Sprayfoam to HFO: the blowing agent’s shift explained

by arslan_ahmed | October 20, 2022 12:30 pm

Photos courtesy Huntsman Building Solutions

By Doug Brady

Spray polyurethane foam (SPF) is a building material commonly used in insulation and roofing applications. The material is manufactured in three core densities which correspond to the material’s application or use. The first is open-cell insulation, commonly offered at 8 kg/m3 (0.5 lb/cf) density, the second is closed-cell insulation, commonly offered at 32 kg/m3 (2 lb/cf) density, and the third is roofing SPF, commonly sourced at 40 to 56 kg/m3 (2.5 to 3.5 lb/cf) density.

The sprayfoam industry is currently leading an important effort which directly impacts closed-cell SPF insulation and roofing SPF. This initiative is a shift from using hydrofluorocarbons (HFCs)-based blowing agents to using hydrofluoroolefins (HFOs)-based blowing agents.

HFCs[2] are any of several organic compounds composed of hydrogen, fluorine, and carbon, while HFOs are unsaturated organic compounds composed of hydrogen, fluorine, and carbon. Unlike traditional HFCs and their blowing agent predecessors, chlorofluorocarbon (CFCs), both of which are saturated, HFOs[3] are olefins, otherwise known as alkenes.

The push towards HFO-based sprayfoam technology is the latest step in an ongoing evolution to phase out the use of chemicals known to harm the ozone and climate. In addition to reducing the negative environmental impacts of sprayfoam insulation and roofing materials, there are also product performance and installation considerations. This article will explain the blowing agent shift and why it matters to those considering the specification of sprayfoam applications in commercial building projects.

The industry shifted towards the use of hydrofluoroolefins (HFOs) in 2020. They offer zero ozone depletion potential (ODP) and a global warming potential (GWP) value of less than 25.9. Some HFOs even offer a GWP value of one.

Blowing agents explained

The Handbook of Foaming and Blowing Agents defines a blowing agent as “a substance which is capable of producing a cellular structure via a foaming process in a variety of materials that undergo hardening or phase transition, such as polymers, plastics, and metals.”1 There are two types of blowing agents: chemical and physical. Above a certain temperature, or in contact with another specific chemical, they initiate a chemical reaction which generates a gas. At the same time, a solid plastic forms; and the formation, along with the generation of a gas (chemical and/or physical) create a solid foam structure. Physical blowing agents are metered into the plastics, most frequently in the form of a melt, and they form bubbles by various means.

Next generation sprayfoam using hydrofluoroolefin (HFO)-based blowing agent applied to commercial facility exterior.

Further, blowing agents are divided into endothermic and exothermic foaming agents. Endothermic chemical foaming agents take heat away from the chemical reaction, producing foams with a much smaller cell structure, resulting in improved appearance and better physical properties. Exothermic chemical foaming agents generate heat during the decomposition process. They liberate more gas per gram of foaming agent than endothermic agents and produce higher gas pressure.

Usually, exothermic blowing agents tend to make larger cells compared to endothermic. In a system, a good balance between endothermic and exothermic blowing agents will make a better dimensionally stable foam. Endothermic blowing agents also give higher R-value to the foam.

HFC- and HFO-based sprayfoam blowing agents are both physical and endothermic blowing agents.

The European FluoroCarbons Technical Committee (EFCTC), a Cefic sector group, defines what makes a good insulation foam blowing agent by stating, “foam blowing agent is selected to provide a closed-cell structure which minimizes heat transfer, in part due to the properties of the foam blowing agent, which is retained within the foam essentially for the lifetime of the foam’s use.”

