The W rating is generally thought
of as a “fitness for use” evalu-
ation and is being specified in
applications where a floor is fre-
quently cleaned with water. The
use of a system with a W rating
provides the building owner and
their reps with the assurance
that water will not pass through
a firestop system and damage
the floor beneath, and that the
system will continue to
serve its role of protecting the
penetration should a fire occur.
Since a W rating is not currently
required by the IBC, any system
which has this rating would cur-
rently exceed the code require-
ment in this regard. W ratings
are provided in classes.
W Rating requirements are yet
to be included in NBC.
MINERAL FIBER
Insulation composed principally of fibers manufactured from rock,
slag or glass, with or without binders. Mineral fiber insulation is
commonly used for pipe insulation or is used as a fire blocking ma-
terial. Fiberglass insulation is included under this definition.
MINERAL WOOL
Synthetic vitreous fiber insu-
lation is made by melting pre-
dominately igneous rock or
furnace slag, or other inorganic
materials, and then physically
forming the melt into fibers. In
many firestop systems, miner-
al wool is used as a backing
or damming material to allow
for the placement of a specific
depth of firestopping material
(Fig 2.9)
47