Zinc for Life FAQ’s

 

What Is Patination?

 

The key to the extraordinary durability of zinc roofs and facades, and often cited as the source of their beauty over time, is patination. Just as copper ages from orange to green, zinc over time develops its distinctive patina, going from shiny silver to matte bluish gray (depending on the precise alloy, other colors and finishes are also possible). In contact with the water, oxygen and carbon dioxide molecules in the atmosphere, the surface forms a closely adhering protective layer of zinc carbonate, which is insoluble in rainwater and will hinder any further exchanges between oxygen and zinc, thereby protecting the zinc from further corrosion. Zinc continues to renew this protective layer throughout its life, although the heaviest formation is usually complete in about five years, and will self-repair any imperfections or scratches. 

 

Explain ...'Embodied Energy' and Why Zinc's is Lower Than Other Metals.

 

Its low embodied energy is one important way that zinc is a green material. Embodied energy includes the total amount of non-renewable energy needed to create one unit of a finished product, including raw material extraction, transport, manufacturing, assembly and installation, and in detailed calculations, to maintain during its useful life and dispose of afterwards. The terms “cradle to grave,” “cradle to cradle” and “total cost of ownership” describe this.

 

Among the non-ferrous metals used in building, zinc has the lowest embodied energy. It is the least energy intensive to produce, requiring one fourth the energy of aluminum, and one third that of copper or stainless steel. Zinc is less expensive to extract than many other metals, and requires lower heat and less energy to process.

 

...Raw Material and Resource Consumption: Zinc is the 23rd most abundant element in the earth’s crust. Increased recycling, currently at a yearly rate of over 30 percent of overall zinc consumption, is also expected to increase and to compensate for future growth in consumption. Zinc is mined worldwide, and various projections have been made for the size of the global supply, but estimates put it up to 750 years at current extraction levels.

 

...Mining: Zinc is predominantly mined from deep mines as opposed to strip mines. Core extraction mining, although more expensive, requires less energy, disturbs less land and risks less environmental damage than strip mining. Zinc is easier to extract than other metals, requiring less gross energy consumption. Zinc alloy manufacturers also have the option of purchasing zinc ingots from suppliers who contract with environmentally conscious mining companies. Current global sustainability initiatives are driving new energy efficient and ecologically low-impact processes.

 

...Smelting and Processing: Emissions during these phases are reduced to a minimum through state of the art manufacturing equipment including new furnaces, heating and cooling systems and electrofilters and other abatement systems that minimize waste and pollution, conserve energy and limit the release of emissions. Zinc has a low melting point of 786 °F (419 °C) compared to aluminum at 1120 °F (660 °C), copper at 1983 °F (1084 °C), and steel at 2372 °F (1300 °C) resulting in lower energy requirements at the smelting stage of production.

 

...Maintenance: The installation of zinc products on job sites typically results in very little pollution and little or no waste, since even scraps have resale value. As discussed below, repair and maintenance costs tend to be minimal throughout the life of the building.

 

...Replacement and Disposal, or Recycling: Replacement costs are likewise few and far between during the long lifetime of zinc materials - 80 to100 years for roofs, 200 to 300 for walls and other building systems. Very few common building materials, including those considered to have low embodied energy, can match the recyclability of zinc material. Removal and disposal of typical building material can be a complex and costly job, and the resulting debris may have low or no value and end up in a landfill, with the associated costs for freight and disposal and the long-term cost to the environment (and the landfill will charge for this privilege). A complete environmental balance sheet must also take into account the high dollar and energy costs of labor to repair or remove old systems such as asphalt roofs, the cost of the replacement materials, the costs and energy used in transportation of materials on each occasion, and tipping fees at landfills.

 

An estimated 95 percent of the energy content embodied in a zinc product is conserved during recycling. Of the millions of tons of discarded building materials taken to landfills every year, there is hardly a scrap of architectural zinc.

 

How Durable Are Zinc Products?

 

Today, zinc products used in architecture for roofs and walls have an extremely long service life: an estimated 80 to100 years for roofs, and 200 to 300 years for walls, depending on the exact product, geographic location and local conditions, including the amount of air pollution.

 

Durability is a key component of sustainability. The National Institute of Standards and Technology defines Life Cycle Cost as the total discounted dollar cost of owning, operating, maintaining and disposing of a building or building system over a period of time. The service life over which zinc materials are evaluated is much longer than with almost any other building material.

 

Durability is not only a matter of simple longevity, but also of the costs necessary in maintaining a material throughout its life, and those involved in disposing of it at the end (or, ideally, at the beginning of its use in yet another product). To take roofs as an example, in a 2004 study conducted by Ducker International, owners and property managers reported performing little or no maintenance on their metal roofs (the study included all types of metal roofs, not just zinc). A comparison of maintenance costs over the life of the roof for metal versus asphalt and single-ply showed that owners of metal roofs spent approximately 3 percent of total installed costs on maintenance, versus 28 percent for asphalt and 10 percent for single-ply.

