Tag Archives: Coatings

What Do You Mean By ‘Polyurethane?’

All photos courtesy Quest Construction Products

All photos courtesy Quest Construction Products

by Steven Heinje

‘Polyurethane’ is not a useful specification term on its own. It is akin to saying, “I want a form of transportation,” as opposed to something much more specific, like, “I want a four-cylinder sedan.” Getting to the point where a manufacturer or supplier will only offer products meeting a specific project’s needs will require more precise and non-proprietary terminology that makes performance the outcome.

The term ‘polyurethane’ simply means many repeated units of urethane, much in the same vernacular as ‘polypropylene’ or ‘polyester.’ Often, these coatings are referred to as ‘urethanes,’ similar to the way terms like epoxy or acrylic are employed. They are all polymers of the key reactive or function group. The urethane group confers many of the traits of a polyurethane—most notably, adhesion—in much the same way most acrylic paints share ultraviolet (UV) resistance.

Typically, a Technical Data Sheet (TDS) for a polyurethane coating will include a long list of tests, often with some impressive numbers. A few of these will find their way into various specifications. Perhaps they will include a benchmark product and later a few ‘equals’ will be added—such a specification is representative of the standard of care for using a polyurethane in today’s construction marketplace.

This article seeks to add some background and a few key details so specifiers understand what type of product is actually being offered, what are its intrinsic performance attributes, and whether it truly has adequate offsets. (The focus is on coatings; polyurethane foams for insulation are outside this article’s scope.) A little chemistry is required to fully grasp the concepts, but the desired outcome is for design professionals to know what questions to ask and ultimately to be able to write better specifications and avoid failures.

This 100 percent aliphatic polyurethane has exceptional ultraviolet (UV) resistance needed to hold this deep blue color on the very visible roof of Marin County Civic Center (San Rafael, California).

This 100 percent aliphatic polyurethane has exceptional ultraviolet (UV) resistance needed to hold this deep blue color on the very visible roof of Marin County Civic Center (San Rafael, California).

The fl exibility and hydrophobicity of a specifi c polyurethane was chosen over an epoxy alternative for this plant near Shanghai.

The flexibility and hydrophobicity of a specific polyurethane was chosen over an epoxy alternative for this plant near Shanghai.

 

 

 

 

 

 

 

 

 

 

Why use a polyurethane?
Polyurethanes have the broadest range of any product group: they can be soft as a baby’s skin or hard enough to be machined and tooled. Some may yellow and chalk severely, while others are among the most light-stable coatings available. Chemical resistance, including water resistance, is similarly variable.

Polyurethanes combine toughness and flexibility—a unifying trait that comes from the urethane linkage itself. Urethanes form a molecular spring based on the intense attraction of the urethane groups to each other, so they form hard domains within a softer and more flexible matrix. This link is flexible, and more importantly, it is recoverable; this leads to products that combine high tensile and high elongation, and even maintain high hardness and flexibility at low temperatures (down to −30C [−22 F]) and up into higher temperatures (75 C [167 F]). This feature allows them to be used as high-performance coatings, as well as durable foams.

In most cases, another key trait is adhesion. As a rule, urethanes bond to various substrates, often better than styrene-ethylene/butylene-styrene (SEBS), acrylic, silicone, and even butyl. Adhesion is important to consider because maintenance coatings are often used over unknown, older surfaces, or even multiple surfaces giving the contractor or specifier a good reason to specify a polyurethane above other more-restrictive options.

Beyond toughness and flexibility, all other traits—gloss retention and resistance against abrasion, water, UV, solvents, and acids/alkalines—depend on the ‘backbone,’ as defined later in this article. Application traits are another mixed bag, relying on the nature of the curing chemistry, which is referred to as the ‘curative.’ With the appropriate formulation, there is no other class of product that has a better balance of adhesion, UV resistance, abrasion resistance, and flexibility. By contrast, epoxies are too hard, acrylics exhibit poor abrasion performance, and silicones show relatively weak physical properties as a product class. There are few properties a urethane cannot be formulated to achieve.

However, high heat resistance is an overall weakness. Below 75 C is urethane territory: applications include roofing and most industrial and sealant applications. While some specialty urethane products can perform long-term above 100 C (212 F), these high temperature applications typically require silicone and epoxy products.

This polyurethane system has exceptional fi re retardancy for use on sloped roofs.

This polyurethane system has exceptional fire retardancy for use on sloped roofs.

A low-toxicity polyurethane coating was used on the structural concrete for this wastewater treatment plant.

A low-toxicity polyurethane coating was used on the structural concrete for this wastewater treatment plant.

Types of urethanes: Varnish to airplane components
ASTM D16, Standard Terminology for Paint, Related Coatings, Materials, and Applications, defines six types of polyurethanes.

Type I: One-package (1K) urethane alkyds1
Like all alkyds, or ‘oil-based paints,’ these cure by oxidation of a drying oil and solvent evaporation. They are used as varnishes, floor finishes, and abrasion-resistant paints. They do not cure by a urethane reaction. In this category, the oil-based paint becomes a platform for using an aromatic polyurethane to enhance the former’s performance. (This is also done with acrylics and epoxies, but in those cases they are not referred to as ‘acrylics’ or ‘epoxies’ in the way varnishes and paints are called ‘polyurethanes.’) Looking at toxicity, they have no free isocyanate, which means they are no more toxic than other alkyds.

Type II: 1K moisture-cured paints and industrial coatings
This important type is often employed in high-performance thin film (i.e. 25 to 75-µm [1 to 3-mil]) floor and industrial paints. This class also includes higher-build (i.e. 0.5 to 2-mm [0.02 to 0.08-in.]) elastomerics such as those described in ASTM D6947/D6947M, Standard Specification for Liquid-applied Moisture-cured Polyurethane Coating Used in Spray Polyurethane Foam Roofing System. This class uses atmospheric moisture to act as the curative, allowing them to be reactive 1K products. This can cause problems and limitations along with advantages.

Unreacted isocyanates, such as those found in Type II urethanes, react with many other chemical species found in wood, metal, epoxies, and acrylics—this gives these resins exceptional adhesion. Moisture cures are often high in solids, relatively low in viscosity, and have moderate volatile organic compound (VOC) content. When they cure, however, they release a lot of carbon dioxide (CO2) gas. Consequently, Type IIs used in flooring and corrosion protection need to be applied thinly, so not too much gas is evolved from curing. Elastomerics have a lower concentration of isocyanate, allowing them to tolerate thicker films before they exhibit the same foaming problems.

The moisture cures require experienced contractors because bubbles, foaming, and blisters present high risks. Most of these Type II products are aromatic, which means they will yellow. ASTM D6947 moisture-cured coatings used in roofing are typically blended with asphalt. These sealants and coatings are not UV-stable, but when used for roof details and crack-bridging or caulk applications at thicknesses approaching 2 mm, they can weather for more than a decade.

Type III: 1K heat/oven-cured elastomers and industrial coatings
These elastomerics are generally not used as maintenance coatings. Instead, they are reserved for industrial products, car bumpers, or technical fabrics for sportswear.

