Why André Missenard’s insight still matters for building design and energy efficiency
When French engineer André Missenard remarked, “The human body can only register a change in heat loss, not a temperature”, he was not making a semantic distinction — he was challenging how we think about comfort, climate control, and even energy efficiency in buildings.
Today, decades after Missenard’s pioneering work in thermal comfort and radiant heating, this idea remains as relevant as ever. It shifts our focus from chasing a magic number on the thermostat to understanding the dynamic way our bodies exchange heat with their surroundings.
1. We Don’t Sense Temperature — We Sense Heat Flow
When you step from a warm living room into a cold hallway, your body reacts instantly — shivering, tightening muscles, changing breathing patterns. This isn’t because your skin “knows” the exact temperature has dropped from, say, 21 °C to 15 °C. Your body is responding to an increased rate of heat loss.
Humans maintain an internal core temperature of around 37 °C, but our comfort depends on balancing the heat we generate internally with the heat we lose to the environment. This loss happens through four main channels:
- Radiation — infrared heat exchange with surrounding surfaces.
- Convection — air movement carrying heat away from our skin.
- Evaporation — moisture leaving our skin (sweat or insensible perspiration).
- Conduction — direct contact with objects or materials.
Under stable conditions, these mechanisms are in equilibrium. When the rate of loss increases — whether because of a cold surface, a draft, or dry moving air — we feel colder, even if the air temperature hasn’t changed. Conversely, when heat loss slows (say, standing near a warm wall or under sunlight), we feel warmer even if the thermostat reading is unchanged.
2. Why This Matters in Building Design
The traditional approach to indoor climate control has been to set and maintain a target air temperature — 20 °C in winter, 25 °C in summer, or whatever a standard suggests. But as Missenard’s observation shows, thermal comfort is not just about air temperature.
Two rooms can both be at 20 °C and feel radically different. Consider:
- Radiant temperature: In a poorly insulated room with cold walls and windows, the mean radiant temperature is lower, increasing radiant heat loss from your body. You’ll feel colder.
- Air movement: A small draft can accelerate convection, making you uncomfortable even if the thermostat is steady.
- Humidity: Dry air increases evaporative heat loss, while humid air slows it down.
For designers and engineers, the key takeaway is that controlling heat loss pathways can be more effective — and more energy efficient — than just raising or lowering air temperature.
3. André Missenard and the Legacy of Radiant Heating
Missenard’s career spanned mechanical engineering, building systems, and human thermal comfort research. He is particularly known for advocating radiant heating — systems where warm water or electric elements heat surfaces like floors, ceilings, or walls.
Radiant systems address heat loss directly: by warming surrounding surfaces, they reduce the radiant temperature difference between the body and the environment. As a result, occupants can feel comfortable at lower air temperatures, saving energy without compromising comfort (ASHRAE on radiant comfort).
4. Practical Applications in Modern Energy-Efficient Buildings
a) Radiant Systems
Low-temperature radiant floors, walls, and ceilings can create stable, comfortable conditions while operating with lower supply temperatures for heating — or higher supply temperatures for cooling. This improves the efficiency of heat pumps and condensing boilers.
b) Insulation and Surface Temperatures
Improving insulation and window performance raises the mean radiant temperature of a room. This doesn’t just reduce heating loads; it makes spaces feel warmer without extra energy input.
c) Airflow Control
Designing HVAC systems to minimize unwanted drafts — particularly in winter — can significantly improve comfort at lower air temperatures. Variable air volume (VAV) systems and diffuser placement are critical here.
d) Humidity Management
Maintaining indoor humidity in the 40–60% range can moderate evaporative heat loss, enhancing comfort without excessive heating or cooling.
5. The Role of Standards and Comfort Models
Thermal comfort standards, such as ISO 7730 and ASHRAE 55, formalize what Missenard articulated intuitively. They define comfort as a condition of mind influenced by temperature, humidity, air movement, and radiant conditions.
These models — including the Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) — acknowledge that air temperature alone is insufficient. Engineers and architects must design for operative temperature, a combination of air temperature and mean radiant temperature.
6. Comfort in the Context of Energy Efficiency
If the aim is net-zero or low-energy building operation, this understanding becomes strategic:
- Lower setpoints in winter: If radiant loss is minimized, occupants can be comfortable at 19 °C instead of 21 °C, cutting heating demand.
- Higher setpoints in summer: If surfaces are cool and air movement is controlled, 26 °C can feel comfortable, reducing cooling loads.
- Targeted upgrades: Replacing single glazing or addressing infiltration can yield both comfort and energy benefits without major system changes.
This is not just theory — field studies consistently show that surface temperature improvements and draft control can save more energy per comfort unit than changing air temperature alone (Berkeley Lab Center for the Built Environment).
7. Why Occupant Education Matters
Even the best-engineered systems won’t deliver efficiency if occupants misunderstand comfort. If people equate comfort solely with thermostat numbers, they may override efficient settings. Explaining how heat loss works — as Missenard did — empowers building users to adapt behaviors: using blinds, dressing appropriately, and avoiding unnecessary thermostat adjustments.
8. Key Takeaways for Designers and Operators
- Design for heat loss control, not just air temperature control.
- Consider all four heat transfer modes when specifying systems and materials.
- Balance radiant and convective elements for stable, efficient comfort.
- Integrate occupant engagement into building operation strategies.
Conclusion
André Missenard’s insight remains a cornerstone of thermal comfort thinking. In a time when buildings must deliver both wellbeing and efficiency, it’s a reminder that comfort is a dynamic process, not a static reading. By focusing on how we manage heat loss — through surfaces, air, and moisture — we can create spaces that feel right, use less energy, and respond better to the people who inhabit them.
In the end, the thermostat is only part of the story. The rest is written in the invisible flow of heat between our bodies and the built environment — the real language of comfort.