The benefits of using architectural zinc in roofing and wall claddings

by arslan_ahmed | June 2, 2023 8:00 pm

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By Charles “Chip” McGowan

Evaluating materials and products to meet projects’ performance requirements and code compliance is an ongoing task for specification professionals. Supporting modern construction goals, sustainable attributes, and outcomes are now part of this evaluation and specification process. Today, owners and designers are increasingly asking specifiers to examine the carbon footprint for each choice and their collective effect.

For roofing and wall cladding products, architectural zinc’s inherent metallic properties can help reduce the embodied carbon footprint for residential and commercial buildings, and improve their energy-efficient, climate-resilient, long-lasting performance.

Carbon concerns, climate change, and construction

When global, national, and local governments, and other authorities having jurisdiction (AHJ) discuss reducing their carbon footprint, the inference is to reduce the effects of climate change due to the generation of greenhouse gases (GHGs) from various sources, including commercial and residential construction.

To fathom the importance of lowering construction’s carbon footprint one must grasp the extant of carbon concerns and climate change.

Carbon emissions, specifically emissions of carbon dioxide (CO₂), are identified as GHGs. In conversations, the terms carbon emissions and GHG emissions are often interchangeable. In application, GHG emissions are typically measured in terms of “carbon equivalent” (CO2eq) and global warming potential (GWP). A 100-year GWP is standard, which represents the energy absorbed by a CO2eq GHG over 100 years.

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CO2eq emissions absorb energy, trapping it in the atmosphere and reflecting it back as heat. The increased GHG levels and higher temperature cannot be sustained by the Earth’s natural environmental processes and are among the causes affecting the climate. These effects are demonstrated in more frequent, extreme temperature fluctuations and weather events, such as hurricanes, cyclones, tsunamis, severe storms, wildfires, droughts, and floods. Shifting patterns also result in record heat waves in formerly cold climates, and snow and hail in formerly warm climate zones. These changes have caused costly damage to critical infrastructure; disrupted food, water, and economic supply chains, and put people’s health, safety, security, and lives at risk.

According to the U.S. Environmental Protection Agency (EPA), total GHG emissions in 2021 accounted for 6,340 million tonnes (6,989 million tons), which is nearly 14 quadrillion pounds of CO2eq. The largest sources of GHGs emissions in the U.S. come from:

• Transportation sources. More than 94 percent
  of the various modes of transportation use petroleum-based fuel.
• Electric power. Approximately 79 percent of electricity generation uses fossil fuels, and the residential and commercial sector use 30 percent electricity, making it the largest end-user.
• Industrial. These emissions are mostly from burning fossil fuels for energy, as well as GHG emissions from certain chemical reactions necessary to produce goods from raw materials.
• Commercial and residential. These emissions are mostly from heating sources using fossil fuel, the use of certain products that contain GHGs, and the handling of waste.¹

The internationally recognized Reporting Standard by Greenhouse Gas Protocol categorizes emissions reporting into three “scopes.”

• Scope 1: Direct emissions associated with the consumption of fuel, including transportation, equipment operation, and facility operation.
• Scope 2: Indirect emissions associated with purchased energy for electricity, steam, heating, and cooling.
• Scope 3: Indirect emissions for activities not included in Scope 1 or 2 that are listed in 15 categories, including waste generated in operations and end-of-life treatment of sold products.²

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Specification professionals can help significantly lower commercial and residential buildings’ GHG emissions on a property across all three scopes by:

1. Reducing “operational carbon”—Addressed in Scopes 1 and 2, this is the CO2eq associated with a property’s fossil fuel energy consumption and its emissions. One may lower operational carbon by using renewable energy sources to fuel the building’s operation, by using high-efficiency electric appliances and equipment, and by incorporating energy-efficient, high-performance systems and technologies.
2. Reducing “embodied carbon”—Addressed in Scope 3, this is the CO2eq associated with the production, use, and disposal of a property’s construction materials and processes. One may lower embodied carbon by selecting materials produced with renewable energy that have a long, useful life and are recycled.

