Classification of Z-girts
Not all continuous insulation Z-girts are created equal. They are categorized into three distinct classes based on key performance criteria, including structural capacity, structural performance, fastener connections, thermal efficiency, and fire resistance.
Classification of Continuous Insulation Z-Girts
Continuous insulation Z-girts are categorized into three distinct classes based on their ability to meet key performance criteria. These criteria include structural capacity, structural performance, thermal efficiency, fire resistance, and the durability of connections over the building’s lifecycle. Each class represents a different level of performance, allowing designers, contractors, and installers to select the most suitable system for their project’s specific demands and requirements.
Class I continuous insulation Z-girts provide the highest thermal performance, strongest structural capacity, and permanent connections. Additionally, these systems eliminate thermal bypass and pass fire safety standards like NFPA 285, ensuring long-term reliability.
Class II continuous insulation Z-girts provide moderate performance in thermal efficiency and structural strength. They ensure permanent connections and comply with NFPA 285, but do not resolve thermal bypass.
Class III continuous insulation Z-girts prioritize thermal performance but can only accommodate moderate structural loads in a temporary capacity. They suffer from unavoidable connection failures that limit their long-term reliability and effectiveness.
CODE-COMPLIANT
Thermally Broken Systems
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NOT CODE-COMPLIANT
Legacy System
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CLASS I
Composite metal hybrid Z-girts
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CLASS II
Perforated thermal metal Z-girts
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CLASS III
FRP Z-girts
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Steel Z-girts
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HIGH
Structural capacity
Crosswise and lengthwise tensile strengthProviding crosswise and lengthwise tensile strength comparable to steel Z-girts, Class I products support and distribute loads effectively, accommodating demanding, heavyweight cladding and strong wind loads. This includes resistance to bending, deflection, and failure. Class I thermal Z-girts are the strongest on the market. |
MODERATE
Structural capacity
Loss of strength and reduced load capacityClass II products have a loss of strength and reduced load capacity due to up to 80% of the steel in their cross-section being eliminated ‒ often requiring additional cost for more girts and closer spacing to achieve capacity comparable to Class I girts. |
LOW
Structural capacity
25% of the initial structural load capacity of steelClass III products have approximately 25% of the initial structural load capacity of steel due to not having the same crosswise strength when used horizontally. Product creep will lead to continued structural decline over time and temperature. |
HIGH
Structural capacity
Crosswise and lengthwise tensile strengthSteel Z-girts support and distribute loads effectively, accommodating demanding, heavyweight cladding or building materials with stability and ease. This includes resistance to bending, deflection, and failure. |
LONG-TERM
Structural performance
Consistently maintain their intended strength, stability, and functionalityClass I products consistently maintain their intended strength, stability, and functionality over the lifetime of a building, even with fluctuating service temperatures, loads, etc. The performance is engineered and verified by single-source finite element analysis. |
LONG-TERM
Structural performance
Consistently maintain their intended strength, stability, and functionalityThe steel component in Class II products consistently maintains its intended strength, stability, and functionality over the lifetime of a building. However, care must be used in reviewing the polymer thermal break component for creep resistance. |
TEMPORARY
Structural performance
Not engineered to permanently maintain their strength, stability, and functionalityClass III products are not engineered to permanently maintain their strength, stability, and functionality, leading to degradation, loosening, and failure over time. No published studies quantifying performance at elevated temperatures. |
LONG-TERM
Structural performance
Consistently maintains their intended strength, stability, and functionalitySteel Z-girts consistently maintain their intended strength, stability, and functionality over the lifetime of a building. |
PERMANENT
connections
Designed to carry specific loads without degradation and "unavoidable failure"Class I products are designed to carry specified loads without degradation and “unavoidable failure,” Permanent steel-to-steel connections ensure reliable, long-term performance throughout a building’s lifecycle. |
PERMANENT
connections
Designed to carry specific loads without degradation and "unavoidable failure"Class II products are designed to carry specified loads without degradation and “unavoidable failure,” permanent steel-to-steel connections ensure reliable, long-term performance throughout a building’s lifecycle. |