Producers dissolve the blowing agent into precursors where it expands to form the foam once injected or sprayed, causing the foaming reaction to start. Optimization is crucial to ensure thermal efficiency and overall performance. Foam blowing agents with low thermal conductivity can improve insulation properties of the foam, allowing better insulation performance or thinner profiles for the same value. The committee further points out how emissions from closed-cell foam are typically less than two per cent annually, so this thermal performance persists over time.2

The evolution of blowing agents

Blowing agents used in SPFs have evolved over time, with the phase-out of specific compounds occurring at various points in the past. The first class of blowing agents, used between 1950 to 1980, in sprayfoam were chlorofluorocarbons (CFCs). They have a global warming potential (GWP) of more than 4000 and an ozone depletion potential (ODP) of one. Second generation blowing agents were hydrochlorofluorocarbons (HCFCs), used between 1980 to 1990, and they have a GWP of more than 725 (and can range up to 2310) and an ODP of approximately 0.055 to 0.11.3

HFCs are the third iteration of sprayfoam blowing agents, they were used in 1990 and are still found in products today. They offer zero ODP; however, they have a GWP value of more than 794 (and up to 3220).4 Once considered a suitable replacement for ozone-depleting substances, HFCs are now the world’s fastest-growing greenhouse gases. HFCs have up to 4000 times more global warming impact than carbon dioxide (CO2).5 Scientists estimate HFCs alone could contribute up to 0.5 C (32.9 F) of global warming by the end of the century.6

It is for this reason the industry has shifted towards the use of HFOs in the year of 2020, which offer zero ODP and a GWP value of less than 25.7 Some HFOs even offer a GWP value of one. Note the dramatic difference between first generation blowing agents (CFCs) and the new, fourth generation of blowing agents (HFOs)—an initial GWP of more than 4000 to a GWP, today, of just one.

A defining moment: 1987’s Montreal Protocol

An international effort to protect the earth is the backdrop for the periodic phase-out of specific sprayfoam blowing agents. This movement began an effort to slow the loss of stratospheric ozone when, in 1987, the international community signed the original Montreal Protocol. The agreement mandated that developed countries begin phasing out the use of CFCs, which are known to destroy the ozone layer. This agreement called for participating countries to achieve a 50 per cent reduction in the use of CFCs, relative to 1986 levels by 1998. The Montreal Protocol was essentially the world’s first step of many in protecting the ozone layer.

However, new data became available afterwards which demonstrated worse than expected damage to the ozone layer. This data ultimately led to a series of amendments to the initial agreement, all of which were aimed at controlling additional ozone depleting chemicals and identifying mechanisms to enforce the compliance of developing countries.8 The amendments, in sequential order, include the London Amendment in 1990, the Copenhagen Amendment in 1992, the Montreal Amendment in 1997, the Beijing Amendment in 1999, and the Kigali Amendment in 2016.

Unlike traditional hydrofluorocarbons (HFCs) and their blowing agent predecessors, chlorofluorocarbon (CFCs), both of which are saturated, hydrofluoroolefins (HFOs) are olefins, otherwise known as alkenes.

The latter amendment is notable as its goal was to phase-down the production and use of HFCs. It addressed how the use of HFCs resulted in greenhouse gases which are highly detrimental to the earth’s climate. Canada was among the first countries to ratify the Kigali Amendment and encouraged others to do the same. By November 2017, many countries ratified the Kigali Amendment to ensure its entry in January 2019.9

To further support global efforts to eliminate HFCs, Canada is also undertaking bilateral projects in collaboration with countries such as Bangladesh, Chile, Mexico, and Panama, to assist them in taking initial steps to control HFCs. As of 2021, HFC sprayfoam products are banned and can no longer be manufactured and installed in Canada.

In addition to direct impacts on the environment, this federal and international history directly impacts the commercial building, insulation, and roofing sectors, as all these industries use various closed-cell sprayfoam solutions. Most notably, top industry leaders in the building products industry are now working to move the construction sector towards adopting next generation sprayfoam systems incorporating HFO-based blowing agents known to reduce global warming inducing greenhouse gases. Provinces and territories complement the federal regulations, aimed at phasing-out the production and consumption of HFCs to HFOs, to help limit increases in global average temperatures and contribute to Canada’s international obligations to combat climate change.

Timeline for phasedown efforts

The Regulations Amending the Ozone-depleting Substances and Halocarbon Alternatives Regulations (amendments) published in Part II of the Canada Gazette in October 2017, came into force in April 2018.

These amendments, mandated by the Government of Canada, established a phase-down of HFC consumption, starting with a 10 per cent reduction in consumption in 2019; and further steps in 2024, 2029, and 2034 to achieve an 85 per cent reduction in HFC consumption by 2036.

