Unlocking Carbon Savings with Plastic Insulation Materials

PLASTIC INSULATION IS typically composed
of a plastic polymer, such as polyurethanes
or polystyrenes, a blowing agent, such as
chlorofluorocarbons (CFCs), a surfactant,
and other flame retardants or additives. The
application of insulation in homes evolved from
hay to fiberglass in the 1930s, followed by the
shift to plastic insulation in the 1970s.1, 2
The method of determining the
environmental impact of plastic insulation
materials is through a life-cycle assessment
(LCA), which is the quantified analysis of
the material and energy inventories and
potential environmental impacts of a product
through the various stages of that product’s
life. An LCA consists of four phases: goal
and scope, life-cycle inventory, life-cycle
impact assessment, and interpretation of the
results. In the building sector, the life-cycle
of insulation products is typically depicted in
an environmental product declaration (EPD)
that communicates the verifiable results of
an LCA. The life-cycle of an insulation product
includes four stages: product manufacture,
construction, use, and end of life. A fifth stage,
depicted by Module D in Figure 1, quantifies
potential benefits and impacts beyond the
building’s system boundary and is often
excluded from the scope of EPDs. The life-cycle
stages are divided further into substages
called modules shown in Fig. 1 module A1
through module C4. Figure 1 also depicts the
four more-common types of life-cycle scopes:
cradle-to-gate, cradle-to-site, cradle-to-grave,
and cradle-to-cradle.
EPDs for insulation products report various
environmental impact categories, including the
embodied carbon of the insulation material,
which is calculated as the global warming
potential (GWP) and expressed as kg CO2e or
kilograms of carbon dioxide equivalent. This
article focuses on the embodied carbon of four
insulation types: expanded polystyrene (EPS),
extruded polystyrene (XPS), spray foam (SPF),
Online Exclusive
Unlocking Carbon Savings with
Plastic Insulation Materials
By Amy Schmidt and Allison Chertack and polyisocyanurate (PIR). EPS is made up
of closed-cell foam plastic beads molded into
a rigid board. XPS is an extruded closed cell
insulation product that comes in the form of
boards. SPF is foamed in place at the job site;
it comes in open cell and closed cell material
types which expands when its two components
react when combined in a spray gun. PIR
or polyiso, is a closed-cell rigid foam board
insulation consisting of a foam core typically
between two facers. The functional unit is m2
of insulation based on an RSI value of 1 based
on a service life of 75 years for each of the four
insulation types. RSI is variable used in the
International System of Units (SI) for thermal
resistance. RSI can be converted to R-value,
the Imperial Units (IP) variable, by multiplying
the RSI value by 5.678. Thus, all analyzed
environmental impacts are reported based
on this functional unit. For example, the GWP
is reported kg CO2e/m2 of insulation based
on an RSI value of 1 based on a service life of
75 years. Data were collected from primary
sources, EPDs from various years and product
category rules (PCRs), and peer-reviewed
reports. The embodied carbon data points were
then grouped by their formulation; the most
recent formulation of each material from a
producer was used.
Over the last several decades, plastic
insulation has included blowing agents
from chlorofluorocarbons (CFCs), to
hydrochlorofluorocarbons (HCFCs),
to hydrofluorocarbons (HFCs), and
Interface articles may cite trade, brand,
or product names to specify or describe
adequately materials, experimental
procedures, and/or equipment. In no
case does such identification imply
recommendation or endorsement by
the International Institute of Building
Enclosure Consultants (IIBEC).
Spring 2024 ©2024 International Institute of Building Enclosure Consultants (IIBEC) IIBEC Interface • 1
hydrofluoroolefins (HFOs). Part I of the
“Results and Discussion” section describes the
shift to blowing agents with lower greenhouse
gas (GHG) emissions and ultimately lower
embodied carbon. The decreasing embodied
carbon of plastic insulation materials was the
result of product reformulations driven by
global concern regarding the environmental
impact of blowing agents. Despite the
globally publicized phase out of blowing
agents with high GWPs, plastic insulation
continues to be scrutinized for its supposed
high embodied carbon and related impacts.
The limited understanding of embodied
carbon improvements inhibits the ability
of the plastics insulation industry to inform
GWP-related policy and develop solutions
surrounding decisions on the sustainability
of plastic insulation. Additionally, there are
insufficient data on the total carbon impacts
of insulation, including the embodied carbon
of insulation material and the carbon benefits
of these materials. Here, total carbon impact
is defined as the net impact of the embodied
carbon investment and the operational carbon
savings associated with a material, as shown
in Fig. 2.3 Therefore, this two-part report aims
to A) highlight the historical reductions in
the embodied carbon of four insulation types
and B) evaluate the life-cycle energy and GHG
savings attributed to the application of plastic
insulation materials in both residential and
commercial building enclosures. Figure 2
demonstrates the inputs required to calculate
the total carbon of a material, which is the
sum of the embodied carbon of a material
and the operational carbon savings of
the same material.
EXPERIMENTAL
Part I
The embodied carbon of each insulation type
is determined by calculating the GWP of the
insulation products in accordance with the
Product Category Rules (PCR) Guidance for
Building Related Products and Services Part
B: Building Envelope Thermal Insulation EPD
Requirements UL 10010-1.4 The PCR includes
modules A1-A5, B1-B5, and C1-C4 (Fig. 1).
