Evolution in sprayed polyurethane foam

April 18, 2017

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Photo courtesy Honeywell

By Rockford Boyer
Growing up in a small town in Northern Ontario, this author was exposed to only one true rivalry—the one between the Montréal Canadiens and the Toronto Maple Leafs. Enrolling in architecture school and being hired by a high-end mineral wool (MW) insulation manufacturer, however, meant being exposed to a conflict that would put both teams to shame: the infamous enmity between the foam insulation and fibrous insulation industries.

Based on this author’s experience specifying insulation, this competitiveness generally is not between companies’ technical experts, but mainly between sales and marketing departments. After 10 years in the MW world, this author decided to enter the sprayed polyurethane foam (SPF) insulation industry. Three factors made the transition easier: the innovation of the SPF industry, environmental aspects of the materials, and whole-system performance.

The intent of this article is to touch on some of the misconceptions related to SPF insulation and to eliminate or minimize the material’s ‘marketed’ attributes. It is far too easy to believe these are its true characteristics if one does not take time to conduct a full review of the SPF industry. It is possible to know enough about the product to design using SPF, but still lack the time or interest required to understand it. Building science practitioners know better than to believe unsubstantiated claims about any type of insulation—because manufacturers are self-promoting, it is crucial to review all technical documentation to ensure the products being used are genuinely the best on the market.

Manufacturing processes
Manufacturing processes are very different between MW and SPF manufacturers—MW is manufactured in a plant, whereas SPF is manufactured onsite. A brief introduction to both processes follows.

Mineral wool
The manufacturing process begins when basalt rock, slag, and coke are delivered and stored onsite. When required, the raw materials are weighed and automatically fed into a melting furnace, where they are melted at 1500 C (2732 F). The liquid melt then flows out of the furnace and onto spinners, where it is spun into wool, and a formaldehyde binder and oil resin are sprayed and added to the individually spun fibres.

The spinning chamber then collects the spun fibres and creates a mineral wool fleece, which is laid on a belt conveyor and delivered to a layering system where the density is determined. The fleece enters a curing oven, and the cured wool proceeds to the cutting section of the line, where it is cut to customer-specified dimensions. Finally, the cut wool continues to the packaging section, where the batts or boards are packaged into plastic wrapping for transport. Additional packaging known as a shroud can be installed over the palletized mineral wool insulation for outside storage, so it can be stored onsite until it is needed.

Sprayed polyurethane foam
To manufacture or install SPF onsite, a trained and third-party-approved installer accurately mixes what the industry calls a ‘set,’ with a Part A and a Part B. The A-side is the isocyanurate (polyiso) portion of the set, and the B-side is the resin portion. When SPF manufacturers discuss the manufacturing processes, they are referring to the B-side or resin side of the foam set, as the A-side is typically purchased from a third-party supplier.

Manufacturing the resin starts when a recipe of precisely weighted chemicals are batched together in a reactor and continuously mixed until the formulation is equally blended. After the resin has been thoroughly mixed, it is placed into 189-L (50-gal) drums or in bulk tanks, ready to be shipped. On the jobsite, the trained installer uses a mobile spray apparatus that equally mixes the A- and B-side of the foam set and, under pressure, sprays the two components from a spray gun, where the components are mixed and reacted. The mixed liquid hits the substrates and creates a reaction that manufactures the foam, expanding to 20 to 30 times its original volume.

If a surface is acceptable for paint, it is also acceptable for SPF. If there is too much moisture on the substrate, however, this can potentially lead to improper curing.

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This image shows the four control layers required to ensure building functionality and resiliency.
Image courtesy RDH

Performance characteristics
Much of the construction industry lumps all insulation products together, making general comparisons between SPF, foam board stock, mineral fibre, and other materials. These comparisons are typically related to characteristics such as R-value, moisture absorption, and acoustical properties—however, not all insulations are created equal. Some are just insulation products, while others are insulation systems controlling additional functions such as air, vapour, and water. The construction industry is moving toward a system approach to enclosure design, so when comparing insulation options, the absolute performance and functions of the system should be identified.

To ensure enclosure functionality and durability, four control layers (thermal, moisture, air, and vapour) should be considered, as they are crucial to the assembly’s overall effectiveness (Figure 1). At the product scale, MW can manage thermal and vapour control, but not moisture and air control. Utilizing a weather-resistive barrier (WRB) membrane behind the MW, however, can ensure all four control layers are covered. Foam board stock also typically needs a membrane behind the insulation, unless tape or flashing is used to create a face-sealed system. However, even with a face-sealed system, three of the four control layers—thermal, moisture, and air—would be managed.

