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Use of component additive method

sunyaer

Registered User
Joined
Apr 21, 2022
Messages
338
Location
Toronto
In Ontario building code SB-2:

2.3.3. Limitations of Component Additive Method
...
(2) The assigned times in Sentences 2.3.4.(2) to (4) are not intended to be construed as the fire-resistance ratings of the
individual components of an assembly, nor are they intended to be construed as times that are applicable or acceptable for
use
beyond the method and systems described in this Subsection. These assigned times are the individual contributions of
each component to the overall fire-resistance rating of an assembly, which are permitted to be derived using the
component additive method described in this Subsection.

1st question:

1. What does "for use beyond the method and systems described in this Subsection" mean?


According to the following text from this link: https://kilolimacode.com/component-additive-method-for-fire-resistance-ratings/ fire-resistance rating of an assembly is not the sum of the times assigned to individual components, then my 2nd question:

2. Fire-resistance rating of an assembly is what is used in fire protection design, is there any practical use of the component additive method, as it doesn't derive the assembly fire resistance rating? If there is no, why is it in the code?

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3. Times assigned are not the fire-resistance ratings of individual components
...
The times assigned to membranes in the CAM are not the same as “finish ratings” sometimes cited in listings. The times assigned to membranes are based primarily on their ability to remain in place during fire tests. A fire-resistance rating, however, also includes a temperature rise limitation criteria. The temperature rise criteria is not accounted for in the times assigned to components in Appendix D, as it relies upon the entire assembly to meet the criteria. Finish ratings provided on listings account for the temperature rise criteria and can be considered as the fire-resistance rating provided by the finish/membrane only in an assembly.

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2.
 
1. The link you posted had a good summary of this section of the code. It notes that the ratings are not time assigned for individual components, but is a rating assigned to the assembly as a whole.

While you simply sum the values for each component to have a total fire resistance rating, you cannot assume components have a fire resistance rating without the other components of the assembly.

2. Component additive method ONLY provides an assembly rating.

3. temperature rise limits are not always required.
 
Appendix D is a tremendously useful tool, but it has to be used cautiously. As noted, the component additive method allows one to attribute a fire resistance rating to an assembly made up of identifiable components. We never attribute a rating to anything other than assembly.
It's also worth noting that appendix D gives some guidance on things such as when one does not have to install dampers on ducts penetrating a ceiling, for example.
 
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