In areas prone to heavy snowfall, building and roof designs should consider how to handle this natural phenomenon. Several factors pour into this process, such as site planning and landscaping, pedestrian and vehicular traffic patterns, wall construction, foundation drainage, wall design, eave and guttering, and roof design.

Experts on the topic say snow retention systems should also be considered in the plan. "The concept that underlies the use of snow retention systems is simple: It is better in some situations to retain snow on the roof so that it evacuates gradually (by thaw), rather than suddenly (by avalanche)," says Rob Haddock in his award-winning technical paper, "Use of Snow Retention Devices - Science or Science Fiction?" Haddock is head of the Metal Roof Advisory Group, and technical advisor to metalmag. (Editor's note: the complete paper can be viewed at www.metalmag.com.)

Matching the design to the need

Haddock emphasizes attention to detail for optimum snow retention. "Most mistakes are a result of failure to design the snow guard system to the specifics of the project. This can result with the snow guards failing because the design loads exceed their capacity; or it can also result with inadvertent gross over-design, which is a waste of money," he says.

Bob McHugh, head of Robert C. McHugh Architects, Paonia, Colo. agrees. "Handling snow anywhere starts with the design of the structure. But what works in one area may not in another because of local snow conditions. In places like Steamboat Springs we have to hold back thousands of pounds of snow, so the snow guard has to be stronger to hold more snow."

Without snow guards, McHugh says, the situation becomes dangerous. "In our area, a metal roof will probably hold snow through January. In February, as it starts to warm up, maybe four feet of snow may zoom off en masse if there is nothing to stop it. It also might start inching off with a layer of ice on the bottom. When it slides,

the ice can damage the roof, rip things in its path and kill anyone standing below it. At a certain pitch, maybe a 5:12 on a house, it will curl off and break the windows under it," he adds. McHugh has designed commercial, residential and institutional structures in the Western Colorado area for more than 30 years. (www.robertcmchugh.com)

Haddock also points out misconceptions about the capability of snow guards relative to icing. "While it is a myth that snow guards cause eave icing, it is also a myth that they will cure any icing problems. On occasion, snow guards are used as retrofit devices with the misguided belief that somehow they will alleviate or mitigate icing problems. They will not."

Fitting your project's needs

The market has many snow retention devices for metal roofs. While manufacturers can provide spacing recommendations and cite holding strengths, Haddock emphasizes the importance of evaluating each project for specific needs. "The frequency and placement of snow guards should be engineered to resist the forces to which they will be exposed in service. Those specifics vary from job to job, as they are affected by slope, roof length, local snow loads, and other factors. But really, it all comes down to a simple matter of mathematics."

Although snow guards vary widely in color, size and design, two basic styles exist: single units and fence systems. They are made from plastic or metal, and can employ a variety of methods to blend with the roof on which they are used, including color-or the absence of color.Installation is accomplished through different methods, including adhesives, screws, clamps, and soldering.

To help start your research, we offer this sampling of products based on supplier information as well as a complete list of snow guard manufacturers.

SnoBlox products are made by the creators of Snojax. Each is a separate company, but both SnoBlox and Snojax products are manufactured using clear UVstabilized polycarbonate materials.

Snojax was patented in 1978, which the manufacturer says makes it the original plastic snow guard. Both companies are exclusive to the snow guard business and do not manufacture or market products not related to snow guards.

SnoBlox single unit-style models are designed to offer high quality at a reasonable price. SnoBlox offers two sizes of patented snow guards to fit most roof panels: the larger ACE model will fit more common panels while the DUECE model is capable of fitting panels with narrower roof spaces. A waffled base is designed for maximum adhesion.

The manufacturer indicates that SnoBlox products can be used on any glossy coated metal roof. SnowBlox also features a new product called Ventsaver designed to protect roof vents, chimneys and masts, and to eliminate the need for crickets. Ventsaver may be used on roofs with or without snow guards. SNOJAX Products

Snojax products are single unitstyle models. The original model, Snojax I, is for use in screw-down applications only. Snojax II offers the same qualities as Snojax I, with the option of adhesive application. The single units are available in two sizes, both of which can be mounted either with adhesives or screws. The manufacturer indicates that Snojax products can be used on any glossy coated metal roof. The company also offers adhesive products, which are posted on its Web site.

Installation and use

The manufacturers of both Snojax and SnoBlox products emphasize that the placement of snow guards on a roof is crucial, and each offers tools on its Web site to help determine the number and spacing of guards. They also note that if adhesives are used, proper temperatures and curing times must be observed. SNOBAR Products

SNOBAR is a snow Retention system in the fence system style: a stainless steel or galvanized bar that spans a portion of a roof, and is attached to the roof's standing seams using a stainless steel clamp. No penetrating screws or adhesives are required for installation. According to the manufacturer, the SNOBAR can be curved to fit tapered roofs, and is offered in either mill-finished stainless steel or can be factory painted to match the metal roof panel.

