Thermal Comfort in the Work Place

Workplaces are encouraged to monitor their thermal environment and the level of thermal comfort their workers experience in general.  

There are three levels of thermal comfort:

1. Thermal stress

2. Thermal discomfort

3. Thermally comfortable

Ideally employers want their workers to be thermally comfortable, but this can be difficult, as people can experience the same thermal environment differently.

What does it mean to be thermally comfortable?

A thermally comfortable person is not aware of being either hot or cold. This is the ideal situation for workers to be in. When a person is thermally comfortable none of their focus or energy is directed at trying to get warm or feel cooler.

What is thermal discomfort?

Thermal discomfort is experienced when a worker feels noticeably hot or cold but not so hot or cold that they are thermally stressed. When workers are in thermal discomfort they are likely to be distracted by it. Their body will use up energy trying to cool or warm the body. They may find it harder to concentrate and be more prone to making errors. People who are overly hot or cold can be more irritable or tired.

It is difficult to create a thermally comfortable environment for all of your workers, but it is worthwhile trying to minimise their thermal discomfort. This is especially true if errors resulting from thermal discomfort have the potential to cause harm or injury. Most workplaces aim for a thermal environment that works for the majority.

What does it mean to be thermally stressed?

A thermally stressed person is experiencing extreme hot or cold conditions to the point where they are in danger of physical harm. This could be hyperthermia for cold conditions or heat stroke in hot conditions.

In some work environments temperature is considered a hazard, such as refrigerated rooms or environments where there are furnaces. In these locations workers need to be given adequate protective gear and break times to ensure they do not experience dangerous levels of thermal stress.

Assessing Your Thermal Environment

When you hear the words ‘thermal environment’ you may think that this refers to air temperature, but in fact air temperature is just one of several factors that combine to create a thermal environment. Other aspects include humidity, radiant heat (such as direct sunlight), air speed and also personal factors like clothing choices and physical activity.

The NZ Health and Safety in Employment Regulations require employers to provide the means to control their thermal environment. This can be as simple as the ability to open and close windows, pull down window shades or by providing more technical solutions such as the ability to turn air conditioning on or off. What controls are necessary will become clear when you assess your thermal environment.

Let’s look at each aspect and the steps you might take to address issues in this area:

Air Temperature

There is no minimum or maximum air temperature for workplaces in the Health and Safety at Work Act 2015 (HSWA) but it does provide some guidelines depending on the type of work being done and the season. They are:

Sedentary Work: 18°C – 22°C Winter, 19°C – 24°C Summer

Physical Work: 16°C – 19°C Winter, 16°C – 21°C Summer

To assess your environment, take regular temperature readings across a day and during different times of the year to get an average. If you find temperatures in certain parts of your building are too high (e.g. due to direct sunlight in summer), you might install shades or apply a reflective coating to the windows.

Humidity

The Health and Safety at Work Act 2015 recommends humidity of 40-70% in workplaces. You can measure the humidity in your workplace using a hydrometer. You could also survey your employees about their thermal comfort and experience of sweating. Sweating is an indicator of an environment with high levels of humidity.

Radiant heat

Consider sources of heat at your workplace that may be causing thermal discomfort, such as direct sunlight, furnaces or computer banks. Machinery that creates heat could be moved to a well-ventilated area or an isolated area.

You might also find that your building is losing radiant heat through poor insulation. Finding ways to capture the heat from the sun or efficiently heat your indoor environment is one thing, ensuring it doesn’t escape as quickly as it enters is another.

Air Movement

Stuffy hot environments can be difficult to work in. Creating a cooling draft via air conditioning or fans can help alleviate hot environments but there are other considerations to make too. Is the air actually cooling workers or just pushing hot air around? Is fresh air being brought in to adequately ventilate a space?  

The New Zealand Standard - Ventilation for Acceptable Indoor Air Quality recommends 10 litres of outside air per second, per person in an office environment. Ventilation systems like fans can help to maintain an even temperature and increase the efficiency of heating or cooling systems. In colder months they can be used to gently circulate air without cooling by dispersing warm air pockets or stratified layers throughout a space.

Physical Activity

Are your workers in sedentary jobs or do they do a lot of moving around? Your environment might be considered cold for office workers but if your workers are doing manual tasks then they might advise you that they are thermally comfortable despite cold air temperatures. Each workplace is different and how much physical movement workers are doing needs to be taken into account.

Clothing

Your workplace may require staff to wear coverings or safety gear. These extra layers will also affect how thermally comfortable they are. In cold environments these layers may allow workers to remain thermally comfortable. In hot environments, being unable to remove protective layers could cause workers to feel overheated and cooling strategies may be required. This could include cooling the room they are in, or providing regular breaks to access fresh air.

Why is Your Thermal Environment Important?

Studies have shown higher levels of productivity and morale in workplaces that maintain a thermally comfortable environment. It also generally correlates with higher levels of health, wellbeing and safety. Research found that staff who felt uncomfortably cold or hot were also more likely to take shortcuts in their work or misuse equipment in order to finish faster, so they could remove themselves from a hot or cold environment.

In 2018 a national survey was conducted online in the US by ‘The Harris Poll’ on behalf of the Career Builder website. 1,012 full-time workers across a range of industries and company sizes took part. It found that 22% of the workers interviewed found it hard to focus in environments that were too hot and 11% said they found it equally difficult in cold workplaces. A month long study completed by Cornell University found that workers who were cold made more errors. They also found that typing errors decreased by 44% when temperatures were maintained at between 20 – 25°C.

Other Important Factors

Businesses that have products sensitive to air conditions need to keep on top of their thermal environment. If you have stock that is sensitive to temperature fluctuations as powders that need to be kept dry or flammable chemicals that need to be kept cool, maintaining a safe thermal environment will be a top priority. It’s also important to note that an optimum thermal environment will help you to maintain your building and equipment by reducing dampness, mould and condensation.