Why do we feel so hot when we enter the attic? Or why is it cold in the kitchen? This subjective assessment is known as comfort or thermal well-being and can be defined as the degree of satisfaction of a person with respect to the room where they are located. Multiple factors beyond ambient temperature intervene in this feeling of comfort, such as humidity, the radiant temperature of the environment, clothing or the physical activity that takes place in the space. Criteria that are generally not taken into account when designing heating or air conditioning installations.
Evaluating the thermal comfort of your home will allow you to take the necessary improvement measures by, for example, reducing energy costs or installing thermal insulators. In short, this is an indicator that can help you turn your home into a more comfortable and energy efficient place, as well as improve your health or encourage your productivity, if your home is also your workplace. Below we explain how it is calculated.
Some of the variables that determine thermal comfort depend on the use that people make of a room, such as physical activity, their own metabolism or clothing. While the rest of the factors are given by the environment and the architectural design. They all influence when evaluating how comfortable we feel with the temperature of the home.
The ISO 7730:2006 standard details the Fanger method, a statistical study in which each occupant values ??their degree of thermal comfort with a number between -3 (very cold) and 3 (very hot). The result is the estimated mean vote or PMV (in English, predicted mean vote) of the people who have voted. In parallel, air temperature, air velocity, ambient radiant temperature and relative humidity should be measured.
Ideally, the PMV should be between -0.5 and 0.5, which indicates that the estimated percentage of people dissatisfied with the temperature is less than 5%. In large-scale energy simulation models, the degree of thermal comfort in a building is studied for all hours of the year according to the outside temperature and the overall percentage of hours in which the air conditioning systems fail to achieve that comfort. If this value is greater than 5%, measures must be taken to correct possible defects in the building’s thermal envelope.
The Fanger method is an indicator that puts people’s satisfaction at the center of architectural design and also helps determine the energy certifications of buildings. In Spain, the ISO 7730 standard also evaluates local thermal discomfort, which can be caused by drafts or excessively hot or cold radiant temperatures.
