American Fire Sprinkler Association
12750 Merit Dr., Suite 350 Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
TECHNICAL UPDATE
APRIL 11 2007
A diagram was attached showing an elevation view of a glass wall
separating a floor level from an atrium. The sprinklers are placed
above the glass wall and a horizontal mullion is located 3 ft above
the floor. You asked the following question:
"There is an atrium separated from the other areas with a glass
wall. Sprinklers are spaced around the glass wall as required by IBC
and NFPA. However, there is an intermediate horizontal mullion 3 ft
above the floor that does not allow water to completely cover the
glass wall. What should be done in order to comply with the code?"
We have reviewed the IBC, 2000 edition and NFPA 13, 2002 edition that
you indicated as the applicable code and standard. Our informal
interpretation is that the sprinkler must spray on the entire surface
of the window and the intermediate horizontal mullion may create an
obstruction that may prevent water spray on the entire surface.
The best option for complying with the codes is to communicate the
sprinkler requirements to the architect where a pane of glass is
provided from floor to ceiling since horizontal mullions present a
problem. A handrail several inches from the glass surface could be
installed in lieu of the intermediate horizontal mullion if there is
any fear of occupants falling through the glass. Another option is
to discuss the situation with the authority having jurisdiction on
the intermediate horizontal mullion. Perhaps it could be
demonstrated that sprinkler coverage is provided to the entire window
surface even with the intermediate horizontal mullion.
The IBC and NFPA 13 Annex have the same message of applying water on
the entire surface of the glass. Section 404.5 in the IBC states, "A
glass wall forming a smoke partition where automatic sprinklers are
spaced 6 feet or less along both sides of the separation wall, or on
the room side only if there is not a walkway on the atrium side, and
between 4 inches and 12 inches away from the glass and designed so
that the entire surface of the glass is wet upon activation of the
sprinkler system." The later editions of the IBC includes the words
"without obstruction" at the end of this section. The information in
Annex D.3 also states, "Glass walls and inoperable windows shall be
permitted in lieu of the fire barriers where automatic sprinklers are
spaced 6 ft apart or less along both sides of the glass wall and
inoperable windows, not more than 1 ft from the glass, and with the
automatic sprinklers located so that the entire surface of the glass
is wet upon operation of the sprinklers." On a side note, the 2007
edition of NFPA 13 now includes information from the Life Safety Code
on atriums in section 21.20.1.2.1 that also includes the very similar
wording. The information in Annex D.3 was also retained in the 2007
edition.
A listed window sprinkler is available from Tyco Fire & Building
Products that is identified as Model WS. This head is a specific
application window sprinkler and has orientations for horizontal and
pendent vertical sidewall installations. This particular sprinkler
was not tested with intermediate horizontal mullions. The window
sprinkler data sheet specifically indicates that window sprinklers
are not listed to protect windows when intermediate horizontal
mullions are present. Thus the intent of the sprinkler manufacturer,
IBC, and NFPA 13 is to provide coverage to glass walls in atrium
without horizontal obstructions.
-----------------
Technical Update is prepared by the Technical Services Dept. of the
AFSA: Vice President of Engineering and Technical Services Roland
Huggins, a PE registered in fire protection engineering; Phill Brown,
a NICET IV certified automatic sprinkler technician and NFPA
Certified Fire Protection Specialist (CFPS) and Tom Wellen, a degreed
fire protection engineering technologist. This is provided with the
understanding that the AFSA assumes no liability for this opinion or
actions taken on it and they are not to be considered the official
position of the NFPA or its technical committees.
Copyright (c) 2007, American Fire Sprinkler Association. All
Rights Reserved
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