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What is thermal comfort in buildings?

Thermal comfort is the condition of the mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation according to ANSI/ASHRAE Standard 55     . Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings.   

Feeling comfortable in an interior space directly impacts people’s moods. Working in optimal conditions enables people to think and perform better, and thermal comfort contributes not only to well-being but even to productivity. Eliminating potential health hazards is also a crucial aspect of maintaining ideal thermal comfort.   

According to the Fanger Method, which is accepted as the most common thermal comfort assessment method worldwide, six factors affect thermal comfort.  

Personal factors  

  • Metabolic rate    (met): The energy generated from the human body 
  • Clothing insulation (clo): The amount of thermal insulation the person is wearing 

   Environmental factors     

  • 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 

There are many different solutions to provide thermal comfort for building occupants while keeping energy consumption low.

Here are a few examples: 

  • Give occupants some control over their immediate environment: Occupant control must be carefully integrated with the overall comfort strategy to avoid situations in which energy is wasted. For example, sometimes occupants change thermostat settings drastically in a misguided effort to get quick results.  
  • Use air movement to increase comfort: Ceiling fans, desk fans, and outdoor breezes can all make people comfortable in conditions that would otherwise be too hot, leading to savings in energy use for cooling.
  • Use displacement ventilation: Introducing cool air to the floor and exhausting it in the ceiling removes heat from the ceiling plane rather than mixing it back into space. Because lights generate heat and warm air tends to rise, removing this warm air from high in the space and exhausting it to the outdoors can reduce the amount of cooling needed. 
  • Capture humidity in ventilation air :  Humidity is difficult to control without using a lot of energy. In mechanically ventilated buildings, devices such as enthalpy wheels can transfer moisture from incoming air to outgoing air (or vice versa). This reduces the need to dehumidify or add moisture allowing cooling equipment to be downsized. 

Sensgreen’s Smart Building IoT Solutions can be used to improve your building’s thermal comfort and energy efficiency.

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