Concealed Space Sprinklers Case Study

You have asked the following questions: “The concealed space sprinklers per 8.15.1.6 indicates that concealed spaces less than 3 ft shall be protected using listed sprinklers. We have an open wood truss construction that is tapered with the above portion being 5 ft and the lower being 2 ft. Concealed space sprinklers have specific requirements one of which is they are not listed in spaces greater than 3 ft. Q1) Should truss spaces be protected by standard spray sprinklers throughout? Q2) Should the space be protected by concealed space sprinklers throughout? Q3): Should space be protected by a combination of standard spray and concealed space sprinklers? If so, which design strategy is applied (area/density or concealed space strategy)?” In response to your questions, we have reviewed NFPA 13, 2016 edition as the applicable standard. Our informal interpretation is that there are several approaches that can be used for this application.
The wording in the standard may not be the best, but this section is requiring the use of sprinklers listed for applications for horizontal combustible concealed spaces less than 36 in. deep. As noted in the Handbook commentary, listed standard spray sprinklers were ineffective for fire control since the shallow space inhibits the discharge pattern development. When the space is greater
The minimum size of the remote area for standard spray sprinklers in this space would be 900 sq. ft. If there is insufficient area, the remote area is carried to the concealed space sprinklers. The other calculation would be the concealed space sprinklers having a minimum remote area size of 1,000 sq. ft. There is no requirement to separate the two types of sprinklers. The exception is the draft curtains required by the manufacturer’s data sheets for the listed concealed space sprinklers. Refer to the sprinkler’s data sheets for the specifics on the draft