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Rigid and flexible plastic foams have a variety of applications that utilize combinations of the inherently high insulating value, resilience, low density, and lightweight structural characteristics of this class of materials. Major types of foam materials and their applications are categorized in Figure 9-1.

Figure 9-1: Major Applications and Types of Foam

As is apparent from Figure 9-1, plastic foams are used in a diverse range of applications. The applications highlighted in Figure 9-1 are most likely to require, and to sufficiently value, the properties of HFCs to justify the comparatively high cost. In the range of applications including packaging foams and resilient cushioning foams, a variety of other blowing agents, including hydrocarbons and CO₂ (both water blown and liquid CO₂) have been adopted.

In this study, the scope is limited to insulating foams, where the majority of HFC blowing agent use is likely to occur and the thermal properties of the blowing agent and the resulting foam have an impact on energy consumption. A major application of insulating foam, refrigerator and freezer wall insulation, is covered in Section 4 of this report, which addressed both refrigerant and foam blowing agent alternatives for home refrigerators and freezers.

The other major foam insulation application, which is addressed in this section, is building insulation. Foam products used for this purpose include:

• Polyisocyanurate board stock, which is widely used for building wall and roof insulation,
• Extruded polystyrene (XPS) board stock.
• Spray polyurethane foam (SPF) roofing which is used for commercial building roof insulation. SPF provides a means to apply a continuous (without seams or joints) layer of roofing that is water tight and infiltration tight,

Applications of foam building insulation reflect the diversity of building construction methods that are in use worldwide. Some of the more common applications include:

• Insulation for steel deck/steel truss-joist roof construction that is typical for low rise, flat roof commercial and industrial buildings. The foam is applied directly over the steel deck and covered with membrane or built-up roofing. In this application, foam insulation is required, because the insulation must support compressive loads. All three of the foam types covered here are used for this purpose.
• Foam board stock is used as an added layer of insulation over conventional woodframe walls and roofs with fiberglass batts filling the space between the studs or rafters.
• Insulation of below grade foundation (basement) walls in commercial and residential construction. In addition to reducing heat loads, insulation of foundation walls prevents moisture condensation during cold weather. Closed cell foam is required, because the insulation must withstand compressive loading and continuous exposure to water in the ground.
• Foam board stock is used in solid masonry construction, often between a concrete block structural wall and a brick outer facade.

Applications for PIR board stock, SPF and XPS board stock overlap to a degree, but the processing technologies are sufficiently unique that blowing agent alternatives need to be addressed individually with respect to each of these three products. Table 9-1 summarizes the progression of blowing agent selections and options through the CFC and HCFC phaseout.

Table 9-1:

In information provided by the U.S. plastic foam industry to the Montreal Protocol Foam TOC, the industry estimated that HFC blowing agent use for all applications globally (including domestic refrigerators) would be approximately 75,000 metric tonnes in 2004 (following the HCFC-141b phase out in 2003), growing to 115,000 tonnes in 2010. By 2010, growth rates will fall in line with growth rates in foam consumption. At this point, HFC will be used as the blowing agent in only 20% of all rigid foam.

Following the phase-out of CFC-11 at the end of 1995, the majority of foam board stock and SPF has been produced with HCFC-141b blowing agent, which provides insulating values close to those obtained with CFC-11. While R-141b is flammable, it is only weakly flammable, and once encapsulated in the closed cells of the foam does not pose a fire hazard. R-141b is a low-cost blowing agent, which is important to the competitiveness of insulating board stock and SPF relative to other alternatives. R-141b has the highest ODP (0.11) of any of the transitional alternatives to the CFCs and will be phased out in the future in much of the developed world (Jan. 1, 2003 in the U.S.)

The alternatives to R-141b that are under evaluation include several HFCs and hydrocarbons:

• Cyclo/isopentane blends
• HFC-245fa
• HFC-356mffm
• HFC-365mfc
• Pentane

The HFC blowing agents will provide foam thermal conductivities and R-Values that are very close to those currently provided by HCFC-141b. With the pentanes, R-Values will be approximately 10% lower and fire-safety issues must be addressed in manufacturing and in use.

