How were the BASE Study buildings selected?

Buildings selected and recruited for monitoring represent both public and commercial office buildings in the United States. Both complaint and non-complaint buildings were included in the study. Complaint buildings that had been highly publicized by the media were excluded. Building selection was randomized to the extent possible, based upon the success in gaining access to buildings.

Because it was believed that office building design and operation are influenced by climatic considerations, various climatic regions were represented in the study, by using a stratified random sampling method across ten climate regions (see Base Climatic Regional Map  -  www.epa.gov/iaq/base/regionalmap.html and BASE Building Distribution by Climate (PDF) - www.epa.gov/iaq/base/pdfs/building_distribution_by_climate.pdf) based on the American Society of Heating, Refrigerating, and Air-Conditioning Engineers' (ASHRAE) 1989 building design specifications. Within these climatic regions, cities with a population of over 100,000 (see the cities chart - www.epa.gov/iaq/base/images/table2.2.jpg ) were randomly selected in each region using a random number generator. Cities with a population of over 100,000 were used to help ensure that sufficient office buildings were available.

Within these cities, tenants within buildings were contacted to determine building eligibility. The building manager/owner was then contacted and asked whether they would allow the study to be conducted in their building. Once it was determined that the building had not been highly publicized as a "sick" or "problem“ building, an initial or preliminary visit (PV) was scheduled to identify at least one potential study area within the building. If at least one study space could be identified as having more than 25 occupants accessible by questionnaire and as being serviced by no more than two air handling units (AHUs), the building was considered acceptable for the study.

A schematic flowchart of the BASE Study Building Selection Process (PDF) - www.epa.gov/iaq/base/pdfs/bldg_sel_diag.pdf is available and a detailed discussion is contained in the report Summary and Analysis Report of the BASE Study Building Selection Process (PDF) - www.epa.gov/iaq/base/pdfs/2005bldgsel.pdf. Based on this analysis, EPA finds that the building selection process introduced limited error and biases, both in design and in execution. The resulting sample provides a useful dataset for future IAQ comparisons for large office buildings.

Read more about the BASE Study at www.epa.gov/iaq/base

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