Building Envelope Systems Comparison

Deciding on a continuous insulation or building enclosure system can be complex, but it doesn’t have to be. Use this side-by-side feature and benefit comparison of the five most-specified continuous insulation and building enclosure approaches. See how GreenGirt CMH™ and SMARTci® systems stack up against the rest. Additionally, access the comprehensive technical resources and systems-specific comparisons for further detailed information.

Every performance claim links to its source: a test standard, a third-party report, or an A2P engineering document.

Comparison of SMARTci, GreenGirt CMH, Steel Z-Girt (16-gauge), Perforated Thermal Metal Z-Girt, and FRP-only Z-Girt systems across 12 performance criteria.
Feature / Benefit	SMARTci®	GreenGirt CMH™	Steel Z-Girt (16-gauge)	Perforated Thermal Metal Z-Girt	FRP-only Z-Girt
Fire tests compliance with NFPA 285 and ASTM E84	Yes Compliant with NFPA 285 and ASTM E84. Components consist of non-flammable materials (glass + steel) with naturally-sourced fire retardants; Declare Label and Red List Free.¹²	Yes Compliant with NFPA 285 and ASTM E84. Components consist of non-flammable materials (glass + steel) with naturally-sourced fire retardants; Declare Label and Red List Free.¹²	Yes Generic steel Z-girts are typically tested and compliant with NFPA 285 and ASTM E84.²	Yes Perforated metal Z-girts are typically tested and compliant with NFPA 285 and ASTM E84.²	Limited Tested only in limited combinations of cladding and insulation; not certified for all commercial wall configurations.²
Permanent fastener retention	Yes GreenGirt CMH continuous insulation profiles use steel-reinforced flanges to deliver permanent steel-to-steel fastening. No creep, no loosening over service life.³	Yes Same steel-reinforced-flange design as SMARTci. Steel-to-steel fastening for permanent retention.³	Yes Steel Z-girts provide permanent fastener retention.³	Yes Perforated thermal metal Z-girts provide permanent fastener retention where the steel is intact.³	No Structural screws anchored in FRP-only Z-girts fail through creep over time.³¹²
Free of halogen, bromine, and any Red-List materials	Yes The GreenGirt CMH framing component meets Declare Label, Living Building Challenge Red List Free, and EPD requirements and is halogen- and bromine-free with naturally-sourced fire retardants. These attributes apply to the GreenGirt CMH component specifically; rigid insulation selected for a SMARTci assembly varies and may not meet all of these criteria.⁴	Yes Same standards as SMARTci. Declare Label, Red List Free, EPD.⁴	Yes Generic steel is halogen-, bromine-, and Red List Free.⁴	Yes Perforated metal Z-girts are halogen-, bromine-, and Red List Free; confirm with manufacturer’s listing.⁴	No FRP-only Z-girts are not free of halogen, bromine, or Red List materials and may not meet green-building standards.⁴
Eliminates both material and fastener creep	Yes Designed and tested to ASTM D2990 to eliminate material and fastener creep.⁵	Yes Same ASTM D2990 testing as SMARTci.⁵	Yes Steel Z-girts maintain structural integrity and fastener retention without creep.⁵	Varies Susceptible to creep under extended loading and force concentrations at the polymer break. GreenGirt Steel maintains structural integrity and fastener retention without creep.⁵	No FRP-only Z-girts are susceptible to creep from extended loading and force concentrations.⁵
Each order includes finite element analysis and expert engineering review/support	Yes Every project receives a single-source FEA and engineering review tailored to the wall assembly.⁶	Yes Every project receives a single-source FEA and engineering review tailored to the wall assembly.⁶	No Generic manufacturers do not include project-specific FEA or engineering review.⁶	Varies Some manufacturers do not include project-specific FEA or engineering review. GreenGirt Steel does include FEA and expert engineering review/support.⁶	No FRP-only manufacturers do not include project-specific FEA or engineering review.⁶
Highest thermal efficiency available on the market	Up to 99% Eliminates through-insulation metal and through-fasteners; achieves up to 99% thermal efficiency across the building’s service life.⁷	Up to 99% Same composite metal hybrid platform; up to 99% lifetime thermal efficiency.⁷	No Highly conductive; creates thermal bridging that reduces effective R-value.⁷	~70–80% Steel Z-profile remains the primary load path; thermal performance typically falls in the 70–80% range.⁷	High FRP-only Z-girts do not provide the highest thermal efficiency compared to other systems on the market.