Impacts of other modules can be voluntarily
included in the EPD but are not included for the
purposes of our analysis. The EPDs are typically
conducted by an insulation association or
insulation manufacturer with the assistance of a
third-party consultant or LCA expert. Although
several potential environmental impacts are
included in a product’s EPD, this report focuses
on GHGs. GHGs are gases that absorb and trap
Figure 1. Displays the life-cycle modules for each life-cycle stage of the insulation and common scopes of life-cycle assessment.
Figure 2. Total carbon of a material evaluates the net greenhouse gas emissions from a product or material’s embodied carbon and emissions
savings attributed to the operational carbon benefits realized after installation and during the building’s use.
Life-Cycle States Life-Cycle Modules Life-Cycle Assessments
2 • IIBEC Interface Spring 2024
heat in the atmosphere; the most common
GHGs include carbon dioxide (CO2), methane
(CH4), and nitrous oxide (N2O). The GHGs are
measured in a metric called global warming
potential (GWP). GWP is used to measure
the impact of different gases on one shared
scale, due to gases having different effects
on global warming. The two main ways GHGs
have variable effects on global warming are
their abilities to absorb energy and the amount
of time they stay in the atmosphere. GWP
measures the amount of energy one ton of a
gas will absorb over a certain amount of time
compared to the amount of energy one ton of
CO2 will absorb over the same amount of time.
As mentioned previously, GWP is measured
as kilograms (kg) of CO2 equivalent, which
allows different GHGs to be compared on the
same scale.
To compare the changes in the GWP of
the four plastic insulation types, data were
collected from primary sources through
a survey. Insulation manufacturers were
requested to provide current and historical
life-cycle data, specifically embodied carbon
data along with its associated PCR version as
applicable and any notable changes that may
have caused the change in embodied carbon
from one PCR or product formulation to the
next. Additional information was collected
from industry and producer EPDs available
on the Building Transparency EC3 database.5
Data from peer-reviewed sources were also
incorporated where applicable to maintain the
parameters of the study for North American
applications.
Part II
To develop new data and gain a more current
perspective on the net, or total carbon impacts
of plastic insulation materials, specifically XPS,
EPS, SPF, and PIR, a modeling project was
conducted by ICF International Inc. This project,
“Determination of Total Carbon Impact of Plastic
Insulation Materials,” examined the energy and
operational carbon impacts associated with
these four plastic insulation materials throughout
their useful life using conservative assumptions,
including thermal resistance properties, climate
zones, building types, and grid makeup.6 The
model results were compared to the embodied
carbon investment of the insulation materials
in the prototype buildings to establish an
understanding of the total carbon payback
and total carbon avoidance (embodied carbon
investment to operational carbon savings).
A case study by Franklin Associates, “Plastic
Energy and Greenhouse Gas Savings Using
Rigid Foam Sheathing Applied to Exterior
Walls of Single-Family Residential Housing in
the U.S. and Canada,” found favorable energy
and carbon payback time frames.7 While this
study used different modeling assumptions
than the recent ICF study and was conducted
nearly two decades prior, the results were
consistent. The Franklin study showed that by
adding an additional 5⁄8 in (16 mm) of exterior
rigid foam insulation to a home with a service
life of 50 years, a GHG payback ranging from
12.5 years in the US to 3 years in Canada could
be achieved, despite the higher embodied
carbon of insulation materials at that time.
Another research report in the Journal of
Industrial Ecology (JIE), “Life Cycle Greenhouse
Gas Emissions Reduction from Rigid Thermal
Insulation Use in Buildings,” published in 2011,
found an average GHG savings to embodied
carbon ratio of 48:1.8 As with the Franklin
study, this study used different modeling
assumptions than the ICF study but found
comparable significant total carbon benefits of
plastic insulation materials when considering
the full life-cycle of the building. It’s important
to note the GHG emissions data per functional
unit in the 2011 study were not subjected to
the same third-party analysis or PCR as with the
ICF study.
There are a handful of other industry-wide
and manufacturer-specific LCAs that model
total carbon benefits, but the majority are
limited to a single insulation type or building
application, further emphasizing the need for
recent, and more extensive studies on the total
carbon benefits of plastic insulation.
The ICF study, included current plastic
insulation embodied carbon data, projected
grid emissions data based on the National
Renewable Energy Lab (NREL) Cambium
scenarios, Climate Zones 3 and 5, and
Department of Energy (DOE) residential
two-story home and medium office building
prototypes.9 ICF utilized DOE’s Energy Plus
software to model the energy data. ICF also
calculated the total carbon impacts of the
insulation materials in the modeled buildings
and used current and projected grid emissions
data to determine the GWP impacts. Using
the data, ICF calculated the plastic insulation
material GWP payback and GWP avoidance
ratios using Cambium High, Medium, and
Low Cost of Conversion to Renewable Energy
grid projections. The data were then compared
to the embodied carbon investment in these
materials in prototype buildings so that an
understanding of GWP payback and GWP
avoidance could be established.
The US is segmented into eight different
climate zones, represented by a number 1-8,
and three categories based on moisture levels,
denoted by letters A, B, and C.11 Climate Zones
3 and 5 were selected for the study because
they are conservatively representative of
heating and a cooling dominated regions of
the U.S. (Table 1). These climate zones are also
home to a large segment of the population and
the representative cities are all found in the top
11 states for housing starts in 2022 according
to the US Census Bureau Building Permits
Survey.10
Representative thermo-physical properties
were established in (Table 2). These values
do not reflect all available or proprietary
insulation properties. They are conservative
representations of materials readily available
in the US.
