As already mentioned in the article “Industry Standards – A Necessity For Going Mainstream“, standards can be a great platform to establish commonalities on a global scale. On the other hand, a plethora of uncoordinated international and national industry standards make it difficult for industry experts across the globe to mean the same thing when they speak about infrared heating systems.  

As example, different definitions are used in Europe, America and Asia for the important term about the infrared heating wavelength spectrum. In order to rectify this unsatisfactory situation, this article utilizes the US ASHRAE Terminology as a starting point and as a basis for future international discussions.


About ASHRAE Terminology

ASHRAE Terminology, a free resource, is a comprehensive online glossary of more than 3700 terms and definitions related to the built environment, with a focus on heating, ventilation, and air conditioning (HVAC), as well as refrigeration, building envelope, electrical, lighting, water and energy use, and measurement terms. The terms in ASHRAE Terminology have been assembled, defined and are updated on an ongoing basis by ASHRAE Technical Committee (TC) 1.6, Terminology.

This searchable glossary was designed for use by engineering professionals but is also useful for architects, building owners and operators, educators, public officials, and homeowners.


ASHRAE infrared heating terms and definitions

In accordance with ASHRAE Terminology and rules, the following provides a list of 10 important terms and their definitions in alphabetical order, as applicable to electric infrared heaters.



Infrared emittance:       
Ratio of the infrared spectrum radiant flux emitted by a physical body to that emitted by a blackbody at the same temperature and under the same conditions.

Infrared radiation:
Range of electromagnetic radiation wavelengths greater than those of visible light and shorter than those of microwaves; generally between 0.8 micrometer and 1 millimeter. IR originates from either incandescent or non-incandescent hot bodies or from flames. The energy is used as a means of direct heat transfer from the source to the object(s) to be heated without materially heating the intervening air.

total radiant flux emitted from a surface through unit projected area by unit solid angle. It includes the self-emitted radiation plus reflections from sources other than the object evaluated as interpreted from the direction of measurement. The term intensity of radiation is sometimes used as a synonym for radiance. See also [radiosity].

Radiant asymmetry temperature:
Difference between the plane radiant temperature of the two opposite sides of a plane element. See also [plane radiant temperature]

Radiant flux:
The time rate of flow of radiant energy (watts).

Radiant flux density:
Measure of radiant power per unit area flowing across or onto a surface. (Also called irradiance).

Radiant panel:
A heating or cooling surface that delivers 50% or more of its heat transfer by radiation, which may be either an integral part of the building (e.g., floor or ceiling heating) or detached from the building elements (e.g., suspended ceiling panel).

Radiant heating system:
A sensible heating system that provides more than 50% of the total heat flux by thermal radiation.

Act or process of radiating, specifically the process by which energy is emitted from molecules and atoms, owing primarily to internal temperature change.

Total radiant flux that leaves unit area of a surface. The sum of radiant flux emitted and reflected by the surface, plus any radiant flux transmitted through that surface. Compare to [exitance].


To request a free Excel file of the complete list of terms and definitions, please send an email to or visit the ASHRAE website at–publications/free-resources/ashrae-terminology.



Oswald Oberladstatter, ME
Perl, Germany
November 2016