Installs twice as fast with stack-and-go installation process	Yes Progressive installation with steel-reinforced flanges and integrated fastener retention eliminates cantilevering and additional insulation retention tools, and reduces field measuring/fabrication. ⁸	Yes Same progressive, stack-and-go installation as SMARTci, with integrated fastener retention.⁸	No Generic steel Z-girts do not feature a progressive installation system. No integrated fastener retention.⁸	Varies No integrated fastener retention; stack-and-go pattern not supported. GreenGirt Steel offers progressive installation with overlapping metal Z-girts and integrated fastener retention eliminating cantilevering, additional insulation retention tools, and reduces field measuring/fabrication.⁸	No FRP-only Z-girts do not feature a progressive installation system. No integrated fastener retention.⁸
Eliminates the need for insulation retention fasteners	Yes SMARTci, utilizing GreenGirt CMH Z-girts, includes ThermaLock insulation retention technology that holds rigid or mineral wool insulation without stick pins.⁹	Yes GreenGirt CMH Z-girts include ThermaLock insulation retention technology that holds rigid or mineral wool insulation without stick pins.⁹	No No integrated insulation retention; stick pins or supplemental fasteners required.⁹	Varies No integrated insulation retention; stick pins or supplemental fasteners required. GreenGirt Steel Z-girts include insulation retention locks that hold rigid or mineral wool insulation without stick pins.⁹	Limited Some FRP products retain insulation; many do not. Refer to manufacturer literature.⁹
Air- and water-tight without the use of caulk or tape	Yes Only system that achieves an air- and water-tight assembly without caulk or tape, when specified with foil-faced polyiso.¹¹	No Does not provide a self-sealing air- and water-tight assembly at the framing; air and water control is handled by the wall’s separate barrier system.¹¹	No Does not provide a self-sealing air- and water-tight assembly at the framing; air and water control is handled by the wall’s separate barrier system.¹¹	No Does not provide a self-sealing air- and water-tight assembly at the framing; air and water control is handled by the wall’s separate barrier system.¹¹	No Does not provide a self-sealing air- and water-tight assembly at the framing; air and water control is handled by the wall’s separate barrier system.¹¹
Highest true R-value per inch of wall system	Yes Highest in market due to custom-profiled insulation. Eliminates through-insulation metal and through-fasteners (DrJ TER 1501-06).¹³	High Eliminates through-insulation metal and through-fasteners but does not achieve SMARTci’s full pressure-sealed R-value per inch.¹³	No Through-insulation metal and through-fasteners reduce effective R-value.¹³	Varies Through-insulation metal reduces effective R-value. GreenGirt Steel eliminates through-insulation metal but does not achieve SMARTci’s full pressure-sealed R-value per inch.¹³	No Connection failures and creep over time reduce effective R-value.¹³
Eliminates gaps, cracks, and thermal bypass: product design, installer, and insulation manufacturer gaps fixed	Guaranteed SMARTci adds a pressure-sealed assembly, GreenGirt CMH Z-girts plus custom-profiled rigid insulation sealed on all four sides, that closes the air pathways around and behind the insulation. This stops the wind-washing and stack-effect air movement that causes thermal bypass, performance the GreenGirt CMH Z-girt alone does not provide. A2P guarantees thermal bypass elimination on SMARTci specifically.¹⁴¹⁰	Partial GreenGirt CMH removes the conductive thermal bridging through the sub-framing, but the Z-girt alone does not create the continuous air seal that stops convective thermal bypass. Full elimination requires SMARTci’s custom-profiled, pressure-sealed rigid insulation; GreenGirt CMH with mineral wool does not close all air pathways.¹⁴¹⁰	No No air seal; allows wind washing and stack-effect air movement behind insulation.¹⁴	No No air seal; thermal bypass is unresolved.¹⁴	No No air seal. Some perforated FRP products add additional thermal loss from stack-effect air movement.¹⁴
Connection durability standard (ASCE)	Yes Connections are steel-to-steel through steel-reinforced flanges, not self-tapping screws into FRP, so the durability concern ASCE raises for pultruded FRP does not apply.¹⁵	Yes Same steel-reinforced-flange (steel-to-steel) connection design as SMARTci; the ASCE pultruded-FRP fastening concern does not apply.¹⁵	Yes Steel-to-steel connections are not subject to the ASCE pultruded-FRP fastening concern.¹⁵	Yes Steel cross-section is fastened steel-to-steel where intact; not subject to the ASCE pultruded-FRP fastening concern.¹⁵	Not recommended The ASCE Design Guide for FRP Composite Connections (page 19) does not recommend self-tapping (sheet-metal) screws for fastening into pultruded FRP, identifying bolted, adhesively bonded, or combined connections instead. Sheet-metal-screw retention in FRP therefore cannot be relied on for permanent durability, what A2P characterizes as “unavoidable failure.”¹⁵

* GreenGirt Steel™, A2P’s steel-based continuous insulation system, is not shown as a separate column above. It delivers the highest thermal efficiency available in a steel-based system and shares GreenGirt CMH’s stack-and-go installation, insulation retention, and steel-to-steel, ASCE-compliant connections. See the GreenGirt Steel system.