The amendments also introduce prohibitions, by specific dates, on the manufacture and import of certain products and equipment which contain, or are designed to contain, HFCs and HFC blends with a GWP above a specific limit. Depending on the different types of products in each sector, different dates for their prohibitions apply.10

Regardless of the different dates, the sprayfoam industry continues to introduce HFO-based, closed-cell sprayfoam systems to provide more environmentally sound solutions for optimizing the performance of both the building envelope and roof.

Closed-cell sprayfoam insulation

Closed-cell SPF is a single-source solution for thermal, air, water, and vapour control, providing architects and builders the ability to seal the building enclosure using one product and eliminating the need to specify numerous additional products. The material is durable, versatile, lightweight, and a rigid foam option.

As a thermal insulator, closed-cell SPF boasts one of the highest R-values per inch of all insulation options available. It is ideal for continuous insulation (ci) applications in commercial structures and can be used in interior and exterior applications where it can replace rigid extruded polystyrene (XPS), mineral wool, fibreglass, and polyisocyanurate (PIR) foam boards. The material boasts low water absorption as well as resistance to mould, as demonstrated with ASTM C1338, Standard Test Method for Determining Fungi Resistance of Insulation Materials and Facings. The sprayfoam also excels as a water-resistive barrier (WRB) on exterior wall applications and is tested in accordance with CAN/ULC S742, Air Barrier Assembly Testing, with a pressure up to 5520 Pa (0.8 psi) for air barrier assemblies and tested in accordance with ASTM E331, Water Penetration Testing. The results showed no leakage through the sprayfoam.

When applied in walls, ceilings, and floors, the Federal Emergency Management Agency (FEMA) names closed-cell sprayfoam a Class 5 material, the highest classification for products indicating strong resistant to floodwater damage. Class 5 materials do not require special waterproofing protection, can survive wetting and drying, and may be successfully cleaned after a flood to render them free of most harmful pollutants.11 While the sprayfoam may be applied as cavity insulation or as ci in commercial structures and still qualify as a Class 5 material, it is the only cavity insulation approved by FEMA with this highest floodwater resistance. When applied under slab as insulation, closed-cell SPF is also flood and radon resistant.

Installer in personal protective equipment (PPE) suit applying hydrofluoroolefin (HFO-) based sprayfoam.

The application of closed-cell SPF in above-grade walls can also increase the structural strength of buildings and assist with wind resistance. The degree of hardening depends primarily on the strength of the building. For example, regarding racking strength, an I-beam modular constructed metal building with a 22-gauge metal panel will benefit significantly less from an interior application of closed-cell SPF than a post-frame constructed building with 29-gauge corrugated metal panels. When installed, closed-cell SPF glues the assembly together, reduces the potential for movement, and adds a tensile strength average ranging from 103 to 172 kPa (15 to 25 psi).12

The Spray Polyurethane Foam Alliance (SPFA) conducted racking performance tests in 1992 and 1996 at Architectural Testing Inc. in Pennsylvania in 2007. The tests demonstrated medium density closed-cell SPF, installed at 32 kg/m3 (2 lb/cf), increases racking strength by 70 to 200 per cent in wall assemblies sheathed with oriented strand board (OSB), plywood, gypsum wallboard, vinyl siding, and polyisocyanurate (ISO) board. The research proved closed-cell SPF significantly increased rack and shear strength in both wood and metal construction. Installed SPF also increases the strength of weaker substrates such as gypsum drywall, vinyl siding, and ISO foam insulation at a much greater percentage than stronger substrates such as OSB and plywood. Notably, special bracing for wind resistance is not required for strengthening purposes when using closed-cell SPF in walls.13

Sprayfoam roofing

One of the most rigid of all SPFs, sprayfoam roofing is applied to the top surface of low-slope roofs. In this application, the material acts as a protective roofing material and as a thermal insulator. Like closed-cell sprayfoam insulation, sprayfoam roofing is known for its air sealing capabilities and its energy efficiency. It is also the highest density sprayfoam as it must provide protection from moisture, rain, wind, hail, and other elements, while withstanding maintenance-related foot traffic. The material offers a compressive strength of 714 to 1071 kg/m
(40 to 60 lb/in.).

