More than ever, commercial building occupants view good indoor air quality (IAQ) as an essential component of a building’s design, construction, and operation.
A Lawrence Berkeley National Laboratory Study (2000) found that building characteristics and indoor environment significantly influence worker performance. After IAQ improvements, the study estimates potential national savings from health and productivity gains to be between $23 and $56 billion.
Something in the Atmosphere
The air we breathe indoors is a mixture of interior air and air surrounding the building. We must contend with outdoor issues such as pollens, dust, moisture, and gases, as well as interior pollutants like mold spores, pollens, allergens, and pathogens.
Chemical pollutants include numerous volatile organic compounds that are emitted from consumer products, building materials, combustion gases, and mold/ mildew, with an estimated 10 million people in the United States developing chemical sensitivity and negative reactions to their presence.
Compounding problems further is the fact that many commercial buildings have poor mechanical ventilation systems not designed (or operated) to provide adequate amounts of filtered outside air. Occupants also tend to have less control over their indoor environment at work than in their homes. The combined result is that there has been a significant increase in the incidence of reported health problems (SOURCE: [www.epa.gov/iaq/largebldgs]).
Step 1: Build Tight
Control airflow/air leakage across the building shell. The interior conditioned air should be separated from the exterior air by a continuous airtight enclosure. Air leakage is responsible for 30 to 40 percent of a building’s heat loss and is the drive mechanism for 90 percent of condensation-related moisture problems.
Historically, creating a continuous air barrier on all six sides of a building has been a labor- and material-intensive process, especially at critical areas such as floor assemblies, outside corners, and multi-faceted roof assemblies.
Typical fibrous insulation systems provide some insulation value, but do not stop airflow across an assembly. Specialty foam products are now available that deliver effective R-value ratings and greatly simplify air sealing procedures.
Step 2: Ventilate Right
Control ventilation. Commercial building ventilation systems are required to provide fresh air on a per-person basis. Depending on building use, this airflow can vary from a low of 15 cfm (cubic feet per minute) for students in a classroom to 60 cfm for smoking lounges. Typical office spaces require 20 cfm per person.
Once the continuous air barrier is in place, outdoor air brought into the building must be filtered and treated to eliminate airborne chemicals, pollens, and dust, and to exhaust stale, moisture-laden interior air.
Indoor environments that produce odors, fumes, dust, or water/moisture need to provide special ventilation fans and air-tight partitions to ensure pollutants are controlled and kept away from occupants. The ventilation air change rate can then be carefully controlled by installing air-handling systems to bring in and filter fresh outdoor air. As a result, this air is distributed throughout the occupied zone.
By carefully designing and constructing a building with proven construction materials and an effective HVAC system, optimal IAQ can be achieved and building owners and occupants can breathe easy.
Randy Nicklas is president at Bend, OR-based Controlled Environments and conducts continuing education seminars on building envelope design at the American Institute of Architects (AIA) on behalf of Icynene Inc. (www.icynene.com).