Table 1. Representative Climate Zones 3 and 5 Modeling Assumptions
Climate Zone Representative City Weather Location HDD65 CDD65
3A Atlanta, Georgia Atlanta/Hartsfield Jackson International Airport, Georgia 2,498 2,099
3B El Paso, Texas El Paso International Airport, Texas 2,012 2,972
3C San Diego, California San Diego/Brown Field Municipal Airport, California 1,377 763
5A Buffalo, New York Buffalo Niagara International Airport, New York 6,242 769
5B Denver, Colorado Denver/Aurora/Buckley AFB, Colorado 5,737 832
5C Port Angeles, Washington Port Angeles/William R Fairchild International Airport, Washington 5,488 20
Note: HDD65 = Heating Degree Days below 65°F (18°C); CDD65 = Cooling Degree Days above 65°F (18°C).
Spring 2024 IIBEC Interface • 3
Table 3. Simulated Scenarios for Residential Prototype
Scenario Description
R0 No Insulation (Baseline)
R1 Basement + Attic Insulation (No Wall Insulation)
R2 Wall + Attic Insulation (No Basement Insulation)
R3 Wall + Basement Insulation (No Attic Insulation)
R4 Whole Home Insulation
Table 4. Simulated Scenarios for Commercial Prototype
Scenario Description
C0 No Insulation (Baseline)
C1 Slab + Roof Insulation (No Wall Insulation)
C2 Wall + Roof Insulation (No Slab Insulation)
C3 Wall + Slab Insulation (No Roof Insulation)
C4 Whole Office Insulation
Table 6. ASHRAE 90.1-2019 Minimum Insulation R-values and Enclosure Components.14
Location
Climate Zone
3 5
Above-Grade Wall
Insulation Steel framed, R-13 cc-SPF in cavity, R-5ci PIR sheathing Steel framed, R-13 cc-SPF in cavity, R-10ci PIR sheathing
Slab Insulation None R-15ci XPS foam sheathing for 24” deep from top of slab down
Roof Insulation
(Entirely Above Deck) R-25ci PIR sheathing R-30ci PIR sheathing
Note: cc = closed cell; ci = continuous insulation; PIR = polyisocyanurate; SPF = spray foam; XPS = extruded polystyrene.
Table 5. 2021 International Energy Conservation Code (IECC) Minimum Insulation R -values and Enclosure Components.13
Location
Climate Zone
3 5
Above-Grade Exterior
Wall Insulation
R-13 oc-SPF/cc-SPF blend 50/50 in cavity, R-5ci XPS/EPS
foam sheathing blend 50/50
R-13 oc-SPF/cc-SPF blend 50/50 in cavity, R-10ci XPS/EPS foam
sheathing blend 50/50
Basement Exterior Wall
Insulation R-5ci exterior XPS R-10ci exterior XPS, R-5ci interior XPS/EPS foam sheathing blend
50/50
Unvented Attic Insulation (Roof and Gable End Wall)
Roof Insulation
R-38 cc-SPF, as allowed by IECC Section R402.2.1,
assuming that insulation is applied to full R-value and
over the top plate at the eaves.
R-49 cc-SPF, as allowed by IECC Section R402.2.1, assuming that
insulation is applied to full R-value and over the top plate at the
eaves
Gable End Wall
Insulation
R-13 oc-SPF/cc-SPF blend 50/50 in cavity, R-5ci XPS/EPS
foam sheathing blend 50/50
R-13 oc-SPF/cc-SPF blend 50/50 in cavity, R-10ci XPS/EPS foam
sheathing blend 50/50
Note: cc = closed cell; ci = continuous insulation; EPS = expanded polystyrene; oc = open cell; SPF = spray foam; XPS = extruded polystyrene.
Table 2. Representative Thermo-physical Properties of Plastic Insulation Materials
Insulation Material R-value per inch
thickness
Thermal Conductivity
Btu/h∙ft∙°F (W/m∙K) Density lb/ft3 (kg/m3) Specific Heat Btu/lb∙°F (J/kg∙K)
XPS 5.00 0.01667 (0.02885) 1.56 (25) 0.36 (1500)
EPS 4.00 0.02083 (0.03606) 1.56 (25) 0.36 (1500)
Closed cell-SPF 6.50 0.01282 (0.02219) 2.18 (35) 0.35 (1450)
Open cell-SPF 3.50 0.02381 (0.04121) 2.18 (35) 0.35 (1450)
Polyisocyanurate 5.80 0.01437 (0.02487) 1.56 (25) 0.36 (1500)
Note: EPS = expanded polystyrene; SPF = spray foam; XPS = extruded polystyrene.
4 • IIBEC Interface Spring 2024
Two prototype buildings were selected for
the study, one residential and one commercial.
Again, conservative prototypes were selected.
The residential prototype selected was
the DOE two-story home.12 This is typically
more conservative than the one-story home
prototype due to its smaller square footage
and area of thermal loss through the ceiling/
roof. The commercial prototype selected was
the medium office building. This prototype is
typically more conservative than other larger,
more energy intensive, buildings like schools
and hospitals.
Four base modeling scenarios were
developed for both residential and
commercial. These scenarios are shown in
Tables 3 and 4.
Plastic insulation types that are commonly
used in these applications were used in the
model. In some scenarios where one of two
materials are typically used, their data were
averaged (50⁄50 blend). The representative
insulation types selected are shown in Table 5
for residential and Table 6 for commercial.