UNAVOIDABLE FAILURE
at connections
Class III products result in "unavoidable failure"The American Society of Civil Engineers (ASCE) states that using sheet-metal fasteners for connections into Class III products result in "unavoidable failure." |
PERMANENT
connections
Designed to carry specific loads without degradation and "unavoidable failure"Steel Z-girts are designed to carry specified loads without degradation and “unavoidable failure,” permanent connections ensure reliable, long-term performance throughout a building’s lifecycle. |
HIGH
static thermal performance
Eliminate thermal bridgingClass I products eliminate thermal bridging, minimize the use of conductive materials, and sustain consistent insulation efficiency over time, resulting in the highest thermal performance of up to 99%. |
MODERATE
static thermal performance
Does not eliminate thermal bridgingClass II products do not eliminate thermal bridging because they are constructed with primarily conductive materials, resulting in inconsistent insulation efficiency, and lower thermal performance -- often in the 70-80% range. |
HIGH
static thermal performance
Eliminates thermal bridgingClass III products eliminate thermal bridging and sustain consistent insulation efficiency, resulting in high thermal performance. |
LOW
static thermal performance
Highly conductive and creates thermal bridgingSteel Z-girts are highly conductive and create thermal bridging, rendering nearby insulation ineffective, leading to low thermal performance. |
YES
eliminates thermal bypass
Prevent unintended movement of air through gaps, cracks, and voidsPressure seals on all sides provide airtight connections. Class I products prevent the unintended movement of air through gaps, cracks, or voids in a building wall assembly. Also eliminates wind washing and stack effect thermal loss. |
NO
eliminates thermal bypass
Allows the movement of air between and behind insulationClass II products allow for the movement of air between and behind insulation within a building wall assembly, contributing to substantial energy loss from thermal bypass, wind washing, and stack effect thermal loss. |
NO
eliminates thermal bypass
Allows the movement of air between and behind insulationClass III products allow for the movement of air between and behind insulation within a building wall assembly, contributing to substantial energy loss. Some perforated FRP products also have additional thermal loss due to window washing and stack effect air movement. |
NO
eliminates thermal bypass
Allows the movement of air between and behind insulationSteel Z-girts allow for the movement of air between and behind insulation within a building wall assembly, contributing to substantial energy loss. |
PASS
NFPA 285
Proven and tested to be NFPA 285 complianceClass I products have been thoroughly proven and tested to be NFPA 285 compliant to effectively contain and limit flame spread. |
PASS
NFPA 285
Proven and tested to be NFPA 285 complianceClass II products have been thoroughly proven and tested to be NFPA 285 compliant to effectively contain and limit flame spread. |
MODERATE
NFPA 285
Tested in a limited number of configurationsClass III products have been tested in a limited number of configurations and contain varying formulations across manufacturers. |
PASS
NFPA 285
Proven and tested to be NFPA 285 complianceSteel Z-girts have been thoroughly proven and tested to be NFPA 285 compliant and effectively contain and limit flame spread. |
Download the Classification of Continuous Insulation Z-Girt Chart
Performance criteria:
Structural capacity
The engineered ability of Z-girts to support and distribute loads effectively, accommodating demanding, heavyweight cladding or building materials with stability and ease. This includes resistance to bending, deflection, and failure.
Structural performance
The engineered ability of a continuous insulation system — including the Z-girts, their connections, and corresponding fasteners — to consistently maintain their intended strength, stability, and functionality over the lifetime of a building. Unlike systems that degrade, loosen, and lead to failure over time.
Connections
The ability of a fastening system to create durable, permanent interfaces between cladding and the continuous insulation sub-framing system. Designed to carry specified loads without degradation and “unavoidable failure,” permanent connections ensure reliable, long-term performance throughout a building’s lifecycle.
Static thermal performance
The ability of continuous insulation Z-girts to minimize thermal bridging, minimize the use of conductive materials, and sustain consistent insulation efficiency over time, resulting in thermal performance levels in the upper 90% range.
Thermal bypass
The unintended movement of energy through gaps, cracks, or voids in a building’s wall assembly, often stemming from design flaws, material inconsistencies or tolerances, and/or improper installation that leads to significant energy losses.
NFPA 285 compliance
Systems compliant with NFPA 285 meet rigorous standards for fire resistance in multi-story buildings, ensuring that facade materials effectively contain and limit flame spread, thereby enhancing the building’s overall safety.
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