TRANSITIONING TO LOW-GWP ALTERNATIVES 

IN BUILDING/CONSTRUCTION FOAMS

Background

This fact sheet provides current information on 

low-Global Warming Potential (GWP) foam blowing agent 

alternatives used in building and construction applications, 

relevant to the Montreal Protocol on Substances that Deplete 

the Ozone Layer. 

Several types of foams are used in building/construction 

applications: extruded polystyrene (XPS) boards and 

polyurethane (PU) rigid continuous panels, discontinuous 

panels, spray, boardstock, block, and pipe-in-pipe. The 

text box (right) describes these types. These foams provide 

insulation in housing and in commercial and industrial 

buildings (in walls, roofs, floors, tanks, and pipes). They 

typically remain intact for the lifetime of the building, which 

ranges from 25 to 70 years. In many places, the amount of 

insulation used in homes/buildings has increased over time, 

as energy efficiency standards have become more stringent. 

The U.S. Environmental Protection Agency estimates that 

global HFC consumption in the building/construction foams 

sector accounted for approximately 38 million metric tons 

of carbon dioxide equivalent (MMTCO2eq.) in 2010, with 

developed countries accounting for 98% of this consumption. 

Developing countries accounted for very limited HFC 

consumption because HCFC use was still permitted and, 

given the high relative cost of HFCs, few users chose to 

adopt HFCs. However, as the first HCFC phaseout obligations 

for developing countries approach in 2013, users are 

considering alternatives. Several low-GWP alternatives have 

become available over the last few years, offering developing 

countries an opportunity to transition directly from HCFCs to 

cost-effective, low-GWP alternatives.

Applications of XPS and PU Foams in the Building/

Construction Sector

XPS Board—used primarily in floor, wall, and roof insulation; a limited amount 

in pipe insulation. Good compressive strength and resistance to water vapor 

permeability provide significant advantages for floor insulation. 

Continuous Panel—used in wall and roof insulation, cladding of commercial 

and industrial buildings (e.g., factory units), and applications requiring constant 

temperatures and hygienic environments (e.g., production of pharmaceuticals, 

electronics, and foods). In North America and Europe, also used in cold stores. 

Discontinuous Panel—used most commonly for internal cold storage (e.g., fish 

or meat storage) in developed countries and, increasingly, in developing countries. 

Also used in wall and roof insulation. Commonly manufactured by small- and 

medium-sized enterprises.

Spray—used primarily to retrofit existing roofs to improve insulation performance. 

Also used in tank and pipe insulation and to provide insulation on a range of 

irregular surfaces. Nearly always applied using portable equipment in situ rather 

than in the factory. 

Boardstock—used in wall and roof insulation and, to a lesser extent, in floor 

insulation. In North America, primarily used as one layer in multi-layer residential 

walls and roofs; in Europe, primarily used in commercial and industrial buildings, 

with recent increases in the housing sector. 

Block—used primarily in pipe insulation and cold stores, and to a limited 

extent, in roof insulation. Often cut into slabs for composite panels (with metal 

or plasterboard surfaces) or cut into pipe sections for use in smaller insulated 

buildings. Typically the first building/construction foam type to be manufactured in 

emerging markets, due to low investment cost and range of end-use applications. 

Pipe-in-Pipe—used primarily in pipe insulation, particularly for district central 

heating systems in cities. 

2010 HFC Consumption 

(Estimates Presented in MMTCO2eq.) 

XPS 

Boards Discontinuous 54% Panels 22%

Continuous 

Panels 6%

Boardstock 

0%

Block 0%

Spray 11%

Pipe-in-Pipe 

7%

Spray

51%

Discontinuous 

Panels 12%

Continuous 

Panels 6%

XPS Boards 

24%

Pipe-in-Pipe 

0%

Block 2%

Boardstock

5%

Developed 

Countries 

98%

Developing 

Countries 2%

Global HFC Consumption Building/Construction Foams Total: 38 MMTCO2eq.
HFC Alternatives and Market Trends

A variety of climate-friendly blowing agents have been or are being developed for use in 

building/construction foam applications to replace CFCs, HCFCs, and HFCs. For example, 

for production of XPS boards, low-GWP hydrocarbon (HC) alternatives already comprise 

more than half of the global market, while CO2 is also being used. Similarly, for PU rigid 

foams, HCs are being used to produce panels, boardstock, block, and pipe-in-pipe foam. 

