Not all code revisions are more conservative.
The 2018 Edition of NFPA 101 has updated the long-held occupant load factor of 100 sqft per person to 150 sqft per person. If you don’t live in the life safety arena, this change allows the calculated occupant load for a business space to be notably less, thereby requiring less exit width, stair width, potentially the number of exits, and other means of egress requirements.
The 1934 Building Exit Code first incorporated the density of 100 sqft per person, which was based upon a 1922 recommendation from the Building Exit code committee. It has since carried through over eight decades of code revisions and has lasted through many differences in office design.
Concentrated Business Use Introduced in 2015
The Life Safety Code introduced the Occupant Load Factor for “Concentrated Business Use” at 50 sqft per person in the 2015 Edition.
The goal with determining occupant loads has always been to provide the means of egress for a maximum probable number of occupants, and the introduced higher density was intended to address higher-density spaces than would normally be expected in a business occupancy. Annex material in NFPA 101 states that this should be applied where occupant concentrations are maximized, such as business call centers, trading floors, or data processing centers.
Modern open office concepts have changed the way we congregate and occupy buildings
Challenges with High Occupant Loads
This 2015 Edition change, according to testimony in committee hearings for 2018, has brought increased scrutiny and sometimes higher occupant loads to business occupancies by review authorities.
Increased occupant loads impact egress capacity, additional exiting, and can be very difficult to achieve higher occupant loads in existing buildings. Without additional horizontal exiting or plumbing fixtures, many existing office buildings cannot accommodate redesigns under higher occupant loads.
Open office concepts have also introduced new challenges. Collaborative spaces are sometimes being reviewed as assembly, even though these small rooms are intended and often used by the same people that are no longer at their workstations. The occupant load could effectively double-count the same occupant for two different work areas.
While terminology for the collaboration rooms is not entirely defined, modern office buildings are often labeling these as huddle rooms, quiet rooms, focus rooms, enclave rooms, or other owner-specific terms. These type spaces appear to meet the intent for the new collaborative room load factors identified below.
Collaboration rooms, often labeled as huddle, quiet, focus, or enclave rooms, are often used for smaller group activities by people who otherwise occupy the open office space. These smaller spaces function differently than traditional conference rooms.
Researching New Load Factors
The NFPA Fire Protection Research Foundation sought to study the appropriateness of the business occupant load factor for modern buildings in 2012.
Two studies stemmed from their initiative; a WPI Student Research project studies office building designs, modern changes in the workplace, and occupancy impacts of flexible employee scheduling and telecommuting. This study suggested it would be reasonable to increase the load factor to 150 sqft per person.
The second study, by Gilbert Group at the University of Canterbury in Spain, found average load factors for modern office buildings averaged 181 sqft per person. Both studies summarized that the 100 sqft per person occupant load was considered conservative.
Further testimony in the committee hearings suggested that at least ten research studies on office buildings conducted since 1935 have indicated that the Occupant Load Factor for businesses was conservative at 100 sqft per person.
The research, motions, and resulting voting brought a few major changes to the 2018 Edition of NFPA 101. Business use occupant load factor has increased from 100 sqft to 150 sqft per person; the “Concentrated Business Use” load factor has remained from the 2015 edition; and lastly small collaboration rooms and large collaboration rooms (with a threshold at 450 sqft) are given occupant load factors of 30 sqft and 15 sqft per person, respectively:
NFPA 101 Updates to Business Occupancies by Year
The new occupant load factors use the more modern net square footage (square footage inside the perimeter of exterior walls with deductions for hallways, stairs, closets, interior wall thickness, columns, and other features, NFPA 101-2018 18.104.22.168.2) instead of gross square footage.
While the discussion above considers the process for NFPA 101 Changes, the International Building Code has similar provisions for the 2018 Edition for Business Occupant Load Factors as well as definitions of net and gross floor areas (Table 1004.1.2 and Chapter 2 Definitions, respectively).
Lastly, occupant loads of 50 people or more in a single space would still consider the space to be assembly and not a business occupancy. Large presentation rooms, training areas, or lecture halls can quickly introduce assembly occupancy requirements that are unaffected by these changes.
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.