Similarly, typical closed-cell SPF installed in a split insulation system can provide thermal, moisture, and air management; installed in an all-outboard approach, it will effectively meet the four-control-layer solution. Installing a medium-density, open-cell SPF insulation in a split insulation system can also manage all four control layers.

Building science has pushed the industry further ahead by utilizing various materials and practices to obtain high performance in buildings, so it is critical when designing an assembly to review the system performance of materials rather than just looking at individual key performance criteria.

Fire performance
Poor fire performance is one of the most common marketed misconceptions of SPF. This is not to say foam does not have the potential to char and burn, but that it poses less of a risk than perceived. Marketing strategies can effectively play on the emotions of the reader to sway him or her toward a specific message, but design professionals should base decisions on building science—technical data, research, and an understanding of physics—rather than on sales strategies.

SPF is a foam plastic, meaning it has the potential to char and burn under certain conditions. However, just because SPF is installed in a building enclosure or separator, that does not mean disaster will follow. Many factors have to align to cause a fire—in reality, most fires that take place in Canada occur when the building is occupied, not when it is under construction. Fires do happen in buildings, mostly from cooking, but those caused by foam insulation only comprise a fraction of the total percentage. (“Fire Losses in Canada,” a September 2011 report by Mahendra Wijayasinghe, PhD, is available at www.ccfmfc.ca/pdfs/report_e_07.pdf[3].)

An article written by Aaron Seward, on the other hand, states: “Water intrusion makes up more than 70 per cent of the construction litigation.” (Read Seward’s June 2011 article, “When It Leaks It Pours.”[4]) If this is so, then to a building science practitioner, it makes more sense to focus on mitigating moisture issues in buildings than fire during construction. Water intrusion may not look as dramatic as a building burning at night, but obtaining remediation for it in court can be.

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This graph compares proprietary closed-cell sprayed polyurethane foam (SPF) to typical construction materials installed in buildings across Canada.
Images courtesy Rockford Boyer

Building codes dictate where and when SPF can be used and applied. Therefore, following building code guidelines will reduce the risk even further. In addition to using code requirements to protect SPF from potential fire issues, the foam plastic industry has taken further steps in developing insulation products that achieve the same goal. Such products can have a global warming potential (GWP) of 1—considered non-flammable by ASTM E-681, Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapours and Gasses). (For more information, read “Understanding Global Warming Potentials.”[6]) This non-flammable liquid blowing agent can drastically reduce the flame spread and smoke development of SPF.

Another example has a flame spread rating of 5 and a smoke development rating of 130, while the code allows for 500 in each category. Special coatings like intumescent paints can also be applied to the SPF insulation to ensure thermal barrier and ignition barrier requirements in the building code are met. Figure 2 features a chart showing the flame spread and smoke development of typical construction materials.

Environmental considerations
Some people believe chemicals or materials manufactured from chemicals are bad for the environment or the occupants that encounter the material. This is just not the case—some SPF insulations are quite safe for both the occupant and the environment. Chemical compounds and formulations for the manufacturing of SPF insulation have significantly advanced environmentally over the past few years. Some SPF foams have been tested to GreenGuard Gold, one of the most stringent standards for indoor air quality (IAQ) of building materials.

Environmental performance considerations to make with SPF include:

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A comparison of blowing agents from common, generic building insulations.

GWP
GWP is one of the most contested environmental issues with any type of insulation on the market. As foam insulation employs blowing agents to install/manufacture the material and ensure its high R-value performance, its environmental contribution can be quite significant. Various blowing agents used in the manufacture of foam products affect the environment, depending on their GWP. Lower GWP will result in less global warming, due to the heat being allowed to escape back out of the atmosphere.

In 2020, the Canadian government will ban the use of blowing agents with high GWP, so all SPF manufacturers will need to reformulate their products. Several progressive SPF manufacturers have already utilized ultra-low-GWP blowing agents successfully for several years. Water-blown-based SPFs are also readily available that boast a GWP of 1. Figure 3 shows typical insulation products with GWPs.

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When properly installed, SPF insulation is both safe and cost-effective.
Photo courtesy Honeywell

Carbon creation
Carbon impact from insulation is quite low. Foam insulations (specifically SPF) typically have a smaller impact on carbon than mineral fibre due to their manufacturing process—there is no need to dig up raw materials (e.g. rock or sand), transport them hundreds of kilometres, melt them at extremely high temperatures, then transport bulky board stock to its destination. In conjunction with the higher amount of carbon created through manufacturing, board stock also generally needs a control layer behind the insulation, the transportation of which leads to an even higher impact on the carbon footprint of the entire building enclosure. This being said, if the use phase of the building is included, all insulation products save carbon, so the differences between the insulations are negligible.

