thermal comfort
indoor environmental quality Bookmark and Share
residential heating design

Human Physiology 1
Human Physiology 2
Human Physiology 3
Human Physiology 4
Human Physiology 5


Fresh Air vs.
Cold and Uncomfortable

Bad Air vs.
Warm and Comfortable


Setting the Record Straight
Indoor Air Quality and Indoor Comfort Quality - differentiated but integrated under the definition of indoor environmental quality (see ASHRAE Guideline 10P, Interactions Affecting the Achievement of Acceptable Indoor Environments).

Industry and consumers alike mistakenly take indoor air quality and indoor comfort quality as the same thing. However, one can be uncomfortable whilst breathing fresh air (think sitting on a ski chairlift at -20 deg F) and one can be breathing bad air while being comfortable (think inhaling carbon monoxide or radon whilst watching a movie in your home theatre).

Indoor Air Quality and Indoor Comfort Quality are in fact two separate and distinct topics though both contribute to indoor environmental quality (see proposed ASHRAE Guideline 10, Interactions Affecting the Achievement of Acceptable Indoor Environments). The American Society of Heating, Refrigeration and Air Conditioning Engineers publish industry standards for building professionals. For indoor air quality in low-rise residential and high-rise buildings, the documents are ANSI/ASHRAE Standard 62.2 and 62.1 respectively; and for thermal environments, ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy.

Each standard explicitly states that one is not about the other. This is congruent with our own body systems where thermal comfort is sensed predominately through our skin whereas air quality is predominately a function of our respiratory and internal responses to inhaled elements.

In building surveys where satisfaction with IEQ is high, one often finds mechanical systems that employ radiant based HVAC for thermal comfort quality with dedicated outdoor air systems for air quality. An example of such a system is featured at our page, "The Total Comfort System - The "Un-minimum" System".

Discuss this online.

ANSI/ASHRAE Standard 55
The purpose of this standard is to specify the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space.

This standard does not address such nonthermal environmental factors as air quality, acoustics, and illumination or other physical, chemical, or biological space contaminants that may affect comfort or health.

ANSI/ASHRAE Standard 62.1(.2)
This standard defines the roles of and minimum requirement for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.

This standard considers chemical, physical, and biological contaminants that can affect air quality. Thermal comfort requirements are not included in this standard.


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