According to the 2019 Global Status Report for Buildings and Construction Sector published by the United Nations Environmental Programme (UNEP), buildings’ construction and operations accounted for:

• 36 percent of final energy use in 2018.
• 39 percent of energy and process-related CO2eq emissions in 2018; 11 percent of which came from manufacturing building materials and products.

The report identifies steel, cement, and glass as having the largest opportunities for carbon footprint reduction. Since 2019, these industries have taken significant steps to lower their carbon footprint.³

The Carbon Smart Materials Palette, a project providing attribute-based design and material specification guidance, states, “It is anticipated that embodied carbon will be responsible for 72 percent of the carbon emissions associated with global new construction between now and 2030.”⁴

Material transparency allows specifiers and building teams to make more informed decisions. Assisting with that evaluation, manufacturers can provide life cycle assessments (LCAs), environmental product declarations (EPDs), Cradle to Cradle certifications, and other documentation. Where industry average EPDs
and other data was once acceptable, product- and facility-specific data are now necessary for more accurate selection criteria and project sustainability reporting.

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Carbon-reduced, high-quality zinc to address the carbon footprint

As a natural metal, zinc is the 24^th most abundant element in the Earth’s crust and the fourth most used metal in the world.⁵ The International Zinc Association (IZA) estimates the world’s zinc use at 20 million tonnes (19.6 million tons) per year. Both mining and recycling are necessary and available to meet anticipated zinc demands. Globally, 12.8 million tonnes (12.6 tons) of zinc are mined and 7.6 million tonnes (7.6 tons) recycled annually.⁶

Mining, extracting, and refining metals can be an energy-intensive process. As material demands and energy costs rise, energy-efficient production maximizes both economic and environmental resources. Since zinc has a low melting point of 418 C (784 F), it takes less energy to process it than other metals and materials. For comparison, aluminum melts at 660 C (1,220 F) and steel at 1,370 C (2,500 F).

A recent study calculated 65 percent of zinc production’s carbon footprint could be attributed to smelting. Choosing zinc manufacturers that have minimized their already low carbon footprint is one more step toward reducing overall GHG emissions.⁷

For architectural applications, raw zinc material is smelted, cast as a material of uniform and certified quality, and wound as a coil in one continuous operation. Rolled zinc sheet is produced by alloying special high-grade (SHG), 99.995 percent pure zinc with minute quantities of copper, titanium, and aluminum. The alloy composition provides the material the necessary strength, while allowing the architectural product to be easily shaped.

IZA provides practical guidance on calculating the carbon footprint for SHG zinc, in compliance with the International Organization for Standardization (ISO) 14040 and 14044, and the Product Life Cycle Accounting and Reporting Standard by GHG Protocol.⁸ As a global average, the IZA calculated the carbon footprint GWP for primary SHG zinc production to be 3.64 kg (8.02 lbs) CO2eq per 1 kg (2.2 lbs).⁹ Many IZA member companies have committed to climate change policies to reach net-zero Scopes 1 and 2 GHG emissions by 2050. An increasing number also are working on Scope 3 targets.¹⁰

One IZA member has further lowered the carbon footprint of its SHG zinc product to achieve a 100-year GWP of 1.85 kg (4.08 lbs) CO2eq per 1 kg (2.2 lbs).¹¹ This savings was gained through energy-efficient production practices that rely on electricity largely generated from renewable sources, including water and wind power. In addition, its product uses recycled zinc material. This investment reduced the product’s impact by 54 percent and saves more than 36,000 tonnes (3,5431 tons) of CO2eq each year, equivalent to the GHG emissions of a small town with 5,400 people. Quantifying this to size and area, a standing-seam roof would have 12 kg (26.5 lbs) CO2eq. This low-carbon architectural zinc material is now available in North America.

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Composition, patination, and installation of architectural zinc

In North America, ASTM B69-21, Standard Specification for Rolled Zinc, is the primary reference document for type 1 and type 2 architectural rolled SHG zinc alloys and their expected characteristics.¹² The zinc alloy composition determines the metal’s coloration. Type 1 tends toward blue-gray and type 2 contains slightly more copper (0.80-1.00 percent), which produces more of a graphite-gray coloration.

