Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
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ndoor Environmental Quality: defined by the various elements which influence occupants within a space.


Definition of Indoor Environmental Quality (IEQ)
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Before "comfort", “indoor environmental quality” and “IEQ” have completely lost their meaning, we want to bring attention to the definition which is a comprehensive term from the field of indoor climate engineering representing the collective influence from the indoor environment on the key physiological sensory systems of the human body which can be represented by a basic formula. Note: Though there are many other personal/cultural/interior design preference parameters which relate to IEQ as noted in Figure 2, these are treated separately from the core physiological sensors common to all human beings.


I = Indoor, Q = Quality

A = Air
T = Thermal  (see Post Occupancy Survey)
L = Lighting
S = Sound
O = Odour (odor)
V = Vibrations

Indoor Environmental Qulaity   

Figure 1. Indoor Environmental Quality: Six key metrics.

impact of IEQ factors on occupant overall workspace satisfaction

Figure 2. Positive/negative impact of IEQ factors on occupant overall workspace satisfaction. The values attached to each bar represent regression coefficients for each IEQ factor’s satisfied occupants (unshaded bar) and dissatisfied occupants (shaded bar) (Kim and deDear, 2012) 3.

Suggested study: ASHRAE Guideline 10-2011

Interactions Affecting the Achievement of Acceptable Indoor Environments

1. PURPOSE: To provide guidance regarding factors and their interactions as they affect the indoor environmental conditions acceptable to human occupants with regard to comfort and health.


2.1 This guideline provides guidance regarding factors and their interactions and includes thermal comfort, indoor air quality, sound and vibration, and non-ionizing electromagnetic radiation (including visible light).

2.2 This guideline applies to the design, construction, commissioning, operation and maintenance of buildings.

2.3 This guideline applies to all indoor or enclosed spaces that people may occupy.
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ASHRAE Guideline 10-2011, Interactions Affecting the Achievement of Acceptable Indoor Environments

Figure 3. ASHRAE Guideline 10, Interactions
Affecting the Achievement of Acceptable
Indoor Environments

Suggested study: CIBSE Guide A: Environmental Design

Excerpt: “The environmental factors considered here include the thermal, visual and acoustic conditions, indoor air quality, electromagnetic fields and static electricity. It is not practicable to formulate a single index that quantifies the individual's response to all these factors, and there may be additive or synergistic effects resulting from interactions among a number of them. For example irritant contaminants, such as formaldehyde, become more noticeable at low air humidity (2).

Therefore, it is necessary to specify measurable limits or ranges for each of the environmental factors, making allowance, where possible, for any interactions that might occur.”

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CIBSE Guide A:Environmental Design

Figure 3. CIBSE Guide A:Environmental Design

The misuse of Indoor Air Quality as a Proxy for Indoor Environmental Quality

As it relates specifically to air and thermal qualities, the ASHRAE Standards are explicit; ANSI/ASHRAE Standard 62.1 and 62.2 - Ventilation and (for) Acceptable Indoor Air Quality state very clearly that the standards do not address thermal comfort referring users to ANSI/ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy; likewise ANSI/ASHRAE Standard 55 states very clearly that indoor air quality is not addressed in the thermal comfort document.

To emphasize the point, post occupancy surveys are not limited exclusively to IAQ but encompass all aspects unless the survey is strictly for IAQ in which case it’s not called an IEQ survey but (wait for it) an IAQ survey – go figure.

We're seeing it more often where IAQ is used as a surrogate or proxy for indoor environmental quality but this in our not so humble opinion is clearly misleading and effectively dilutes the term just as the incorrect use of green and sustainability have led to the dilution of their meanings.

IEQ is really about putting humans (the whole mind and body) at the center of the design process - now there's a novel thought!

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"The vast majority of buildings today suffer from inadequate performance, such as excessive energy
consumption, thermal comfort issues, and insufficient daylighting. These deficiencies are often the result
of an inability of the design team to consider a wide variety of design options for all these criteria in an
integrated and systematic way. Budget, schedule, and technology constraints mean that less than a
handful of design options are typically modeled and analyzed today." source: Haymaker, J. and Welle, B. (2008). "An Integrated Conceptual Design Process for Energy, Thermal Comfort, and Daylighting." 2008 Precourt Institute for Energy Efficiency (Stanford University)

Additional Resources:

  1. Race, G. L. (2006). CIBSE knowledge Series: Comfort. The Chartered Institution of Building Services Engineers, London, UK

  2. Nicol, F. (2013) The limits of thermal comfort: avoiding overheating in European buildings, CIBSE TM52. The Chartered Institution of Building Services Engineers, London, UK

  3. Kim, J., de Dear, R. How does occupant perception on specific IEQ factors affect overall satisfaction? Network for Comfort and Energy Use in Buildings. Proceedings of 7th Windsor Conference: The changing context of comfort in an unpredictable world. Cumberland Lodge, Windsor, UK, 12-15 April 2012. London

  4. CIBSE TM40 Health Issues in Building Services (FREE download)

  5. CIBSE Guide A: Environmental Design

  6. ANSI/ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy

  7. Education and the Built Environment

  8. ASHRAE Guideline 10, Interactions Affecting the Achievement of Acceptable Indoor Environments

  9. ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality

  10. ANSI/ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings

  11. ISO 7730:2005, Ergonomics of the Thermal Environment- Analytical Determination and Interpretation of Thermal Comfort using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria.

  12. ISO Standard 7933: Ergonomics of the thermal environment - Analytical determination and interpretation of heat stress using calculation of the predicted heat strain.

  13. ISO Standard 7726: Ergonomics of the thermal environment - Instruments for measuring physical quantities.

  14. Center for the Built Environment, Occupant IEQ Survey Development and Implementation Costs, 2009

  15. Fanger, P.O. 1982. Thermal Comfort. Malabar, FL: Robert E. Krieger Publishing Co.

  16. Frontczak, Monika: Human comfort and self-estimated performance in relation to indoor environmental parameters and building features, 2012.

  17. Temperature Wars: Savings vs. Comfort, International Facility Management Association (IFMA), 2009

  18. Wyon, D.P., Wargocki, P., Effects of indoor environment on performance, ASHRAE Journal March 2013

  19. Friedman, R., 2013. Want More Productive Workers? Adjust Your Thermostat, Psychology Today, accessed July 19th, 2013 <>

Related Links:

  1. Indoor Environmental Quality: Affects on Productivity, Learning and Energy Efficiency

  2. Begin With the End in Mind: A Model for Sustainability

  3. Thermal Comfort Surveys - Post Occupancy, Part I

  4. Thermal Comfort Surveys - Post Occupancy, Part II

  5. Lights Out (Nature of Things)

  6. Julian Treasure: Why architects need to use their ears (TEDtalk)

  7. HVAC Systems and Indoor Environmental Quality (Assorted research papers)

  8. Dr Jessica Greens TEDtalk on microbes in the environment

  9. Dr. Charles J. Weschler, Healthy Buildings 2012 Plenary Lecture

  10. PBS NOVA Broadcast on Epigentics

  11. Indoor environments: Self assessment

  12. Where will your indoor climate system score?

  13. How to "ball park" your budget for indoor climate control.

  14. Thermal Comfort: A 40 grit perspective for consumers

  15. Built to code: What does it mean for consumer thermal comfort?

  16. Thermal Comfort: A Condition of Mind

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