For the residential model, the insulation
configurations for both the roof deck and on
the gable ends was defined. The insulation
types specified for modeling purposes in this
study are not representative of all potential
plastic insulation materials that can be used in
these applications.
These assumptions were used to inform the
assembly thermal resistance values used in the
EnergyPlus model.
A few changes were made to the EnergyPlus
model to better represent the configuration of
enclosure layers and the location of insulation
elements. For example, the modeling of
residential insulation at the roof deck versus
the attic floor was used to simulate an unvented
attic. These adjustments are described in detail
in the ICF report.6
A 75-year useful life was assumed, which is
the same service life assumption that is included
in the PCR for thermal insulation materials.
There were 147 simulations modeled: 120
for residential and 27 for commercial. There
were more simulations run for the residential
model due to the 4 different heating systems
(electric resistance, gas furnace, oil furnace,
and heat pump) in the EnergyPlus model.
Additional simulation details can be found in
the ICF report.6
RESULTS AND DISCUSSION
Part I
While there are many factors that have led
to reductions in the embodied carbon of
insulation products, using lower GHG blowing
agents are attributed to the most significant
improvements. CFCs were first synthesized in
the 1920s in a combined effort by Frigidaire,
General Motors, and DuPont to replace less
desirable substances with refrigerant qualities.15
CFCs were utilized as blowing agents in foam
insulation materials where they formed air-filled
pockets that restricted heat transfer and reduced
the density of the foam insulation. In 1974,
scientists discovered the risk CFCs posed to
the deterioration of the ozone layer upon their
release. The depletion of ozone, a gas with
ultraviolet radiation absorption properties, could
increase the amount of radiation that reaches the
earth’s surface, subsequently heating the planet.
Like the ozone-depleting characteristics of CFCs,
these gases were determined to have a significant
embodied carbon demonstrated by their high
GWP. According to a study of the GHG emissions
of rigid thermal insulation, a formulation of XPS
(principle blowing agent CFC-12) used in North
America from 1971‑1989, had an embodied
carbon of more than 900 kg CO2e/m2.7
As a result of rising concerns associated
with the ozone-depleting nature of CFCs, a
global environmental treaty, the Montreal
Protocol to Reduce Substances that Deplete
the Ozone Layer, was adopted in 1987.16 The
treaty outlined a plan to phase out several
ozone depleting substances, including CFCs,
by placing controls on the production and
consumption of these substances. In the
absence of CFCs two new classes of substances
were created with similar insulating properties,
Figure 3. Reductions in embodied carbon of extruded polystyrene (XPS) insulation based on formulations in 1971, 1990, 2010, 2013, and 2018.
*The X-axis cuts-off at 300 kg CO2e/m2 to accommodate the more recent embodied carbon metrics that are significantly below 100 kg CO2e/m2.
However, the actual embodied carbon for XPS in 1971 is shown within the data bar as 981 kg CO2e/m2.
Spring 2024 IIBEC Interface • 5
HCFCs and HFCs. HCFCs proved to be beneficial
substitutes with a significantly lower GWP than
CFCs, as demonstrated by the 1990 formulation
of XPS (principle blowing agent HCFC-142b)
with a GWP of less than 230 kg CO2e/m2.
However, HCFCs had similar potential to
CFCs to deplete the ozone layer, prompting an
amendment to the Montreal Protocol outlining
their planned phase out too. This precipitated
the substitution of HCFCs with HFCs. While
HFCs do not have ozone depleting properties,
they have significant embodied carbon or
GWPs that resulted in the adoption of the
Kigali Amendment in 2016. This amendment
outlines the plan to phase out HFCs before
2050, due to the high GWPs ranging from 12
to 14,800.17 These substances will be replaced
by lower GWP blowing agents, such as HFOs or
pentanes.
Figure 3 showcases the reductions in
embodied carbon of XPS insulation materials
over the last several decades. The years indicated
on the X-axis correlate to the year a new
generation of XPS was introduced. The embodied
carbon of XPS has been significantly reduced
since 1971, primarily as a result of innovations in
new blowing agents and polymers, production
efficiencies, and material sourcing. While
some product generations may overlap, the
higher GWP materials are continuing to be
phased out as the industry trends shift towards
greater sustainability. Although the most recent
formulation was introduced in 2018, more recent
XPS products with EPDs published in 2021 and
beyond, show a continual downward trend in the
embodied carbon.
Similarly, Figure 4 displays the reductions
in embodied carbon of PIR insulation materials
over the last several decades. The years
indicated on the X-axis correlate to the year
a new generation of PIR was produced. The
embodied carbon of PIR has been reduced
significantly since 2001, resulting from
innovations in new blowing agents and
polymers, production efficiencies, and material
sourcing. While some product generations
may overlap, the higher GWP materials are
continuing to be phased out as the industry
trends shift toward greater sustainability.
Although the most recent formulation was
introduced in 2006, more recent PIR products
with EPDs published in 2021 and beyond,
show a continual downward trend in the
embodied carbon.
The scope of Part I included the embodied
carbon of four types of plastic insulation.