Untreated, architectural-grade zinc looks bright and shiny, and is light reflective. Over time, a natural matte patina develops, creating a dynamic appearance as the material ages. A patina’s formation is the process of zinc carbonate “freckles” gradually growing together. The rate of its formation is related to the slope of the surface. The patina will form more slowly on a vertical wall surface than on a slightly pitched roof. The patination speed varies between six months and five years or more, depending on climatic conditions. The more exposure to wetting and drying cycles, the quicker the patina will develop.

Some manufacturers offer pre-weathered zinc material that accelerates the patina formation under controlled conditions. Factory-finished options are also available to achieve an initial, uniform aesthetic. Typically, these finishes are painted or phosphate architectural coatings applied in the factory under environmentally controlled conditions.

Architectural zinc coils are unwound, cut, and fabricated into panels, tiles, and other formed exterior and interior architectural products. Sheets also can be perforated and fashioned into ornamental accents. Since zinc is a lightweight material, it can help reduce the structural load and associated materials on a building.

Qualified contractors can install zinc products as wall cladding and facade systems; on low-sloped, steep-sloped, flat, and mansard roofs; and as hip and ridge caps, drip edges, alleys, step flashing, dormers, cupolas, parapets, gutters, downspouts, and more. Fabricators can also customize seam profiles to the project’s requirements.

Meeting building projects’ sustainable goals, contractors, fabricators, and installers provide high-performance, low-carbon product solutions. Some are considering the environmental impact of their own practices. Federal agencies and other AHJs can require reports for operational, transportation, and equipment GHG emissions; “buy clean” energy and material sourcing, recycling, and landfill waste streams.

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Climate-resilient, long-lived performance of architectural zinc

Architectural zinc has been used in coastal communities for generations and can be seen on building projects across many climate zones. Installed properly, zinc roofing and wall systems will resist air and water infiltration, and withstand high winds reaching up to 241 kph (150 mph).

Zinc’s natural patina will appear lighter when used in marine locations where the air contains chlorides (salt). Deposits will not be as visible on lighter blue-gray zinc. For aesthetic reasons, it is recommended to clean the surface of the material with clean water (not seawater) at least twice a year in maritime climate zones, depending on local conditions. If the metal is scratched, scuffed, or fingerprinted, zinc will heal itself by re-patinating. With time and exposure to wetting and drying cycles, the former blemish will patinate and blend to match.

In areas facing multiple climate challenges, such as marine environments that are susceptible to wildfires, architectural zinc offers a noncombustible solution as it is also non-corrosive. Research from the Association for Materials Protection and Performance (AMPP) estimates the cost of corrosion to the U.S. construction industry at $50 billion.¹³

Along with zinc’s climate-resilient, non-corrosive performance, it also provides a long lifespan to support reduced-carbon sustainable design and operational goals. Reduced-carbon architectural zinc and other metal roofing materials have a lifespan of 100 years or more.

In the U.S., asphalt has been a key material for roofs. Primarily made from petroleum, asphalt is a high-carbon material. The lifespan of an asphalt roofing is approximately 20 years.¹⁴ While the initial material purchase price of asphalt is less expensive, over the life of the roofing, architectural zinc costs less.¹⁵ Although similar lifespan cost comparisons of roofing assemblies could be made—asphalt was selected as it is the most popular in the U.S.

Replacing a roof is not only a material and labor expense, but it also disrupts the property’s operation and occupants, resulting in lost productivity. For example, rooftop photovoltaic (PV) arrays have a lifespan of approximately 25-30 years for residential homes and longer for more robust commercial buildings systems.¹⁶ This means during a PV array’s lifetime use, one would need to replace an asphalt roof at least once, interrupting renewable solar energy power generation. A zinc roof provides a platform to mount solar panels without replacing the roof, and will outlast the PV array’s lifespan.

In addition to accommodating power-generation systems, gutters, and downspouts fabricated from architectural zinc offer decades of continuous use in rainwater collection and harvesting systems. Its run-off is non-staining and non-toxic.

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During their many years of use, zinc building products do not rot, rust, or need repainting. No paint, varnish, or sealants are necessary. Architectural zinc products require very little maintenance, repair, or replacement, which further lowers their associated economic and environmental costs. At the end of its long life of use on a property, one can also recycle the zinc material.