Sprayfoam roofing is ideal for use when: the roof deck is an unusual shape; the region experiences extreme storms, wind, or hail (regions with heavy snowfall wind or rainstorms are also examples); a sloped application is needed for drainage; the substrate has multiple penetrations (such as with solar panel supports) or there is equipment mounted to the roof requiring flashing; the structure is unable to withstand additional weight on the roof; and when removing the existing roof is deemed too expensive (as sprayfoam roofing may be applied over an existing roof in a cost-effective retrofit application).

Installed on the roof, sprayfoam creates a protective, monolithic layer which serves as continuous thermal insulation layer, WRB, air barrier, and vapour retarder. The material requires an additional coating overtop to protect the surface from ultraviolet (UV) radiation, foot traffic, and any other weather cycling and elements. Acrylic- and silicone-based coatings are two which are more commonly used.

Applied to the underside of a roof, closed-cell sprayfoam can increase wind uplift resistance. Applied to built-up roofing and metal substrates, wind uplift resistance is enhanced further. A study conducted by the University of Florida in 2007 found that applying closed-cell sprayfoam under a roof deck provides up to three times the resistance to wind uplift for wood roof sheathing panels when compared to a conventionally fastened roof.14

SPF roofing is also resistant to progressive peeling failure, which leads to flashings and copings being pulled away from their original locations by wind. Following Hurricane Katrina, the National institute of Standards and Technology (NIST) examined roofs and found buildings with sprayfoam roofs performed well without blow-off of the SPF or damage to flashings.15

Since it is closed-cell, sprayfoam roofing, like closed-cell sprayfoam insulation, is also a Class 5 FEMA flood damage-resistant material. It is impermeable to moisture and may be cleaned and dried.

Since they are requirements of the building code itself, the new blowing agents will not change any of these properties, rather, the industry is modifying their products to meet these requirements instead.

Manufacturing and performance considerations for sprayfoam systems

When developing sprayfoam systems, manufacturers must be mindful of the inherent established precedents in the market. For instance, the plethora of impingement mix 1:1 ratio in the industry today forces manufacturers of new closed- and open-cell sprayfoam systems to match this chemical blend. The same may be said for when designing sprayfoam solutions for the next generation of blowing agents.

Closed-cell insulation using hydrofluoroolefins (HFOs) in Montreal, Quebec, at the Îlot Rosemont building project.

Compared to HFC, HFO molecules tend to break down faster in resin. Consequently, new catalysts were necessary to pair with the HFO blowing agent to sustain the six-month shelf-life industry expectation. This was one of the most difficult hurdles for sprayfoam manufacturers.

The HFO molecule does have a strong benefit over HFC. Thermal conductivity is lower in HFO than HFC. This translates to better thermal performance, on average, compared to a HFC-based sprayfoam While the blowing agent is the primary driver of the R-value of a sprayfoam the overall composition of the resin, in combination with isocyanate, determines its R-value. There has been an increase in aged R-values in systems containing HFO blowing agents.

As for the construction site, the impact of HFOs is minimum as they offer better spraying abilities and less equipment clogging.

Environmental Product Declarations (EPDs) and energy modelling

Many buildings use both types of SPF, closed-cell (exterior or interior) and open-cell (interior), because of their great thermal resistance and air barrier properties. SPF is commonly installed in residential projects, such as single houses, townhouses/condos, as well as commercial, institutional, and agricultural projects, such as schools, hospitals, arenas, stores, restaurants, storage facilities, data centres, and grow houses. The shift to HFO led architects towards greener alternatives, as institutional projects now require GWP building products.

To reduce the construction and building operations sectors’ contribution to global warming, it is imperative to do two things.16 The first is to use products which demonstrate reduced embodied carbon. EPDs are important tools for this as they tell the life cycle story of a product in a single, comprehensive report. They provide information about a product’s impact on the environment, including GWP, smog creation, ozone depletion, and water pollution. While EPDs do not rank products, and having an EPD for a product does not indicate if environmental performance criteria is met, they are an important disclosure tool to help purchasers better understand a product’s sustainable qualities and environmental repercussions, so they can make informed product selections.17

Secondly, buildings must be constructed tighter, better sealed, and more energy efficient to reduce their operational carbon emissions. To assess performance in this area, energy modelling is useful. The pre-construction, whole-building assessment of energy efficiency uses computer programs for calculation. Designers create a model of the entire building on a computer and run it through simulations to show energy performance, usually for an entire year and based on meteorological information. The modelling accounts for all systems within a building and examines how they impact each other.18

Some SPF solutions are based on cradle-to-grave life-cycle assessment (LCA), which communicates transparent, objective, and comparable information about the entire life-cycle environmental impact of products. Some brands have gone as far as to include proprietary polyol with recycled content and a new generation HFO blowing agent with a GWP of one, which is responsible for diminished environmental impact.

