Adding insulation to a "Listed" floor/ceiling assembly, additional requirements?

[khsmith55]

As I've always understood there are basically three paths when selecting fire resistive assemblies; 1) prescriptive method like 2015 IBC Tables 721.1 (1-3) (usually least restrictive), 2) GA Fire Resistance Manual or 3) UL Fire Resistance Manual (usually most restrictive), all three paths being code compliant. The "wild card"......both GA and UL have the note for adding insulation, however 2015 IBC Table 721.1(3) has no similar footnote I can find. For an example......could you use Table 721.1(3), Item 21-1.1 with the trusses (or floor joists, for sound) filled full depth with non-combustible insulation with no additional requirements (less restrictive than GA or UL), in lieu of a GA or UL listed assembly? Food for thought, huh.

From UL Fire Resistance Directory (GA Manual has a similar note)

II. General

17. Blanket Insulation

Unless specifically described in the individual designs, the addition of insulation in the concealed space between the ceiling membrane and the floor or roof structure may reduce the hourly rating of an assembly by causing premature disruption of the ceiling membrane and/or higher temperatures on structural components under fire-exposure conditions.

– For 1-hour-rated G500, L500, M500, and P500 Series assemblies, fiberglass insulation, loose-fill, batts, or blankets may be added to the plenum or joist space above the gypsum wallboard, provided an additional layer of gypsum wallboard is added to the assembly.

Your feedback would be appreciated.


Thanks in advance,

Ken

 

[RLGA]

You're missing a fourth: The calculated method per Section 722.

 

[RLGA]

Here’s an option:

Per IBC Section 721.1, it states “Where materials that change the capacity for heat dissipation are incorporated into a fire-resistance-rated assembly, fire test results or other substantiating data shall be made available to the building official to show that the required fire-resistance-rating time period is not reduced.” Then, reference the UL Fire Resistance Directory as “substantiating data” for adding insulation.

 

[cda]

I thought /khsmith55. Post was interesting

Because we see it a lot in place of sprinkling combustible concealed spaces.

 

[khsmith55]

Here’s an option:

Per IBC Section 721.1, it states “Where materials that change the capacity for heat dissipation are incorporated into a fire-resistance-rated assembly, fire test results or other substantiating data shall be made available to the building official to show that the required fire-resistance-rating time period is not reduced.” Then, reference the UL Fire Resistance Directory as “substantiating data” for adding insulation.

Thanks Ron! You have put my mind at ease, I have ALWAYS added the additional layer of Gypsum Board even when using the IBC floor/ceiling assemblies.

Ken