For spray foam, low-GWP alternatives, such as CO2, are being explored. Other low-GWP 

options, such as methyl formate and HFOs,1 have also been proposed across various 

building/construction foam applications. These alternatives are described further below.

HCs (cyclopentane, cyclopentane blends, isobutane, and 

n-pentane)

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New equipment needed to handle flammable agents

Good blowing efficiency (requires less blowing agent in the system than HCFCs)

Blended easily to provide a combination of properties

CO2

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Lower insulation value compared to HCFCs requires 30–50% increase in 

foam thickness 

Non-flammable

Can be generated in situ 

Commonly used as a co-blowing agent in PU rigid foams 

Di-methyl Ether 

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New equipment needed to handle flammable agents 

Established market (primarily due to use in XPS and one-component foams in Europe 

and China) with growing capacity

Methyl Formate

• Good blowing efficiency (requires less blowing agent in the system than HCFCs)

Methylal

• Under evaluation as co-blowing agent with HCs and HFCs in a range of building/

construction foam applications

HFOs (HFO-1234ze, others)

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Few facility modifications required to transition from HCFCs

Low to mild flammability

Good solubility properties 

Being evaluated for building/construction foam applications; could be available as 

early as 2013

The actual and potential transition to these alternatives in each of the building/

construction foam applications is described on the following page.2

Europe’s Experience 

The European Union phased out HCFCs in 2003 and 

much of the building/construction sector transitioned 

directly to HCs, having used these blowing agents since 

1992. Some smaller companies, as well as those making 

foams with stringent end-use flammability standards, 

used HFCs. Through product development, most of these 

standards now can be met with HC-based foams, and 

HFC use has diminished. The only exception is the spray 

foam application, which still relies on HFCs.

Chemical GWP ODPa

CFC-12 10,900 1

CFC-11 4,750 1

HFC-227ea 3,220 0

HCFC-142b 2,310 0.065

HCFC-22 1,810 0.055

HFC-134a 1,430 0

HFC-245fa 1,030 0

HFC-365mfc 794 0

HCFC-141b 725 0.11

HFC-152a 124 0

Cyclopentane <25 0

n-Pentane <25 0

Methyl Formate <25 0

Methylal <25 0

Other HFOs <25 0

HFO-1234ze 6 0

Isobutane 3 0

Di-methyl Ether 1 0

CO2 1 0

a

ODP = ozone depletion potential
XPS Board

XPS boards historically used CFC-12 as the blowing agent, and then 

predominantly transitioned to HCFC-142b/22 blends. In developed 

countries, HFC-134a and HFC-152a have replaced some ozone-depleting 

substances (ODS) use, but other low-GWP options—isobutane, di-methyl 

ether, blends of those two agents, and CO2—are also used. HFO-1234ze is 

also being evaluated for this application. 

Blowing Agent Transition: XPS Board

CFC-12

HFO-1234ze

Di-methyl Ether, 

Isobutane, Blends

CO2

HCFCs (142b, 

22, Blends)

HFCs 

(134a, 152a)

Continuous and Discontinuous Panels 

Most of the rigid panel foam industry transitioned from CFC-11 to HCFC141b, except for a number of European manufacturers that transitioned 

directly to HCs. Subsequent transitions have been to HFCs—typically 

HFC-365mfc/227ea blends and HFC-245fa—although with technological 

advances in recent years, there has been an increasing shift toward HCs 

(n-pentane and cyclopentane blends). Methyl formate and HFOs are being 

evaluated for these applications and may become viable alternatives.