XPS is produced by injecting a blowing agent (whose boiling point is below room temperature) in the molten polystyrene before it reaches the extrusion die. As this mixture exits the extrusion die the blowing agent vaporizes, expanding the molten resin into foam and creating a fine cell structure. As the foam leaves the extrusion die, it expands in width and thickness. Originally CFC-12 was used as the blowing agent; since the CFC phase-out, HCFC-142b has been used. The most viable non-ozone depleting alternatives are HFC-134a and CO₂. XPS would be processed the same way with either of these alternatives. XPS has flame retardant, but it cannot meet fire code requirements with a hydrocarbon blowing agent. With HFC-134a as the blowing agent, the resulting foam R-value is 5 (°F/in)/Btu-hr-ft²) (aged R value, guaranteed), the same as currently obtained with HCFC-142b; with CO₂, the R-value drops by 10-15% to approximately 4.3 to 4.4.

Spray polyurethane foam (SPF) roofing is a fast-growing segment of the building insulation foam market. SPF roofing is applied in a continuous layer on top of the roof deck of commercial buildings. SPF roofing provides numerous performance benefits, some relating directly to building energy consumption:

• SPF is applied in a continuous layer on top the roof deck, eliminating thermal shorts (thermal bridging) through fasteners and structure
• The continuous, joint-free layer of SPF is an effective infiltration barrier, eliminating both the latent and sensible loads associated with infiltration
• SPF has a high aged R-value of 6.0 per inch
• Light colored coverings (typically used) over the SPF reduce summer roof temperatures and solar heat gain and winter radiant heat loss

Other advantages of SPF roofing relate to the overall service life and cost effectiveness of the building operation:

• The effective infiltration barrier reduces moisture infiltration and condensation related damage, over time, to the building structure and interior
• SPF provides an extremely durable, impact (such as hail) resistant, long-lived, easily maintained roofing system
• SPF contributes to the structural strength of the roof
• SPF roofing is applied with minimal construction waste
• SPF roofing can be applied directly over an existing roof

SPF is foamed on site, using a liquid blowing agent. The non-ozone-depleting blowing agent options are the same as for polyisocyanurate boards stock. Worker safety considerations favor the use of a non-flammable HFC blowing agent.

Not in kind alternatives to foam board stock include other insulating materials traditionally used in the building industry, such as mineral wool and fiberglass. Traditionally, vacuum panels would be cost-prohibitive for building insulation applications, but newer, low cost vacuum panels have been developed that might make them a viable alternative for the future for specific, thickness sensitive, building insulation applications. Insulation for flat roofs and below grade foundation walls requires the compressive strength and moisture resistance of closed cell foam and cannot be replaced with other insulating materials.

Plastic foam insulation saves significant energy for heating and cooling buildings by reducing both winter heat loss and summer heat gain. In conventional wood-frame, fiberglass batt insulated residential/light commercial construction, PIR and XPS board stock sheathing provides a means of increasing the overall wall or roof R value by 25% to 50% that is low cost, maintains high-value interior floor space, and results in a negligible increase in the outside dimensions of the building. For building foundation walls and flat, steel deck roofs, foam insulation is the only viable method of insulation. For foundations, the compressive strength and water resistance of closed cell foam is essential. For flat, steel deck roofs, the compressive strength of plastic foam is essential. The energy impact of foam insulation and blowing agent is calculated for representative applications of each of these insulation applications in the subsections that follow.

The energy impact of foam roof insulation is illustrated by comparing the heating and cooling energy use per square foot of roof area for an uninsulated roof with roofs having 4 inches of XPS insulation or equivalent. The energy savings of the insulated roofs were calculated using the Owens Corning Global Energy Masser, Version 1.12, computer model. To arrive at an estimate that is representative of the U.S. climate as a whole, energy savings were calculated for roofs located in Knoxville, Los Angeles, Orlando, Providence and Minneapolis, with the average results for heating and cooling taken as representative. The results are summarized in Table 9-2.

Table 9-2: Average Annual Space Conditioning Energy Savings Per Square Foot in the U.S. for Flat, Steel Deck Roofs in Commercial and Industrial Buildings (Compared to no Insulation)

A study recently completed by Franklin Associates compared energy for conventional wood frame residential wall construction with and without an added layer of 5/8 foam board stock sheathing. Typical residential housing was examined in the United States and in Canada, and heating and cooling load calculations were performed for a range of climatic regions - ranging from the very warm in the Southern U.S. to the very cold in Northern Canada. The potential energy savings nationwide with both XPS and PIR boardstock sheathing were calculated. The results are summarized in Table 9-3, for application to all single family homes in the U.S. and Canada.

