How do I tell if my building is considered an “open building”?

A building is considered open if each wall is at least 80 percent open (ASCE 7-16, Section 26.2, “BUILDING, OPEN”). This condition is expressed for each wall by the equation A_o ≥ 0.8 A_g where

A_o = total area of openings in a wall that receives positive external pressure, in ft² (m²)

A_g = the gross area of that wall in which A_o is identified, in ft² (m²)
EXAMPLE:

Open Building

However, a building that meets both the “open” and “partially enclosed” definitions should be considered “open” (ASCE 7-16, Section C26.2, “BUILDING, ENCLOSED; BUILDING OPEN; BUILDING PARTIALLY ENCLOSED”).

From the ASCE 7-16 Commentary C26.2 Definitions:

BUILDING, ENCLOSED; BUILDING, OPEN; BUILDING, PARTIALLY ENCLOSED; BUILDING, PARTIALLY OPEN:

These definitions relate to the proper selection of internal pressure coefficients, (GCpi). “Enclosed,” “open,” and “partially enclosed” buildings are specifically defined. All other buildings are considered to be “partially open” by definition, although there may be large openings in two or more walls. An example of this would be a parking garage through which the wind can easily pass but which does not meet the definition for either an open or a partially enclosed building. The internal pressure coefficient for such a building would be ±0.18, and the internal pressures would act on the solid areas of the walls and roof. The standard also specifies that a building that meets both the “open” and “partially enclosed” definitions should be considered “open.”

See also “Enclosed Building”  and “Partially Enclosed Building”