UP TO THE CHALLENGE: ACHIEVING SUSTAINABILITY WITH STEEL ATTACHMENT SYSTEMS

The material for a cladding support system impacts its sustainability. Steel’s strength, predictability, and durability make it an inherently resilient design material. Additionally, it helps satisfy environmental goals.

Steel is sustainable and is the most recycled material on Earth. Steel products are 100 percent recyclable at the end of their useful lives. Once produced, steel can be continually recycled into new steel products─a steel beam can become another steel beam, or a food can, refrigerator, or roof panel.1 The sourcing of steel by country and process significantly affects the embodied emissions of steel building materials.2 The American steel industry is the least carbon-intensive of all major steel-producing countries. Steel is typically fabricated off site, reducing on-site labor, cycle time, and construction waste.

Most structural steel produced in North America contains 93 percent or more recycled steel.3 Steel framing typically contains a minimum of 25 percent recycled steel and is continually recyclable. It is a versatile, strong, and long-lasting material. Steel’s inherent durability and recyclability make it an ideal fit for the no-waste circular economy.

In addition to its inherent material attributes, steel meets green building program requirements.

Product Declarations

Environmental Product Declarations, or EPDs, are documents that summarize the results of a life cycle assessment (LCA) for specific products. The latest USGBC green building ratings program─LEED V4─includes credits for buildings that use products for which EPDs have been developed. The steel industry actively supports the transparent reporting of environmental impacts associated with construction products. Many rating systems (LEED V4), standards (ASHRAE 189.1), green building codes (IgCC), and specific customers require the submission of environmental product declarations (EPDs) for products delivered to the project site. These EPDs rely on the results of life-cycle assessments to provide information on a number of environmental impacts related to the manufacture of the product, including global warming potential, ozone depletion, acidification, eutrophication, and ozone creation.

The Steel Framing Industry Association (SFIA) works with mill members to develop industry-wide EPDs for steel produced in the United States. In addition to quantifying the impacts of the mill processes, it is also required that producers quantify the industry average environmental impacts per ton of the fabrication process.

The low environmental impacts of fabricated steel are vetted by third parties and transparently disclosed in EPDs. The scope of EPD is cradle-to-gate, including raw material extraction and processing, transportation, steel manufacture and hot dip galvanization, transportation to manufacturing facilities, and steel framing products manufacture. For cold-formed steel framing (CFS), the contributions to total impact indicator results are dominated by the raw material extraction and production stage, primarily from HDG (Hot Dip Galvanized) steel production. The manufacturing process of CFS contributes significantly to its sustainability after extraction. During fabrication, the steel is rolled into desired shapes and cut into ordered lengths, minimizing waste. This precise production also reduces the amount of energy required and minimizes the environmental impact associated with traditional steel fabrication processes. Because steel is 100 percent recyclable, cold-formed steel can be recycled multiple times without losing its strength or durability, making it a highly sustainable material. Additionally, CFS framing can be deconstructed by hand and reused with minimal damage.

Specifiers can encourage the transparent disclosure of fabricated steel's environmental impacts by requiring the submission of EPDs in their bid packages.

Certain manufacturers may provide further product documentation, such as a Declare Label from the International Living Future Institute™. Manufacturers voluntarily disclose product information on Declare labels, which are designed to provide clear information. These labels report all product ingredients and use a simple color code system to flag chemicals of concern. Further information is provided on the product’s final assembly locations, life expectancy, end-of-life options, and overall compliance with relevant requirements of the Living Building Challenge (LBC).

Product transparency and certifications are essential building blocks for whole-building certification. Steel rainscreen attachment systems with EPDs and other product disclosures can help achieve points in several leading green building programs.

Green Building Certifications

The Living Building Challenge addresses development on all fronts, with the core underlying principle being that buildings should mimic nature and natural systems. Toxic materials (Red List Chemicals) are not permitted on projects and LBC aims to eliminate their use. A flower metaphor is used to illustrate that all elements of the built environment are rooted in place. The Petals of the Living Product Challenge has specific Imperatives that define the actions needed to achieve that Petal.

The WELL Building Standard is an evidence-based system for measuring, certifying, and monitoring the performance of building features that impact health and well-being. It is also the world’s first building standard focused exclusively on human health and wellness. The standard is divided into 10 concepts: Air, Water, Nourishment, Light, Movement, Thermal Comfort, Sound, Materials (specifically deals with material transparency), Mind, and Community.

Steel rainscreen attachment systems also are recognized under LEED. LEED v4.1 addresses materials through Fostering Material Sourcing & Transparency through Building Product Disclosure & Optimization credits, aimed at increasing market transparency concerning the sourcing & contents of Materials. The environmental benefits of steel framing, particularly high recycling rates, recycled content, and steel’s inert, non‐organic nature, make key contributions to achieving LEED certification. Specific LEED credit categories for steel include Materials and Resources (MR): Building Life Cycle Impact Reduction, MR: Building Product Disclosure and Optimization – Environmental Product Declarations, MR: Building Product Disclosure and Optimization – Sourcing of Raw Materials, MR: Building Product Disclosure and Optimization – Material Ingredients, MR: Design for Flexibility, MR: Construction and Demolition Waste Management, Indoor Environmental Quality (EQ) Credit: IAQ Assessment, and IN Credit: Innovation.

THE STRENGTH TO PROTECT: LIFE SAFETY AND TESTING IMPLICATIONS FOR RAINSCREEN ATTACHMENT SYSTEMS

Rainscreen systems have largely been absent from the International Building Code (IBC), until now. This does not mean the use of a rainscreen system on an exterior wall had no requirements or standards to meet. But they could possibly have been overlooked. Various elements of a rainscreen system have certainly been included.

Terms

As mentioned at the onset, Rainscreen System is now defined within the IBC. This may seem to be of little consequence at first glance, however, the use of the term is now proliferated throughout the code. How so? A Rainscreen System is included, explicitly, as an example of an Exterior Wall Assembly. Consequently, everywhere Exterior Wall Covering is used within the code, Rainscreen System could essentially be substituted for the term.

Loads

The IBC has an entire chapter dedicated to exterior walls because they are very important. Within this chapter, several general requirements must be met. The most important requirement of exterior walls is to be designed and constructed to safely resist the superimposed loads required by Chapter 16. This verbiage has been present for many cycles. However, in 2024, Section 1402.3 expands the requirement from beyond the broad term of the exterior wall to also include exterior wall coverings (rainscreen systems) amongst other elements. Therefore, this would include evaluations for the cladding and the cladding support systems that make up the rainscreen system. As mentioned, the system design typically evaluates wind load, dead load, and seismic load. Attachment design can include engineering and/or tested assemblies whereby the test proves the ability of the assembly to resist the loads that will be on the building. Given the broad nature of designs within the commercial industry, relying on testing is difficult as configurations of the cladding and the support system behind it change from project to project. Therefore, engineering analysis is by far the more economical and efficient approach to satisfying the requirements. Essentially, it is imperative for the cladding support system to be designed, and specifying this requirement can help ensure this critical requirement is met.

Photo courtesy of Knight Wall Systems

Example of an intact continuous structural connection, post fire test.