 

For most conventional roofing materials, their removal, disposal and replacement, on average every 17 years but in many cases more often, also represents a major environmental factor. The need for multiple roofs over a building’s lifetime makes roofing materials a large contributor to the waste stream. For example, it is estimated that at l east 9 to 10 million tons of asphalt roofing materials from tear-offs and installation scraps ends up in landfills every year. A 2007 U.S. Army Corps of Engineers technical bulletin cites an estimate that 7 to 10 percent of the nation’s landfill space has gone to roofing waste over the last 40 years. An asphalt shingle will take some 300 years to decompose.

 

When costs are extended over multiple generations, the sustainability of building components with very long service lives - even those with relatively higher costs at some points in their life cycle - may be better, and their overall environmental impact lower, than that of alternatives with much shorter service lives and problematic maintenance, repair and replacement profiles.

 

Zinc material requires little maintenance over its service life; its patina constantly renews itself as it weathers and ages and will “heal over” scratches and imperfections, requiring no touch-up or repainting. Because the metal is uncoated, there is no possibility of the fading, chipping or peeling that otherwise needs recurrent attention. A single zinc roof, with a lifespan of 80 to 100 years may well outlast the building it has been sheltering. And if or when zinc material is removed, it will never see a landfill.

 

Can Zinc Building Materials Be Recycled?

 

Metallic zinc can be recycled indefinitely without loss of its chemical or physical properties. This theoretically infinite recyclability is, in fact, being approached in reality in the case of zinc used in buildings.

 

Architectural-grade zinc must be very pure, and so it contains higher percentages of pure ore than industrial-grade zinc. However, once the pure architectural alloy has been created, it can be recovered and reprocessed for use in new architectural products. Some current zinc manufacturers achieve very high levels of this recycled content in their architectural zinc, over 45 percent, almost all of which is post- consumer content. The overall recycling rate for architectural zinc - for example, recovered from renovations and removal from old building - is over 90 percent in some countries because of its high value and the preservation of all its chemical and physical properties. Buildings whose zinc parts outlasted them are numerous in Europe. Virtually no zinc on a building ever goes to a landfill.

 

Recycling of zinc is a well-established industry because products can be recovered easily at the end of their life and there is an extensive network of buyers offering advantageous prices. Even small amounts of scrap zinc generated on jobs are valuable and readily sold.

 

The amount of energy used to produce zinc from ore is already the lowest of non-ferrous metals, as discussed further above. But recycled zinc conserves approximately 95 percent of that initial energy content. It is also energy efficient to reprocess. Only a fraction—between 0.49 percent and 19.7 percent—of the energy used to produce zinc from ore is necessary to produce zinc from recycled material.

 

Can LCA Data Be Used to Assess the Local Environmental Impacts of Production Sites?

 

No, Life Cycle Assessment (LCA) cannot be used to determine any local impacts. This is because LCA considers potential impacts with varying geographic scope, from regional to global. Moreover, the underlying Life Cycle Inventory (LCI) data will usually be averages from different sites and regions.

 

How Then Can LCA Help to Make More Environmentally Responsible Products?

 

Life Cycle Assessment (LCA) and the underlying Life Cycle Inventory (LCI) data can identify the relevant drivers of environmental performance, e.g. pointing out a weakness along the product system where great amounts of energy are consumed or large amounts of waste arise. Similarly, such an analysis may also indicate where an improvement of efficiency is desirable or possible.

 

What is the Difference Between Life Cycle Assessments (LCA) and Life Cycle Inventory (LCI)? 

 

LCA involves an assessment of the environmental impacts of the material and energy flows through the product system. The LCI does not comprise this impact assessment step, but only the list of material and energy flows. Additionally, it is common practice to provide LCI data for a single industrial production process as opposed to the whole product system from raw materials to product to waste. These partial studies are often called ‘from cradle to gate’, or eco-profiles.

 

What is Life Cycle Assessment? 

 

"Zinc for Life" relies on Life Cycle Assessment (LCA) studies. LCA is a standardized scientific method for systematic analysis of all mass and energy flows as well as environmental impacts attributed to a product system, from raw materials acquisition to end-of-life management. This full life cycle scope is often described as ‘from cradle to grave’. In accordance with the international standards on Life Cycle Assessment (ISO 14040–44), an LCA study has four phases: Goal and Scope determining the object, framework and goals of the study Life Cycle Inventory compiling an input/output analysis of material and energy flows from operations along product system Life Cycle Impact Assessment evaluating the environmental relevance of material and energy flows (e.g. with regard to resource depletion or global warming potential) Interpretation drawing conclusions (e.g. main drivers of environmental performance). LCA can thus be used to examine the environmental performance of competitive products or material applications and to identify optimization potentials.

 

Do LCI Data Allow for a Distinction Between Good and Bad Materials?

 

No, using Life Cycle Inventories (LCI) for comparing 1kg of material A with 1kg of material B is nonsense. LCI are only building blocks of Life Cycle Assessment (LCA) studies. LCA, in turn, can only compare whole systems which provide the same service. Different materials have different properties and functions and/or are used in different designs – so comparisons on a material level are meaningless. LCA rather considers how the service for the user or consumer is achieved and then compares which system has the smaller environmental footprint.