This past week UL, "the trusted source across the globe for product compliance" held a symposium in Phoenix Arizona. Titled, Designing Fire Safety into Residential Construction: Perspective, Ideas, and Trends, the program was immensely educational and provided different outlooks from numerous stakeholders.
I was most impressed with the presentation by Steve Kerber, Fire Research Engineer at UL. I will share the information provided during his presentation titled, Today's Residential Fire Environment: What's Different and Why it Matters. Mr. Kerber talked about the differences between modern residential construction and legacy construction.
He discussed the following fire formula:
Larger homes + Open Spaces+ Increased Fuel Loads + Void Spaces +Changing Building Materials =
· Faster fire propagation
· Shorter time to flashover
· Rapid changes in fire dynamics
· Shorter escape time
· Shorter time to collapse
Larger homes
He spoke about the new home building environment in which 26% of houses built in 2008 were >3000 sq. ft. and 50% were multiple level homes.
Open spaces
Great rooms, open spaces 9-14ft. ceilings; all these features and a greater volume of air allows the fire to grow and smoke to spread more rapidly. Open floor plans mean more air, more fuel, easier room to room fire communication.
Increased fuel loads
Fuel load in homes is now dominated by synthetic material. Older material, cotton batting and cotton covers have been replaced by newer materials, completely synthetic, polyurethane foam, polyfill batting, and polyester covering. These furnishings provide more potential energy per unit mass than wood or natural materials. A single upholstered chair can provide enough energy to bring a 10X12 room to flashover. A sofa can provide three times the energy of a single chair. He then showed a video comparison between a legacy room and a modern room. The legacy room achieved flashover in 29:25 minutes vs. the modern room in 3:25 minutes.
Void spaces
Today’s house geometries are limitless. Attic and floor voids, especially in larger homes, assist in the spread of fire and smoke throughout the structure.
Changing building materials
Solid board home sheathing has been replaced by cardboard. Wall lining has changed from plaster lath to gypsum. The structural components have changed considerably from old growth lumber to engineered lumber. Windows are now vinyl framed. These newer windows fail substantially faster than old windows. Solid core doors have been replaced by composite doors.
He spoke about the home in the picture below where a young firefighter died. The home was three years old and an approximately 6000 square foot, two-story plus finished walkout basement, non-sprinklered residential structure that was constructed of wood framing with vinyl siding and a brick veneer front on the exterior. The residence had a large 700 square foot wood deck that ran three quarters the length of the rear of the structure on the first floor (C-side). The roof consisted of wood rafters with fiberglass shingles over oriented strand board sheathing.
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