Zinc is 100 percent recyclable, without degradation to its performance properties. Sixty percent of all zinc produced is still in use and 45 percent of all zinc produced is recycled. Zinc in building and infrastructure represents the largest stock by far with high product-specific recycling rates. Globally, 95 percent of rolled zinc sheet is recycled.¹⁷

The sustainable attributes and applications of architectural zinc products support criteria for several green building programs including Building Research Establishment Environmental Assessment Method (BREEAM) certification, the Green Globes system, the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) rating system, and the Cradle to Cradle Products Innovation Institute’s certification system.

Products that have earned Cradle to Cradle certification demonstrate: no release of any toxic substances during usage, deconstruction, and recycling; retainage of original properties without loss of performance; and re-useability as a new item of at least equal value.¹⁸

Global and industry support for climate resilient materials and construction

Climate change is a worldwide issue and actions to limit its effects are global undertakings. At the 2015 United Nations Climate Change Conference, world leaders signed an international legally binding treaty, now known as the Paris Agreement. Its overarching goal is to hold “the increase in the global average temperature to well below 2 C (3.6 F) above pre-industrial levels” and to pursue efforts limiting global temperature rise to 1.5 C (2.7 F).¹⁹

In 2019, the UNEP’s Emissions Gap Report research indicated that efforts were not on track to achieve the 1.5 C (2.7 F) goal. The report called for GHG emissions to drop 7.5 percent per year through 2030. In recent years, new data have stressed the need for faster and deeper emission cuts to meet the 1.5 C (2.7 F) goal and to avoid severe climate change impacts.¹⁹

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Supporting climate-resilient action, the U.S. Inflation Reduction Act (IRA) 2022 invests $369 billion to modernize the U.S. energy system and—in combination with the Bipartisan Infrastructure Law of 2021, other enacted policies and past actions—to drive 2030 economy-wide GHG emissions to 40 percent below 2005 levels.²⁰

The IRA expected emissions reductions anticipated by 2030 total nearly 1,150 million tonnes (1,131 million tons) CO2eq, equivalent to the approximate combined annual emissions released from every home in the U.S. The U.S. Department of Energy (DOE) expects the pollution reductions from these provisions to increase across all sectors beyond 2030, ensuring continued progress toward the nation’s 2050 net-zero emissions goal.²¹

The IRA’s tax credits, grants, loans, and other programs are funding the construction, renovation, and improvement of energy-efficiency homes and multifamily residences, commercial buildings, and government facilities including schools and federal buildings. State, county, and city policies and laws, corporate and nonprofit practices, building codes, and sustainable building programs also provide additional support.

Focused on lowering buildings’ energy consumption and GHG emissions, 73 percent of the 20 largest architecture/engineering firms, responsible for more than $100 billion in construction annually, have adopted the 2030 challenge. According to a recent poll of design industry leaders, approximately 40 percent of all U.S. architecture firms have adopted the challenge.²²

Call to action and architectural zinc

Specification professionals have a unique role in mitigating climate change and its effects through selecting materials, products, and practices that reduce buildings’ operational and embodied carbon. Architectural zinc material and product manufacturers can offer support and sustainable solutions as well.

In North America, architectural zinc can be specified as manufactured with energy-efficient, low-carbon processes, validated with product-specific documentation. The installation of architectural zinc as roofing, wall cladding, and other building products, supports climate-resilient, low-maintenance performance, and occupants’ safety and health. With a lifespan of 100 years or more, architectural zinc saves time, material, and money. Infinitely recyclable, zinc continues to add value beyond the life of the building.