Type IV: Two-package (2K) products
These materials are similar to the Type IIs; in fact, some may simply be a Type II product offered with a liquid curative. This eliminates the need to rely on atmospheric moisture to cure the resin, and it avoids the release of CO2 gas. They generally have higher solids content and moderate pot-life in the range of an hour. They are still prone to problems with CO2 gas when used carelessly.

As an example of diversity within polyurethanes, there is a Type IV industrial that uses a pure aliphatic resin cut in solvent and is cured as a polyurea—it achieves 34,475 kPa (5000 psi) tensile and 400 percent elongation, is easily sprayed, and has a two-hour pot-life. Further, as a polyurea, it is not affected by moisture at all.

Another case is a sub-group used in roofing and flooring: moisture-triggered (oxazolidine) cured aliphatic urethanes. They are described in ASTM D7311/D7311M-10, Standard Specification for Liquid-applied, Single-pack, Moisture-triggered, Aliphatic Polyurethane Roofing Membrane. This is another example of a specific urethane chemistry not prone to gassing even in thick films due to the special chemistry of the oxazolidine curative.

Type V: 2K urethanes
Important commercial products used in industrial applications (and to a lesser extent in roofing), these urethanes are typically used in a 1:1 volume ratio with plural component equipment.2

Most are 100-percent-solids elastomers or coatings. A sub-group, called ridged polyurethanes, is specifically devised for tank, pipe, and petrochemical use. Some have enough pot-life to be rolled or squeegeed, but most require plural component equipment, in-line heat, and will cure within minutes. Also within this group are the so called polyureas, which represent another approach of avoiding the issue of atmospheric moisture and CO2 gassing by using curatives that produce an almost instantaneous reaction. These require the use of an impingement mixing plural component spray gun. The reality is most polyureas are hybrids of both polyurea and polyurethane reactions and should be treated as another flavor of the Type V polyurethanes.3

Type VI: One-package solvent-based urethane lacquers
VOC restrictions have largely eliminated this type of polyurethane from commerce, but they may still be found in adhesive applications. (Water-based urethanes, or ‘urethane latex,’ could also be included here.) Often blended with acrylic emulsified resins, these are finding use in floor coatings, primers, and other high-performance and specialty applications.

There are a few words of caution related to the use of the term ‘urethane,’ which can be a marketing selling point. There are examples where a urethane material has been used to thicken an acrylic latex product, which is then illegitimately branded as a urethane. In other cases, a low level of a legitimate urethane resin may be added for marketing purposes. A urethane’s key properties—being flexible and tough—does not ‘play well’ with the high levels of fillers typically included in vinyl, styrene-acrylic, and acrylic paints. If a product has a high density (i.e. > 1.4 g/L [11.7 lb/gal]), then it is functionally not a urethane.

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For this underground concrete storage tank, a polyurethane able to resist alkaline patching materials was required.

For this underground concrete storage tank, a  polyurethane able to resist alkaline patching materials was required.

Form follows function: A primer on the chemistry
With so many different types of polyurethanes, a specifier has many factors to consider in selecting the right product for the job. The three key components to understanding what a polyurethane provides in terms of performance are:

  • isocyanate used;
  • curing chemistry; and
  • backbone.

For most specifiers, the best understood difference between types is aliphatic (highly UV-stable) versus aromatic (less UV-stable) urethanes, which is based on the type of ‘iso’ they have. The curing chemistry is generally recognized and understood in terms of application by the experienced contractor.

Less obvious is how the curing chemistry also has an impact on the film or membrane’s long-term performance. Most specifiers understand urethane varnish acts and bonds like a varnish. They know 2Ks and moisture cures tend to have good adhesion (due to unreacted isocyanate) and they know ‘polyureas’ require specific equipment and are not very moisture-sensitive. However, less visible to specifiers, is the ‘backbone.’

The backbone is the softer portion that forms a matrix around the urethane groups. The backbone is itself a polymer, and so it bring its own set of strengths and weaknesses. For example, if the backbone is not UV-stable, even an aliphatic urethane may not exhibit good weathering. This level of detail gets lost in technical data and specifications; it is rarely adequately captured by the test reports—and this is where things can go wrong.

While the list of materials shown in Figure 1 covers most products, it is not comprehensive—there are more than 300 potential combinations, and each could perform quite differently. Further, this list does not take into account the fact coatings are compounded products that allow blending of these materials in various ratios. Fortunately, a much smaller subset sees use as coatings.

Figure 2 lists polymer backbones representing at least 95 percent of the commercial volume of coatings and their typical application. Drilling down a little deeper, the resistance properties in Figure 3 make product selection clearer and more specific. For example, an aliphatic acrylic is a step above most polyester-based urethanes, and so they find use in automotive applications. Castor is a bit weak physically, but its water-resistance and low viscosity mean it can be used to good effect in a 100 percent solids adhesive.

Castor backbones can be found blended with other agents to achieve a lower VOC. This is significant because increasingly restrictive VOC rules favor materials inherently lower in viscosity. One hears more about polyethers, castor, aspartic esters, and polyetheramines (as polyureas) being used to meet VOC restrictions. Often, the backbones that require the most solvent are the toughest. Materials including polytetrahydrofuran (PTHF) and acrylic polyols are seeing less use. The material polycaprolactone, which once might have found use in a high-end roofing product, will now be used as a substitute for an acrylic in a less cost-sensitive industrial paint application as it moves up the VOC and cost ladder. Products are changing in response to regulation, and achieving lower VOC content is linked to changes in the backbone and curative chemistry.

For this reason, one should always specify with reference to the backbone. When a certain product worked as a low-build industrial finish for metal, and was an aliphatic acrylic, then “aliphatic with acrylic backbone” should be accordingly specified. It is important not to overlook referencing the material safety data sheet (MSDS) as a possible source for this information.

At the same time, a specifier will be forced to accept compromises to meet VOC restrictions; he or she must be careful about these inevitable substitutions.

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Urethanes in systems
Another area where urethanes excel is to serve roles within coating systems to meet specific challenges. A common roofing practice is to use an aromatic primer or base coat with an aliphatic top coat. These pairings can also be done with other properties.

Today, a manufacturer might use a primer based on aromatic isocyanate and castor that will have lower costs, reduced VOC content, and excellent corrosion resistance, and then pair it with an impact-resistant, aliphatic polyester top coat that meets a lower VOC rule—together, they cover the needs.

A traditional combination is to use an epoxy primer and an aliphatic urethane surface coat. This works because the epoxy primer typically has unreacted amines available to the isocyanate for reaction—a single molecule between the primer and surface coat. The point is these products work as a system, and substitutions that are not specific cannot be expected to perform the same.

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Specifications, testing, and what data sheets do not reveal
In the paint industry, there is little standardization and few requirements for third-party testing. In roofing, there are more specific protocols, but not many for polyurethanes. When looking at a technical data sheet, the reality is the values shown—for example, “250% elongation per ASTM D412”—may state a method, but are not well-defined and often lack sufficient context for the public bid process and apples-to-apples comparisons.

