Essential Zinc: Building For The Future

Low-maintenance zinc gains popularity for buildings that last
This course is no longer active
[ Page 5 of 5 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5
Sponsored by Umicore Building Products
Janet Zaso

ENVIRONMENTAL QUALITIES OF ZINC

An examination of the environmental impact of architectural zinc and its contributions to sustainable building logically begins with the base element. As an essential element with the atomic number 30, zinc is the 23rd most abundant element in the earth's crust and one that is necessary to the growth of humans, animals and plants. In fact, it is the second most common trace element found in the human body and exists naturally in air, water and soil. Understanding its impact on the environment and its contributions towards sustainable building requires assessing its supply and demand, manufacturing, recycling potential, product attributes, soil concentration and human/animal health impacts.

Of all the metals produced worldwide, zinc ore is ranked fourth in the amount of tonnage produced. According to a United States Geological Survey in 2006, 10 million tons were produced worldwide, with China, Australia, Peru and the U.S. being the top 4 countries in terms of zinc mining production. The U.S. alone that year mined 699,000 metric tons (t) of zinc in 6 states including Alaska, Idaho, Missouri, Montana, New York and Washington. In the same year, 350,000 tons of the metal were recovered from waste and scrap material for reuse in products. Just one year later, the amount recovered had increased by 20 percent and the trend is expected to continue. Nearly a third of the metallic zinc produced today is used in galvanization, a process that protects an object that is prone to corrosion by giving it a protective coating of zinc.

Photo courtesy of Umicore Building Products

 

The demand for zinc has fueled a robust recycling market for the metal. In fact, about 90 percent of the zinc used worldwide is recycled for additional usage as part of a recycling loop that is efficient for recapturing zinc from end-of-life products. The zinc used in building materials and galvanized steel, are included in this recycling loop, with both scrap material and end-of-life products being candidates for recycling. Nearly 70 percent of the zinc from end-of-life products becomes recycled, according to the International Zinc Association. That represents around 3 million megatons (MT) of zinc being recycled annually, and the numbers are increasing.  This recycled zinc goes into products such as sunscreens and paints, and some goes back into building products.

Energy consumption in the manufacturing process contributes to zinc's environmental record from cradle to grave when compared to other metals. Zinc ores are core mined in the traditional method, not strip mined, and during refinement zinc uses a quarter of the energy needed to refine aluminum and half the energy of copper or steel.

Continuing in the production process, the amount of energy used to produce zinc from ore is lower than any other nonferrous metal marketed today. The energy consumption is even lower when the zinc is produced from recycled material. Put another way, zinc requires less "embodied energy" to produce than both steel and aluminum, which means that the amount of energy needed to manufacturer it and supply it to the point of use is lower than these metals. As zinc recycling improves and develops, zinc manufacturers expect to further reduce energy consumption by using more recycled material.

Some design professionals and owners turn to zinc to assist with implementing their goals for environmental conservation. For example, a residential project in Maine utilized a zinc roof, gutters and flashings as part of a rainwater collection and treatment system that allowed the homeowners to use rainwater nearly exclusively for all household needs. The project depended on the metal to facilitate water collection without having a negative effect on the final water quality. While the presence of zinc in drinking water is common and not harmful, it could show a chalky appearance and taste metallic at levels higher than the EPA standard of 5 milligrams per liter. The home's water treatment system handles this possibility.

Other factors to consider when gauging zinc's environmental record is soil concentration from building materials and the metal's related affects on humans, animals and plants that become exposed to varying levels. These factors apply to building inhabitants as well as local populations. As stated previously, zinc is an essential element for sustaining life and is present in trace amounts in living things. The element plays a role in the functioning of 300 different enzymes in the human body and is essential for many biological and metabolic processes as well as antiviral and immune-enhancing activities. People are routinely exposed to zinc by ingesting it in the water and food supply and through the air. The FDA recommends a total daily intake of 11 milligrams for adult men and 8 milligrams for women. To protect workers, OSHA has set an average daily limit of 1 milligram per cubic meter for zinc chloride fumes and 5 milligrams per cubic meter for zinc oxide dust and fumes. These limits predominantly concern the manufacturing environment where such levels are more likely to be experienced.  While zinc is not classified as a carcinogenic, the EPA, FDA and OSHA have issued guidelines because the consumption of large amounts of zinc - zinc overdose - as well as zinc deficiency can have adverse health effects. An overdose is considered to be a level that is 10 to 15 times higher than the amount needed for good health. Neither zinc deficiency nor overdose is at all common in the U.S.

Run-off from zinc into surrounding soil at a building site is limited. Not all the zinc that detaches during corrosion becomes run-off. The soluble part, which is zinc sulfate, does run off, and at a rate that is 50 to 80 percent lower than the corrosion rate. On average, the amount of zinc that normally exists in the soil to a depth of 3 feet is greater than the amount of zinc run-off from a building over a 30-year period. Zinc is not bio-available upon contact with soil, making it harmless to humans and animals when run-off enters the ground. Bioavailability is a measure of the amount of a contaminant that is absorbed into the human body after contact, ingestion or inhalation. In the case of zinc in the soil, most of it stays bound to soil particles rather than dissolving in water and entering the water supply. The EPA has not issued any requirements for limitations of zinc discharges under the Clean Water Act.

BUILDINGS THAT LAST

Across the U.S., design professionals increasingly turn to zinc for its inherent beauty, malleability and long-lasting appeal for commercial, public and residential projects. These buildings will stand the test of time, lasting for many, many years while reflecting their natural zinc patina for people to admire. Meanwhile, their owners will also enjoy these investments for their low-cost maintenance needs. Architectural zinc roofs and walls - with their curves, domes, textures and patterns - contribute to the industry's sustainable building ideals and the possibilities of unique design forms. As the misconceptions about zinc are cleared away, more professionals are choosing it for meeting customer demand for long-lasting, low maintenance products that can have a low impact on the environment.

 

Umicore Building Products

Umicore Building Products is the world's leading producer of zinc construction products, which have been used successfully for more
than 150 years throughout Europe and now for more than a decade in North America. Umicore's line of VM ZINC® panels for roofs and wall systems has been used on a wide range of projects including colleges and universities, museums, airports, libraries and an array of prestigious buildings across the country.www.vmzinc-us.com

 

[ Page 5 of 5 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5
Originally published in Architectural Record
Originally published in April 2009

Notice

Academies