Blowing Agent Transition: Continuous and Discontinuous Panels

CFC-11

HCs (n-Pentane, 

Cyclopentane 

Blends)

Methyl 

Formate

HFOs 

HFCs

(365mfc/227ea, 

245fa)

HCFC-141b

Spray

In North America, HCFC-141b was replaced by HFCs, primarily HFC245fa, in spray foam applications. In Europe, both HFC-245fa and 

HFC-365mfc/227ea blends have been adopted, mostly co-blown (diluted) 

with CO2. In Japan, CO2, including super-critical CO2, is being used to a 

limited extent, in addition to HFC-245fa. Technologies being evaluated 

for spray foam include methyl formate and HFOs. Hydrocarbons have 

not been used extensively in this application due to safety concerns. 

Additional research and development are needed to fully transition this 

end-use to low-GWP alternatives. 

Blowing Agent Transition: Spray

CFC-11 HCFC-141b

HFCs (245fa, 

365mfc/227ea) 

with CO2

HFOs

Methyl 

Formate

CO2

Boardstock

Most of the boardstock foam industry transitioned from CFCs to HCFC141b, although a number of European manufacturers transitioned directly 

to HCs, such as n-pentane and cyclopentane. The use of cyclopentane in 

Europe began later than n-pentane, when availability of cyclopentane 

increased and prices decreased. Since the phaseout of HCFC-141b in 

2003, North America has also shifted primarily to HCs (cyclopentane). 

A few manufacturers in other developed countries transitioned to HFCs 

(HFC-245fa, HFC-365mfc/227ea blends) to meet product fire requirements 

and/or where the cost burden could be absorbed—although most of 

these applications can now use HCs. Currently, most developing countries 

producing boardstock foam rely on HCFC-141b. Methyl formate and HFOs 

may become viable alternatives. 

Blowing Agent Transition: Boardstock

CFC-11

Methyl 

Formate

HFOs

HCs (Cyclopentane, 

n-Pentane)

HCFC-141b HFCs (245fa, 

365mfc/227ea)

Block

After transitioning from CFC-11 to HCFC-141b for the production of block 

foam, the majority of developed countries transitioned to HFCs—with 

Europe relying primarily on HFC-365mfc/227ea blends and North America 

on HFC-245fa. However, some producers transitioned directly from HCFC141b to n-pentane. Today, most production in Europe is with n-pentane. 

Methyl formate is being explored as a potential alternative, but concerns 

related to flammability exist.

Blowing Agent Transition: Block

CFC-11 HCFC-141b

HFCs 

(245fa, 365mfc/ 

227ea)

Methyl

Formate

n-Pentane

Pipe-in-Pipe

A number of European manufacturers have adopted optimized HC systems 

based on cyclopentane in pipe-in-pipe foam, while other developed 

countries have adopted HFC-245fa or HFC-365mfc/227ea blends. The 

technology options being explored for pipe-in-pipe PU foams in developing 

countries are focused on HC technologies, as there is little penalty in 

insulation thicknesses and the manufacturing process is sophisticated, with 

proven engineering solutions. Moreover, since pipe-in-pipe products are 

largely used underground, they represent little intrinsic hazard.

Blowing Agent Transition: Pipe-in-Pipe

CFC-11 HCFC-141b HFCs (245fa, 

365mfc/227ea) Cyclopentane
Challenges to Market Entry and Potential Solutions 

The following table summarizes the challenges associated with the adoption of various alternatives as well as potential solutions to overcoming the challenges.

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Alternative Foam Type Challenges to Market Entry Potential Solutions

HCs •	

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XPS Boards 

Continuous Panels

Discontinuous Panels

Boardstock

Block

Pipe-in-Pipe

High Flammability Engineering Design and Pre-Blending

Research and Development to Improve 

Thermal Performance

New Equipment Required to Handle 

Flammable Agents

CO2 •	

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 XPS Boards

 Spray

Other (As a Blend to Primary Blowing 

Agent) 

Increased Quantities of Foam Required to 

Accommodate Lower Insulation Value 

Poor Stability When Used as Sole Blowing 

Agent 

Poor Gas and Foam Thermal Conductivity 

High Permeability Through Cell Walls

Higher Densities to Compensate for 

Poor Stability 

Di-methyl Ether •	XPS Boards Moderate Flammability Engineering Design and Pre-Blending

New Equipment Required to Handle 

Flammable Agents

Methyl Formate Potential Use in Several Applications 

(e.g., Discontinuous Panels, Spray, 

Block)

