Climate Change 2001:
Working Group III: Mitigation
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A3.3 Foams

A3.3.1 Insulating Foams

The global market for thermal insulation materials is large, complex, and has substantial regional variation. Since the prime purpose of insulation in addition to energy conservation is to maintain appropriate ambient conditions within a defined space, insulation use is affected most by external climatic conditions. However, in developing countries per-capita use is often lower than local climatic conditions would predict. Increasing insulation use can therefore often go towards improving comfort levels as well as saving energy use and resultant carbon dioxide emissions.

Climatic conditions, space constraints, local building code requirements, and construction costs can all influence the choice of insulation material. In mass markets polymeric foams offer the best insulation performance at higher unit cost. The thermal efficiency of foam is influenced by the choice of blowing agent, and HFCs promise to yield a performance similar to that of previously used HCFCs (UNEP, 1998d).

In Europe, where construction applications dominate, the market for insulation foams, polyurethane, extruded polystyrene, and phenolic resins accounts for about 13% of the total insulation market. Mineral fibres and expanded polystyrene have historically been the dominant materials in terms of volume and mass (roughly 80%), primarily on grounds of lower unit cost. However, performance characteristics are becoming an increasingly important factor in material selection to meet the demands of greater prefabrication.

In North America, the timber frame method of construction has contributed to a more widespread use of polyurethane (PU), polyisocyanurate (PIR), and extruded polystyrene foams. The PU and PIR systems also have better production economics than in Europe because of higher line speeds and less stringent thickness tolerance criteria. In Japan, the market is shaped by strict fire codes and much of the construction is based around concrete. PU spray foams have done particularly well in enclosed spaces and use of phenolic foam is preferred in some exposed applications because of its lower flammability compared to other alternatives. In developing countries, the use of foam for cold storage applications predominates.

Where HFCs are used, they will be emitted during the manufacturing and over the life of the foam (25–50 years). Retention in the foam at end-of-life will generally depend on the thickness of the foam and the facings used.

A3.3.2 Insulating Foams in Appliances

Appliance foams are currently produced with either hydrocarbons or HCFC-141b. Foams produced with HCFC-141b generally provide 5%-15% more insulation per unit of thickness than those produced with other blowing agents. HFCs (primarily “liquid” HFCs such as HFC-245fa and HFC-365mfc) are anticipated to partly replace HCFCs because they produce foams with similar insulating properties. The contribution of the foam to the overall energy efficiency of the appliance is important since the energy used to operate the appliance accounts for the majority of the global warming impacts in most cases.

Where HFCs are selected, options to reduce emissions include the use of formulations that minimize the amount and GWP of the blowing agent used, and the end-life destruction of the HFC. The latter is particularly important, since it is technically possible to recover and destroy over 90% of the HFC blowing agent at an estimated cost-effectiveness of between US$30 and US$100/tCeq (AFEAS, 2000).

A recent study for the European Commission (Harnisch and Hendriks, 2000) estimates that in Europe about 70% of all polyurethane foams for appliances will be blown with hydrocarbons and about 30% with HFCs by 2010. HFCs are more likely to be selected where more stringent energy standards exist. In contrast, the investment related to the introduction of a new blowing agent might play a determining role in developing countries. However, in practice, this effect has been broadly offset by the supporting activities of the multilateral fund. Significant concern about hydrocarbon use exists in North America and Japan, related to product liability and process safety costs.

Vacuum panels may partly replace insulation foam in the future but the cost-effectiveness of this option is uncertain. A few domestic and commercial applications already use vacuum insulation panels in combination with polyurethane foams. These systems have up to 20% lower energy consumption than those using CFC or HCFC blown foam insulation systems (UNEP, 1998d).

A3.3.3 Insulating Foams in Residential Buildings

The use of HFC blown foams in the residential sector is expected to be relatively limited because of the high cost-sensitivity of this market. However, it is preferable to base the choice of insulation for all buildings on a proper consideration of the LCCP, including the comparative energy saving impacts of alternative insulation materials, the potential emissions of blowing agents, and the embodied energies of the insulating materials themselves. Where HFCs are used, the cost to destroy the HFC will be determined primarily by the cost of separating the construction materials. There are trends towards prefabricated construction and requirements for recycling of building materials in some regions that could lower these costs in time. Emissions of HFCs partially offset the benefits of low energy consumption arising from their use.

