Taking ceilings into the clouds safely

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Cloud ceilings are a type of suspended ceiling system consisting of decorative panels separated by gaps. The panels come in a variety of shapes, sizes, and styles and give ceilings a more architectural look, compared to a traditional flat acoustical ceiling tile system. We’ve recently used cloud ceiling installations in several projects with great success, and these systems are gaining popularity with designers. Harrison High School Cafeteria – Harrison, NY. From a mechanical engineering standpoint, however, cloud ceiling systems present a new challenge for fire sprinkler design. The gaps in the ceiling panels provide an area for heat from a fire plume to pass through and develop a gas layer at the underside of structure. Additionally, the spray from the sprinkler heads can become obstructed by the panels. The National Fire Protection Association (NFPA) 13, the design guideline used for fire sprinkler design, does not yet contain specific guidelines for sprinkler installation in the clouds. Currently, NFPA recommends using the guidelines for obstructions and deflector position requirements. In doing so, fire sprinklers may be required above and below the ceiling. Harrison High School Cafeteria – Harrison, NY. In an effort to start establishing these new requirements, the NFPA Research Foundation recently studied how cloud ceilings affect sprinkler actuation. Using simulations, NFPA tested factors such as gap size, ceiling heights, and fire growth rate on large-area, non-combustible cloud ceiling systems. Based on their modeling, the NFPA concluded that “the permissible gap size is a function of ceiling height.” The study offered two potential rules based on the modeling—a One Part Rule and a Two Part Rule. The One Part Rule states: “For cloud ceilings where the clouds and structural ceiling are of non-combustible constructions, the clouds are sufficiently large and spaced such that each cloud will have at least one sprinkler based upon the normal listed spaced, and where the clouds are level and co-planar, sprinklers can be omitted in the structural ceiling if the gap between a wall and any cloud or between two adjacent clouds is less than or equal to 1 inch of gap per foot of ceiling height.”

The Two Part Rule States: “For cloud ceilings where the clouds and structural ceiling are of non-combustible construction, the clouds are sufficiently large and spaced such that each cloud will have at least one sprinkler based upon the normal listed spacing, and where the clouds are level and co-planar, sprinklers can be omitted on the structural ceiling if: The gap between a wall and any cloud is less than or equal to 1 inch of gap per foot of ceiling height, or The gap between any two adjacent clouds is less than or equal to 1 1/4 inch of gap per foot of ceiling height.” These initial findings will provide a technical basis for sprinkler installation requirements and will be used for proposed changes to the next edition of NFPA 13. The study also makes recommendations for future NFPA studies of cloud ceilings. If you’re an architect or engineer considering a cloud ceiling installation in your next design, you can find NFPA’s complete research report, along with a helpful video, here. Natalie Kovac, P.E., LEED AP, is a Project Engineer in H2M’s Mechanical Engineering group. You can reach Natalie at nkovac@h2m.com.