What Is Comfort, Really?
Ideal temperature… or something more? What comfort really means.
“Comfort.” A simple word, used every day — yet it describes a reality far more complex than it seems. Whether in our daily lives or in our work at Caeli Énergie, comfort lies at the heart of many questions.
Why do we sometimes feel too hot or too cold when the thermometer shows nothing unusual? Why does a well-ventilated room still feel uncomfortable?
To answer these questions, we first need to understand what thermal comfort actually means.
Comfort: A Multi-Faceted Concept
In the building and energy world, “comfort” covers several distinct dimensions:
- Thermal and humidity-related comfort, linked to temperature, humidity, and how we perceive them
- Indoor air quality, often overlooked, but essential to overall well-being
For most people, comfort is mainly about having the “right temperature.” That’s understandable — it’s what we feel first.
But in reality, thermal comfort is a subtle balance between our body, our environment… and how we perceive both.
Thermal Comfort: A Matter of Perception
Comfort isn’t an objective value. It depends on many factors — physical, physiological, and psychological. We don’t all feel the same in the same environment.
Still, there are some consistent parameters that help us better assess it.
The Physiological Perspective
The human body keeps its internal temperature stable at around 37°C (98.6°F), no matter the outside conditions. To do that, it relies on natural mechanisms:
blood vessels dilate in the heat, we sweat to release excess heat, and shiver to warm up.
But how well the body regulates its temperature depends on many factors: age, sex, physical condition, health status, and even body fat percentage. Then come the environmental variables.
The Physical Perspective
What we feel indoors is influenced by six main factors:
- Physical activity level (metabolism)
- Clothing
- Air temperature
- Surface temperatures (walls, windows, etc.)
- Air humidity
- Air movement (ventilation)
These combined factors determine what we call perceived temperature.
For example, high humidity reduces sweat evaporation, making it harder for the body to cool down — especially when the temperature goes over 25–26°C (77–79°F).
Want to dig deeper? Météo France offers a clear explanation of perceived temperature.
The Psychological Perspective
Comfort perception is also shaped by cultural, social, and individual factors.
Our habits, tolerance to heat or cold, past experiences, and even our mood can influence how we feel.
There’s no universal comfort setting.
But certain recommended ranges are widely recognized as ideal for indoor comfort.
So, What Makes a Home Comfortable in Summer?
Everyone experiences temperature differently, but here are some general guidelines for maintaining comfort during hot weather:
- If you’re using air conditioning, avoid setting the indoor temperature more than 5 to 7°C (9–13°F) lower than the outdoor temperature. This helps prevent thermal shock and discomfort.
- The World Health Organization (WHO) recommends aiming for an indoor temperature of 25–27°C (77–81°F) during heatwaves to avoid overcooling.
- These recommendations are supported by ADEME (the French Energy Agency) and the French Ministry of Health, who also emphasize the importance of keeping temperature differences moderate — for both health and energy efficiency.
And What About Humidity?
According to ADEME, the ideal indoor humidity level should be between 40% and 60%.
Keeping humidity within this range is key for both comfort and health:
- Below 40%, the air is too dry: it can irritate your skin, dry out mucous membranes, trigger allergies… and even harm your houseplants.
- Above 60%, the air feels sticky: sweat doesn’t evaporate properly, discomfort increases, and excess moisture encourages condensation, mold, and respiratory issues.
Toward Better-Controlled Comfort
Bottom line? Thermal comfort isn’t just about the number on the thermostat. It’s about balance — between temperature, humidity, air movement, and how you actually feel.
There’s no perfect rule, but there are smart guidelines to help you stay comfortable, even in extreme heat.
With Caeli One, thermal comfort becomes an everyday reality.
Our indirect evaporative cooling technology delivers a refreshing, natural-feeling breeze — without dry air or harsh cold drafts — for genuinely comfortable indoor air.
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