As for a wall assembly with only HFO SPF versus assemblies insulated with mineral wool, HFO XPS board stock, or fibreglass insulation, replacing all insulation and membranes in the assemblies with a closed-cell solution at an equivalent R-value, the assembly’s GWP is nearly cut in half.

On the construction site, the impact of hydrofluoroolefins (HFOs) is minimum as they offer better spraying abilities and less equipment clogging.

Some advantages in comparison to other insulation types include:

SPF provides high insulation value per inch, and keeps building components in better conditions longer, giving them longer lifespans. This promotes the reuse of materials and encourages building projects to reduce the reliance on new construction and the need for virgin materials. It is an insulation alternative which is quick to install, has perfect adhesions, and does not settle over time. Lastly, it also has air and vapour barrier properties, exceeds indoor air quality standards, is mould resistant, and has a WRB that is ideal for Canadian weather.


Architects and engineers are constantly looking for the most effective methods to minimize the environmental impact of upcoming projects and developments through specifying low-carbon materials with HFO blowing agents.

Although HFO can be costly and during the pandemic, it was hard to get which led to higher lead time, the sprayfoam industry’s shift to HFO-based blowing agent technology is a crucial step towards reducing the industry’s global warming contributions. Shifting from third generation HFC-based blowing agents to HFO-based options will decrease the use of products with zero ODP, a GWP value of more than 794, and bring in substantially improved newer generations of SPF with zero ODP and a GWP which can, in certain products, reach a value of one. To be better informed about sprayfoam insulation, roofing system’s individual performance, and climatic impact, architects and specifiers are encouraged to request EDPs and seek energy modelling information.


1 Consult George Wypych, Handbook of Foaming and Blowing Agents, 2017.

2 Review European FluoroCarbons Technical Committee, “Insulation Foam Blowing Agent,” www.fluorocarbons.org/applications/insulation-foam-blowing-agent[10].

3 Read the Environmental Protection Agency’s (EPA’s), “Transitioning to Low-GWP Alternatives in Building/Construction Foams,” www.epa.gov/sites/default[11]/files/2015-07/documents/transitioning_to_low-gwp_alternatives_in_building_and_construction_foams.pdf.

4 See note 3.

5 Watch TEDxReImagineScience, Unpacking the #1 Global Warming Solution, www.youtube.com/watch?time_continue=65&v=tXkYZgQaLr4&feature=emb_logo[12].

6 Review the North American Sustainable Refrigeration Council’s (NASRC’s), “The HFC Problem,” https://nasrc.org/the-hfc-problem.

7 See note 3.

8 Refer to the Environmental Protection Agency’s (EPA’s), International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer, www.epa.gov/ozone-layer-protection/international-treaties-and-cooperation-about-protection-stratospheric-ozone[13].

9 Learn about the Montreal Protocol at https://www.canada.ca/en/environment-climate-change/corporate/international-affairs/partnerships-organizations/ozone-layer-depletion-montreal-convention.html[14]

10 See note 11.

11 Refer to the Federal Emergency Management Agency’s (FEMA’s), “Flood Damage-Resistant Materials Requirements for Buildings Located in Special Flood Hazard Areas in Accordance with the National Flood Insurance Program,” Technical Bulletin 2, August 2008.

12 Review Honeywell, “Insulation and Waterproofing for Metal Buildings and Metal Roof Systems: The Case for Using Better Insulation and Waterproofing Technologies in Metal Roof Systems and
Metal Buildings.”

13 Refer to Architectural Testing, Performance Test Report Rendered to Spray Polyurethane Foam Alliance, Project: Racking Load Tests, 2007.

