This thought process led UL to develop a second set of criteria for
evaluating the performance of perimeter fire containment systems.
The early listings from UL were done using the test apparatus
described in ASTM E 2307, but with more stringent conditions of
acceptance. The UL method developed two rating criteria—an
Integrity rating and an Insulation rating. These terms are borrowed
from the international fire-resistance test standards. The conditions
of acceptance for these two ratings are as follows:
Integrity Rating: The criteria for the Integrity rating include the
requirements for the F rating of ASTM E 2307 in addition to a
requirement that the system must prevent the passage of flames
through openings in the curtain wall anywhere above the protected
void. Put another way, the criteria for an Integrity rating prohibits
flaming through all the three paths discussed earlier.
Insulation Rating: The criteria for the Insulation rating include the
requirements for the T rating in addition to the requirement to limit
the temperature rise to 325°F (180°C) above the starting temperature
anywhere on the interior surface of the curtain wall above the
protected void. Put another way, the criteria for an Insulation rating
limits the temperature rise anywhere on or above the floor level of
the test assembly, including the vertical mullions and vision glass.
As this discussion implies, the UL criteria increase the level of
protection achieved by prohibiting flame passage and limiting the
temperature rise anywhere on or above the floor level. UL now
requires the F and T ratings as the minimum level of protection.
However, the Integrity and Insulation ratings are offered as an option
for those manufacturers who would like to demonstrate a higher
level of safety. These higher performance levels are not required by
the IBC. Ultimately, the designer or owner will have to determine if
the level of protection required by the code is adequate or a higher
level of protection provided by a T rating, and Integrity rating or an
Insulation rating is required. For a code official to require this higher
level of safety, he or she would need to either amend the code or
demonstrate that the higher safety level is needed due to something
unique with that project.
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