Although an ASTM test is cited, the values reported could have been derived in many ways and under different conditions. For example, manufacturers could run the same test methods under two conditions to get optimal values for tensile and elongation. This is not to suggest TDSs are all useless or deceptive, but if one were to compare products between manufacturers based on independent testing and technical data, the information may be nebulous. Third-party testing organizations tend to maintain a more consistent practice and should be requested.

The more accurate way to compare data is to reference a specific protocol. In roofing, these would be:

  • ASTM D6497, Standard Guide for Mechanical Attachment of Geomembrane to Penetrations or Structures;
  • ASTM D7311; or
  • ASTM WK9048, Elastomeric Coatings Used in Spray Polyurethane Foam Systems (the current designation for the new classification due to be published next year).

These material standards include specific test methods: they define how the test is run, how the sample is cured, how thick it is, and other parameters allowing the data to be used for commercial comparisons.

Another hard truth about testing is it is often not demanding. In many cases, procedures are run without comparison to some type of control or to unfavorable conditions; consequently, they are unlikely to be run until failure. For example, it is not unlikely for a urethane to sport a D412 tensile of 13.8 MPa (2000 psi). That same product tested after immersion in water for 28 days might only have a tensile of 2758 kPa (400 psi), but this would not be reported on the TDS. Unfortunately, the post-immersion tension value is the more appropriate one for a deck coating. Another product may note a 6895 kPa (1000 psi), but may have a 8274 kPa (1200 psi) after 28 days of immersion. In short, traditional paint testing does not predict service life.

Most troubling is how this data gets used in commerce. A bid may be lost for $0.20 on a basis of $30 per gallon, which is less than one percent of the total. This process rests on the assumption testing values are the most relevant factor, and they allow for direct comparison between different products. The tests are not nearly as precise as the accounting, and worse, the tests typically are not run in the same manner. If the product is only described as a ‘polyurethane,’ the chances are good one will be picking a product based on only the tensile value under ASTM D412, Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers.

There are many other important product attributes that need to be considered beyond this limited view—for example, ASTM D471, Standard Test Method for Rubber Property: Effect of Liquids, which tests the effects of water, is singularly useful. It is important to bear in mind any number without context is not necessarily good information and a low test value is not reason enough to reject a product with a long track record of performance. “Or equal” substitutions in specifications involving polyurethanes are intrinsically risky.

Construction specification documentation needs to be better for this group of products. Using the ASTM D412 test for tensile/elongation as an example, instead of accepting:

ASTM D412 > 23.8 N/mm (2000 psi)

one should call for:

ASTM D412 Tensile initial and after 1000 hours of ASTM D4798 weathering at 0.35 watts/m2 @340 nm.

Part of a material standard can be called out even when it does not quite fit, such as ASTM D6497. When the application is critical, a ratio—rather than a minimum value—should be specified. This example adds specific parameters to the test method, along with a ratio:

less that 30% loss of the original value when run per ASTM D-6497.

Another approach is the addition of a basic chemical description, such as:

aliphatic polyurethane using polyurea curative, IPDI and polyether chemistry per ASTM D6497.

Conclusion
Polyurethanes are a useful and necessary part of coatings technology, but they are often misunderstood—the confusion can ultimately lead to failures. Specifying a polyurethane by its backbone chemistry is the most important and necessary step to ensure the right product is being chosen for the job.

Before selecting a product, specifiers must ask themselves what does it really need to do, where do these products go wrong or how do they fail, and are the properties that play into these failures really reported?

Knowing which tests and standardized test methods, or ratios, to use for a specific application can provide the same benefit: a specification that links the track record and expected service life with the specific parameters required for the application. The best approach, however, is not a long list of random test methods, but rather specific testing protocols such as those cited in this article that give the type of comparable data needed for use in open bids.

Notes
1 ‘One-package’ (also written as 1K for ‘Kompent,’ the traditional abbreviation) means the entire product is a single can that does not require mixing in or another catalyst, agent, or Part B. (back to top)
2 The SSPC: The Society for Protective Coatings has information on the various types of Type V urethanes. Molded parts can even be made with these products. Search www.sspc.org for more data. (back to top)
3 Design professionals can learn about these products from the Polyurea Development Association (PDA). Visit www.pda-online.org. (back to top)

Steven Heinje is the technical service manager for Quest Construction Products, headquartered in Phoenix, Arizona. He has degrees in biology and chemistry, along with an MBA. Heinje has 30 years of experience in roof coatings, specializing in acrylic elastomers and urethane coatings. He is a vice president and board member of the Roof Coatings Manufacturers Association (RCMA), and leads several task groups in ASTM D08 roofing, as well as maintaining active memberships with American Society for Quality (ASQ), RCI, Reflective Roof Coatings Institute (RRCI), and the American Chemical Society (ACS). Heinje can be reached at heinje@quest-cp.com.

Solar Reflective Roof Coatings

Enhancing longevity and efficiency
by John Ferraro

A reflective acrylic coating was used to offer roof protection and yield energy savings at this Bank of India building in Mumbai, India.  Photo courtesy Quest Construction Products

A reflective acrylic coating was used to offer roof protection and yield energy savings at this Bank of India building in Mumbai, India.
Photo courtesy Quest Construction Products

Cool roof coatings have achieved more than 30 years of proven energy savings. However, the federal government and building code bodies have only recently embraced the use of these reflective coatings.

For decades, the Roof Coatings Manufacturers Association (RCMA), the national trade association for manufacturers of cold-applied protective roof coatings and cements, has promoted industrial and maintenance roof coatings, including solar reflective materials. Due to these efforts, there has been greater exposure to the value of coatings, as well as increased use.

The association’s Solar Reflective Coatings Council (SRCC) serves acrylic and elastomeric reflective coatings producers. The council has implemented a program that actively responds to targeted governmental and regulatory issues, researches technical matters and activities, and provides membership services and programs. The council focuses on promoting the use of solar reflective roof coatings by increasing awareness of the related environmental and economic benefits.

Solar reflective coatings benefits
Most solar reflective roof coatings consist of a binder—usually an organic polymer, bitumen, or inorganic polymer—blended with pigments (e.g. titanium dioxide or dispersed aluminum) and other additives to produce a durable exterior coating.

The resulting product can range from a white- or light-colored surface finish to an aluminized reflective surface. Solar reflective roof coatings protect roof membranes with a weather barrier that reflects sunlight, contributing to longer lifecycles through the reduction of the thermal shock stress associated with large temperature changes, while eliminating the intrusion of water and ultraviolet (UV) degradation. As a result, these coatings can extend the life expectancy of many different types of commercial roofing assemblies simply by reducing the high roof temperatures associated with exposure to the sun. Additionally, the reflection of solar radiation can result in lower air-conditioning costs for building owners.

Most building owners appreciate that reflective surfaces result in savings on cooling costs, but enhanced roof longevity is another major benefit resulting in significant savings. Without reflective surfaces, roof temperatures rise steeply in the hot summer months, and because insulation in the roof system prevents the heat from dissipating into the building, the roofing membrane temperatures can soar. This stress can reduce the roofing membrane’s long-term durability, increasing the chance a costly full-roof replacement will be needed much sooner.

