Lawrence E. Keenan, AIA, PE, director of engineering with Hoffmann Architects, an architecture and engineering firm specializing in the rehabilitation of building exteriors, discusses winter deicing options.
Evaluating Deicing Options
Lower Supply, Higher Costs
With winter weather upon us in many areas, building owners and managers face another season of snow removal and ice melting. With the high liability of slippery surfaces, maintaining safe sidewalks, plazas, and parking areas is a must. But reports of salt shortages and higher prices may mean reassessing available options this season to meet operating budgets. While rock salt or calcium chloride might suffice to get the job done, the expense of repairing damage from these corrosive chemicals often justifies the costs of premium products and alternative methods. In addition to economic factors, each facility’s climate, usage, location, construction type, and exposure will dictate the appropriate deicing strategy.
Comparing Deicing Options
When planning for winter, building owners and managers have a number of options from which to choose, each with benefits and drawbacks. Because there is no one product that meets all needs, a combination of materials, incorporated into a comprehensive snow and ice removal program, is the best approach to meeting cold weather demands (see chart below).
The most commonly used deicing chemicals include sodium chloride (rock salt) and calcium chloride. Rock salt, historically the cheapest option, is the deicing standard used by transportation departments for roadways. However, sodium chloride is extremely corrosive to steel and destructive to masonry and concrete. Because of its low cost, rock salt has retained its popularity in spite of these properties, but this year’s high salt prices may mean that savings is insufficient to justify subjecting building materials to such a caustic chemical. Calcium chloride, while more expensive, is the most effective deicing chemical; it is the benchmark by which other compounds are measured. While calcium chloride can have the same detrimental effects as rock salt, these tend to be much less severe. In an effort to avoid these damaging properties, other chemicals have been developed, but they may not be as effective, particularly at lower temperatures.
In addition, there are many proprietary products available, which claim to correct the deficiencies of any one compound. These products usually combine various deicing chemicals, sometimes alongside other performance-improving agents, such as corrosion inhibitors or traction enhancers (e.g. corn starch). While proprietary blends pledge greater effectiveness than their simpler counterparts, they also come at a higher price.
Ice Melting Or Ice Loosening?
For the purpose of this discussion, it is important to differentiate between ice melting chemicals and ice loosening chemicals. Ice melting chemicals remove ice by transforming it into water, which flows away; the chemical is typically washed away with the melting ice, requiring frequent reapplication. Ice loosening chemicals, by contrast, do not melt snow or ice, but rather create a slurry at the surface that interferes with the bond of the ice to the pavement, aiding mechanical removal. Ice loosening chemicals work best if applied before it snows, and they typically last longer than ice melting chemicals.
The chemical that is most sympathetic to existing structures—and most highly recommended—is CMA; however, CMA does not work at lower temperatures, must be applied before snowfall, and demands expeditious, and, often, continuous snow removal. Should an ice melting chemical be required, opt for potassium chloride, magnesium chloride, or a blend of the two, but not outside their operating temperature range. For colder, more severe conditions, it may be necessary to use calcium chloride or a proprietary blended material to maintain safety. In all cases, application of grit/sand greatly increases traction and diminishes the amount of deicing chemical required.
As the days turn colder, building owners and managers should consider snow removal options—before the first big snowfall forces last-minute decisions. Ideally, proposed materials should be pilot tested to verify suitability and performance, then integrated into a multi-faceted snow and ice removal strategy. A design professional experienced in exterior maintenance planning can assist in evaluating deicing needs and making informed choices.
Keenan, AIA, PE, director, engineering with Hoffmann Architects, has specialized experience in parking structure, plaza, and building exterior rehabilitation, including investigation, repair, and surface treatment consultation. Founded in 1977, Hoffmann Architects, Inc., specializes in the rehabilitation of the building envelope. The firm has offices in Hamden, CT; New York City; and Arlington, VA.