Unknown Flammability

Lack of Application Data

High Permeability Through Cell Walls

Research and Development

Methylal Potential Blend Component in 

Several Applications 

Slight Flammability 

Limited Experience as the Sole Blowing 

Agent

Research and Development

HFOs Potential Use in Several Applications 

(e.g., XPS Boards, Discontinuous 

Panels, Spray, Boardstock)

Not Commercially Available Research and Development

Future Outlook

Most building/construction foam applications have readily available, low-GWP alternatives that will naturally be adopted as HCFCs are phased 

out. However, in the case of spray foams, continued research and development are needed to identify technically feasible, low-GWP alternatives. In 

other types of foams, continued research and development may expand the list of available low-GWP options. Together, the suite of currently known 

alternative chemicals and new technologies can significantly reduce future HFC consumption in both the near and long terms, while simultaneously 

completing the HCFC phaseout. Although much work remains to fully adopt these chemicals and technologies, and some unknowns still remain, the 

industries currently using HCFCs and HFCs have proven through the ODS phaseout that they can move quickly to protect the environment. Already, 

a number of projects are underway to transition building/construction foam production away from HCFCs to low-GWP alternatives in developing 

countries—including the production of spray foam using super-critical CO2 in Colombia; the production of discontinuous panels and block foam using 

pre-blended HCs in China; and the production of panels, spray, block, and pipe-in-pipe foam in Brazil using methylal.

1 HFOs (hydrofluoro-olefins) are unsaturated HFCs.

2 For all transition diagrams, solid arrows represent alternatives already available in the market for these systems; dashed arrows 

represent those likely to be available in the future. U.S. Environmental Protection Agency

EPA-430-F-11-005 • www.epa.gov • February 2011

Printed on 100% recycled/recyclable paper with a minimum 

50% post-consumer waste using vegetable-based inks
References

Babyak, Richard. 2009. “Insulation: Alternative Blowing Agents.” Available online at: http://www.ecomatesystems.com/pdfs/news/alternative_blowing_

agents.pdf. Accessed January 12, 2011.

California Air Resources Board/California Environmental Protection Agency. 2010. “Developing an Inventory for Ozone Depleting Substances (ODS) and 

Hydrofluorocarbon (HFC) Foam Banks and Emissions from Foams.” Draft Report. Prepared by Caleb Management Services Limited. 

DuPont. 2009. “Development of Nobel Blowing Agents for Polyurethane Foams.” Presented by John McMenamin, Mark L. Robin, Gary Lol, and Joseph 

A. Creazzo. Available online at: http://www2.dupont.com/Formacel/en_US/assets/downloads/UTECH_presentation_20090331.pdf. Accessed January 

12, 2011.

European Commission. 2010. “Identifying and Assessing Policy Options for Promoting the Recovery and Destruction of Ozone Depleting Substances 

(ODS) and Certain Fluorinated Greenhouse Gases (F-Gases) Banked In Products and Equipment.” Prepared by ICF International.

Honeywell. Undated. “Synthetic and Natural Refrigeration Fluids: Recent Developments.” Presented by Tom G.A. Vink. Available online at: http://www.

fluorocarbons.org/documents/Chemical%20Families/HFOs/TVink_Honeywell_EcoCool10.pdf. Accessed January 12, 2011.

Technology and Economic Assessment Panel. 2010. “TEAP 2010 Progress Report, Volume 2: Progress Report.” Available online at: http://ozone.unep.

org/Assessment_Panels/TEAP/Reports/TEAP_Reports/teap-2010-progress-report-volume2-May2010.pdf. Accessed January 8, 2011.

United Nations Environment Programme. 2010. “Guidance on the Process for Selecting Alternatives to HCFCs in Foams Sourcebook on Technology 

Options for Safeguarding the Ozone Layer and the Global Climate System.” Prepared by Caleb Management Services.

United Nations Environment Programme. 2007. “2006 Report of the Rigid and Flexible Foams Technical Options Committee: 2006 Assessment.”

United States Environmental Protection Agency. 2011. Preliminary estimates developed in consultation with Dr. Mike Jeffs.