However, there was limited data publicly
available that met the parameters of the study,
including the functional unit and geographical
location. Plastic insulation produced,
transported, installed, and disposed of in
other countries or regions, such as Europe,
may have varying GWP results compared to
plastic insulation materials produced in the
US. This is because of potential differences
in the grid’s fuel sources, since some energy
sources have higher emissions than others
when combusted. Furthermore, expired
EPDs are removed from databases and
other building resources to ensure that only
current data on the contents and embodied
carbon of plastic insulation materials are
communicated. While beneficial in reducing
the communication of outdated metrics, this
presents a challenge in collecting historical
information. Additionally, the tracking of
plastic insulation’s embodied carbon through
EPDs is a more recent process, further adding
to the limited data available. However, it’s
important to recognize that other plastic
insulation materials, including SPF and EPS,
were not previously produced with high GWP
components, such as CFCs, HCFCs, or HFCs.
Moreover, the current EPDs for both EPS and
SPF showcase embodied carbons comparable
to most recent formulations of XPS and PIR.
This emphasizes the continual trend for plastic
insulation products to have low embodied
carbon throughout their life-cycles.
Part II: Determination of Total
Carbon Impacts
To determine the total carbon impacts
associated with plastic insulation materials,
the embodied carbon of the insulation
materials, and the operational carbon savings
Figure 4. Reductions in embodied carbon of polyisocyanurate (PIR) insulation based on formulations in 2001, 2006, and 2021.
*The YX-axis cuts-off at 10 kg CO2e/m2 to accommodate the more recent embodied carbon metrics that are significantly below 10 kg CO2e/m2.
However, the actual embodied carbon for PIR in 2001 is shown within the data bar as 87 kg CO2e/m2.
6 • IIBEC Interface Spring 2024
Table 7. Impact of Insulation on Total Site Energy Savings by End Use and Climate Zone for the Case with Current Heating Systems Mix (residential)
Climate Zone Scenario Total Site Energy Savings [kBtu] 3
Whole Home Insulation Impact 71,468
Wall Insulation Impact 39,203
Basement Insulation Impact 6,040
Attic Insulation Impact 26,927
5
Whole Home Insulation Impact 257,647
Wall Insulation Impact 137,697
Basement Insulation Impact 29,940
Attic Insulation Impact 100,420
Table 8. Impact of Insulation on Total Site Energy Savings by End Use and Climate Zone for the Case with Natural Gas Heating (commercial)
Climate Zone Scenario Total Site Energy Savings [kBtu] 3
Whole Office Insulation Impact 472,512
Wall Insulation Impact 142,056
Slab Insulation Impact —
Roof Insulation Impact 309,987
5
Whole Home Insulation Impact 969,178
Wall Insulation Impact 327,591
Slab Insulation Impact 2,594
Roof Insulation Impact 622,109
Table 9. Embodied Carbon Per Functional Unit of Plastic Insulation Materials
Insulation Material Embodied Carbon (kg CO2e/m2)
XPS 5.63
EPS 3.78
PIR (Wall) 3.49
PIR (Roof) 3.46
cc-SPF 4.21
oc-SPF 1.68
50/50 XPS/EPS 4.71
50/50 cc-SPF/oc-SPF 2.95
Note: cc = closed cell; EPS = expanded polystyrene; oc = open cell; PIR = polyisocyanurate; SPF = spray foam; XPS = extruded polystyrene.
associated with the modeled buildings
were summed.
The operational energy consumption and
savings were determined through the modeling
for the various scenarios. Modeling was done
using current heating and cooling system
energy mixes and to simulate a future 100%
heat pump conversion.
The total site energy use for each of the
scenarios utilizing the current heating systems
can be found in the ICF report.6 From this
consumption data, the energy savings of the
insulation elements associated with each
scenario were determined and summarized in
Table 7 (residential) and Table 8 (commercial).
The ICF report noted, consistent with
anomalies experienced with EnergyPlus,
that the software seems to undervalue slab
insulation contributions.6 Although these
values were expected to be much lower
than other insulation elements, there is
more investigation needed to understand
the potential shortcomings of the existing
EnergyPlus capabilities for this element.
Additional details about this phenomenon are
available in the ICF report.
The modeling to simulate a future 100%
conversion to electric heat pumps was done to
understand how the results may differ if the
goal of 100% electrification is achieved. The
Spring 2024 IIBEC Interface • 7
energy savings associated with this assumption
can be found in the ICF report.
To determine the embodied carbon of the
insulation materials for each of the scenarios,
representative emissions values of the
materials were used. The representative values
include materials that are available today
and for the foreseeable future. It is important
to note that there are values of materials
currently available that were not used due to
known material and blowing agent phase out
programs.
Embodied carbon values for each of the
material types were taken from public sources.
Embodied carbon is reported per functional
unit as specified in the UL Product Category
Rule for Building Envelope Thermal Insulation
Requirements.3 In some cases, industry-averaged
EPD was used and in some cases,
manufacturer-averaged EPD data were used. A
summary of the embodied carbon per functional
unit used in this study can be found in Table 9.
Using the building prototypes, the total
embodied carbon investment in the buildings
for each of the enclosure elements was
calculated. This data were used to calculate the
carbon payback and carbon avoidance ratios in
the report. The total embodied carbon values
are summarized in Table 10 (residential) and
Table 11 (commercial):
In addition to modeling scenarios that
include a 100% conversion to heat pumps,
several different future-looking grid scenarios
were used to understand the carbon payback
and the carbon avoidance ratios associated
with the use of plastic insulation materials.
