What is thermal comfort and how to achieve it?

23 February 2023

When people do not feel comfortable in the thermal environment they are in, it creates a risk to their health and prevents them from doing their jobs effectively. Thermal comfort thus becomes an important factor in everyone's physical and emotional well-being.

Generally speaking, it is the feeling of satisfaction with the thermal environment when it is neither too cold nor too hot. At the same time, thermal discomfort is associated with all those irritants in the environment around us that we wish to remove - such as cool or dry air, cold floors, walls, surfaces, etc.

How is thermal comfort measured?

Like any perception, it can be a subjective feeling and vary from person to person. It is most commonly associated with air temperature, but in reality there are several other factors that are key to comfort in a room, and these are:

  • The temperature of surrounding surfaces (walls, floor, ceiling, windows, devices, and objects)
  • Relative humidity
  • Airflow speed (stagnant indoor air can make rooms stuffy, smells can occur and people feel uncomfortable)
  • Metabolism (physiological state, health, activity, nutrition, fatigue, time of day)
  • Psychological attitude
  • Clothing

Assuming that the other factors are normal, the second factor comes to the fore - the temperature of the surrounding surfaces. It is relevant because there are two main types of heat exchange affecting indoor thermal comfort - convective and radiant.

Convective heat exchange takes place between the human body and the air in a room and depends on the air temperature. And between the human body and the surrounding surfaces, there is a radiant heat exchange, which is linked to the temperature of the walls, floor, ceiling, windows, devices, and objects in the room.

Important fact: When there are no serious deviations in other factors, thermal comfort depends only half on the air temperature. In the other half, the temperature of the surrounding surfaces is decisive.

What is temperature sensation?

In this case, it is an average value combining several of the thermal comfort factors listed above. By using the temperature of sensation, a universal definition of the thermal environment is achieved and thermal comfort is guaranteed.

It is calculated as the average of two factors: the room air temperature and the average temperature of all surrounding surfaces: TUS = (TV + TP,r)/2. For example, if the air temperature is 28°C and the temperature of all surfaces is 20°C, the sensible temperature is 24°C.

The temperature of sensation is used in assessing the thermal environment of each person, and in setting standards for thermal comfort. For example, the ISO7730 standard specifies an optimum sensation temperature of 22°C in winter and 24.5°C in summer. The standard also specifies a range of deviation from the optimum value of ±2°C in winter and 1.5°C in summer. Within these ranges, due to the subjectivity of each person's assessment of the thermal environment, 10% of occupants will be dissatisfied and the remaining 90% will be comfortable.

Where does the comfortable radiant energy come from?

In space heating and cooling, there is convective heat exchange between the air and surrounding surfaces and radiant heat exchange between the surfaces themselves. When using area systems (floor, ceiling, wall heating or cooling) it is also important exactly which surface will contribute to heating or cooling.

People feel comfortable when heating is done by underfloor heating and cooling by ceiling cooling. They are also comfortable when the surface temperatures of opposite walls are close in value.

It is no coincidence that radiators are placed under windows. In this way, the heat from the radiator offsets the cold surface of the window and the remaining cold surface of the outside wall. This reduces the difference between the average surface temperature of the wall concerned and that of the wall opposite.

Thermal activation of entire surfaces by area heating and cooling systems overcomes radiant differences and improves thermal comfort. Such an approach also uniformises the difference between the air temperature and that of the surrounding surfaces. This allows thermal comfort to be monitored and regulated by the easily measurable air temperature, rather than the sensible temperature.

Today, thermal comfort can be easily achieved using modern design and sustainable solutions.

Re Energy provides the best room temperature control through systems that are more energy efficient than other alternatives, do not create unnecessary noise, and utilise space in the most comfortable way possible.

The combination of high efficiency and low cost is now fully possible thanks to new technologies and environmentally friendly heating and cooling methods. Re Energi guarantees a supply of energy that is stored by the earth and is not influenced by external factors. Changes in the prices of fossil fuels, electricity, and water thus have no impact on the final bills of consumers and businesses.

Providing thermal comfort through geothermal energy has two major advantages over alternative methods - many times higher efficiency and minimal maintenance.

At the same time, activating entire surfaces in the home or office (floor, ceiling, and walls) ensures a comfortable balance between convective and radiant heating and cooling.

Achieving thermal comfort has been proven to make people feel better, increase their ability to concentrate and perform their duties, and eliminate some environmental health risks.

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