What makes up the IEQ?

IEQ is a general indicator of the quality of conditions inside a building. IEQ is determined by many factors, including lighting, air quality, and damp conditions.

Air = Indoor air quality (airborne contaminants)

1. Basic IAQ parameters

  • carbon dioxide (CO2)
  • particulate matter (PM2.5), or else airborne particles
  • carbon monoxide (CO)
  • volatile organic compounds (VOCs)

2. Complementary IAQ parameters

  • particulate matter (PM10)
  • formaldehyde (CH2O)
  • sulphur dioxide (SO2)
  • nitrogen oxides (NO2)
  • ozone (O3)
  • total microbial count

Thermal = Indoor thermal quality (thermal comfort)

3. Physical parameters

  • air temperature, alternatively operative air temperature
  • vertical air temperature difference
  • mean radiant temperature
  • radiant temperature asymmetry, otherwise floor surface temperature
  • relative humidity
  • air speed (velocity including draughts and ventilation)

4. Psychological parameters

  • metabolic rate
  • clothing insulation

Light = Indoor lighting quality (visual comfort)

5. Lighting comfort

  • illuminance, also of surrounding areas and task area
  • illumination intensity, distribution and uniformity
  • ambient lighting

6. Complimentary occupant satisfaction with lighting environment

  • lighting controllability
  • access to daylight and views

Sound = Indoor sound quality (acoustical conditions)

7. Sound pressure

  • noise criteria
  • reverberation time
  • vibration
  • electromagnetic frequency levels

Note: There may be other parameters related to IEQ, directly or indirectly, such as odour, etc.


To sum up, the indoor environmental quality (IEQ) equation equals: indoor air quality (IAQ); indoor thermal quality (ITQ) or else known as thermal comfort;  indoor lighting quality (ILQ), or also known as visual quality with factors as daylighting / lighting / views, and indoor sound quality (ISQ), as acoustical conditions.