Highly reflective roof restoration systems provide durability and energy savings and can be a sustainable solution for extending the life of an aged modified-bitumen (mod-bit) roof system.  Photo courtesy Tremco

Highly reflective roof restoration systems provide durability and energy savings and can be a sustainable solution for extending the life of an aged modified-bitumen (mod-bit) roof system.
Photo courtesy Tremco

Addressing air infiltration for condensation control
Any time a design fails to address how a roof limits or controls air movement, condensation becomes a concern, both for cool roofs and traditional black assemblies. Although this condensation potential may be increased when using a cool roof, research indicates with proper design considerations, condensation can be managed. (For more information, see Manfred Kehrer and Simon Pallin’s presentation, “Condensation Risk of Mechanically Attached Roof Systems in Cold-Climate Zones.”)

Additionally, the building owner needs to confirm the roof system is up to date with the local ventilation building codes before a project begins. Several steps can be taken, including taking infrared photos of the roof, to ensure moisture is not contained in the roofing system.

If air infiltration is addressed, cool roofs work effectively for the assembly’s lifetime in all climate zones. Based on RCMA member experience, there is little evidence to suggest significant problems with condensation in cool roof systems, including adhesively attached membranes, built up roofing (BUR) systems, and sprayed polyurethane foam (SPF) roof systems. Most studies of roof failures identify a host of design and installation problems that combine to cause moisture problems.

Some roofs, most notably mechanically attached ethylene propylene diene monomer (EPDM) membranes with loose-laid insulation, require the roof be a self-drying assembly. In these cases, a cool roof can be a significant design change to an existing roof. This issue can often be mitigated by limiting the roofs air gaps. RCMA recommends air-infiltration and past condensation issues be addressed when converting these assemblies into cool roofs.

Energy savings in northern climates
Both data and practical examples demonstrate the energy benefit of reflective roofing in northern climates. Many factors, including insulation and building design, contribute to a roofing system’s energy efficiency. Reflective roofs lower peak electrical demand during summer months, reducing the energy required to cool buildings, and decreasing the strain placed on the electrical grid during peak usage times.

In colder climates, many buildings have extra insulation built into the roof system in order to retain heat in the winter. However, this additional insulation can thermally isolate the roofing system during summer months, potentially trapping the heat build-up in a roof system and accelerating the aging process. Coating such insulated roof systems with reflective materials can provide building components with a longer service life. This is due to the coating’s ability to protect the roof from the elements, as well as its role in significantly reducing the heat load by reflecting much of the sun’s heat. A longer roof system life translates to a sustainable benefit in terms of reduced landfilling of discarded materials, and to decreased re-roofing costs for the building owner.

Sustainability benefits of roof coatings
Roof coatings, including reflective coatings, are part of the broader movement toward sustainability in the building industry. Various roof coatings can be used to prevent leaks and to extend the service life of a roof system, which reduces the amount of discarded roofing material sent to landfills.

Roof coatings not only sustain applicable in-place roof systems, but the use of periodic re-coats can also extend and protect roof life virtually indefinitely. This is important, considering roofing materials are one of the highest contributors to waste in landfills.

This white reflective coating contributes toward satisfying credits under Leadership in Energy and Environmental Design (LEED).  Photo courtesy Garland Co.

This white reflective coating contributes toward satisfying credits under Leadership in Energy and Environmental Design (LEED).
Photo courtesy Garland Co.

Cool roofs offer additional benefits in that they limit expansion and contraction cycles, reduce the roof assembly’s heat aging, and minimize the amount of energy expended on air-conditioning. One reason why solar reflective roof coatings are such an attractive option is they can be applied at nearly any point in the roof’s useful service life. Roof coatings and cool roofs are effective tools for increasing the sustainability of today’s roofing inventory in all climatic conditions.

Conclusion
Solar reflective roof coatings protect membranes, contribute to longer roof lifecycles, and reflect solar radiation that not only significantly lowers air-conditioning costs, but can also contribute to the improved comfort of the building occupant.

John Ferraro serves as the executive director of the Roof Coatings Manufacturers Association (RCMA), providing oversight, guidance, and strategic counsel to the board of directors. He also delivers operational management to numerous committees and task forces, including the Solar Reflective Coatings Council (SRCC). Ferraro earned a bachelor’s degree in political science and international affairs and a master’s in American politics and policy, both from Florida State University. He can be contacted by e-mail at jferraro@roofcoatings.org.

Reducing Environmental Impact with Coatings

Images courtesy Sto Corp.

Images courtesy Sto Corp.

by Rankin Jays, MBA

A quick review of the new 2012 International Building Code (IBC) is evidence enough the environmental lobby continues to grow. Broadly speaking, the new code requires more insulation, a tighter envelope, improved ducts, better windows, and more efficient lighting. As it becomes understood the planet cannot sustain the environmental impact associated with meeting a growing energy demand, energy conservation needs to improve.

However, the code is merely the minimum acceptable standard and it still leaves choices—especially the option to make a bigger individual contribution toward energy savings. The professional community recognizes the opportunity to influence these choices on an even larger scale. Architecture 2030—a non-profit, non-partisan, and independent organization—was established in response to the climate change crisis in 2002. According to the group:

Buildings are the major source of global demand for energy and materials that produce by-product greenhouse gases (GHG). Slowing the growth rate of GHG emissions and then reversing it is the key to addressing climate change.1

The U.S. Green Building Council (USGBC) launched Leadership in Energy and Environmental Design (LEED) in 1998 as a voluntary, market-driven program to recognize environmental stewardship and social responsibility in building design, construction, operations, and maintenance. The knock-on effect was to focus the building supply chain on the industry’s products, how they were made, efficiency, and where and how they were brought to market.

Buildings are the problem and buildings are the solution. Inadequate insulation and air leakage are leading causes of energy waste in most projects, and coatings selection can play a big role in energy saving opportunities.2

Cool roofs
According to the U.S. Department of Energy (DOE), cool roofing is the fastest growing sector of the building industry, as owners and facility managers realize the immediate and long-term benefits of roofs that stay cool in the sun.3 The Oak Ridge National Library (ORNL) have explored the energy efficiency, cost-effectiveness, and sustainability of cool roofs and have developed a calculator that computes the reduction in energy consumption by substituting a cool roof for a conventional roof. Cool roofs can create a cooler interior space in buildings without air-conditioning, making occupants more comfortable, reducing carbon emissions by lowering the need for fossil-fuel generated electricity to run air-conditioners, and potentially slowing global warming by cooling the atmosphere.4

Cooler building surface temperatures reduce energy demand.

Cooler building surface temperatures reduce energy demand.

Cool (i.e. white) flat roofs have been a requirement in California since 2005, while it has been relatively easy to get building owners to adopt this it was not without incentives such as federal tax credits for approved roofing systems.5 The cool roof requirement was extended to include sloped roofs in certain Climate Zones in 2009 as part of the California’s Title 24, Building Energy Efficiency Standards. Further, roofing systems meeting LEED’s Solar Reflectance Index (SRI) criteria could qualify for LEED-New Construction (NC) v2.2 Sustainable Sites (SS) credit 7.2, Heat Island Effect–Roof.

