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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 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 include those 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, resilient cushioning foams, and insulating foams such as boardstock, sandwich panels and slabstock, a variety of other blowing agents, including hydrocarbons and CO2 (water blown, gaseous, and liquid CO2) are in the process of being 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 (PIR) board stock, which is widely used for building wall and roof insulation,
• Extruded polystyrene (XPS) board stock, which is widely used for building wall, roof and foundation insulation, where a variety of compressive strength and moisture resistance is needed,
• Spray polyurethane foam (SPF) roofing which is used for commercial building roof and wall insulation and air barrier applications. SPF provides a means to apply a continuous (without seams or joints) layer of roofing that is water tight and infiltration tight,
• Sandwich panels with pour in place polyurethane or XPS or PIR boardstock
• Foam core entry doors and garage doors

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: Blowing Agent Options

In information provided by the U.S. plastic foam industry to the UNEP Flexible and Rigid Foams Technical Options Committee, 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 production phase out in the U.S. 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. HCFC-141b is a low-cost blowing agent, which is important to the competitiveness of insulating board stock and SPF relative to other alternatives. HCFC-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.)

There are three main applications for polyisocyanurate board stock in building applications --- roof insulation, wall insulation, and residential air barrier applications Residential wall sheathing insulation also avoids thermal bridging, resisting heat movement in all directions and provides reliable performance under varying climatic conditions. This better climate control saves energy and makes the building more comfortable for the occupants. Polyisocyanurate board stock has a high aged R-value of 6.0 per inch and is used as the primary thermal insulation in over 60% of all commercial low-slope roofing. Light colored covering membranes, frequently used over the polyiso, reduces summer roof temperatures and solar heat gain and winter radiant heat loss.

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

• Cyclopentane, normal pentane, iso pentane, and blends
• HFC-245fa
• HFC-134a
• HFC-365mfc and blends with HFC-227ea (will not be available as a blowing agent in the U.S. due to patent/license agreements)
• And blends of all of the above

The HFC blowing agents will provide foam thermal conductivities and R-Values that are very close to those currently provided by HCFC-141b. With early non-commercial formulations with the pentanes, R-Value losses up to 10% were experienced. Fire-safety issues must be addressed in manufacturing and in use. The major manufacturers in the boardstock industry have decided to convert to hydrocarbon blowing agents, due to the higher cost of HFC blowing agents.

XPS is very versatile and suited for a variety of diverse applications such as: cavity walls, steel or wood framed wall sheathing, furred walls, foundation walls, precast and tilt up concrete walls, under concrete slabs, and in decks. It is also ideal for roofing applications including single ply, tapered, built up roofing, and protected membrane systems.

XPS has numerous performance benefits including:

• High R-value which achieves net savings in energy consumption and greenhouse gas emissions
• Excellent moisture resistance which prevents the loss of thermal performance in the presence of water
• High compressive strength for a variety of applications
• Resistance to mold and mildew
• Lightweight for ease of handling and U.S. marketplace constraints for insulation products

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 in the early 1990's, HCFC-142b has been used. The phase-out date for HCFC 142b is not until 2010. Thus, unlike some of the other foams in this chapter, a commercially-viable, technically-feasible substitute alternative has yet to be identified. The XPS industry continues to conduct research to develop technically-feasible alternate blowing agent options. At this date, the most viable non-ozone depleting alternatives for the XPS industry are HFC-134a and CO2 or blends thereof.

Very preliminary research shows that using 100% HFC-134a as the blowing agent, the aged R-value would yield an R-Value of 5 (°F/in)/(Btu/hr-ft2) for the resulting foam, the same as currently obtained with HCFC-142b. However, it would be difficult with known technology, to make a commercially-viable foam for the U.S. building and construction marketplace using 100% HFC 134a. When CO2 is used, preliminary research shows the R-value drops by 10-15% to approximately 4.3 to 4.4 per inch. XPS would be processed the same way with any alternative; but most likely, a blend of blowing agents will be required which would lower the theoretical R-value of HFC 134a blown XPS foam to something less. Since an acceptable alternative for XPS has yet to be identified, much less used in actual commercial applications, the industry cannot predict the actual amount of any R-Value loss that might occur using alternative blowing agents.

There are three main applications for spray polyurethane foam (SPF) in building applications --- roof insulation, wall insulation, and air barrier applications.

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, at a density of 2.5 to 3.0 lb/ft³. 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

Three SPF systems are used within the building envelope; high density (1-1/2 - 2 lb/ft³), low density (less than 1/2 lb/ft³), and sealant foaMs. Low density (< ½ lb/ft³) foams are open celled and are normally water blown.

High density SPF is used when strength, high moisture resistance and high insulating value is desired.

Low density SPF is used when insulation, air barrier and sound control is desired.

Sealant foams are used to caulk around windows, doors, sill plates and other locations to seal against unwanted air infiltration

SPF by providing a continuous air barrier, preventing moisture infiltration through air leakage, minimizing dew point problems and condensation within the building, avoiding thermal bridging, resisting heat movement in all directions and providing reliable performance under varying climatic conditions provides better climate and moisture control Better climate control saves energy and makes the building more comfortable. Better moisture control reduces building deterioration increasing the life of the building. SPF's climate control ability enables a downsizing of the heating and cooling equipment of a building, further reducing energy use. Side-by-side energy efficiency comparisons have shown up to 40% energy savings by using SPF over the commonly specified insulation materials. The use of high density SPF within the building can add significant structural strength minimizing damage from building movement and racking events [NAHB, 1996], [NAHB, 1992].

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 Master, 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, 2000] 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 a mix of 60% XPS and 40% 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 (60% XPS, 40% PIR) 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, options for disposal include land filling, shredding and land filling, or incineration. Initial research [Kjeldsen and Scheutz, 2002] indicates that less than 25% of the blowing agent may be released upon shredding and before being land filled. Once the foam has been land filled, diffusion to the atmosphere is very slow. Moreover, recent laboratory and field studies [Scheutz and Kjeldsen, 2002] indicate that microbes in the soil breakdown a variety of fluorochemicals such as CFC-11 and 12 and HCFC-22, further reducing the amount emitted to the atmosphere. Additional research is being conducted to determine the extent to which these microbes also breakdown HFC blowing agents such as HFC-245fa. Absent hard quantitative data, the highly conservative assumption is made 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 of installation. 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 three primary safety considerations involved in the use of HC blowing agents in building foam insulation --- manufacturing plant/job site safety, transportation of the foam and polyol premixes containing HC blowing agents, 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. However, boardstock products are shipped on open trailers so no extra precautions are expected to be necessary
• Prior to commercial use, boardstock foams must pass a series of fire tests in order for their installation to be approved under current model building codes. These tests evaluate the complete product and account for any differences in blowing agent flammability.

The major manufacturers of PIR foam board stock have decided to convert from HCFC-141b to hydrocarbon blowing agents, so these issues are being addressed. The major XPS manufacturers are focused on considering HFC alternatives.

SPF roofing and wall insulation favors 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.