🟧 Why Walls Need to Be Warm

Infrared Heating vs Convection

🟧 1. Humans Do Not Feel Air Alone

Most heating systems are designed to heat air.

However, thermal comfort is not determined by air temperature alone.

According to ASHRAE Standard 55, comfort is defined by operative temperature, which consists of:

~50% air temperature

~50% mean radiant temperature of surrounding surfaces

This means:

👉 You do not feel air alone — you feel walls, floors, and objects.

🟧 2. Cold Walls = Invisible Heat Loss

When walls are cold:

• your body radiates heat toward them

• you experience a sensation of cold

• - even at +22°C

This is why people often say:

• “It feels warm… but not comfortable.”

• This is not psychological. It is physics.

🟧 3. The Radiant Effect (Proven)

Studies show that people feel comfortable at lower air temperatures when surrounding surfaces are warm.

Result:

🟧✓ reduced heat loss from the human body

🟧✓ faster perception of comfort

🟧✓ up to ~10–13% lower energy consumption

🟧 4. Conventional Heating vs Reality

❄️ Convection Heating:

• heats the air

• warm air rises

• walls remain cold

Result:

• uneven comfort

• cold zones

• higher energy demand

🟧 Infrared Heating:

• heats walls, floors, and objects

• heat is stored in surfaces

• heat is re-radiated into the room

Result:

• uniform comfort

• lower required air temperature

• more efficient heating

📊 Infrared Heating vs Convection

	🟧 Infrared Heating	❄️ Convection Heating
What is heated?	Walls, floors, objects, people	Air
Wall temperature	Warm	Cold
Comfort level	Uniform	Uneven
Perceived comfort at +22°C	Warm	Often cool
Required air temperature	Lower (~19–20°C)	Higher (~22–23°C)
Heat loss	Lower	Higher
Heat distribution	Even	Accumulates near the ceiling
Response time	Fast	Slower
Energy consumption	Lower	Higher

🟧✓ Comfort is determined not by air — but by surfaces.

🟧 5. Why This Is Especially Important in Northern Climates

• cold external walls

• older building stock

• large glazed areas

If heating systems only warm the air:

• higher temperatures are required to compensate

• energy costs increase

• comfort remains suboptimal

  
  

🟧 6. Infrared Heating Is Surface Physics

Infrared heat does not directly heat the air.

It heats:

• walls

• floors

• objects

• people

Only afterwards:

These surfaces warm the air

🟧 7. Walls Become a Secondary Heat Source

When walls are warmed:

• they radiate heat back into the room

• they help stabilize the indoor climate

Effectively:

Walls become radiators without radiators

Result:

🟧✓ more stable microclimate

🟧✓ reduced temperature fluctuations

🟧✓ longer-lasting comfort

🟧 8. Emissivity and Comfort

Comfort depends on:

• surface temperature

• surface emissivity (the ability to emit thermal radiation)

Result:

🟧✓ reduced heat loss from the human body

🟧✓ improved comfort at lower temperatures

🟧 9. Lower Temperature = Lower Energy Consumption

When walls are warm:

• air temperature can be reduced

• while maintaining the same level of comfort

Result:

🟧✓ lower energy consumption

🟧✓ reduced system load

🟧 10. Interaction Between Surfaces and Radiation

• walls absorb heat

• walls re-radiate heat

This:

🟧✓ reduces heat loss

🟧✓ stabilizes the indoor environment

🟧 11. Radiant Heat Dominates Indoors

A significant portion of heat exchange indoors is radiative rather than convective.

This fundamentally changes the approach:

❌ heating air

✅ controlling surfaces

🟧 12. Real Example

Consider a room at +22°C:

Convection:

• walls are cold

• perceived as cool

Infrared:

• walls are warm

• comfortable even at +20°C

Result:

🟧✓ lower temperature required

🟧✓ lower energy consumption

Conclusion:

• Heating is not about air.

• It is about surfaces.

Reality:

• people feel surfaces

• walls determine comfort

  
  

Key Point:

🟧✓ Warm walls = comfort

🟧✓ Cold walls = heat loss

💣 Key Insight:

Comfort does not start with a thermometer — it starts with walls.

📚 Sources and References

• ASHRAE Standard 55

• Thermal perception and energy consumption (radiant vs convective heating)

• MDPI Buildings — radiant heating studies

• Radiative heat transfer (physics fundamentals)

• DLR / RWTH Aachen research on radiant systems

  
  

🟧 Sundirect Approach

100% heat to you. Not to the air.