by CSA Z412-17 Office Ergonomics – An application standard for workplace ergonomics include:

  • Summer conditions: optimum temperature of 24.5°C with an acceptable range of 23-26°C
  • Winter conditions: optimum temperature of 22°C with an acceptable range of 20-23.5°C.

What humidity level should an office be?

CSA recommendations for temperature (above) are listed at an average of 50% humidity.

Relative humidity levels below 20% can cause discomfort through drying of the eyes and mucous membranes and skin. Low relative humidity levels may also cause static electricity build-up and negatively affect the operations of some office equipment such as printers and computers. Relative humidity levels above 70% may lead to the development of condensation on surfaces and within the interior of equipment and building structures. Left alone, these areas may develop mould and fungi. Higher humidity also makes the area feel stuffy.

The Health and Safety Executive (UK) states that a relative humidity between 40% and 70% does not have a major impact on thermal comfort.

What impact does air velocity have?

Air velocity can be created by the air conditioning or ventilation system, and by cold surfaces (e.g., air flowing towards the floor). Thermal comfort is affected by this air movement. Drafts, especially on the head region (head, neck, and shoulders) and leg region (ankles, feet, legs) can cause discomfort.

Generally speaking, temperatures considered in the comfort zone will increase with increased airspeed.

What role do the other factors play?

Thermal comfort also depends on the metabolic rates (activities being done), the clothing a person wears, and the radiant temperatures of other surfaces.

Metabolic rate (activities) and clothing will vary from person to person, even if every person wears the same clothing and performs the same activity. Where possible, allow individuals to have some control over clothing options and pace of work.

Radiant temperature sources include floors and windows. For example, poorly insulated windows can create a cold area in the winter, and sunshine can create a warm area in the summer. Humans are most sensitive to warm ceilings, and to cold vertical surfaces such as windows. Floor surface temperatures that are too high or too low, and that are different than air temperatures also contribute to thermal discomfort.

Preventative Measures to minimize stress or discomfort in thermal working conditions:

Air Temperature

  • Locate the sources of heat or cold in the periphery
  • Eliminate the sources of hot or cold air
  • Insulate the hot surfaces
  • Exhaust hot or cold air locally
  • Ventilate without draughts
  • Use clothes with lower or higher insulation

Humidity

  • Eliminate the leaks of vapour and water
  • Enclose the surfaces cooled with water or any evaporating surface
  • Use clothes that are waterproof, but permeable to vapour

 

Thermal radiation

  • Reduce the radiating surfaces
  • Use reflecting screens
  • Insulate or treat the radiating surface
  • Locate workstations away from radiating surfaces
  • Use special protective clothes reflecting radiation

Air movements

  • Reduce or eliminate air draughts
  • Use screens to protect locally against draughts
  • Locate workstations away from air draughts

Physical workload

  • Reduce the movement during work
  • Reduce displacements 
  • Reduce the speed of movements
  • Reduce the efforts, use mechanical assistance
  • Improve the postures

Clothing

  • Improve the design of the clothing
  • Select more suitable materials
  • Look for lighter materials.

Thermal Comfort Tool:

CBE Thermal Comfort Tool for ASHRAE-55 (berkeley.edu)

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