Notes

1. U.S. Environmental Protection Agency, “Sources of Greenhouse Gas Emissions,” www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions[9], accessed April 30, 2023.
2. World Resources Institute & World Business Council for Sustainable Development, Greenhouse Gas Protocol: Technical Guidance for Calculating Scope 3 Emissions, Version 1.0, 2013
   www.ghgprotocol.org/sites/default/files/ghgp/standards/Scope3_Calculation_Guidance_0.pdf[10].
3. United Nations Environmental Programme, 2019 Global Status Report for Buildings and Construction, worldgbc.org/article/2019-global-status-report-for-buildings-and-construction[11].
4. Carbon Smart Materials Palette, an Architecture 2030 Project, “Why Embodied Carbon?” materialspalette.org[12]/, accessed April 30, 2023.
5. International Zinc Association (IZA) “Environment – Zinc is Natural,” www.zinc.org/environment-2[13]/, accessed April 30.
6. IZA, Zinc Recycling Material Supply, 2022, www.zinc.org/wp-content/uploads/sites/30/2022/10/Material-Supply_VF_1_23.pdf[14].
7. The International Journal of Life Cycle Assessment, “A global life cycle assessment for primary zinc production;” Van Genderen, E., Wildnauer, M., Santero, N. et al.; Nov. 2016 link.springer.com/article/10.1007/s11367-016-1131-8[15].
8. IZA, “Carbon Footprint Guidance,” www.zinc.org/carbon_footprint_guidance[16]/, accessed April 30, 2023.
9. IZA, “Life Cycle Assessment,” www.zinc.org/life-cycle-assessment[17]/, accessed April 30, 2023.
10. IZA, “Climate Change,” www.zinc.org/climate_change[18]/, accessed April 30, 2023.
11. RHEINZINK, “prePATINA Eco Zinc,”
    www.rheinzink.com/products/materials-surfaces/prepatina-eco-zinc[19]/, accessed April 30, 2023.
12. ASTM B69-21, “Standard Specification for Rolled Zinc,” www.astm.org/b0069-21.html[20], accessed April 30, 2023.
13. Association for Materials Protection and Performance, “Economic Impact,” impact.nace.org/economic-impact.aspx, Appendix A: Assessment of Global Cost of Corrosion, Dec. 23, 2015, impact.nace.org/documents/appendix-a.pdf[21], accessed April 30, 2023.
14. 1 American Chemical Society, Chemical & Engineering News, “What’s That Stuff? Asphalt,” Michael Freemantle, Vol. 7, No. 42, Nov. 22, 1999, pubsapp.acs.org/cen/whatstuff/stuff/7747scit6.html[22].
15. Consumer Reports, “Roofing Buying Guide,” April 8, 2022, www.consumerreports.org/home-garden/roofing/buying-guide/[23].
16. PV Magazine, “How Long Do Rooftop Residential Solar Panels Last,” Ryan Kennedy, Sept. 27, 2022, pv-magazine-usa.com/2022/09/27/how-long-do-rooftop-residential-solar-panels-last-2/[24].
17. IZA, “Circularity,” www.zinc.org/circularity-2/, and “2050 Demand Supply,” www.zinc.org/wp-content/uploads/sites/30/2022/10/2050-Demand-Supply_VF_11_22.pdf[25], accessed April 30.
18. Cradle to Cradle Products Innovation Institute, c2ccertified.org/[26], accessed April 30, 2023.
19. United Nations Climate Change, “UNFCCC Process – The Paris Agreement,” unfccc.int/process-and-meetings/the-paris-agreement[27], accessed April 30, 2023.
20. United Nations Environmental Programme, Emissions Gap Report 2019, www.unep.org/interactive/emissions-gap-report/2019[28].
21. U.S. Department of Energy, Office of Policy, “The Inflation Reduction Act Drives Significant Emissions Reductions and Positions America to Reach Our Climate Goals,” Aug. 2022, www.energy.gov/sites/default/files/2022-08/8.18%20InflationReductionAct_Factsheet_Final.pdf[29].
22. Architecture 2030, “How widely adopted is the 2030 Challenge?” architecture2030.org/about/faq/#toggle-id-3[30], accessed April 30, 2023.

Author

Charles (Chip) McGowan is the president of RHEINZINK America Inc. and has more than three decades of experience working with architectural, specifications, and installation professionals on projects featuring metal building products. He is a member of ASTM B02 Nonferrous Metals and Alloys Committee and represents RHEINZINK’s membership in the Metal Construction Association (MCA), U.S. Green Building Council (USGBC), and the American Institute of Architects (AIA). McGowan can be reached at charles.mcgowan@rheinzink.com.

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