The use of hydrocarbon and carbon dioxide as blowing agents for polyurethane and extruded polystyrene insulation foams is expanding. A recent European study (Harnisch and Hendriks, 2000) estimated that by 2010 about 50% of all polyurethane and extruded polystyrene foams in this sector will be blown by hydrocarbons and carbon dioxide, respectively. It is estimated that substituting the remaining HFCs by hydrocarbon use in the mass markets of polyurethane foam production would cost between US$90 and US$125/tCeq. There is some concern about the use of flammable hydrocarbons in the residential environment and indoor air quality could also be affected. The replacement of HFCs by CO2/water blown polyurethane spray systems is estimated to be available at a cost-effectiveness of about US$80/tCeq (Harnisch and Hendriks, 2000). In Europe, one major producer is converting its extruded polystyrene production lines to use CO2 as the blowing agent. The cost-effectiveness of the use of CO2 as the blowing agent for extruded polystyrene is estimated at US$40/tCeq (March, 1998) and at US$25/tCeq (Harnisch and Hendriks, 2000) for the remaining manufacturers in Europe.

Fibrous insulation materials and expanded polystyrene are used extensively for residential construction in most parts of the world. The increased thickness required to achieve a desired energy efficiency can cost more; however, builders have been willing to increase the cavity wall size substantially since the 1970s to comply with increasing insulation standards in some regions.

A3.3.4 Insulating Foams in Commercial Buildings

For commercial buildings, the choice of foam type and facings is more likely to be based on lifetime costs (performance related) than on initial cost. An additional factor is the increased use of prefabricated building techniques, particularly in Europe. Both aspects suggest that HFC blown foams could penetrate the commercial and industrial sectors to a greater extent than the residential sector previously discussed. Harnisch and Hendriks (2000) estimate that avoiding HFCs in most mass applications by switching to hydrocarbon systems would cost in the region of US$90 to US$125/tCeq. For the switch from HFC to CO2 use in extruded polystyrene, one study estimates US$40/tCeq (March, 1998), whilst another (Harnisch and Hendriks, 2000) estimates US$25/tCeq for the remaining European manufacturers.

Fibrous insulation materials and expanded polystyrene are used extensively for commercial construction and are expected to play a significant role in the future. However, whether this role will expand technically seems in doubt.

A3.3.5 Insulating Foams in Transportation

Hydrocarbon blown foams and vacuum insulation panels are alternative options. Hydrocarbon blown foams have a somewhat lower insulating value per unit of thickness than HFC blown foams, and the vacuum insulating panels currently cost substantially more. Insulating performance is crucial in this sub-sector and serious thickness constraints exist, limiting the available options.

A3.3.6 Other Insulating Foams

Another application of HFCs for insulating foams will be in industrial process applications, where an estimated 2500 tonnes will be used – primarily in process pipework. Owing to high foam densities in this sector the differences in insulation performance between different blowing agents are small. For Europe it is estimated (Harnisch and Hendriks, 2000) that in 2010 hydrocarbons will have a market share of 50% of the pipe insulation production.

Both the building industry and the do-it-yourself market use one-component foams in a variety of applications, including sound and thermal insulation applications. The thermal conductivity of the foam, however, is not a critical requirement. HFC-134a and HFC-152a, hydrocarbons, propane, butane, and dimethyl ether (DME) are all technically suitable and in use. These are frequently used in blends; for example, a blend of HFC-134a/DME/propane/butane is widely used in Europe (UNEP, 1998d). Some replacement of HFC use in this sector is likely although concerns over the flammability of mixtures may delay this process in some regions.

A3.3.7 Non-Insulating Foams

Non-insulation HFC blown foams are expected to be used only in those applications where product or process safety are paramount, for example, integral skin foams for safety applications. Harnisch and Hendriks (2000) project that HFCs will not be required for the production of non-insulation foams in Europe. However, in view of different product specifications elsewhere in the world, liquid HFCs could replace a significant part of the current small use of HCFCs.

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