If you are installing a new roof or reroofing an existing building, a systems approach to providing an energy-efficient roof should be taken with a cool roof considered.

Simply put, traditional dark-colored roofing materials strongly absorb sunlight, making them warm in the sun and heating the building. White or special ‘cool color’ roofs absorb less sunlight, staying cooler in the sun and transmitting less heat into the building. This reduces the need for cooling energy if the building is air-conditioned, or lowers the inside air temperature if the building is not cooled.

Steven Chu, PhD, has been talking about the benefits of white roofs since being appointed as U.S. Secretary of Energy. In 2010, he mandated all new roofs on Energy Department buildings be either white or reflective. In a statement, he noted the cooling effect white roofs have on buildings, especially air-conditioned ones, as well as their ability to drastically lower energy costs—an estimated $735 million per year, if 85 percent of all air-conditioned buildings in the country had white roofs.

“Cool roofs are one of the quickest and lowest cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change,” Chu said.

White roofs can also reduce the urban heat island effect. This is a phenomenon caused by all the dark, heat-absorbing surfaces in urban areas. A study by the Lawrence Berkeley National Laboratory’s (LBNL’s) Heat Island Group6 showed increasing the reflectivity of road and roof surfaces in urban areas with populations of more than one million would reduce global carbon dioxide (CO2) emissions by 1.2 gigatons annually—the equivalent of taking 300 million cars off the road.7

IR-reflective pigment coatings
Infrared (IR) reflective pigment technology in coatings were first used more than 30 years ago, although full commercialization has only been quite recent.8 The technology and entry costs are relatively lower now than in the past, but the manufacturing process and quality control remains specialized within the scope of only a small number of manufacturers.

Combining the IR reflective pigmentation with the performance of current polymer coatings technology can produce a long-lasting coating offering significant energy-saving potential along with numerous other benefits. The higher solar reflectance increases the coating lifecycle by reducing thermal expansion and contraction of the substrate. The cooler surface temperature reduces polymer degradation within the paint film; reduced energy demand carries the obvious economic and environmental advantages. Additionally, they also make a positive contribution toward the reduction of the urban heat island effect.

The primary purpose of IR-reflective coatings is to keep objects cooler than they would be using standard pigments. These coatings can reduce the heat penetrating the building though the roof and exterior walls, lowering the load on the air-conditioning system and thereby increasing a building’s energy efficiency. An overview of the basics behind this technology is described on the Eco Evaluator website, stating:

These thermally emissive/reflective coatings offer a range of applications such as on roofs and walls of buildings. These coatings will adhere to a variety of materials such as composite roof shingles, metal roofs, and concrete tile roofs as well as stucco, plywood, and concrete block walls. When considering thermally emissive/reflective cool coatings be sure to look for metal oxide and infra-red emissive pigments. These ingredients are necessary to block ultra violet rays and reflect infrared radiation.9

Infrared (IR) reflective coatings are gaining in popularity as exterior design incorporates more vibrant and saturated colors.

Infrared (IR) reflective coatings are gaining in popularity as exterior design incorporates more vibrant and saturated colors.

In 2005, ORNL produced a lengthy study on the efficacy of IR reflective exterior wall coatings and found they can offer up to 22 percent savings on cooling energy costs when compared to a regular architectural coating of the same color. Overall effectiveness depends on the darkness of the coating color and how exposed the surfaces are to direct sunlight.

Radiant heat barriers
Passing on the whole exterior repaint is an option—a radiant heat barrier in the attic space, primarily designed to reduce summer heat gain and decrease cooling costs, can be considered. The barrier consists of a highly reflective material that ‘bounces’ radiant heat and reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic, such as air-conditioning ducts.10

Air barriers
A report from the National Institute of Standards and Technology (NIST), “Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use,” confirms continuous air barrier systems can reduce air leakage by up to 83 percent and energy consumption for heating and cooling by up to 40 percent.

In new construction where we may have been accustomed to seeing a building ‘wrap,’ air barriers are now commonly fluid-applied air and moisture barriers, providing a continuous and fully adhered membrane across the sheathing’s entire surface with obvious durability advantages gained from having a chemical and mechanical bond between the air barrier and the substrate.

Liquid technology also allows for faster, easier application of the air barrier and reduces the risk of improper installation as they are spray-, brush-, or roller-applied to the surface. The exception would be where mesh, fabric, or transition products are embedded and sealed within the fluid applied products.

As building codes continue to evolve with an emphasis on energy efficiency and sustainability, the value of air barriers is becoming much more apparent. In fact, research has proven air barriers actually play a larger role in energy efficiency than exterior continuous insulation.11

V

This image shows a spray application of a vapor permeable fluid applied membrane.

Niche or not?
With the exception of cool roof coatings, why have the rest of these technologies not amounted to much more than niche products? There is perhaps a large amount of skepticism following early entrants in the market that made outlandish claims of paint’s insulating qualities that were revealed as scams.

For skeptics out there, look no further than the stripes on a zebra for a lesson on reducing radiant heat. The black and white pattern on these animals can reduce the animal’s surface skin temperature by 8 C (17 F). The temperature differences over the black and white stripes result in differential air pressure, which produces minute air currents that cool the surface.

As an example of biomimicry of this natural phenomenon, the concept was commercialized by Daiwa House in Japan where the interplay of black and white on the façade reduced the summer indoor air temperature by 4.4 C (8 F).

It should be noted, cool roof and IR coatings will only have an impact where cooling costs are higher than heating costs. In higher/cooler latitudes there could be a heating cost penalty during the winter as a result of using these coatings. Following the zebra’s example they are only provided with an insulating layer of fat beneath their black stripes since the tissue below the reflective white stripes does not need it.

Conclusion
Coatings are in no way meant to replace insulation, but they can make an effective contribution in reducing the downstream environmental impact by reducing energy usage. With new coatings in the market, and more coming in every day, these products are contributing to energy savings and reducing energy dependency.

Notes
1 Visit www.architecture2030.org/2030_challenge/the_2030_challenge. (back to top)
2 Visit www.ornl.gov/sci/roofs+walls/insulation/ins_01.html, Department of Energy. (back to top)
3 For more on cool roofing, see “Rethinking Cool Roofing: Evaluating Effectiveness of White Roofs in Northern Climates” by Craig A. Tyler, AIA, CSI, CDT, LEED AP, in the November 2013 issue. (back to top)
4 Visit www1.eere.energy.gov/buildings/pdfs/cool_roof_fact_sheet.pdf. (back to top)
5 Visit www.energy.ca.gov/2008publications/CEC-999-2008-031/CEC-999-2008-031.pdf. (back to top)
6 For more, see Lawrence Berkley National Laboratory 2009, Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets. (back to top)
7 Visit inhabitat.com/having-white-roofs-would-save-the-u-s-735-million-per-year/. (back to top)
8 For more on IRCCs, see our web-exclusive article, “Reflecting on the Versatility of IRCCS,” by Lynn Walters at www.constructionspecifier.com. (back to top)
9 Visit www.ecoevaluator.com/building/energy-efficiency/heat-reflective-paints.html. (back to top)
10 Visit www.ornl.gov/sci/ees/etsd/btric/RadiantBarrier/. There is a great fact sheet from Oak Ridge National Laboratory with more information on radiant heat barriers. (back to top)
11 See, NISTIR 7238, “Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use.” (back to top)

Rankin Jays is a product manager (coatings) for Sto Corp. He joined the company this year to oversee the coatings product line, introducing new products such as architectural coatings. Jays’ experience with coatings goes back nearly 30 years, starting as a paint maker while at Victoria University in New Zealand. He received his MBA from Massey University. Jays can be contacted by e-mail at rjays@stocorp.com.