14 See the University of Florida Department of Civil and Coastal Engineering, “Wind Uplift Behavior of Wood Roof Sheathing Panels Retrofitted with Spray-applied Polyurethane Foam,” August 31, 2007, www.yumpu.com/en/document/read/45544489/wind-uplift-behavior-of-wood-roof-sheathing-panels-david-o-.[15]

15 Review the National Institute of Standards and Technology (NIST), “Performance of Physical Structures in Hurricane Katrina and Hurricane Rita: A Reconnaissance Report,” 2006, www.nist.gov/publications/performance-physical-structures-hurricane-katrina-and-hurricane-rita-reconnaissance[16].

16 Read “The Urgency of Embodied Carbon and What You Can Do About It,” Building Green, Inc., buildinggreen.com/feature/urgency-embodied-carbon-and-what-you-can-do-about-it, and “Climate Impact of Plastics,” Mckinsey & Company, mckinsey.com/industries/chemicals/our-insights/climate-impact-of-plastics[17].

17 Refer to UL, Fact Sheet: Environmental Product Declarations Program, www.ul.com/resources/environmental-product-declarations-program[18].

18 See the International Building Performance Simulation Association (IBPSA), About Energy Modeling, www.ibpsa.us/about-energy-modeling.


[19]Doug Brady is chief strategy officer for Huntsman Building Solutions, a global manufacturer of spray polyurethane foam (SPF) solutions used in insulation, roofing, and specialty applications.

  1. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/Application-HFO-.-Impression-1.jpg
  2. HFCs: https://www.britannica.com/science/hydrofluorocarbon
  3. HFOs: https://en.wikipedia.org/wiki/Hydrofluoroolefin
  4. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/DSC09781-Edit-2.jpg
  5. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/ImagesRetouchedNov15-9_corr.jpg
  6. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/DSC00448-Edit-2.jpg
  7. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/Heatlok-Commercial-7.jpg
  8. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/DSC00359-Edit-2.jpg
  9. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/ImagesRetouchedNov15-7_corr.jpg
  10. www.fluorocarbons.org/applications/insulation-foam-blowing-agent: https://www.fluorocarbons.org/applications/insulation-foam-blowing-agent/
  11. www.epa.gov/sites/default: https://www.epa.gov/sites/default/files/2015-07/documents/transitioning_to_low-gwp_alternatives_in_building_and_construction_foams.pdf
  12. www.youtube.com/watch?time_continue=65&v=tXkYZgQaLr4&feature=emb_logo: https://www.youtube.com/watch?v=tXkYZgQaLr4&t=65s
  13. www.epa.gov/ozone-layer-protection/international-treaties-and-cooperation-about-protection-stratospheric-ozone: https://www.epa.gov/ozone-layer-protection/international-treaties-and-cooperation-about-protection-stratospheric-ozone
  14. https://www.canada.ca/en/environment-climate-change/corporate/international-affairs/partnerships-organizations/ozone-layer-depletion-montreal-convention.html: https://www.canada.ca/en/environment-climate-change/corporate/international-affairs/partnerships-organizations/ozone-layer-depletion-montreal-convention.html
  15. www.yumpu.com/en/document/read/45544489/wind-uplift-behavior-of-wood-roof-sheathing-panels-david-o-.: https://www.yumpu.com/en/document/read/45544489/wind-uplift-behavior-of-wood-roof-sheathing-panels-david-o-
  16. www.nist.gov/publications/performance-physical-structures-hurricane-katrina-and-hurricane-rita-reconnaissance: https://www.nist.gov/publications/performance-physical-structures-hurricane-katrina-and-hurricane-rita-reconnaissance
  17. mckinsey.com/industries/chemicals/our-insights/climate-impact-of-plastics: https://www.mckinsey.com/industries/chemicals/our-insights/climate-impact-of-plastics
  18. www.ul.com/resources/environmental-product-declarations-program: https://www.ul.com/resources/environmental-product-declarations-program
  19. [Image]: https://www.constructioncanada.net/wp-content/uploads/2022/10/AA_Brady_Headshot.jpg

Source URL: https://www.constructioncanada.net/sprayfoam-to-hfo-the-blowing-agents-shift-explained/