Citations & Source References

A2P engineering reports on NFPA 285 compliance and configuration coverage: GreenGirt and NFPA 285 (Use of Composite Metal Hybrid for NFPA 285 Fire-Rated Continuous Insulation Systems); and GreenGirt & SMARTci NFPA 285 Compliance, CMH 1b Wall Configurations. Multi-configuration approval is supported by an Engineering Judgment from Priest & Associates Consulting (NFPA 285-approved products from Atlas, Rmax, Hunter, Carlisle, and Dow, mineral wool, and high-pressure laminate claddings) and validated by DrJ TER 1501-06.
A2P Engineering Best Practices: Fire Resistance. greengirt.com/engineering/best-practices/fire-resistance/.
A2P engineering brief: A2P3001 — Fastener Failure in FRP vs. Permanent Fastening Steel. Supporting article: Short-term Fastening (FRP) vs. Permanent Fastening (Steel CMH).
A2P Engineering Best Practices: Environmental Impact, with Declare Label / Living Building Challenge / EPD documentation. greengirt.com/engineering/best-practices/environmental-impact/.
ASTM D2990 — Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics. A2P test results.
A2P engineering brief: A2P3002 — Best Practice Structural Engineering for Composite Substructure Materials (CMH vs. Generic FRP). A2P Engineering overview: greengirt.com/engineering/.
A2P engineering brief: A2P2001 — Designing with Composite Z Sub-Framing & Fastener Performance for Building Envelope Service Temperature. Independent 3D thermal modeling by Morrison Hershfield/Stantec (ASHRAE and CSA standards): greengirt.com/engineering/thermal-performance/.
A2P Engineering Best Practices: Ease of Installation. greengirt.com/engineering/best-practices/ease-of-installation/.
A2P product reference: What is CMH? greengirt.com/what-is-cmh/.
A2P article: Understanding and Addressing Thermal Bypasses in Building Enclosures.
A2P third-party report: DrJ TER A2P SMARTci Exterior Wall Continuous Insulation System (TER 1501-06).
A2P Engineering: FRP’s “Unavoidable Failure.” greengirt.com/articles/unavoidable-fastener-failure/.
DrJ TER 1501-06 and A2P2001. Effective R-value per inch of wall system, A2P SMARTci platform.
A2P Engineering Best Practices: Thermal Bypass, and A2P engineering brief: SMARTci Thermal Bypass Elimination Guarantee. greengirt.com/engineering/articles/thermal-bypass-elimination/. Guarantee terms verified via A2P engineering legal review (Pillar 2 documentation).
ASCE Design Guide for FRP Composite Connections (American Society of Civil Engineers), page 19, which does not recommend self-tapping screws for fastening into pultruded FRP and identifies bolted, adhesively bonded, or combined connections instead. ASCE Library, DOI 10.1061/9780784406120. A2P summary: greengirt.com/articles/unavoidable-fastener-failure/.

The full Continuous Insulation Z-Girt Comparison Chart

The chart above covers the headline differences. This one compares the same Z-girt systems across all performance categories.

Frequently Asked Questions (FAQs)

Do FRP Z-girts creep over time?

FRP-only Z-girts are susceptible to creep from extended loading and force concentrations (and perforated metal Z-girts are also described as susceptible). Read more in Screw Pull-Out and Creep Rupture in FRP Materials.

Why can steel Z-girts hurt thermal performance, even though they're structurally strong?

Steel Z-girts are commonly used because steel resists deflection well and allows fast, durable fastener connections with strong pull-out and torque retention compared to fastening into FRP. The trade-off is that steel is not thermally efficient and creates a thermal bridge through the wall assembly, contributing to energy loss, higher energy costs, and increased condensation risk. GreenGirt CMH™ resolves this by combining steel-reinforced flanges with a fiberglass profile, delivering fastener performance close to steel without the thermal bridge. Read more in Z-Girt Material Differences: Steel vs FRP vs CMH.