# Thermal Comfort 1

What is Thermal Comfort?

Thermal comfort describes the human satisfactory perception of the thermal environment. It refers to a number of conditions in which the majority of people feel comfortable. Thermal comfort is rated amongst the most important conditions for improving comfort and satisfaction of occupants with their indoor environment, based on a review of various studies

It is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation. Thermal comfort is the occupants’ satisfaction with the surrounding thermal conditions and is essential to consider when designing a structure that will be occupied by people.

## Factors Affecting Human Comfort

There are six factors to take into consideration when designing for thermal comfort. Its determining factors include the following:

• Metabolic rate (met): The energy generated from the human body
• Clothing insulation (clo): The amount of thermal insulation the person is wearing
• Air temperature: Temperature of the air surrounding the occupant
• Radiant temperature: The weighted average of all the temperatures from surfaces surrounding an occupant
• Air velocity: Rate of air movement given distance over time
• Relative humidity: Percentage of water vapor in the air

The environmental factors include temperature, radiant temperature, relative humidity, and air velocity. The personal factors are activity level (metabolic rate) and clothing.

Thermal comfort is calculated as a heat transfer energy balance. Heat transfer through radiation, convection, and conduction are balanced against the occupant’s metabolic rate. The heat transfer occurs between the environment and the human body, which has an area of 19 ft(1.81 m2) .  If the heat leaving the occupant is greater than the heat entering the occupant, the thermal perception is “cold.” If the heat entering the occupant is greater than the heat leaving the occupant, the thermal perception is “warm” or “hot.”

A method of describing thermal comfort was developed by Ole Fanger and is referred to as Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD).

Ref: Autodesk 2017 and ecophon group