Innovation in Applications

Because of the versatility and wide range of possible building applications of zinc, it is possible to be very creative in its use to achieve sustainable building designs. Some of these innovations can take the form of advanced building envelope solutions such as rain screen designs, roofing variations, sun screens, etc. Zinc based batteries and fuel cells can be a contributing portion of an onsite renewable energy solution for buildings. Architects looking for advancing the state of green building design through innovation will find plenty of opportunity to pursue creative solutions when considering zinc for those solutions.

With all of these sustainability and durability qualities, zinc has become commonly used as a stand-alone metal product or in combination with other metals for a variety of uses that most designers are probably already familiar with. This includes mixing zinc with copper to form brass or using it to galvanize steel based on a chemical reaction that protects the steel from rust and corrosion. Zinc is also used in batteries and recently in fuel cells for alternative energy solutions. Metal flashings and roof accessories including historical building ornaments (such as metal finials, vanes, campaniles, dormers, etc.) can all be fabricated from zinc as an alternative to copper and other less sustainable metals. Similarly, rainwater collection gutters and downspouts made from zinc are a popular non corroding alternative to other metals. Finally, when formed into rolls and sheets zinc is ideal for fabrication into roof panel systems and interior and exterior wall panel products.

Zinc Roofing Applications

Photo courtesy of VM Zinc The ability to use zinc on low sloped and steep sloped applications makes it suitable for a variety of building forms.

The success of zinc roofing can be summed up in a few words: long-lasting, malleable, flexible, aesthetic and prestigious. Because zinc roofing is suitable for all roof pitches above 1:12 and for all types of shapes (straight, curved, folded, etc.), it offers a great deal of freedom of expression for roof design. It is important however, to address zinc corrosion properly which can be impacted by environmental conditions such as salt spray, acid rain and construction or masonry dust. Generally, one of three approaches is used to prevent zinc corrosion from moisture. Skip sheathing is the oldest method and involves placing pine boards beneath the zinc roofing. The boards are spaced apart so that when condensation on the back side of the metal forms and drips off, it will drip behind the pine boards where it can dry from air flow behind it. This approach is still followed in Europe in some places and contributes to the longevity of some European buildings. A newer approach calls for installing a drainage mat beneath the zinc roofing. And the latest protection approach is a special backside polymer coating. These coatings range from 30 to 60 microns thick and protect the zinc metal from coming into contact with moisture from condensation. The first generation of coatings was white in color, but today gray coatings can be found to aesthetically match the natural patina color of zinc.

What about protecting zinc from corrosion due to salt spray? Sea salt can alter the chemical patina process and result in a lighter or streaked color. Therefore, in seaside locations, zinc products may need regular rinsing with fresh water.

Based on all of these roofing properties, manufacturers offer a variety of choices and options to suit different conditions and design criteria:

Batten Seams

Batten seam roofs are one roofing style option that is suitable for virtually all building types, particularly complex shapes. Experienced installers only need simple tools for the work which involves fastening a strip or bar to the structural deck and then attaching the zinc roofing panels to it. The zinc sheets are held in place by a zinc batten clip supporting the peripheral upstands. The capping strips are placed into position by overlapping, thus ensuring that the roof is watertight. This style has the key performance advantage of being adaptable to complex shapes and roof penetrations. From a design standpoint, it provides expression of strong, conspicuous contours, shadow effects and urban character. From a construction standpoint, installation is straightforward and easy with the ability for easy dismantling for repair, changes, or end of life deconstruction. When working with zinc in this manner, if the batten cap is to be bent downward, the legs of the cap must be bent at an angle less than 90 degrees. The angle is important to accommodate for thermal expansion and contraction. A straight 90 degrees could not allow enough play for this movement. The proper leg angle is a common mistake made by inexperienced installers. In some cases the leg is not bent down at all, but is simply capped off.

Standing Seam

Zinc roofing is also very suitable for standing seam applications. In a standing seam roof, the long seams on adjacent zinc panels are bent up, overlapped or folded to create the weathering surface. Note that the seam is fabricated in a manner to allow for the expansion and contraction of the material. The height of the seam is typically one inch however heights up to one-and-a-half inches are common for snowy areas or low slope roofing applications. This traditional standing seam system allows long strips of zinc panels to be assembled over a sizable area. The sheets of zinc are laid on continuous decking and anchored using stainless steel fixing clips. Ideally suited to large roofing areas, this style of roofing will readily adapt to almost any design with very discreet joins. Since it provides maximum water and wind resistance, it is well suited to areas with harsh climates, strong winds, or heavy rains. This well-known technology provides for a fairly easy and cost effective installation and it is possible to optimize metal consumption and minimize waste with the judicious layout of the seams.

Decorative Shingles

In steep roof situations (greater than 25 percent) zinc metal shingles can be used for a more decorative solution. As with shingle installations, the intent is to shed water, not repel it, so consideration should be given to the weather and climate conditions when considering this style.

Given the design flexibility, aesthetic diversity, and sustainable durability of zinc roofing, it is easy to see why it has become a material of choice for metal roofing, particularly on green buildings. For similar reasons, the use of zinc for wall systems is on the rise.