HFCs have been widely used as insulation foam blowing agents due to their technical performance and non-flammability. The F-Gas Regulation 517/2014 bans the use of HFCs with a GWP >150 in the manufacture of all foams by 1 January 2023 and for extruded polystyrene (XPS) by 1 January 2020. The very low GWP (≤ 7) non-flammable HFOs and HCFOs used as foam blowing agents provide a level of insulation performance which not only allows the replacement of blowing agents with high-GWPs, such as HFCs, but also has the potential to replace some elements of the hydrocarbon and CO2-blown sectors, based primarily on improved thermal properties.
The very low GWPs (≤7) of HFOs and HCFOs mean that any blowing agent emissions that occur during foam blowing process, or for spray foam, during the use phase and at end of life have an extremely small impact on global warming. In fact, the GWPs of these HFOs and HCFOs are less than the main hydrocarbon foam blowing agent (pentanes).
Insulation and energy consumption
High quality, high performance insulation improves energy efficiency primarily by reducing heat transfer. For building insulation, it reduces heat loss or heat gain which improves occupant comfort and can lower energy costs. For cold and chilled storage and transport, it reduces heat gain and helps maintain good temperature control.
In “Buildings & Climate Change: A Summary for Decision-makers UNEP’s Sustainable Buildings & Climate Initiative (SBCI)”, it is stated that not only do buildings use about 40% of global energy for heating and cooling, but in addition, that they emit approximately one third of all greenhouse gas (GHG) emissions. Therefore, increased building insulation offers great potential for achieving significant GHG emission reductions, in developed and developing countries1 .
The revised energy performance of buildings directive 2 improves energy efficiency in buildings and encourages building renovation. Decarbonising the existing, highly inefficient European building stock is one of its long-term goals. The long-term renovation strategy requires each Member State shall establish a long-term renovation strategy to support the renovation of the national stock of residential and non-residential buildings, both public and private, into a highly energy efficient and decarbonised building stock by 2050.
Consistent with these energy performance issues, for both new construction and renovation, the demand for thermal insulation has increased substantially as the role of buildings in reducing energy dependency and greenhouse gas emissions has been recognised. Retrofitting insulation in the shells of existing buildings can significantly cut energy consumption. In addition, the insulation performance for cold and chilled storage and transport is critical to the energy consumption of the cold chain (for food and pharmaceuticals) and the drive to improve overall energy efficiency.
There are a wide range of insulation such as fiberglass, rock wool, cellulose, and natural fibres, rigid foam boards and reflective foils. For a wide range of applications, insulation foams have advantages:
The insulation performance is superior to a range of other insulation materials.
The insulation and physical properties can be designed for specific applications.
For a defined insulation performance, an insulation foam can be thinner, lighter and use less material than some other options.
It can be formed in situ or used as prefabricated board stock.
Spray foam using non-flammable blowing agents can be used to insulate building stock or other structures as an efficient means of insulation which would be difficult to achieve in other ways, due to shape or location.
It can provide a good water barrier. Extruded polystyrene (XPS) has a particular advantage in relation to its moisture resistance, which makes it especially useful for under-floor insulation and cold storage applications.
Insulation Foam Blowing Agent
The 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 use3. The blowing agent used can be a liquid or a gas that is dissolved in the foam precursors and expands to form the foam once it is injected or sprayed and the foaming reaction begins. Optimization is crucial because thermal efficiency and overall performance is highly dependent on the formulation. The foam blowing agent and foam matrix, which may be bonded to impermeable metal facings, are selected to minimize migration of the blowing agent out of the foam which increases its thermal conductivity. Foam blowing agents with low thermal conductivity can improve the insulation properties of the foam, allowing either better insulation performance or thinner profiles for the same insulation value.
HFOs/HCFOs very low GWP, non-flammable high performance blowing agents
In recent years, the search for low-GWP, high performance blowing agents without the limitations of hydrocarbons and CO2 has resulted in the emergence of HCFOs and HFOs which seem to be offering a level of performance which not only allows the replacement of blowing agents with high-GWPs, such as HFCs, but also has the potential to replace some elements of the hydrocarbon and CO2-blown sectors, based primarily on improved thermal properties. In practice, and for cost reasons, blends of HCFOs or HFOs with other blowing agents are likely to be favoured.
The very low GWPs (≤7) of HFOs and HCFOs mean that any blowing agent emissions that occur during foam blowing process, for spray foam, during the use phase and at end of life have an insignificant impact on global warming. The GWPs of these HFOs and HCFOs are less than the main hydrocarbon foam blowing agent (pentanes).
HFOs and HCFOs blown foams are increasingly being used for a range of polyurethane insulation applications including transport refrigeration, refrigerated appliances, cold storage rooms, and spray foams, and, using gaseous HFOs, for high insulation performance XPS (extruded polystyrene)5 primarily used as building insulation. The HFOs and HCFOs are likely to be targeted mostly where the there is a requirement for improved thermal efficiency and, also where a non-flammable blowing agent is necessary.
Polyurethane Spray Foam
Polyurethane spray foam has been used for many years as an efficient means of insulating structures which would be difficult to insulate in other ways, because of shape or location. An example would be that of an insulated road tanker. Another would be the insulation of large flat roofs, which may not be as flat as might be presumed! More recently, however, polyurethane spray foams have emerged as a vital component of renovation strategies for existing buildings. Again, the efficiency and versatility of application, as well as the relative durability and thermal efficiency are all characteristics, which have contributed to the rapid growth of PU spray foam in both developed and developing regions 4. Non-flammable HFOs and HCFOs with low toxicity and very low GWPs (≤7) are particularly suitable for high insulation performance spray foam applications where flammable blowing agents are not acceptable.
1 Report of the Technology and Economic Assessment Panel, June 2016, Volume 1, Progress Report
2 Directive (EU) 2018/844 of the European Parliament and of the Council of 30 May 2018 amending Directive 2010/31/EU on the energy performance of buildings and Directive 2012/27/EU on energy efficiency (Text with EEA relevance). Further information can be found here
3 Emissions of the foam blowing agent from closed cell foam are typically less than 2% per year, so that the thermal performance is maintained.
4 UNEP 2014 Assessment Report of the Rigid and Flexible Technical Options Committee
5 Extruded polystyrene (XPS) should not be confused with expanded polystyrene (EPS – also sometimes called ‘bead foam’) which uses pre-expanded beads of polystyrene containing pentane. EPS has never used fluorocarbon blowing agents.