Inside the box: What have we learned about IAQ?

[Guest guest]

http://www.industrialsourcebook.com/cgi-bin/archivef.pl?id=575

Inside the box

September 2003

Author: Tom Tamblyn

Building occupants have known for a long time that breathing recycled air in stuffy quarters is far from ideal for our health. After spending considerable time, money and effort trying to correct indoor air quality problems, what have we learned? We have learned a great deal about the science of indoor air quality - a good thing. We have learned very little about the application of new learning at "the front lines" in building operation and maintenance - a bad thing. Know the building inside and out Most indoor air quality work has focused on these parameters: thermal comfort, physical contaminants, chemical contaminants and biological contaminants. Indoor air quality studies often extend these parameters to include noise and lighting in the building environment. Testing in buildings has focused on finding the parameter problem and fixing the problem. We know from American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) research, for example, that with an "ideal" temperature we can expect 80 percent of the building occupants at best to be satisfied with the temperature. At least 20 percent of the people will be somewhat dissatisfied with any given temperature. A building operator cannot achieve 100 percent satisfaction for thermal comfort without individual temperature control. IAQ parameters do not provide us with a complete picture. In order to understand IAQ problems, we have to view the building from a systems perspective. Five factors interact at the building level to determine indoor air quality: • Building occupancy and use; • Building material and internal contaminants; • HVAC and lighting systems; • Air movement inside the building; and • Outdoor air quality. These five factors are all interdependent. Building occupancy and use will determine the heating, cooling and ventilation requirements. The building occupancy becomes interdependent with the heating, ventilation and air conditioning (HVAC) system operation and controls. Most building HVAC systems were not commissioned to ensure that operation met the design intent and the occupancy and use of the building. Absence of commissioning isn't the only problem with buildings. Renovations to air handling systems often bring modifications that block return air flows. The result is that building air flows are never what the building designer intended. Building material, furnishings, and occupant processes can also contribute to the flow of contaminants. To ensure good IAQ, we must understand the nature of these contaminants and know how they relate to the other system factors. Operations and maintenance (O & M) personnel don't always understand air movement inside buildings. The mechanical airflows must be checked and balanced at regular intervals. Natural air movement inside buildings can move contrary to the intended design. For example, air moves in buildings due to "stack effect." The stack effect is a function of temperature difference and building height. Tall buildings in severe winter temperatures have air infiltration on lower floors and exfiltration on upper floors. The warm air inside the building sets up a pressure profile with the most negative pressure on the entry level floor and the highest positive pressure on the top floor. The pressure created by stack effect can overcome exhaust fan pressure on upper floors. The result is that air can flow out of (not into) exhaust grilles on upper floors in winter conditions! Finally, let's consider the outdoor air quality from a systems perspective. Outdoor intakes should be located near sources of contaminants which can be introduced into buildings. One example of this problem was noted in the famous case of Legionnaires disease in a Philadelphia hotel. The cooling tower water in this case was not maintained with chemicals. Legionella, a bacteria that can cause a pneumonia-like disease, grew in the cooling tower water and was transferred by aerosol to the outdoor intake and spread through the hotel. For more information on these factors, please read: Healthy Building Manual prepared for the Ontario Ministry of Energy in 1988 (Tom Tamblyn and Shalan Khandekar). Standards of performance The media has adopted the term "sick building" to describe a building with indoor air quality problems. The inference is that you either work in a healthy building or in a sick building. The reality is that most buildings have some degree of "sickness." We need the right combination of systems factors to create the IAQ problem. Consequently, a "healthy" building may be only one system factor event away from a "sick" building. Maintenance of HVAC systems is an important aspect of assuring good IAQ. Many buildings today use a corrective maintenance approach and have no planned preventive maintenance program in place.. Our building stock is aging; our baby boomer buildings from the sixties and seventies are now approaching 30 years of age. We need substantial building renewal. A lack of capital has resulted in both deferred renewal of building systems and deferred maintenance of major equipment. Not exactly a prescription for improving our indoor air quality. The surest solution to the issue is the development of standards of performance for building O & M. Although the cleaning contractor for a building has standards for good cleaning, we find that O & M personnel in North America have no similar documentation for good operation and maintenance. From a building management perspective, standards must be measureable and quantifiable. They must address the five IAQ factors mentioned previously and their interdependence. Standards would allow us to manage by exception and take corrective action when an IAQ parameter departs from its acceptable standard. How to develop standards of performance: • Review each building system to identify major components; • Create single line system schematics that can be updated; • Define the system variables that can be measured to ensure good IAQ; • Develop monitoring systems to report on variables; and • Measure variables and respond to exceptions. The development of the standards and the documentation is good business practice. Detailed design documents are very costly to update. The single line schematics and documentation described can be kept up-to-date using inexpensive CAD software. Documentation and monitoring can be integrated using the existing building automation system. The entire cost of the documentation process will depend on building size and complexity, but the cost should not exceed a $15,000 effort for a building of 150,000 sq ft. Standards of performance and building documentation work best when personnel are trained in O & M. Documentation developed by "professionals" sits on the shelf in the O & M office. When the O & M personnel develop their own documentation, however, the result is very different because they are more likely to use it. The key point about O & M documentation is that it must be sustainable. The standards must be measureable and the documentation must be updated at regular intervals. ASHRAE has published information on a guideline for the documentation of HVAC systems. The business case for standards of performance is very strong. Building tenants pay at least $25 per sq ft per year for their building rent. The payroll cost of building occupancy is at least $250 per sq ft per year, an order of magnitude higher. A 10 percent change in productivity will equal the entire rental cost for the year! The field research has shown that worker productivity can vary by 10 percent based on indoor air quality variables. One such study at West Bend Insurance head office in Wisconsin showed productivity changes in the three to 15 percent range with individual temperature control. Our own research in Toronto and Montreal buildings has confirmed productivity effects in the 10 percent range. New developments in building systems There is good news. A more hygienic and comfortable work environment is within reach, and the technology continues to improve. Individual temperature control is becoming more common in new buildings. The same concept can be applied in building retrofit. The temperature control devices can be located in duct work and be activated by individual infrared remotes or through the local computer network. This concept has been researched and tested successfully in the last ten years. If we can have individual controls on airplanes and cars, why not at our desk? The business case for better thermal comfort has been made in a number of field studies. Expect to see better temperature control in our future. Ultraviolet light is now being used as a biological IAQ control. UV light has been used in selected water and air treatment but has rarely been used in general building applications. I expect to see more common use of UV light in air handling systems to kill biological contaminants such as mould and viruses. The UV light can be located in air handling plenums where the concentration must be high enough to kill the major biological contaminants. Kill rates exceeding 99 percent are possible with well designed systems. Selective coatings are now being developed to address the issue of VOCs (volatile organic compounds) in buildings. The selective coatings will be used as catalysts to breakdown VOCs into harmless bi-products. I expect to see these coatings deployed as part of new air handling systems or added to retrofit projects. Tom Tamblyn, B.A.Sc, P.Eng., MBA, is an independent consultant with more than 25 years of experience with engineering, operations and maintenance in commercial buildings.