Table 9-3: Estimated Potential Energy Saving with Foam Insulating Sheathing in All Single Family Homes in the U.S. and Canada

The LCCP has been estimated, using the energy savings calculated above and comparing with the greenhouse gas emissions associated both with blowing agent emissions and manufacture of the foam board stock.

The AFEAS/DOE sponsored TEWI-1 study compared CFC-11 and CFC-12 blown PUR/PIR boardstock with various HCFC blowing agents and with other alternatives including expanded polystyrene and fiberglass type insulation. The TEWI 1 study addressed a wide range of residential and commercial building wall and roof configurations and supported the importance of building insulation in addressing global warming concerns. The TEWI-2 study updated the results of the TEWI-1 residential cases and attempted to begin the comparison of HCFC blown foams with various replacement blowing agents. This report suffered from the lack of available thermal performance data (in 1994) of foams produced with new blowing agents. SPF roofing was not addressed in the TEWI-1 or 2 studies. No other systematic TEWI/LCCP analysis of building systems was found in the literature.

Blowing agent losses/emissions occur at several stages of the life cycle of closed cell foam. On the order of 10% is emitted during manufacture of the foam product. Over the time that the insulating material is installed in the structure, very gradual diffusion of blowing agent out of (and of air into) the foam occurs. Even after many years of service, a significant amount of the blowing agent is retained in the foam. If the foam is removed from the building, or if the entire building is demolished, the foam is likely to be broken into pieces and landfilled. Little quantitative data exists on the rate of blowing agent loss. Data referred to in [Johnson, 1999] suggests that the half life for blowing agent diffusion from unfaced foam is of the order of 75 years; when contained between impermeable surfaces, the rate of diffusion out of the foam can be much lower. Absent hard quantitative data, it is assumed that 75% of the initial blowing agent is emitted within a relevant time scale.

LCCP calculations are summarized in Table 9-4, based on the energy impacts summarized in Table 9-2, a 50 year life, and lifetime emission of 75% of the blowing agent. In all cases, the reduction of indirect warming impact due to energy savings attributable to effective roof insulation exceeds the direct warming impact of blowing agent emissions by a factor of 10 to 20.

Table 9-4: Average LCCP for Space Conditioning Per Square Foot in the U.S. for Flat, Steel Deck Roofs in Commercial and Industrial Buildings

LCCP calculations are summarized in Table 9-5. The basis of the calculation is the energy savings summarized in Table 9-3 and 10% blowing agent loss between manufacture and installation. Energy for manufacture of foam is included. For both the XPS and the PIR insulating sheathing, the annual reduction of energy consumption and the associated carbon dioxide emissions offset the warming impacts of manufacturing the foam within 3 to 4 years. Over the first 30 years that the insulation is in place, the reduction in energy related carbon dioxide emissions will be about ten times the warming impacts associated with manufacturing the foam.

Table 9-5: LCCP of Foam Boardstock Insulating Sheathing for Residential Wood Frame Walls

These results show that far more energy is saved than consumed by manufacturing the foam and that far more greenhouse gas emissions due to space condition energy consumption are avoided than are emitted in the manufacture of the foam.

There are two primary safety considerations involved in the use of HC blowing agents in building foam insulation - manufacturing plant/job site safety and the fire rating of the foam.

Fire safety issues associated with flammable hydrocarbon blowing agents arise at several stages of the product life cycle.

• Manufacturing - during manufacturing, hydrocarbon blowing agent vapors are a fire hazard and also a VOC issue. As discussed in other parts of this document, the methods to handle flammable liquids and vapors safely in a manufacturing environment are well known, but add both capital cost and operating cost
• Transportation of the foam product - during the period immediately after a foam product is produced, it is not unusual for some blowing agent to outgas. This needs to be taken into account by pre-outgasing the foam and providing adequate ventilation in a closed trailer or shipping container.
• In use, outgasing of flammable blowing agent could pose a fire hazard, but unless the product is in a tightly confined space, flammable concentrations are unlikely to accumulate

SPF roofing requires a non-flammable blowing agent due to worker safety considerations during installation. In many code jurisdictions, fire safety regulations currently prohibit the use of a flammable-blowing agent.

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