Putting a Fresh Face on Historical Façades: Project teams

Hallidie Building Project Team
Owners: Edward J. Conner and Herbert P. McLaughlin
Owner’s Representative: The Albert Group Inc.
Architect of Record: McGinnis Chen Associates
Preservation Architect: Page & Turnbull Inc.
General Contractor: Cannon Constructors
Surface Preparation Shop Coatings and Field Applicator: Abrasive Blasting & Coating (ABC) Inc.
Specialty Engineering and Testing: Professional Service Industries Inc.
Coating Consultants: Amos and Associates

ZCMI Project Team
Owner: City Creek Reserve Inc.
Engineer, Surface Preparation, and Primer: Historical Arts & Casting Inc.
Architect: Hobbs & Black
General Contractor: Jacobsen Construction Company Inc.
Field Applicator: Daniels Painting
Coating Consultants: Protective Coatings Intermountain Inc.
Miami County Courthouse Project Team

Owner: Miami County
Architect: John Ruetschle Associates Inc.
Engineer: Historical Arts & Casting Inc.
Construction Management Team: Cast Iron Restoration Management
General Contractor: Shook Construction Company
Shop Applicator: Brian Painting Company
Field Applicator: E.B. Miller Company
Coating Consultants: Ohio Coating Consultants

To read the full article, click here.

Putting a Fresh Face on Historical Façades

Photo courtesy Robert A. Baird/Historical Arts & Casting Inc.

Photo courtesy Robert A. Baird/Historical Arts & Casting Inc.

by Jennifer Gleisberg

Across the country, communities are preserving and restoring historically significant architectural façades recognized for ornamental sheet metal and cast-iron features such as colonnades, domed roofs, cornice sections, dentil blocks, frieze panels, and pendants. Many historical façades dating back to the second half of the 19th century have been neglected and damaged from impacts, moisture intrusion, corrosion, or flawed castings.1

Water intrusion resulting from the absence or failure of adequate waterproofing systems often leads to deterioration of not only the structural steel, but also the clips, brackets, and fasteners used to attach ornamental components. Fissures, or pitting in cast iron or other decorative metal pieces, can also trap moisture and airborne corrosive materials, causing oxidation or rust to occur over time.

Restoring these landmarks to like-new condition requires craftsmanship, technical expertise, and high-performance coating systems that comply with demanding standards for aesthetics, durability, and resistance to corrosion and ultraviolet (UV) light.2 This marriage of skill and technology is especially evident in the three projects highlighted in this article:

  • San Francisco’s Hallidie Building;
  • Zions Cooperative Mercantile Institution (ZCMI) cast-iron storefront in Salt Lake City, Utah; and
  • the cast-iron domed roof façade of the Miami County Courthouse in Troy, Ohio.

The Hallidie Building’s curtain wall
After 2.5 years of remediation work, the iconic Hallidie Building’s main façade was complete. Architects involved with the project were McGinnis Chen Associates and preservation architects, Page & Turnbull. Additional specialists involved with the restoration included a materials scientist, sculptor, testing agency, structural engineers, curtain wall consultant, and coatings consultant.3

Named for Andrew S. Hallidie, the inventor of the cable car and a regent at the University of California, the building was listed in 1971 on the National Registry of Historic Places and the San Francisco Historic Landmarks and Districts. Originally designed by Willis Polk and constructed in 1917–1918 by the University of California, the building is noted for its glass curtain wall façade, which was considered unique for its time, but has now become a common element in modern architecture.4

The building is described in San Francisco: Building the Dream City, in the following passage:

The glass façade was hung, curtain like, away from the actual structural frame of the building, in a separate frame of elaborate cast iron, with ornate fire escapes at either side. The ornamental iron fretwork relieves the cold severity of an all-glass wall, and the result is highly decorative.5

Annie K. Lo, LEED AP, project manager for McGinnis Chen Associates, was responsible for evaluating, labeling, photographing, and documenting each piece of the building’s curtain wall, frieze panels, ornamental balconies, and fire escapes. She explained the uniqueness of the glazed curtain wall at the time of construction is significant. Considering available technology in 1918, Polk was inventing something, rather than using an example to model after.6

Numerous challenges were encountered with the Hallidie Building’s water-damaged structural steel, corroded frieze panels of stamped zinc, and ornamental fire escapes and balconies. At the time of construction, sealants or flashing with adequate waterproofing were not available. Also, the design did not support metal expansion and contraction normally required in a curtain wall.

Phase I of the restoration involved removal, repair, and reinstallation of approximately 735 sheet metal and railing components for the ornamental balconies and fire escapes, along with 360 windows around the perimeter of the curtain wall façade. Phase II of the project, completed April, involved the removal, repair, and reinstallation of the remaining 153 windows in the curtain wall.

For the project team, getting to Phase I was a challenge, explained Lo.

“We started working with the city and the Historic Preservation Commission on obtaining approvals to remove the metal pieces since this was a salvage and disassembly project for a notable landmark building,” she said. “Each piece had to be tagged and given an identification number so it could be tracked throughout the repair process and reinstalled on the building.”

Originally, the project’s architects envisioned restoring the frieze panels by making spot repairs to severely corroded sections. This repair methodology was changed after the existing lead coatings were removed and the severity of damage to the panels was determined. The back side of the panels was reinforced with a spray-applied layer of fiberglass, which enabled more of the original historic material to be salvaged.

More than 90 years of exposure to water caused damage to the structural steel and decorative metal of the Hallidie Building façade. Photos courtesy Annie K. Lo/ McGinnis Chen Associates

More than 90 years of exposure to water caused damage to the structural steel and decorative metal of the Hallidie Building façade. Photos courtesy Annie K. Lo/ McGinnis Chen Associates

Another change involved the method used by the coating applicator to remove the multiple layers of lead paint that had built up over decades. Early in the project, it was envisioned the paint would be removed by dipping pieces into a chemical stripping solution. However, this method proved too slow and did not provide the cleaning needed to apply a zinc-rich, aromatic urethane primer.

Due to the fragile and thin condition of ornamental cornice sections, dentil blocks, frieze panels, and pendants, these components were prepared in accordance with Society for Protective Coatings/NACE International–The Corrosion Society (SSPC-SP6/NACE) No. 3, Commercial Blast Cleaning, prior to the application of the primer. Window frames, window sashes, metal grates, and railing sections were prepared in accordance with SSPC-SP10/NACE No. 2, Near White Blast Cleaning, before priming with the same zinc-rich coating.

Structural steel used to support the ornamental balconies was so badly corroded from water infiltration it could not be salvaged or reused and had to be completely replaced.

