Indoor Environment Quality

Humans working and living in the western world generally spend 80-90% of their time indoors, occupying artificially created environments (Bluyssen, 2013).

The indoor environments have a direct and prolonged impact on the well being and health of its occupant and their quality of life. In fact, the CSIRO has estimated that the cost of poor internal air quality in Australia may be as high as $12 billion per year due to mental and physical ill-health and lost production.

Those most at risk are people with weak immune systems, including children
and the elderly. While most will only ever experience medium health effects such as headaches or tiredness, others may suffer more serious health effects due to “sick” buildings. On the other hand, studies also show that an enhanced indoor environment quality in offices can be linked to staff’s improved work performance and reduced sick leave.

Good indoor environment quality at home or in the workplace are essential to enhance well-being and reduce the likelihood of ill-health. Through the implementation of passive design principles, good indoor environment quality also leads to energy savings due to reduced energy demands for heating, cooling and artificial lighting.

Which room would you rather work in?

Which room would you rather work in?

What is indoor environment quality?

Indoor environment quality describes the quality of an artificial interior environment. The quality is commonly defined through the combined impact of the following sub-systems:

  • Light – Daylight throughout the day and comfortable artificial lighting provided for all other times.
    • Horizontal illuminance
    • Vertical illuminance
    • Daylight factor: Ratio of internal light level to external light level. Defined as: DF = (Ei / Eo) x 100% where, Ei = illuminance due to daylight at a point on the indoors working plane, Eo = simultaneous outdoor illuminance on a horizontal plane from an unobstructed hemisphere of overcast sky.
    • Occupant Control
    • Flicker
    • Light colour
    • Glare

    Considerations For Lighting:

    • Daylight access (Orientation: North/South) (Diffused or indirect light)
    • Daylighting from windows
    • Reflective surfaces
    • Secondary light sources (computer screens)
    • Reflection from internal colour
    • Artificial lighting from lamps
  •  Air quality (indoor air quality) – Ensure that the indoor air contain sufficient levels of oxygen and acceptable levels of pollutants from internal or external sources. Good ventilation (preferably naturally but where this is impractical, mechanically) and to provide quality fresh air.
    • Particulate matter (dust)
    • Outdoor pollutants (exhaust)
    • Carbon dioxide (ventilation rates)
    • Total Volatile Organic Compounds (TVOC)
    • Other hazardous components such as microbial (mould), bacteria, nitrogen dioxide, pesticides, ozone, carbon monoxide, asbestos, toluene, styrene, sulphur dioxide, phthalates, bisphenol A, formaldehyde, etc.

    Considerations For Air Quality:

    • Low levels of TVOC building material and finishes
    • HVAC design (rate of supply air)
    • Filters (maintenance)
    • Quality of external air
    • Furniture, paints and linings
  •  Thermal comfort – Comfortable temperature throughout the year.
    • Clothing insulation
    • Activity level
    • Air velocity (movement)
    • Relative humidity
    • Ambient and radiant temperature
    • External conditions (i.e temperature)
    • User control

    Considerations For Thermal Comfort:

    • Building orientation
    • Thermal bridging
    • Sun shading
    • HVAC duct
    • Windows
    • Insulation
    • Radiant temperature from lights, occupants, solar and electric appliances
    • Natural ventilation (operable windows)
    • Evaporative cooling or refrigerated cooling
    • Material choice (thermal mass)
  •  Acoustics / Noise –  Sufficient insulated from external noise sources and minimise internal reverberation and noise levels
    • Mechanical noise (inside sources)
    • Background noise (external sources)
    • Privacy and acoustics
    • Reverberation
    • Speech intelligibility
    • Sound absorption/ Sound Amplification
    • Signal to noise ratio

    Considerations For Acoustics:

    • HVAC choice
    • Sound absorption / reflection from materials such as ceiling tiles, carpet and furniture
    • Location of windows
    • Location / Floor plans (contextual issues)
  • Occupant control – Provide the ability for occupants to control their environment, e.g. through the opening and closing of windows and blinds and operating heating and cooling services
  • Visual environment and space – Aesthetics and connection to surrounding environment
  • Perception, social and psychological – Sense and feeling provoked but through the building’s conceptual design.

The four basic environmental factors in the indoor environment that influence the perception of that indoor environment through the senses, but also have an effect on the physical and mental state (comfort and health) of occupants (Bluyssen, 2009, p.45).

How to design good quality indoor environments that perform well?

The IEQ performance inside a building can be impacted upon by how the building has been designed, constructed, maintained and/or operated by the occupants (Vittori, 2002). The design must first identify the function purpose of the building and the needs of the occupant in order to tailor the conceptual design. Good indoor environment quality is contextual.

There is a casual relationship between the sub-systems so design of good indoor environments requires a holistic approach. Due to the range of factors effecting indoor environment, there is no standard methodology to quantify indoor environment quality and performance to allow comparable assessment between buildings. Post Occupancy Evaluation (POE), the process of evaluating buildings in a systematic and rigorous manner after they have been built and occupied for some time”, is also required to build on knowledge. Results can also be subjective and difficult to compare objectively.

When builidings are designed well, health and wellbeing of occupants can be translated to productivity benefits.

Other Measures

Thermal Comfort: Predicted mean vote (PMV) and Percentage of people dissatisfied (PPD) is used to measure thermal comfort on a seven point scale with 0 as neutral, -3 is cold and +3 is hot. CBE Thermal Comfort Tool calculates compliance with ASHRAE Standard 55-2010

Efficiency: Energy bills, water bills, waste minimisation and recycling

Staff survey: Measure tenants feedback on air quality, temperature, ventilation, noise, etc. Satisfaction index and self-assessment of productivity


Source: , City of Yarra: Sustainable Design Assessment in the Planning Process Fact Sheet; Bluyssen, 2009; Vittori, 2002.

One thought on “Indoor Environment Quality

  1. Pingback: Efficient HVAC Systems | Energy Systems & Sustainable Living

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