Reduced cost and Increased T ratings
When you think of the dangers of a structural fire, you probably think of flame spread and smoke travel… but there is more to consider.
A fire can quickly reach over 2000 degrees Fahrenheit, and fully develop in under 5 minutes.
Even at temperatures, of 325 degrees, it is possible for spontaneous combustion to occur. This spontaneous combustion allows the transfer of fire with out flames ever leaving the area of the fire’s origin. Thermal transfer can be difficult to control, especially with metal pipes and other materials that rapidly spread heat.
A properly selected and installed firestop system will prevent both the spread of flame and heat transfer.
F ratings indicate the duration in time which flames do not pass through the tested assembly.
T ratings measure the time it takes the non-fire side of the tested assembly to reach 325 degrees Fahrenheit above ambient air temperature.
Since at least 2003 the International Building Code has required F and T ratings for through penetrations of no less than 1 hour but not less than the rating of the floor being penetrated. This T requirement reflects the danger of heat transfer during fire situations. Although there are exceptions, the requirement and the importance of the rating should not be disregarded.
Although every tested system has F and T ratings listed on the system, they are not always equal. Where F ratings simply stop fire from transferring through a rated assembly the T rating is a measure of heat transference through an assembly. It is difficult to achieve T ratings for penetrating items that conduct heat very readily. Metallic penetrations are good examples of items that can easily have F ratings of 2, 3 and 4 hours but generally have T ratings of 0 hours.
Historically to be in compliance with code requirements for T ratings, it was necessary to use firestop systems that covered the penetrating item on the top and bottom side of the floor with expensive calcium silica duct wrap material.
Fortunately, there are new third-party tested systems with T ratings up to 3 hours and a pipe diameter of up to 10” that have simplified and lowered the cost. For example:
Underwriters Laboratories tested system C-AJ-1601, which gives protection of metallic penetrants of up to 10 inches for F and T ratings of up to 2 hours and penetrants up to 4 inches for up to 3 hours. A maximum height of 24 inches of any UL listed insulation in the classification BKNV with a flame spread of index of 25 or less or a smoke development index of 50 or less.
The cost savings are realized because you can use any UL listed insulation vs. a single sourced brand. For example, Fyre wrap is over $200 per 25’ roll, where standard fiberglass duct wrap is under $100 per 25’ roll.
Fire safety and firestopping are two of the most important aspects of specification, construction and inspection for occupied structures. Every aspect of life safety and building code must be followed to ensure a minimum amount of protection to people who are living, working, and visiting buildings that require firestop.
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