Removal of ornamental metal was carefully monitored for compliance with environmental regulations, in accordance with Section 02085, Federal and State Occupational Health and Safety Administration (FED-OSHA) 29 Code of Federal Regulations (CFR) 1019, 1025, and California-OSHA under Title 8, CCR 1532.1, which relates to the proper capture and disposal of lead-based paint.

All surface preparation and paint removal was performed in blasting chambers offsite. The exterior coating system for both ornamental metal and structural steel consisted of a spray-applied zinc-rich primer, an aliphatic urethane intermediate coat, and a fluoropolymer topcoat in both satin and semi-gloss finishes.

The coating system was selected to achieve the highest level of performance in terms of color retention and longevity. Keeping the associated costs in mind, the durability and lifespan of the coating system was an important concern. A zinc-rich primer offering a high level of corrosion protection on bare metal was specified for the project. When this is applied with a proper intermediate coat, additional corrosion protection is attained.

Fluoropolymer topcoats offer aesthetic performance, gloss retention, and protection against UV light and climate conditions. The coatings were custom-matched to the building’s original colors. The project’s preservation architectural firm conducted a coating analysis that involved scraping down to the original first and second coatings and matching them to a Munsell color card, which was then provided to the coatings manufacturer.

Blue and gold were the original colors used on the building and the coatings created through the color match were accurate. Originally, a gold coating resembling true gold leaf was used on ornamental sheet metal and designers were able to replicate this. Once the ornamental metal pieces were reinstalled onto the curtain wall, coatings were used to touch-up welds and scratches.

Early this year, the Hallidie Building project was named winner of the Charles G. Munger Award at the annual Structure Awards sponsored by the SSPC. The award is presented to an outstanding industrial or commercial coatings project demonstrating longevity.7

This is the Hallidie Building before its architectural façade restoration.

This is the Hallidie Building before its architectural façade restoration.

The Hallidie Building is one of the world’s first glass curtain-wall buildings. Photo © Sherman Takata, Takata Photography

The Hallidie Building is one of the world’s first glass curtain-wall buildings. Photo © Sherman Takata, Takata Photography

Restoring the ZCMI façade
Recognized as one of the earliest department stores in the nation, Zions Cooperative Mercantile Institution was founded by Brigham Young in 1868. The structure’s three-story, classical cast-iron façade was constructed in three separate phases, beginning with its center section in 1876, followed by an extension to the south in 1880, and a north addition in 1901. The façade was placed on the National Register of Historic Places in 1970 and was subsequently listed on Salt Lake City’s historic register.8

Cast-iron façades were popularized throughout the second half of the 19th century due to their fire-resistant properties and ability to replicate sandstone and limestone. In addition to providing structural support to upper floors, cast iron also allowed large display windows for merchandise, allowing light into the building’s interior.9

In 1971, plans for a new downtown mall had called for demolition of the original building, including its cast-iron façade. A coalition of the Utah Heritage Foundation and community preservationists was successful in saving and restoring the façade to become part of the ZCMI Center Mall. Restoration architect Steven T. Baird was enlisted to develop procedures for dismantling, reconditioning, and reconstructing the façade from 1974 to 1976. Working primarily out of his garage, Baird is credited with creating the model for other cast iron renovation efforts across the country.10

The 23 x 43-mm (75 x 140-ft) ZCMI façade is now attached to the west face of Salt Lake City’s new Macy’s department store. [CREDIT] Photo courtesy Robert A. Baird/Historical Arts & Casting Inc.

The 23 x 43-mm (75 x 140-ft) ZCMI façade is now attached to the west face of Salt Lake City’s new Macy’s department store. Photos courtesy Robert A. Baird/Historical Arts & Casting Inc.

More than three decades later, the company owned and operated by Baird’s sons—Historical Arts and Casting Inc.—was commissioned to restore the façade a second time as part of the mixed-use redevelopment project. Today, the landmark façade fronts the west face of Salt Lake City’s new Macy’s department store.11

Measuring 23 x 42 m (75 x 140 ft), the façade consists of cast-iron colonnades with 63 bays for windows and openings, a cornice section made of galvanized sheet metal, and thousands of mechanically fastened ornate castings. For both restoration projects, each component was carefully numbered, cataloged, and moved offsite for reconditioning or replacement.

Restoring historical cast-iron façades like ZCMI presents major challenges. Cast iron’s ability to replicate stone was enhanced by mixing sand into paint, which was then applied in thick coats to the casting. Locating fasteners under several layers of old paint was a challenge during the first restoration in the 1970s. Additionally, many of the façade’s original cast-iron components were severely deteriorated due to moisture penetration and had to be recast.12

The preferred method for removing old paint from cast iron is blast-cleaning in accordance with SSPC-SP6/NACE No. 3, followed immediately by the application of a primer to prevent surface rust. Since most old paint found on historic cast-iron façades contains lead, blasting debris must be captured and disposed of in accordance with U.S. Environmental Protection Agency (EPA) regulations (e.g. 40 CFR Subchapter 1, “Solid Wastes.”13

When surface preparation uncovered pitting or other imperfections in the cast iron, a surfacing epoxy to recondition the surface, followed by zinc-rich aromatic urethane, and intermediate epoxy primers that doubled as a field-applied tie coat, were used. Structural steel used to secure cast-iron components to the building was blast-cleaned and primed by the fabricator with a zinc-rich aromatic urethane primer.

The façade’s galvanized-metal sections were prepared in accordance with SSPC-SP1, Solvent Cleaning. Abrasive blasting was originally tried, but the sheet metal was too thin; therefore a chemical stripper on the metal was used and it was then pressure-washed.

The cornice sections were shop-primed with a polyamide epoxy coating, followed by a finish coat of high-solids fluoropolymer coating specified for its ultraviolet (UV) light stability and durability. Four custom colors were specified, including a metallic gold that mimicked 24-karat gold leafing. An acrylic polyurethane metallic clearcoat was applied over the metallic gold finish wherever it was used.

The cast-iron façade on Zions Cooperative Mercantile Institution (ZCMI) consists of thousands of ornamental components assembled together on columns.

The cast-iron façade on Zions Cooperative Mercantile Institution (ZCMI) consists of thousands of ornamental components assembled together on columns.

During reassembly and the application of field coatings the façade was surrounded by scaffolding and enclosed to help control environmental conditions. Tie-coats, fluoropolymer finish coats, and gold accent finishes were brush-, roller-, and spray-applied to the cast-iron colonnades and ornate castings then reattached to the façade by screws using detailed drawings as a guide.

Approximately 2300 work hours and 1892 L (500 gal) of coatings were needed to complete the field coatings and installation, which was completed in the spring of 2012.14

Bringing order to the Miami County Courthouse
The decorative exterior of the Miami County Courthouse in Ohio, constructed between 1885 and 1888, was also restored. The original Greco-Roman design by Joseph Warren Yost featured four corner domes, a central dome, and four pavilions built of cast-iron cladding over riveted iron frameworks.15

After nearly a century, the building’s decorative cast iron had severely corroded due to water intrusion, which threatened the building’s interior courtrooms that had been renovated in 1982. In 1989, an architectural firm was contracted to conduct a condition survey that included a preliminary specification for what would eventually become the largest restoration of cast-iron construction in the country.16

In 1995, the county retained a construction management team to oversee the project. The following year, a local construction company was awarded the primary restoration contract, which called for dismantling and restoring the cast iron from the building’s five domes and four pavilions. The contract also called for replacement of the building’s slate roof, copper flashing, windows, exterior lighting, copper statues, and clock tower.

