2411 [OSHPD 1, 1R, 2, 4 & 5]-Thermal Barriers in Aluminum Mullion Systems — 2025 California Building Code

The requirements of this section address the use of thermal barriers composite in aluminum mullion systems. The ther- mal barriers shall consist of either poured and debridged or mechanically locked pre-formed construction. The thermal barrier systems used shall be those tested and complying with AAMA TIR-A8. The thermal barrier manufacturer, formulation number or insulating strut size/material and aluminum extrusions shall be consistent between testing, design and construction.

Exception: Single-story Type V skilled nursing or intermediate care facilities utilizing wood-frame or light-steel-frame construction.

2411.1.1 Structural Design. Structural design of thermal barrier mullions shall satisfy the following requirements: 1. The allowable design stresses for thermal barrier materials composite with aluminum extrusions shall be determined by AAMA TIR-A8 testing for in-plane shear, tension and eccentric load at a minimum of ambient and high temperature using a factor of safety determined by AAMA TIR-A8 Section 6.7. 2. The shear modulus, G c , of the thermal barrier in similar composite aluminum extrusions shall be determined by AAMA TIR-A8 testing for flexure in AAMA TIR-A8 Section 7.2 at a minimum of ambient and high temperature. 3. The aluminum extrusions used to determine allowable stresses in the thermal barriers and the shear modulus, G c , shall be from a specific aluminum extrusion manufacturer and the aluminum sections used in the project. The similarity of the composite aluminum extrusions shall be subject to approval by the building official. 4. The effective moment of inertia of the in-plane composite thermal barrier-aluminum section used in flexural design, based upon the tested G c , shall not exceed 85 percent of the moment of inertia of the combined unbridged aluminum portions of the composite section, unless substantiated and approved by the building official. 5. A high temperature of not less than 120°F shall be used for composite section flexure design for wind pressure where the historical high temperature exceeds 100°F. The minimum high temperature for in-plane shear, tension and eccentric load thermal barrier design shall be determined by AAMA TIR-A8 Section 6.5. 6. The lowest allowable stress value and shear modulus, G c , from the ambient and high temperature testing shall be used for design. 7. Structural analysis and design for loads on pour and debridged thermal barriers with skip-debridging that has not been tested under AAMA TIR-A8 with skip-debridged test specimens for the specific actions or load direction shall be based upon the relative stiffness between the remaining aluminum bridge and the thermal barrier material and size. 8. Reactions on supporting thermal barrier mullions where the thermal barrier resists the concentrated load, the load shall not be assumed to be distributed over a length greater than 12 inches (305 mm) on the supporting mullion. 9. Mechanically locked, preformed thermal barriers shall be designed and used in pairs.

2411.1.2 Testing and Inspection. Testing and Inspection of thermal barrier mullions shall satisfy the following requirements: 1. Thermal barrier material properties shall be tested in accordance with AAMA TIR-A8 Section 6.1 by the manufacturer. All other testing shall done by an approved testing laboratory or agency. 2. Testing shall include AAMA TIR-A8 Section 7.2 for the flexural tests using the composite section under ambient and high temperature. Thermocouples shall be placed on the outside and interior surfaces and in the middle of the thermal barrier for high temperature testing. Test cycles shall be in accordance with AAMA TIR-A8 Section 7.2.3. 3. Testing shall include AAMA TIR-A8 Section 7.3 for in-plane shear, tension and eccentric load using the composite section under ambient and high temperature. 4. The flexural test for the composite section shall include a span length of 12 feet (3660 mm). The maximum P load in the test shall generate close to a L/175 deflection, where L is the span length, center to center of supports, but shall not exceed the allowable design stresses for the aluminum composite section in meeting that deflection. Permanent deflection shall not exceed the requirement in AAMA TIR-A8 Section 7.2.2.5.

24-12 2025 CALIFORNIA BUILDING CODE

GLASS AND GLAZING

5. A minimum of two different simple span lengths shall be used to determine G c under the flexural test. The span lengths tested shall include a short span. 6. The shear modulus, G c , of the thermal barrier shall be determined using the lowest average I et from the flexural testing for each composite aluminum extrusion, temperature and span length tested. 7. Each different composite aluminum extrusion in the project shall be tested to the requirements of AAMA TIR-A8. The magni- tude of eccentricity of load on the thermal barrier shall be considered in selecting composite aluminum extrusions for testing. 8. The applicability of existing AAMA TIR-A8 testing of thermal barrier mullions that satisfy the requirements of this section shall be permitted, in lieu of project-specific tests, when approved by the building official. 9. Periodic special inspection to ensure compliance with the AAMA TIR-A8 processing for the thermal isolator material shall be performed. Inspections shall include tests of thermal barrier material properties per the manufacturer’s recommendation and AAMA TIR-A8 Section 6.1 and composite performance requirements per AAMA TIR-A8 Sections 7.2 and 7.3. 10. Periodic special inspection of pour and debridge thermal barrier shall include: a. Verification that the thermal barrier formulation being used matches that in the design and construction documents. b. Verification that poured wet or dry shrinkage as set forth in AAMA TIR-A8 Section 4.1.3.1 does not occur. c. Proper adhesion of poured thermal barrier material per AAMA TIR-A8 Section 4.2.1. d. Confirmation of proper manufacturing process per the manufacturer’s recommendations and AAMA TIR-A8 Section 4.3.

e. Inspection of fabrication and handling practices in accordance with AAMA TIR-A8 Sections 4.3 and 4.4. f. Testing for thermal barrier material properties per the manufacturer’s recommendation and AAMA TIR-A8 Section 6.1. g. Periodic special inspection of the removal of the temporary thermal bridge shall be provided to ensure that no thermal barrier material is removed in the process. 11. Periodic special inspection of mechanically locked, preformed thermal barriers shall include: a. Verification that the insulating struts being used match those in the design and construction documents. b. Verification that the mechanical lock cavity distortion and locking distortion does not exist as set forth in AAMA TIR-A8 Sections 4.1.3.3 and 4.1.3.4.

c. Verification of proper knurling of the aluminum and crimping of the insulating struts per AAMA TIR-A8 Section 4.2.2. d. Confirmation of proper manufacturing process per the manufacturer’s recommendations and AAMA TIR-A8 Section 4.5.

e. Inspection of fabrication and handling practices in accordance with AAMA TIR-A8 Sections 4.5 and 4.6.

24-14 2025 CALIFORNIA BUILDING CODE

CALIFORNIA BUILDING CODE – MATRIX ADOPTION TABLE

CHAPTER 25 – GYPSUM PANEL PRODUCTS AND PLASTER

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

The state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.

25-2 2025 CALIFORNIA BUILDING CODE