Table 11. Total Embodied Carbon for Different Enclosure Elements Insulation for Climate Zone 3 and Climate Zone 5 (commercial)
Scenario
Embodied Carbon [metric tons CO2e] Climate Zone 3 Climate Zone 5
Wall Insulation 15.6 19.6
Slab Insulation — 1.51
Roof Insulation 25.3 30.4
Whole Office Insulation 40.9 51.5
Table 12. Electricity Emission Rates for Low RE Cost, Medium RE Cost, and High RE Cost
Year
Electricity Emission Rate (kg CO2e/MWh)
Low RE Cost Medium RE Cost High RE Cost
2024 327.0 302.7 255.0
2026 342.4 266.7 234.0
2028 330.5 211.6 176.1
2030 324.1 188.7 97.9
2035 325.0 132.1 40.8
2040 313.2 87.8 25.2
2045 315.8 63.7 39.6
2050 282.6 57.6 34.9
Note: RE = renewable energy.
Table 10. Total Embodied Carbon for Different Enclosure Elements Insulation for Climate Zone 3 and Climate Zone 5 (residential)
Scenario
Embodied Carbon [metric tons CO2e] Climate Zone 3 Climate Zone 5
Wall Insulation 1.74 2.53
Basement Insulation 0.51 1.46
Attic Insulation 3.13 4.11
Whole Home Insulation 5.39 8.09
8 • IIBEC Interface Spring 2024
Table 13. Global Warming Potential (GWP) Payback Period Using Different Electricity Rates for Scenario 1: Current Heating Systems Mix (residential)
Scenario
GWP Payback Period [months] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 2.8 3.0 3.5 2.2 2.3 2.5
Basement Insulation Impact 5.5 5.9 6.8 6.3 6.5 7.0
Attic Insulation Impact 7.5 8.1 9.3 5.0 5.2 5.6
Whole Home Insulation Impact 4.8 5.2 6.0 3.8 4.0 4.3
Table 14. Global Warming Potential (GWP) Payback Period Using Different Electricity Rates for Scenario 2: 100% Heat Pump Systems (residential)
Scenario
GWP Payback Period [months] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 2.7 2.9 3.5 1.4 1.5 1.8
Basement insulation Impact 5.3 5.8 6.8 3.2 3.4 4.1
Attic Insulation Impact 7.4 8.0 9.4 3.0 3.3 3.9
Whole Home Insulation Impact 4.7 5.1 6.1 2.3 2.5 3.0
Table 15. Global Warming Potential (GWP) Payback Period Using Different Electricity Rates for Scenario 1: Current Heating System Mix (commercial)
Scenario
GWP Payback Period [months] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 4.9 5.3 6.3 2.8 3.1 3.6
Slab Insulation Impact — — — 72.5 84.6 93.8
Roof Insulation Impact 3.7 4.0 4.8 2.6 2.8 3.2
Whole Office Insulation Impact 3.9 4.2 5.0 2.7 2.9 3.4
Table 16. Global Warming Potential (GWP) Payback Period Using Different Electricity Rates for Scenario 2: 100% Heat Pump Systems (commercial)
Scenario
GWP Payback Period [months] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 10.1 10.9 13.0 6.0 6.5 7.7
Slab Insulation Impact — — — NA* NA NA
Roof Insulation Impact 7.5 8.1 9.6 4.4 4.8 5.7
Whole Office Insulation Impact 7.9 8.6 10.2 4.9 5.3 6.3
*NA indicates that negative savings result in infinite payback period. Recall that negative savings were primarily due to the fact that insulation is only
applied to the perimeter of the slab in addition to inherent limitations on the F-factor method modeling assumptions.
Spring 2024 IIBEC Interface • 9
Table 17. Global Warming Potential (GWP) Avoidance Ratio Using Different Electricity Emissions Rates for Scenario 1: Current Heating Systems
Mix (residential)
Scenario
GWP Avoidance Ratio [-] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 295 114 84 386 251 229
Basement Insulation Impact 149 59 44 137 94 87
Attic Insulation Impact 109 43 32 171 112 103
Whole Home Insulation Impact 171 67 50 222 146 134
Table 18. Global Warming Potential (GWP) Avoidance Ratio Using Different Electricity Emissions Rates for Scenario 2: 100% Heat Pump Systems
(residential)
Scenario
GWP Avoidance Ratio [-] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 299 87 52 590 171 103
Basement Insulation Impact 152 44 26 255 74 44
Attic Insulation Impact 110 32 19 270 78 47
Whole Home Insulation Impact 172 50 30 348 101 60
Table 19. Global Warming Potential (GWP) Avoidance Ratio Using Different Electricity Emission Rates for Scenario 1: Current Heating System Mix
(commercial)
Scenario
GWP Avoidance Ratio [-] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 166 50 31 287 90 58
Slab Insulation Impact — — — 12 8 7
Roof Insulation Impact 218 67 42 319 108 73
Whole Office Insulation Impact 208 63 39 305 100 66
Table 20. Global Warming Potential (GWP) Avoidance Ratio Using Different Electricity Emission Rates for Scenario 2: 100% Heat Pump System Mix
(commercial)
Scenario
GWP Avoidance Ratio [-] Climate Zone 3 Climate Zone 5
High RE Cost Med RE Cost Low RE Cost High RE Cost Med RE Cost Low RE Cost
Wall Insulation Impact 80 23 14 136 39 24
Slab Insulation Impact — — — NA* NA NA
Roof Insulation Impact 109 32 19 183 53 32
Whole Office Insulation Impact 103 30 18 164 48 29
*NA indicates that negative savings result in infinite payback period. Recall that negative savings were primarily due to the fact that insulation is only
applied to the perimeter of the slab in addition to inherent limitations on the F-factor method modeling assumptions.