A new product introduced at METALCON 2002 in October is the SNOBAR system that uses a U bracket. This variation on the original SNOBAR is for use on corrugated panels, primarily those with exposed fasteners. .

A screw-down, stainless steel U bracket holds the bar in place with a tek screw. As with the original SNOBAR, both brackets and bars can be painted to match the roof panels.

Ice stoppers are available for both SNOBAR systems; this optional equipment hangs from the bar to help keep snow and ice from sliding underneath the bar. Ice stoppers come in aluminum or stainless steel, and can be painted to match the roof material.

Installation and use

SNOBAR encourages the use of snow guards to protect not only gutters and roof stacks, but also any possible pedestrian traffic, expensive landscaping, and HVAC equipment. When it comes to installation, the manufacturer says it always checks to make sure the building is properly designed by examining ground snow load, roof slope, and panel widths and lengths. Clamps should be set properly on seams, and manufacturer instructions for clamps and set screws must be carefully followed.

SNOGEM offers a total of four different single unitstyle snow guards, two made from polycarbonate materials, and two made from metal forms. The Original SNO-GEM and SNOGEM, Jr. are both created in the shape of a crystal. The SNO-GEM, Jr. is half the size of the Original SNO-GEM. According to the manufacturer, virgin-grade, UVstabilized polycarbonate materials are used-and by using a mold injection process, color can be added for a uniform match to any roofing material. The polycarbonate models can be applied to the roof using one of three methods: tube adhesive; 3M pre-applied peel-andstick tape; or mechanical fastener.

The company has a new entry, the Original Metal SNO-GEM offered in a smaller size and known as the Half-Carat SNO-GEM. The guards are made with metal forms and can be created from a choice of metals to match the roofing material, says the manufacturer. The Original Metal SNO-GEM and Half-Carat SNO-GEM can be installed using the same three methods as the company's polycarbonate models. In addition, the company offers a method for soldering copper units.

Installation and use

SNO-GEM says its snow guards should be specified according to the roof panel profile, and that its products can be adopted to fit a variety of panels. The manufacturer emphasizes that no steps in the installation process should be ignored. Start with cleaning the roof, and finish with sealing the entire perimeter of the guard. Layout is also important, and adhesive application should be done only in proper temperatures and a dry environment.

Berger Bros. manufactures Real- Tool, a commercial line of snow guard products that includes five models in both the single-unit style and the fence style. Guards are offered in copper, stainless steel, bronze, galvanized iron, clear polycarbonate, and in a variety of stamped patterns and ornamental castings.

For standing seam metal roofs, Berger Bros. offers two series of single-unit style models: RT and AP. According to the manufacturer, both models are fastened to the seams without penetrating the roof surface. The RT and AP series are offered in mill finish, black primer, or a custom color; the RT models also are available in bronze.

The SM and CL series (also single-unit style) are designed for flat areas of metal roofs, and are applied using adhesives. Models in the SM and CL series are available in mill finish, black primer, custom color, and clear polycarbonate, depending on the application. The company also offers adhesives on its Web site.

Also from Berger Bros. is the FRail, a fence style snow guard that is affixed to standing seams. The FRail system uses a bar that sits below the standing seams, which the manufacturer says is designed to eliminate any space between the bar and roof surface. The company also offers a full line of snow guards for residential applications.

Installation and use

Berger Bros. recommends using a professional roofing contractor, instead of the building owner attempting installation. The company also urges careful use of adhesives, in only the proper weather and temperature conditions.

S-5! Metal Roof Innovations originated mechanical, nonpenetrating attachment technology for standing seam rooftop accessories. S-5! Utility clamps grip the panel seam without piercing by using round-point setscrews to ensure a positive engagement without damage to the panel material or violation of roof system warranties. Holding strengths of the S-5! are lab tested and published on the company's website.

S-5! offers three snow retention systems: ColorGard, SnoFence, and SnoRail. All use continuous crossmembers and are metalurgically compatible with any metal roof type, and available for any seam profile.

ColorGard is attached to standing seam profiles with S-5! clamps, and to face-fastened metal and other roof types with the VersaBracket. ColorGard utilizes the same factory finished material as the roof for a perfect color match.

SnoRail and SnoFence are cylindrical in shape and come in mill finishes of stainless, brass or aluminum. For attachment to facefastened panel systems, the manufacturer recommends the VersaBracket with pre-applied sealant in the base for flawless waterproofing of the attachment.

Installation and use

S-5! snow retention systems can be installed in any climate at any time of the year with tools that are common to the trade. Each system is custom engineered to the specifics of each project, and sitespecific design and layout is available from independent distributors nationwide or through the S-5! website. Tested holding strengths are guaranteed by the manufacturer not to degrade with time and exposure.