1. Whole Building Physical Characteristics

The BASE study collected data from 100 randomly selected buildings in 37 cities in 25 States. Ownership of the BASE buildings was primarily split between private and commercial (n=41) and government (n=44), the remaining 15 buildings were classified as academic. Most of the BASE study buildings were classified as being in urban surroundings (73%). Twenty-three percent were in suburban surroundings and 4% were in rural surroundings.

1. Building Age : The age of BASE buildings varied considerably from buildings constructed prior to 1900 to buildings constructed in the 1990’s. The highest percentage of BASE buildings was constructed in the 1980’s (30%) followed by a large number of buildings constructed in the 1960’s and 1970’s.
    
2. Building Size: The BASE buildings are most representative of large office buildings with 50 or more employees. It is estimated that the office buildings with 50 or more employees roughly represent 11% of the US office building stock and 73% of all US office workers.
   • A detailed discussion of the "representativeness" of the BASE data to the US building stock can be found in chapter 5 of the Summary and Analysis report of the BASE Study Building Selection Process.
      
3. Building Floor Area: The overall gross floor area of BASE buildings ranged from 1,665 square meters to 134,195 square meters. The median occupied floor area was 8,477 square meters (1,444,475 square feet) and ranged between 629 square meters (6,771 square feet) and 98,474 square meters (1,059,974 square feet).
    
4. Building Stories: The BASE study included single-story buildings as well as buildings that were thirty stories and greater. Most of the buildings however, were ten stories or less. Twenty-five percent of the BASE Buildings were buildings between one and three stories.
    
5. Occupancy: The total building occupancy was obtained from interviews with building staff. Typical building occupancy including visitors refers to the total number of people, employees and visitors that occupy the building during normal business hours. The distribution of total building occupancy across the BASE study buildings is presented graphically below. The median total occupancy of the study buildings was 705, the minimum was 87 and the maximum was 6,500.
    
6. Operable Windows: Operable windows can be used as a ventilation strategy in naturally ventilated buildings and can also supplement ventilation provided through a building mechanical system. For BASE buildings, fifty-five had non-operable windows and 44 had some percentage of windows that were operable. One building studied was not equipped with windows.

1. Special Use Spaces: A variety of special spaces were found within the BASE study buildings. The types and frequencies of special use spaces are shown below. Of particular interest is that many of these special use areas with activities that generate indoor pollutants did not have dedicated ventilation systems or exhaust systems.
    
2. Water Damage: Eighty-five percent of the buildings experienced water damage in the past, which may be largely related to the wide-ranging age of BASE buildings. Forty-five percent of the buildings were experiencing ongoing problems with leaks causing water damage, 34% of the buildings had current leaks in occupied spaces. For the buildings reporting past water damage and current water leaks, the majority was reported to have occurred in the occupied spaces of the building.
    
3. Fire Damage: Twelve of the 100 BASE buildings reported damage to the building caused by fire. In all cases, the fire damage was limited to localized areas of the building.
    
4. Pest Control: Fifteen percent of the buildings had no interior pesticide applications and 33% of the buildings had no exterior pesticide applications. It is worth noting that the most common interior pesticide application interval was monthly (34%). Another thirty-one percent of the buildings had interior pesticide applications on an as-needed basis. The most common exterior application interval was on an as-needed basis (33%). Further, interior pesticide applications exceeded exterior pesticide applications.

A. Special Use Spaces

figure caption: Special Use Areas Among BASE Study Buildings

B. Water Damage

figure caption: Past Water Damage and Current Water Leaks Among BASE Study Buildings

D. Pest Control

figure caption: Interior and Exterior Pesticide Application Frequency Among Base Study Buildings

Whole Building HVAC Characteristics

1. Ventilation Strategy: Ventilation provided to BASE Buildings was introduced through mechanical or natural means. Two of the 100 BASE Buildings relied solely on natural ventilation while all other buildings had some form of mechanical ventilation. One building utilized natural ventilation in the study area and mechanical ventilation in other areas of the building.
    
2. Building Cooling Systems: Ninety-one of the BASE buildings were equipped with some sort of cooling system. Some BASE buildings relied on a combination of two or more cooling systems as the primary cooling. The predominant type of primary cooling system employed in BASE buildings consisted of central air handling systems with chilled water cooling coils as shown graphically below. Roughly three quarters of the buildings were equipped with central chiller systems.
    
3. Building Heating Systems: All of the BASE study buildings were equipped with some sort of heating system. Over 75% of the buildings used steam or hot water as the primary means of space heating. For these buildings, one quarter were served by central heating plants not located in the building. The predominant type of heating system employed in BASE buildings consisted of central air handling systems with heating coils.

B. Building Cooling Systems

figure caption: Primary Cooling Systems Among BASE Study Buildings

C. Building Heating Systems

figure caption: Primary Heating Systems Among BASE Study Buildings