10 • IIBEC Interface Spring 2024
The National Renewable Energy Lab (NREL)
Cambium Database low-, medium-, and
high-cost predictions of grid conversion to
renewable energy for Georgia were selected.
Since Cambium only estimates grid emissions
rates up to 2050 it was assumed that 2050 rates
prevailed for the remainder of the building
life-cycle. The emission rates used from the
Cambium database are found in Table 12.
Utilizing the background data described in
the above tables, the GWP payback of plastic
insulation materials was calculated assuming
current heating system and 100% heat pump
scenarios. All insulation elements had a GWP
payback under one year except for commercial
Climate Zone 3 Low Renewable Energy (RE)
Cost of conversion walls with 100% heat pumps
and Climate Zone 5 slab insulation scenarios.
As described previously, it is suspected to
be hampered by the current capabilities of
EnergyPlus modeling software. This is the case
even if the grid rapidly converts to renewable
energy and when 100% of heating systems
are converted to heat pumps. Residential wall
insulation in Climate Zone 5, assuming 100%
heat pump conversion and a High RE Cost of
grid conversion, had the most rapid payback at
1.4 months. The carbon payback in months for
the residential prototype are found in Table 13
(current heating system mix) and Table 14
(100% heat pumps).
The carbon payback in months for the
commercial prototype are found in Table 15
(current heating system mix) and Table 16
(100% heat pumps).
The lifetime GWP savings and the GWP
avoidance ratios attributed to plastic insulation
were also calculated. Except for the slab
insulation, which is limited by modeling
capabilities, it was found that plastic insulation
in all other applications had net carbon savings
over its useful life. Excepting slab insulation,
plastic insulation saves between 14 times and
590 times its embodied carbon during its
useful life. The residential GWP avoidance ratios
for all scenarios are found in Table 17 (current
heating system mix) and Table 18 (100% heat
pump mix) below.
The GWP avoidance ratios for all commercial
scenarios are found in Table 19 (current heating
system mix) and Table 20 (100% heat pump
mix) below.
CONCLUSION
This report concludes that plastic insulation
manufacturers, through their own product
stewardship and sustainability goals,
have made steady improvements to their
manufacturing processes and product
formulations of plastic insulation materials.
These improvements have resulted in
significant embodied carbon reductions
of insulation materials in the market.
Improvements to embodied carbon are likely
to continue as production technology improves
and the energy sources transition to lower
GHG options.
Additionally, the report concludes that the
investment of embodied carbon in plastic
insulation materials is trumped by its GHG
savings benefits during its useful life in
buildings. This is true for our current energy
grid GHG intensity and the projected grid
transition to a cleaner mix even at aggressive
conversion speeds. Furthermore, the report
shows that the embodied carbon invested in
plastic insulation materials has rapid payback
times of under one year in nearly all scenarios
even when it is assumed that all buildings are
converted to heat pump systems.
Outside the building enclosure, insulation
also can support global efforts to reach a point
of drawdown, where GHGs in the atmosphere
stop increasing and decline through many
carbon mitigation strategies. This analysis,
called Project Drawdown, cites building
insulation as one of the climate solutions
needed to reach this turning point, further
underscoring the benefits of plastic insulation
in a low carbon economy.18 Project drawdown
indicates that a steady implementation of
low-embodied-carbon insulation materials
could lead to more than 15 gigatons of avoided
GHG emissions.
Insulation LCA and EPD data should be
used in the context of whole building LCA or in
combination with total carbon benefit data for
insulation materials that includes the use-phase
carbon benefits to make smart policy, design,
and product selection decisions for the building
sector. Evidence shows that including embodied
carbon impacts of insulation without considering
total carbon analysis would be counterproductive
to our global and national carbon reduction
goals. Policies, building specifications, industry
tools and other resources that include or aim
to set maximum embodied carbon limits for
insulation or deselect/disincentivize insulation
materials based on embodied carbon content
alone is misguided and are not recommended in
our opinion.
It should be noted that the carbon savings
attributed to eliminating the additional air or
water resistive barrier were not factored into
the carbon savings in this report. These savings
can be significant and should be considered
by design professionals when making material
selections. Furthermore, there can often be
cost savings associated when an additional air
or water barrier can be eliminated through the
sealing of foam insulation. In many cases, the
energy savings can lead to the l downsizing of
HVAC and renewable energy equipment due to
the reduced heating and cooling loads. Further
study would need to be done to quantify
these benefits.
REFERENCES
1. Wall, B. J. 1994. “CFCs in Foam Insulation: The
Recovery Experience.” Proceedings of the ACEE,
269-276.
2. Bozsaky, D. 2010. “The historical development of
thermal insulation materials.” Periodica Polytechnica
Architecture, 41(2), 49-56. https://pp.bme.hu/ar/
article/view/12/12.
3. American Chemistry Council, and WAP
Sustainability. 2023. “The Benefits of a Whole
Building LCA or Total Carbon Analysis.” American
Chemistry Council. https://www.americanchemistry.
com/better-policy-regulation/plastics/resources/
the-benefits-of-a-whole-building-lca-or-totalcarbon-
analysis.
4. UL Environment Standard. 2024. Product Category
Rules (PCR) Guidance for Building Related Products
and Services Part B: Building Envelope Thermal
Insulation EPD Requirements (UL 10010-1).
https://www.shopulstandards.com/ProductDetail.
aspx?productId=ULE10010-1_3_S_20230406.
