Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
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Blackbody Curves of Melting (NAAP)
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A movie showing the heating and eventual melting of a nail, and the theoretical blackbody curve produced in the process. Note: radiant heating and cooling systems operate between 60F and 90F surface temperatures which corresponds approximately to far infrared wavelengths of 9.5 μm to 10 μm respectively. This range is not even close to the 6000 K (10,340F) solar temperature measured just below the photosphere, i.e. daylight at shortwave lengths of 0.5 μm; this is important to consider when people incorrectly state that floor heating heats you like the sun....if this were true your house would be on fire. This simulation is part of the Light & Spectra module of the ClassAction project, a collection of think-pair-share questions and resources for astronomy education.

Source Credit: The NAAP Basic Coordinates and Seasons Lab, used with permission.

Calculating wavelength from a surface temperature
Wien's Displacement law
ʎ T=  2.898 mmK ∙ 1000,  T in K, ʎ in μm
  Solar Floor Heating Floor Cooling
Constant, mm K 2.898
Surface temperature in Kelvin, T 6000 305 292
Wavelength in microns, ʎ 0.48 9.50 9.92


  • Micrometer (μm), a micrometre is an SI unit of length equal to 1,000,000 of a metre. It is also commonly known as a micron. It can be written as 1 m / 1,000,000.

  • Nanometer (nm), a nanometre is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. It can be written as 1 m / 1,000,000,000.

Learn more about radiant, light and other forms of heat transfer:
Human thermal plume
Conduction animation
Radiant animation
Convection animation
Mean radiant temperature

Emissivity, absorptivity and reflectivity
Seasons Simulator (NAAP)
Blackbody Curves & UBV Filters (NAAP)
Sun's Rays Simulator (NAAP)
Blackbody Curves of Melting (NAAP)
Sun Motions Demonstrator (NAAP)
Azimuth/Altitude Demonstrator (NAAP)

Hydrogen Atom Simulator
Infrared: Beyond the Visible (NASA)

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