Before cast-iron components could be removed, more than 18,143 kg (40,000 lb) of pigeon waste and other debris was taken from the belfry. The disposal of this material followed the same guidelines as removal of asbestos or lead. 17, 18

Rather than prepare the cast iron for recoating onsite, it was prepared, primed, and given an intermediate coat offsite. Once the material was returned and reinstalled, the field touch-up and finish coats were applied.

Coating consultant Dan Haines compared the removal of cast-iron components to “an architectural dig”—each piece of the cladding was cataloged using a numerical coding system identifying the exact location it needed to be reinstalled.

Crews worked from scaffolding and used an exterior elevator lift to move more than 15,000 cast-iron pieces, which were dismantled and taken offsite in phases to be reconditioned or replaced. Historical Arts and Casting was responsible for recasting more than 50 percent of the severely corroded cast iron, requiring more than 700 patterns to be manufactured.19

It was determined a lack of sufficient waterproofing led to the failure of the decorative cast iron on the courthouse, so replacement pieces were molded with flanges and lap joints enabling moisture to run off rather than collect on the surface. Vertical and horizontal joints were caulked with a silicone system to prevent water penetration and adhesion testing was conducted to verify the coating system’s ability to bond to the prepared cast-iron components.20

Both replacement parts and reusable cast-iron components ranging in weight were prepared in accordance with SSPC-SP6/NACE No. 3, Commercial Blast Cleaning, and shop-primed with a zinc-rich aromatic urethane primer. They also received a shop-applied intermediate coat of polyamide epoxy coating.

Structural iron was cleaned and field-coated with a high-build modified polyamidoamine epoxy coating. Once the shop-primed cast-iron cladding was reinstalled, it received a field-applied coat of a light gray aliphatic acrylic polyurethane topcoat, followed by a urethane clear coat. 21

Cast-iron cladding that covered the domes and pavilions of the Miami County Courthouse was dismantled and removed to an offsite location for restoration or replacement and recoating. [CREDIT] Photo © Mike Ullery

Cast-iron cladding that covered the domes and pavilions of the Miami County Courthouse was dismantled and removed to an offsite location for restoration or replacement and recoating. Photos © Mike Ullery

Built in 1888, the Miami County Courthouse was listed on the National Register of Historic Places in 1975.

Built in 1888, the Miami County Courthouse was listed on the National Register of Historic Places in 1975.

 

 

 

 

 

 

 

 

 

 

 

 

Conclusion
The restoration and preservation of historically significant sheet metal and cast-iron façades requires the special skills and expertise of craftsmen and professionals who share an understanding and appreciation of these architectural treasures. These specialists spend countless hours assessing the condition of structural and ornamental metalwork, dismantling components, removing old coatings, and restoring or replacing thousands of individual pieces. Given the exhaustive amount of work and care involved with restoring these national landmarks, specifiers must rely on high-performance coating systems that offer long-term substrate aesthetics and protection against corrosion caused by moisture intrusion, UV light, and thermal cycling.

Notes
1 The resource is written by J. Waite, AIA, with an introduction by cast-iron preservationist Margot Gayle. See, Preservation Briefs, “The Maintenance and Repair of Architectural Cast Iron,” 1991, Technical Preservation Services, National Park Service at www.cr.nps.gov/hps/tps/briefs/brief27.htm. (back to top)
2 Important standards include ASTM D4060, Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser; ASTM D4141, Standard Practice for Conducting Black Box and Solar Concentrating Exposures of Coatings; ASTM D4587, Standard Practice for Fluorescent UV-Condensation Exposures of Coatings; and ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus.  (back to top)
3 For more, visit American Institute of Architects (AIA), San Francisco Chapter’s website at www.aiasf.org/about/history/hallidie-renovation/. (back to top)
4 For more, see Business Wire’s news release, “San Francisco’s Urban Design Community Celebrates Restored Hallidie Building” at www.businesswire.com/news/home/20130501006221/en/San-Francisco%E2%80%99s-Urban-Design-Community-Celebrates-Restored. (back to top)
5 See J.B. Alexander’s, San Francisco: Building the Dream City (Scottwall Associates, 2002). (back to top)
6 This comes from an interview with Lo in April 2013. (back to top)
7 Visit, Durability + Design’s article, “Curtain Wall Project Earns Accolades,” at www.durabilityanddesign.com/news/?fuseaction=view&id=9002. (back to top)
8 Visit www.downtownrising.com/DTR-media/city-creek/downloads/ZCMI_Facade_Fact_Sheet.pdf. (back to top)
9 See Note 1. (back to top)
10 See Salt Lake Magazine’s article, “Restoration 2.0,” by J. Pugh. Visit www.saltlakemagazine.com/blog/2012/01/12/restoration-20/. Historical Arts and Casting also has a video, ZCMI A Legacy Cast in Iron. (back to top)
11 For more, see City Creek Reserve’s news release, A Familiar Face Returns to Main Street: ZCMI Façade is Back at www.downtownrising.com/DTR-media/city-creek/downloads/ZCMI_Facade_Release.pdf. (back to top)
12 This is from an interview with R. Baird in April 2013. An interview was also conducted with M. Call in February 2012. (back to top)
13 For more, see R. Baird and Historical Arts and Casting’s “Restoring Cast Iron Facades (Part 1),” at www.historicalarts.net/restoring-cast-iron-facades-part-1-of-2/. (back to top)
14 This is also from an interview conducted by the author with M. Call in February 2012. (back to top)
15 For more see R. Baird and Historical Arts and Casting’s “The Rebirth of A Cast Iron Gem (Part 1).” (back to top)
16 See Note 15. (back to top)
17 For more see R. Baird and Historical Arts and Casting’s “The Rebirth of A Cast Iron Gem (Part 2). (back to top)
18 This is from an interview conducted with D. Haines in April 2013. (back to top)
19 See Note 17. (back to top)
20 See Note 17. (back to top)
21 See Note 18. (back to top)

Jennifer Gleisberg is an architectural sales coordinator for Tnemec Company Inc., where she provides support for sales and marketing of protective coatings for concrete, steel, concrete masonry unit (CMU), dry wall, and decorative cast iron and sheet metal substrates used on historical landmarks. She is an active member, or has received credentials, from NACE (NACE Coatings Inspector – Level I Certified), The Society of Protective Coatings (SSPC), and the United States Green Building Council (USGBC), where she is a Leadership in Energy and Environmental Design (LEED) Green Associate (GA). With more than 10 years of experience in the coatings industry, Gleisberg brings a customer service perspective to architectural projects that require coating solutions for lasting aesthetics, as well as protection from corrosion, impact and abrasion. She can be contacted at gleisberg@tnemec.com.

To read the sidebars about the project teams, click here.