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The Importance of Indoor Environmental Quality

A while back, I mentioned to some coworkers how CO2 is a “trace gas” used to estimate metabolic rates and odour within a building, and that controlling CO2 levels to 1,000ppm above outside levels keeps these undesired odours at a reasonable level.  I was quickly proved wrong.

One of our engineers, Carlin Sweeney, piped up and corrected me.  She brought up new research showing that high CO2 levels also cause reduced performance of people performing specific tasks.   In scientific terms, there is not just a correlation, but a causation between CO2 levels and reduced performance.  (The study in question, Is CO2 an Indoor Pollutant?  Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance took special care in keeping all other factors such as VOCs,  ventilation rates, temperature and humidity the same.)

As Energy Engineers, it is our responsibility to show building owners all of the benefits/costs of an energy conservation measure (ECM).  Sometimes, however, ECMs with great financials come at a cost to occupancy comfort, or worse, occupancy health.

Several studies show that productivity can be influenced by temperature, volatile organic compounds (VOCs), particulate matter (PM2.5), lighting quality and, as discussed above, carbon dioxide (CO2).  Many of these studies show only a slight increase in productivity when changing, say, temperature or VOC levels.  But a slight increase in productivity can have huge changes in the tenant’s profitability.

It is important to quantify all benefits and costs when recommending an energy conservation measure, including productivity and occupant health.

IEQ vs Productivity

What can the Studies tell us?

Summary of UL Environment Technical Brief: Effects of Indoor Environmental Quality on Performance and Productivity, 2016.

  • 14% of healthcare costs are driven by conditions related to Indoor Environmental Quality (IEQ)
  • IEQ consists of:
    • Lighting, IAQ, Damp Conditions.  (NIOSH 2015)
      • Contaminants (gasses and particles) from Office Equipment, cleaning products, construction activities, carpets & furnishings, perfumes, cigarette smoke, water-damaged building materials, microbial growth (fungal, mold, bacterial), insects, and outdoor pollutants.
      • Temperature, relative humidity and ventilation levels.
  • Performance consists of:
    • Speed of work, quality of work, presence or lack of respiratory symptoms, or absenteeism.
  • Performance measurements include:
    • Disability Adjusted Life Years, DALY – Years of healthy life lost.  (WHO)
  • Ventilation Rate Performance
    • See Figure 1
    • 2013, Chan et al. provided a risk assessment for exposure to VOCs and particulate matter (PM2.5) as a function of ventilation rates.  VOCs fall with increased ventilation, PM2.5 increases with ventilation but can be controlled through proper filtration.
  • Temperature and Performance
    • See Figure 2: Relative performance vs Temperature
    • Optimal performance occurs when occupants are at optimal thermal comfort.  Performance may be increased by giving occupants individual control of local temperature settings.
  • VOCs and Performance
    • Negative correlation between VOCs and Performance
    • Different VOC combinations affect individuals uniquely
    • More study is required
  • Carbon Dioxide and Performance
    • Historically used as a representative gas
    • ASHRAE Standard 62 guideline for CO2 is 1,000ppm above outdoor levels, but is based on recommended rates for body odour control under idealized steady-state conditions, not heath impacts of CO2
    • A handful of studies show a stronger correlation (causation?) between CO2 and performance.  See Figure 2: Impact of CO2 on human decision making performance
  • Studies have consistently shown that increased productivity does outweigh the cost of increased energy usage in a building
Sources of Productivity Gain Strength of Evidence Potential US Annual Savings or
Productivity Gain (1993 USD$)
Reduce respiration disease Strong $6-$19B
Reduce allergies and asthma Moderate $1-$4B
Reduce sick building syndrome symptoms Moderate to Strong $10-$20B
Improve worker performance:
From changes in thermal environment
From changes in lighting
$12-125B ($186B: Harvard Study)
  • Harvard study (2015):  Doubling ventilation rates cost less than $40/person/yr in all climate zones investigated, and would improve worker performance by 8% or $6,500/employee/yr.