Nebraska Insulation and Roofing Articles and Brochures

Application Guidelines and Solutions

It is valuable to note that closed-cell spray foam (ccSPF) roofing systems can address numerous challenging conditions associated with metal building and roof assemblies. All roof installations are quality inspected by the manufacturer or accredited third party before the warranty is issued. The following is a partial list of those items and the solutions offered by the use of ccSPF roofing systems:

1. Movement due to thermal shock expansion and contraction. Metal expands and contracts with varying ambient temperatures, causing fasteners to wear and pull out, flashing to delaminate and separate, metal panels to separate, and welds to break loose — which can cause roofs to start leaking. Serious water damage and loss of structural integrity can be the result.
   Installed in a roofing system, ccSPF eliminates thermally induced movement by providing a continuous layer of a highly effective insulation above the roof deck. Metal is an effective heat conductor. Lawrence Berkeley National Laboratories has measured dark-colored roof substrates up to 190°F (87.8° C) on a 95° F (35° C) day, and up to 160° F (71.1° C) on a dark, gray-colored surface (the color of most metal roofs). In addition, research conducted by Dr. Mark Bomberg of Syracuse University demonstrates that the application of a seamless, continuous insulation on top of the metal roof deck and metal framing members reduces the temperature differential between the roof metal deck and the interior temperatures. This, in effect, “puts the roof to sleep,” minimizing thermal expansion and contraction caused by varying temperature.
2. Condensation. Metal is a good conductor and will promote condensation if the exterior climate and interior climate collide on the metal surface, creating dew point conditions. Proper installation and use of vapor retarders, continuous insulation, and effective air barriers can help prevent condensation. In practice, however, the many angles, tight corners, irregular surfaces, cracks, and crevices on a typical roof can make it difficult to install these climate-control measures properly. Poorly insulated and poorly sealed metal buildings will experience a significant amount of sweating, especially if the buildings are climate-controlled. The moisture condensation can cause water damage to the interior of the building and premature corrosion of the metal. Corrosion to a metal roof decking system can be a major safety hazard for anyone who has to access the roof for rooftop service or repairs.
   Condensation can easily form inside a poorly insulated metal building with interior humidity as low as 20 percent. With a ccSPF roofing system sprayed to the existing roof deck, a continuous layer covers fasteners, metal roof panels, and penetrations through the roof (such as pipes and supports) and completely separates metal beams, joists, purlins, and the metal roof deck panels from contact with outside temperature and humidity. This thermal break eliminates the potential for condensation.
3. Air movement within the building. Metal buildings are hard to make airtight. Metal panels typically do not have good continuous air seals along the intersections of walls, roofs, and floors. For that reason, large amounts of air can travel into and out of metal buildings unless an effective air-barrier system is installed. Peel-and-stick membranes can be difficult to install in these buildings. The tight, irregular-shaped edges, corners, and junctions make it challenging to apply the membranes effectively as an air seal.
   The National Institute of Standards and Technology (NIST) estimates that effective air-barrier systems could save up to 83 percent of air leakage in nonresidential buildings, which would save more than 40 percent on gas bills and more than 25 percent on electrical consumption.
   ccSPF is sprayed onto the roof surface as a liquid and expands 30 to 40 times its original volume to form a lightweight insulation that fills in cracks, crevices, and voids. It completely air-seals around and through roof protrusions, such as vents, pipes, stacks, structural supports, parapet walls, drains, and the like. Combined with an interior air-barrier system on the walls and floors of the building, ccSPF can completely control air leakage within a metal building.
4. Thermal bridging. Thousands of fasteners and welds intersecting with hundreds of metal beams and metal panels conduct heat into and out of metal buildings, causing insulation to be less effective. Reflecting research by the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) and the Oak Ridge National Laboratories (ORNL), fasteners alone can reduce the effective insulation value between 1.5 to 31.5 percent, depending on the number and type of fasteners.
   ccSPF eliminates thermal bridging by providing a continuous, fully adhered layer of insulation over existing thermal bridges in the roof deck and/or assembly.
5. Solar absorptivity and the "urban heat-island effect." The typical gray-colored metal roof can reach up to 160° F (71.1° C) on a 90° F (32.2° C) day. The resulting heat transmitted into the building makes the HVAC equipment work harder to cool the building. The situation becomes worse if metal roofs are coated with darker coatings, thereby absorbing additional heat that is transmitted to the interior. Dark-colored roofs, parking lots, and roads collectively contribute to an increase of temperature in an urban area, causing what scientists call the "urban heat-island effect."
   Commercial ccSPF roofing systems can cover dark-colored roof planes with continuous insulation that is then covered typically with a high-reflective and low-emissivity (low-E) cool roof coating. The combination of a radiant energy-refracting insulation with a reflective coating significantly reduces rooftop temperatures. ccSPF Energy Star-rated systems are available, so consult the specific manufacturer and Energy Star for more details.
6. Preventing leaks, and sealing irregular surfaces and junctions. With metal roofs and buildings, it can prove challenging and costly to identify and locate water leaks due to the irregular surfaces and angular corners and junctions. Flashings tend to move, increasing the potential for water leaks that may be hard to detect and to stop.
   On the other hand, ccSPF conforms to the irregular surfaces, corners, and junctions, forming a fully adhered, seamless waterproofing membrane that helps eliminate leaks. The closed-cell physical properties of the ccSPF material prevent water leaks from penetrating through the foam and traveling laterally.
   In terms of analyzing vulnerability to wind or hail damage, a recent report sponsored by the National Roofing Foundation (NRF) surveyed 140 ccSPF roofs ranging from new to 27 years old. The NRF research discovered that where roofs had experienced hail strikes, the damage was localized to the upper surface of the foam. Most roofs were repaired rather than replaced, which is often the case with other types of roofing systems.
   Closed-cell foam inhibits water from traveling laterally, even if the foam surface is damaged. Repairs can be easily made with sealant or foam packs.
7. Energy efficiency. There is great potential for poor energy efficiency in metal buildings if factors such as air infiltration, radiation, and thermal bridging are not adequately addressed. Traditional insulation techniques provide poor solutions to controlling these factors; for that reason, the forces of convection, conduction, and radiation heat transfer rob many metal buildings of their energy efficiency.

On the other hand, ccSPF roofing systems increase energy efficiency in metal buildings four ways:

1. ccSPF roofing systems are applied above the roof deck (providing a complete separation between exterior and interior temperatures).
2. ccSPF eliminates thermal bridging by providing a continuous layer of insulation over existing thermal bridges in the roof deck and/or assembly.
3. ccSPF has a very high aged R-value of between six to seven per inch.
4. ccSPF roofing systems typically are surfaced with light-colored, reflective coatings.

Research compiled by Dr. Mark Bomberg on the energy efficiency of ccSPF roofing systems confirms that the roofing system can dramatically increase the energy efficiency of metal buildings and metal roof assemblies. The Davis Energy Group has used Dr. Bomberg’s data to create the "SPF Roof Energy Calculator."

For example, the calculator estimated that fiberglass batt insulation installed to the underside of a metal roof in a conditioned warehouse would provide negligible insulation value, while ccSPF installed as a roofing system would provide a higher R-value performance than the rated R-value of the foam.

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