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Architects & Planners

III. Zinc FAQs
— Architects & Planners —

III.

Zinc FAQs

Zinc questions and answers

Many of the most common zinc questions, answered:

Where does zinc naturally occur?

Zinc is part of nature. Most soils and many minerals contain different amounts of zinc. Zinc occurs in nature, in the air, in water and in the soil. The average natural proportion of zinc in the earth’s crust is 70 mg/kg (dry weight) and can vary between 10 and 300 mg/kg depending on regional characteristics. Due to natural erosion processes such as weathering and the removal of rocks, soils and sediments by wind and water, a small but important fraction of the natural zinc is constantly moved and transported into the environment. Volcanic eruptions, forest fires and the suspended matter formation above the oceans also contribute to the natural transport of zinc. These processes create a zinc cycle in the environment, which contributes to the natural background concentration in the air, surface water and soil. In general, the natural zinc cycle is much more important than that caused by humans. In addition, zinc is found as an important trace element in almost all living things, i.e. plants and animals, since it takes on important tasks for maintaining health. (IZA, “Behavior of zinc in the environment – essentiality and bioavailability”, 2014)

Zinc is an "essential trace element". What does that mean for me?

All substances are considered essential which are essential for the survival of living organisms but which the body cannot produce itself. This means that these substances have to be ingested with food. Zinc is an essential trace element for all living things – including humans. It is significantly involved in many vital metabolic functions in our body. Skin healing is promoted by zinc, for example. During pregnancy, as well as in infancy and puberty, zinc intake contributes to healthy development and the immune system also needs zinc. A balanced diet generally provides people with sufficient zinc. An adult needs around 10 to 15 milligrams of zinc per day. Since the body does not store zinc, excess zinc is excreted again. Only with very high overdoses can zinc have an unhealthy effect. (“Zinc in Human Health”, published by Lothar Rink, IOS Press 2011, online at: https://ebooks.iospress.nl/volume/zinc-in-human-health), (“Zinc: the metal of life” , Kuljeet Kaur et al, in Comprehensive reviews in Food Science and Food Safety, Volume 13 (2014), online at: https://onlinelibrary.wiley.com/doi/10.1111/1541-4337.12067/epdf)

I have heard that zinc is assigned to heavy metals. Is this important for health and the environment?

Whether an element is considered a heavy metal or not only says something about its physical density. This is primarily of interest to material researchers and physicists, but has no meaning as to its importance for health and the environment. On the contrary: Zinc is an essential, that is, indispensable trace element for the human organism and is involved in many metabolic processes and health maintenance.
(“Zinc in Human Health”, published by Lothar Rink, IOS Press 2011, online at: https://ebooks.iospress.nl/volume/zinc-in-human-health), (“Zinc: the metal of life”, Kuljeet Kaur et al, in Comprehensive reviews in Food Science and Food Safety, Volume 13 (2014), online at: https://onlinelibrary.wiley.com/doi/10.1111/1541-4337.12067/epdf).

Looking at the group of heavy metals, which includes elements with a density of more than 4.5 or 5 g/cm3, zinc with a density of 7.14 g/cm3 is included, but also iron (7.87 g/cm3), silver (10.49 g/cm3), gold (19.32 g/cm3) and platinum (21.45 g/cm3). Like zinc, iron is a trace element that is vital for humans and is actively involved in the transport of oxygen in the blood. Gold is used, for example, as a denture. The statement that all heavy metals – and therefore zinc – are in principle toxic is therefore incorrect.

I plan to use zinc sheet in the roof or facade area. What do I have to know?

In most cases, zinc can be used in construction without any problems. Under extreme climatic conditions or in special environmental protection areas in which the discharge of rainwater into a body of water is planned, local environmental or building authorities occasionally require additional information. In such cases, for example, the impact of the zinc surface on the environment can be calculated in advance in the planning phase using a computer program. 

What about the patina on the zinc surface?

Uncoated zinc forms a firmly adhering layer of zinc oxide and basic zinc carbonate on the surface due to weather conditions. This wafer-thin layer is called a patina. The formation of the patina is shown by the color change of the initially silvery-bright color of the titanium zinc to a matte, gray surface. The patina gradually grows into a uniform surface. (F. Porter, Zinc Handbook, Marcel Dekker, 1991) This very dense and “self-healing” layer on superficial scratches acts as long-term protection against corrosion and ensures that zinc sheet lasts a very long time – theoretically up to 200 years
(“Life-long” Dachbaumagazin 12 / 2011, online at: https://www.initiative-zink.de/fileadmin/iz_web_daten/D_O_K_U_M_E_N_T_E/Medienspiegel/dachbaumagazin_Lebenslaenglich_201112.pdf)

I plan to use zinc sheet in the roof or facade area. The rainwater is said to be infiltrated locally. What do I have to consider?

The local infiltration takes place over the vegetated topsoil, over hollows or trenches. In all these cases, zinc contained in the rainwater is bound in the soil during seepage. In general, the discharge of rainwater into the groundwater does not require a water permit, if it is “harmless”. The provisions of the Federal Soil Protection Ordinance are often used below infiltration systems to assess the impact path of soil-groundwater. For zinc from a value of 500 µg / l, an individual case test must be carried out. According to the Groundwater Ordinance, zinc, like many other metals, is generally one of the substances whose entry into the groundwater has to be limited. The groundwater ordinance does not set a limit for this. Zinc is often present in the groundwater anyway, because the surrounding rock contains zinc. There is also no limit for zinc in the drinking water regulations.

What does zinc washout mean?

