The Economics of good Indoor Air Quality (IAQ)


Tedd Nathanson

Senior Engineer, Building Air Quality

Public Works and Government Services Canada

Ottawa Canada K1A 0M2



Salary dollars are the single, most important cost in an office building, being more than two orders of magnitude (100 times) more than energy costs and more than ten times building design and construction costs. It would therefore seem reasonable that the benefits of providing a comfortable and productive workplace should be compared against the cost of designing, constructing, operating and maintaining a building with an optimum indoor environment. While it is probably not possible to have a building where occupants never complain, there are simple, cost-effective means to reduce dissatisfaction with their environment.


There are many individual and collective influences on building occupants affecting their well-being, comfort and tolerance at work. While IAQ and building design operation and maintenance issues will be elaborated on, there are many other factors which influence perception of the work environment. These can include environmental stressors such as lighting, noise, vibration, overcrowding, factors such as ergonomics interior design, and psychosocial issues such as company organization, culture, job satisfaction, security, health and family-related problems. To attempt to understand and improve the occupants’ perception of the work environment truly requires a multi-disciplinary approach.

The external and internal factors that influence the indoor air quality of a building also depend on the different roles and responsibilities of the building owner, architect, systems engineer, manager, operator and tenant. Some factors influencing IAQ include:

  • building design and location
  • the outside air quality
  • supply temperature and relative humidity
  • system design and capacity
  • ventilation, air supply rate
  • system control strategy
  • filtration performance
  • hours of system operation
  • system maintenance and cleaning
  • office cleaning routines, cleaning compounds
  • office furnishings (walls, partitions, carpets, etc.)
  • pollution migration and entrainment
  • occupancy levels
  • work activity


At an approximate value of $2727 per square metre per year [$30,000 average salary plus 30% benefits divided by 14.3 m2 ] [$273/Ft.2] salary is far more expensive than building site purchase, design and construction costs at $160/m2 [$16/Ft.2] per year, and heating and cooling cost at $15/m2 per year [Indoor Air Quality Update, August 1989, pp 13-15, Cutter Information Corp. MA.].

While building owning and operating costs and salary costs are tangible, productivity losses or gains are not readibly apparent. It is clear however that a small decrease in productivity can be costly; a 1% loss is almost double the total building heating and cooling cost.

Building productivity surveys and questionnaires aside, it should be patent that working in less that optimal conditions or in the extreme, working in a building labelled as “sick”, will negatively affect productivity. How productive are workers in a building where over 20% of them complain about their work environment? Do occupants need more time away from their office and take longer coffee breaks or lunch times? Are people working effectively? Has absenteeism increased?


A Study done by Dorgan Associates for the National Energy Management Institute, Alexandria, Virginia, estimates that improving IAQ in buildings could result in a payback in terms of improved productivity and decreases in medical costs in less than two years [IAQ Update, May 1994].

Some of the beneficial modifications include:

  • increase minimum ventilation rate to ASHRAE Standard 62-1989
  • improve thermal comfort to ASHRAE Standard 55-1992 Standard
  • provide contaminant source control (exhaust or product selection)
  • increase air circulation and ventilation effectiveness
  • design systems with an economizer cycle
  • maximize filtration system performance
  • provide individual control over thermal comfort
  • improve system operations and maintenance
  • assess system retrofit and rebalance requirements when office layout/functions change
  • monitor and regularly audit the IAQ; have a proactive program

Implicit in the provision of good IAQ is the assumption that the building and its systems are properly designed and performing as intended. It is therefore necessary to follow a proper “commissioning” process during the building delivery cycle. Commissioning will not be addressed in this paper suffice to note that it is an important and vital process that has many benefits and ASHRAE Guideline 1-1989, Guideline for Commission of HVAC Systems, is a good place to start.

Ventilation-energy programs have been run for various North American cities and depending on the system, an increase in the ventilation rate from 2.4 to 10 L/s/person can increase the annual energy cost between 5 to 10%.

Increasing filter efficiency will result in a proportionally much higher increase in the collection of small respirable particulates, between 0.1 to 10 micron diameter. This is the size range of concern for IAQ. For example, a 70-75% dust spot efficiency filter collects only 15% of 0.3μ particles while a 90-95% filter collects 83%. The difference in initial resistance is minimal. High efficiency filters not only reduce indoor particulate levels they also result in cleaner system components (heating/cooling coils, fans), ducts and interior office surfaces (walls and ceilings).

Finally, proposed new regulations for the Canada Labour Code sets out procedures for a proactive approach to IAQ and systems for buildings under Federal jurisdiction. This will include the appointment of a “qualified person” who will investigate IAQ problems, keep records and document the design, operation and maintenance procedures of the heating, ventilating and air conditioning system.


To quote Mark Mendell of the National Institute of Occupational Safety and Health (NIOSH): “Until we identify specific causes [of SBS], appropriate mitigation and prevention of building-related symptoms may need to be at the level of prudent design, operation, and maintenance practices, focused on factors which reduce the likelihood of problem indoor exposures and conditions” (Indoor Air, December 1993, Munksgaard, Copenhagen).

There are cost-effective ways to improve the indoor environment in office buildings. While it is best to incorporate good IAQ practices in the building design and construction, existing facilities can be retrofitted to provide a more comfortable and productive workplace. Working together in a total building approach, the many disciplines involved can indeed provide a most satisfactory environment.