Transporting SPF is quite efficient, as a set of 0.9-kg (2-lb) closed-cell SPF comprises 10.6 m3 (4500 fb) of insulation, and a set of 0.2-kg (0.5-lb) open-cell SPF comprises 42 m3 (18,000 fb). That being said, the amount of board feet per truckload of SPF can range between 425 m3 (180,000 fb) for 0.9 kg of closed-cell SPF and 1699 m3 (720,000 fb)
for 0.2 kg of open-cell SPF. These amounts are at a minimum 9:1 transportation ratio of board stock insulation to a traditional closed-cell SPF insulation system. Not accounted for in this ratio is the control layer membrane that must be installed in conjunction with the basic board stock insulation product. Transporting SPF results in fewer trucks on the road, which in turn results in lower carbon emissions and reduces the flow of everyday traffic and onsite congestion.

Throughout this author’s 15 years in the construction industry, some architects have been heard to say they will not put “plastic on their walls.” Yes, using SPF means ‘plastic’ is being placed on walls, but it provides a function—namely, water control, vapour control, air control, and thermal control. Board stock—whether foam or mineral fibre—also uses plastic in production, for packaging. Packaging is useful for shipping, but does not have a function afterward, except to keep the product together. In other words, plastic is being used regardless of the insulation type, but with board stock it is diverted to the landfill once the product is installed. A quick calculation estimates there can be more than 650 m2 (7000 sf) of wasted plastic packaging per truckload (based on an R-20 board packaged and shrouded). There is potential for the plastic packaging to be recycled, but the chances of this happening are quite small.

IAQ
IAQ is always a concern for potential clients determining whether SPF insulation is a viable choice for a project, perhaps because of the ‘astronaut suits’ applicators must wear to install this type of insulation system. However, there is no need to worry—when the SPF system is installed, the occupied space should be vacant and ventilated for 24 hours or another time frame identified by the manufacturer. There are even SPF products available that meet the GreenGuard Gold certification for IAQ. The off-gassing from this type of SPF insulation system is on par with and sometimes even lower than any other type of mineral fibre insulation readily available.

Conclusion
As the famous saying goes, “There is no bad insulation, just bad application.” As a building science practitioner, this author follows that motto, striving to understand the benefits and challenges of all insulation. In a world of self-promotion, it is very important to understand all aspects of a material’s performance and how it interacts with the dynamic environment.

Manufacturing of SPF is very different from mineral wool, as manufacturing of SPF happens onsite by trained professionals, whereas MW is created in a large, static facility. Insulations are not equal, and aspects of performance should be judged based on a system (i.e. building enclosure system) approach. Foam products/systems have the potential to char or burn, but the chances are very low, and following building codes will limit the potential risks. Finally, chemicals have changed over the past few years, and can be environmentally responsible, with a negligible impact on air quality.

At the end of the day, if emotions are involved, it is hard to change the thought process of the designer, but it is in the best interest of the industry to do research and due diligence when specifying construction products and/or building systems.

[9]Rockford Boyer is the technical manager, building enclosure at Elastochem Specialty Chemicals. He has a diploma in civil engineering, a degree in architecture (building science option), and is currently completing the Master of Building Science program at Ryerson University. Boyer has more than 15 years of experience in the enclosure design field, including five years with AMEC, Earth and Environmental and 10 years with Roxul Insulation. He can be reached via e-mail at rboyer@elastochem-ca.com[10].

Endnotes:
  1. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/SPF_DSC_0173.jpg
  2. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/SPF_fig1.jpg
  3. www.ccfmfc.ca/pdfs/report_e_07.pdf: http://www.ccfmfc.ca/pdfs/report_e_07.pdf
  4. “When It Leaks It Pours.”: http://www.architectmagazine.com/technology/when-it-leaks-it-pours_o
  5. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/SPF_fig2.jpg
  6. “Understanding Global Warming Potentials.”: http://www.epa.gov/ghgemissions/understanding-global-warming-potentials
  7. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/SPF_fig3.jpg
  8. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/SPF_spf.jpg
  9. [Image]: https://www.constructioncanada.net/wp-content/uploads/2017/04/Boyer_headshot.jpg
  10. rboyer@elastochem-ca.com: mailto:rboyer@elastochem-ca.com

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