Even though zinc is a very stable material, it is attacked by air pollutants such as sulfur dioxide or chlorides, so that minimal amounts of zinc are released from the patina. The zinc is then washed off the surface by rain. As air pollution has decreased significantly in the past few decades, the zinc runoff rates are also at their lowest level in the past 40 years. (WJM van Tilborg et al, “Significantly reduced zinc erosion”, Metall 50/5, 1996). How much zinc is flushed depends largely on the local air pollution, the amount of rain, the roof pitch and orientation and the climate zone (I. Odnevall Wallinder et al, corr. Sci. 42, 2000).

What happens to the dissolved zinc from the rainwater in the soil after the wash-off?

Practical investigations have shown that soils have the property of stably binding zinc even in the top centimeters. It makes an active contribution to the supply chain of plants and living things close to the ground. Zinc binds to earth minerals (adsorption on oxides, silica, carbonate, clay particles) or to organic substances. If the pH of the soil increases (it becomes “more basic” or “more alkaline”), the soil can bind zinc better. Clay soils with a high pH (“basic”) have higher zinc contents, while sandy soils have lower zinc contents. (I. Odnevall Wallinder, “Outdoor and Indoor Atmospheric Corrosion”, 2002) Information on the legal background for the seepage of rainwater: Data sheet DWA-M 153: Recommendations for dealing with rainwater. DWA German Association for Water Management, Waste Water and Waste eV., 2012.

Where can I find information about the legal regulations for the discharge of rainwater?
  • Information can be found, for example, from the Metal Business Association (Mr. Buchholz) at buchholz@wvmetalle.de
  • The Water Resources Act (WHG) with link? Contains general regulations for dealing with rainwater. E.g. https://gesetze-im-internet.de/whg_2009/BJNR258510009.html
  • More detailed explanations and authorization requirements for the treatment of rainwater can be found in the state water laws or in the individual rainwater exemption regulations of the individual federal states
  • Recommendations for dealing with rainwater, such as in the seepage of rainwater, can be found in leaflet DWA-M 153 “Recommendations for dealing with rainwater” by the German Association for Water, Wastewater and Waste. V., 2012
  • Information on the planning, construction and operation of infiltration systems can be found in worksheet DWA-A 138: “Planning, construction and operation of systems for infiltration of rainwater”. DWA German Association for Water, Wastewater and Waste e. V., 2005
What is the term “anthropogenic camp”?

An anthropogenic warehouse is a man-made deposit for raw materials – in contrast to natural deposits, e.g. B. of ores in rock and soil. This also applies to zinc. Since construction zinc can be completely recycled, buildings with roof coverings and facade claddings made of zinc represent a resource store. In the future, this can be used to reintroduce zinc into the material cycle through recycling and to process it into new, equivalent products. Zinc scrap does not have to be landfilled, thermally recycled, composted or biodegraded after use – it is naturally and simply reused.

Can zinc from anthropogenic deposits replace mining in natural zinc deposits?

Even if more than 95% of the zinc sheet used today is returned to the cycle, an anthropogenic warehouse can supplement the mining of zinc ores, but it cannot replace it. The reason for this is the long useful life of zinc of up to 200 years and the resulting low availability of scrap. Since only 5% of the primary energy requirement is required for zinc recycling, which would otherwise have to be used for the extraction of zinc from ores, recycling zinc from anthropogenic stores is essential to protect nature and the climate. By increasing the use of scrap quantities product use, the ecological balance sheet for zinc will increasingly improve in the future.

How will the anthropogenic zinc camp develop?

There are currently around 118 kg of zinc in Germany for every inhabitant (9.4 million tons in 2014 *), which is mainly found in galvanized metal products and as construction zinc. An increase of 1.22 kg zinc per inhabitant is expected for the coming years, so that the zinc inventory will increase to approx. 12.9 million tons in 2050 *. The anthropogenic warehouse for zinc will grow with it and can increasingly serve as a source of valuable materials for recycling. * Source: “Climate protection potential of metal recycling and the anthropogenic metal warehouse”, M. Buchert et al., 2016, Öko-Institut. eV

The development plan prohibits the use of metal sheets for optical reasons. Is this allowed?

In individual cases, the development plan may restrict an individual’s freedom of design with precise justification. This can be done in the B-Plan as part of a design statute. B. relate to the shape of the roof, the use of colors or the use of certain building materials and thus also zinc sheet for the facade cladding or roof covering. Are certain materials prescribed, e.g. B. to get the overall impression of a historically grown appearance, these requirements must be observed. Restrictions are often made, e.g. B. Declare permanently shiny metal surfaces as inadmissible. Zinc surfaces are often allowed in this case due to the expected blue-gray patina formation.

The development plan prohibits the use of uncoated metal sheets for environmental reasons. Is that right?

No, zinc sheets are usually titanium zinc for which there is a CE marking and is therefore generally approved for construction applications. The CE marking confirms that the product complies with all applicable European regulations and is therefore subject to the EU Construction Products Regulation. In addition, no further requirements may be placed on CE-marked products. This is regulated in the Construction Products Regulation (BauPVO), according to which EU member states must not prohibit or hinder the use of CE-certified products. This also applies to the requirement for coatings, e.g. B. to avoid possible washing away of metal ions. The infiltration of rainwater derived from zinc surfaces is generally permitted. In addition, the establishment of building materials in B plans is subject to state law. A ban on zinc sheets in development plans due to local regulations is therefore lacking the legal basis.

What can I do if I would like to use zinc sheet on my house but this is prohibited according to the development plan?

If this prohibition is based on design requirements, you must adhere to it. If there are other reasons that indicate a seepage ban or water or environmental protection reasons, you can contact your building authority with a prepared letter, which we have prepared for you here.

— Architects & Planners —

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