CoatingsPro Magazine

JUL 2018

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 42 of 68

42 JULY 2018 COATINGSPROMAG.COM Science Behind It Protective Coatings for Spray Foam Roof Systems By Rick Duncan, Technical Director of SPFA S pray polyurethane foam (SPF) roofing systems offer a continuous, air-sealing layer of insulation adhered to the roof deck. SPF roof systems are self-flashing and can help to promote positive water drainage, but the foam's chemistry requires that it be protected with a coating. What Is SPF? SPF, also referred to as spray foam, is a fluid-applied insula- tion material that is made by the chemical reaction between two components: an A side and a B side or resin. Typically, the SPF used for roofing has a density between 2.5 and 4.0 lbs./ft.³ (40.0 kg/m³ and 64.1 kg/m³). e roofing foam is denser than the polyurethane foam used as building insula- tion because it needs to provide the compressive strength to withstand routine foot traffic and also vegetative rooftops, as in the case of Foam Tight Roofing & Coatings, Inc./BN Contracting, LLC on the Public Service Electric and Gas (PSE&G) project. ASTM International, under ASTM C1029: Standard Specification for Spray-Applied Rigid Cellular Polyurethane ermal Insulation (Type III and IV) and ASTM D7425/ D7425M: Standard Specification for Spray Polyurethane Foam Used for Roofing Applications (Type I and II), define the perfor- mance requirements for closed-cell foam used in SPF roofing applications in particular. The Importance of Elastomeric Coatings e application of SPF to the roof deck or exiting roofing provides water resistance for the SPF roofing systems, but a covering, such as an elastomeric coating, is required to shield the SPF from harmful ultraviolet (UV) light and other weath- ering processes, which will degrade SPF. W hen exposed to UV rays from sunlight, the SPF surface will turn from a light cream color to a dark tan or brown within a few weeks or months. is discoloration is actually UV damage that is limited to the foam layer near the exposed surface. Water resistance and durability of the SPF roofing system would be reduced if not protected. In addition to protecting the polyurethane foam from weathering processes, the coating can be used to inhibit moisture transmission, resist impact, provide chemical resistance, protect against mechanical damage and abrasion, decrease slipping hazards, improve aesthetics, reflect heat (e.g., cool-roof coatings), and help to provide code-compliant fire resistance. e choice of coating depends on several factors, including building use, contractor experience, and local weather conditions (e.g., ambient temperature ranges, hail, ice, solar exposure, and wind). e Spray Polyurethane Foam A lliance (SPFA) recog- nizes five generic types of coatings for the protection of the SPF roofing system in SPFA-102: • Acrylic • Butyl Rubber • Silicone • Polyurethane • Polyurea Maintenance and Inspection PSE&G's SPF roofing system, as with all SPF roofing systems, can last the lifetime of the building if properly maintained. ere were numerous SPF roofs installed in the late 1960s to 1980s that are still in service today. Longevity of SPF roof systems begins with regular inspection and maintenance of the roof coatings. Because the SPF system needed to be coated, the coating also needs to be included in the inspection and maintenance plan. Most elastomeric coatings used to cover SPF on a roof will last 10‒20 years before re-coating is needed; however, non-vegetated SPF roofs should be regularly cleaned and inspected on an annual basis and immediately after any severe weather event where roof damage from hail or airborne debris can occur. Any damage to the SPF/coating system should be repaired as soon as possible to prevent degradation of the SPF system. In general, with the right system in place, SPF can offer a continuous, air-sealing layer of insulation for the roof. CP

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