5. Building Transparency. 2023. “EC3 FAQ.” Building
Transparency. https://www.buildingtransparency.
org/ec3-resources/ec3-faq/ .
6. ICF International, Inc. 2023. “Determination of
Total Carbon Impact of Plastic Insulation Materials.”
Reston, VA: ICF. https://www.americanchemistry.
com/better-policy-regulation/plastics/resources/
determination-of-total-carbon-impact-of-plasticinsulation-
materials.
7. Franklin Associates. 2000. “Plastic Energy and
Greenhouse Gas Savings Using Rigid Foam
Sheathing Applied to Exterior Walls of Single Family
Residential Housing in the U.S. and Canada—A
Case Study.”: Pollution Prevention Infohouse.
https://p2infohouse.org/ref/47/46152.pdf.
8. Mazor, Michael H., Mutton, John D., Russell, David
AM, and Keoleian, Gregory A. 2011. “Life cycle
greenhouse gas emissions reduction from rigid
thermal insulation use in buildings.” Journal of
Industrial Ecology, vol. 15, issue 2. pg. 284-299:
Wiley Online Library. https://doi.org/10.1111/j.1530-
9290.2010.00325.x.
9. Gagnon, Pieter. n.d. “Cambium.” NREL: U.S.
Department of Energy. https://www.nrel.gov/analysis/
cambium.html .
10. Bureau, US Census. 2019. “Building Permits Survey
(BPS).” United States Census Bureau. Washington,
D.C. www.census.gov/construction/bps/index.html.
Spring 2024 IIBEC Interface • 11
11. American Society of Heating, Refrigerating, and Air
Conditioning Engineers (ASHRAE). 2021. Climatic
Data for Building Design Standards (ANSI Approved).
ASHRAE 169-2021, Peachtree Corners, GA: ASHRAE.
https://www.techstreet.com/standards/ashrae-169-
2021?product_id=2238548.
12. U.S. Department of Energy. 2024. “Prototype
Building Models.” Building Energy Codes Program.
Washington, D.C.: U.S. Department of Energy.
https://www.energycodes.gov/prototype-buildingmodels.
13. International Code Council (ICC). 2021. “2021
International Energy Conservation Code (IECC): ICC
Digital Codes.” ICC DIGITAL CODES. https://codes.
iccsafe.org/content/IECC2021P1/index.
14. ASHRAE. 2024. “Preview ASHRAE Standards and
Guidelines.” ASHRAE Standards. Peachtree Corners,
GA: ASHRAE. https://www.ashrae.org/technicalresources/
standards-and-guidelines/read-onlyversions-
of-ashrae-standards.
15. Elkins, James W. 2005. “Chlorofluorocarbons
(CFCs).” National Oceanic and Atmospheric
Administration (NOAA), Climate Monitoring and
Diagnostics Laboratory (CMDL). Boulder, CO. Gml.
noaa.gov/hats/publictn/elkins/cfcs.html.
16. U.S. Department of State. n.d. “The Montreal
Protocol on Substances That Deplete the Ozone
Layer.” U.S. Department of State. Washington,
D.C.: U.S. Department of State. www.state.gov/
key-topics-office-of-environmental-quality-andtransboundary-
issues/the-montreal-protocolon-
substances- that-deplete-the-ozone-layer/
.
17. Clark, Ezra, and Sonja Wagner. 2016. “The Kigali
Amendment to the Montreal Protocol: HFC Phase-
Down.” Ozon Action UN Environment (UNEP). Paris,
France: Ozon Action.
18. Arehart, Jay H., Allard, Ryan F., and Frischmann,
Chad. 2023. “Insulation.” Project Drawdown. drawdown.
org/solutions/insulation.
ABOUT THE AUTHORS
Amy Schmidt,
joined the American
Chemistry Council
(ACC) in 2022 as
director of building
and construction for
the plastics division
durable materials
team. She came to
ACC with more than
14 years of advocacy
experience having
worked for Dow Chemical and DuPont building
and construction businesses. Her team supports
the safe and effective use of durable plastic
building materials in resilient high-performance
applications.
Schmidt has served on ASHRAE 90.1 Main
and Envelope Subcommittees, the National
AMY SCHMIDT
ALLISON CHERTACK
Green Building Standard Committee, and is
currently on the International Code Council’s
International Energy Conservation Code
Residential Main and Residential Envelope
Subcommittees. She has also served on the
Board of Directors for the Alliance for National
and Community Resilience. Schmidt holds
a Bachelor of Business Administration from
Northwood University and is certified as a LEED
Green Associate.
Allison Chertack is
an associate director
of plastics life-cycle
and sustainability
within the American
Chemistry Council’s
plastics division.
She is responsible
for positioning the
benefits of plastics
through life-cycle
assessments and
data analyses and leads the division’s work on
Operation Clean Sweep (OCS). Prior to ACC,
Chertack worked for a plastics distribution
company in environmental health and safety
in her hometown of Buffalo, NY. She holds
a Bachelor of Science in Environmental
Studies and a Master of Science in
Sustainability Systems.
Please address reader comments to chamaker@iibec.org,
including “Letter to Editor” in the subject line, or IIBEC, IIBEC Interface Journal,
434 Fayetteville St., Suite 2400, Raleigh, NC 27601.
12 • IIBEC Interface Spring 2024