MEMORANDUM

To: Margaret Sheppard , U.S. EPA

From: Emily Herzog and Mark Wagner, ICF International 

Date: April 7, 2010

Re: Summary of HFO-1234yf Emissions Assumptions (Deliverable under EPA Contract Number 

EP-W-06-008 Task Order 038, Task 06)

This memorandum summarizes the proposed emissions assumptions to be used in the sensitivity analysis 

of the revised Assessment of the Potential Impacts of HFO-1234yf and the Associated Production of TFA 

on Aquatic Communities and Local Air Quality. As previously conducted, the baseline analysis will be 

based on Vintaging Model emission assumptions for HFC-134a while the sensitivity analysis will be 

based on the findings of Papasavva et al. as described in their 2009 paper Estimated 2017 Refrigerant 

Emissions of 2,3,3,3-tetrafluoropropene (HFC-1234yf) in the United Stated Resulting from Automobile 

Air Conditioning. The memorandum is organized as follows:

1) Overview of Vintaging Model HFC-134a Assumptions

2) Summary of Findings from Papasavva et al. (2009)

3) Proposed Sensitivity Analysis Assumptions

Please contact Mark Wagner at 202-862-1155 with any questions or comments.
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1) OVERVIEW OF VINTAGING MODEL HFC-134A ASSUMPTIONS

ICF used EPA’s Vintaging Model to estimate potential emissions of HFO-1234yf, a new refrigerant to be 

used as a drop in replacement for HFC-134a in new MVAC systems. ICF assumed that emissions of 

HFO-1234yf from all systems will be the same as emissions from commercially available systems. The 

Vintaging Model emissions assumptions for HFC-134a from the MVAC sector are described below in

Table 1.

1

Table 1: HFC-134a MVAC Sector Assumptionsa

Assumption Unit

Vehicle lifetime 12 years

Light duty vehicle (LDV) charge size 555 g/vehicle

Light duty truck (LDT) charge size 793 g/vehicle

LDV market share 58b %

LDT market share 42b %

Percent of fleet retired each year 8

b %

Leak rate 8 %

Servicing leaks (annualized) 10 %

End-of-life loss rate 42.5 %

a VM IO file_v4.4_12.16.09.xls

b Number varies depending on the year. Estimated average through 2050 is shown

2) SUMMARY OF FINDINGS FROM PAPASAVVA ET AL. (2009)

Papasavva et al. (2009) reported on their team’s research on the estimated emissions of HFO-1234yf from 

MVAC systems. The general findings from Papsavva et al. (2009) are described in Table 2 below.

Table 2: Summary of Findings from Papasavva et al. (2009)

Leak Source Range Units

regular leaks 13.6 - 14.1 g/vehicle/year

irregular leaks 17 g/vehicle/year

service leaks 40 - 70 g/vehicle/service

DIY service leaks 160 g/vehicle/service

End-of-life emissions 100 - 450 g/vehicle

Papasavva et al. (2009) noted that the sum of the average annual regular and irregular emissions per 

vehicle represents 5.6% of total refrigerant charge, assuming a typical sedan MAC with a 550 g charge. 

They also noted that on average in the U.S., a vehicle goes for a MAC service once during its 9-year 

lifetime, so vehicle servicing accounts for between 4.4 and 17.8 g/y of annual refrigerant emissions. 

Combined with regular and irregular annual losses, Papasavva et al. (2009) estimated annual leaks to be 

35 - 48.4 g/yr or 6 - 8.8% of the original charge.2

 

1 Changes to the VM MVAC sector assumptions have been made since the most recent version of the TFA 

Assessment was delivered to EPA on 8/4/09. Assumptions presented in table 1 reflect the current version of the VM 

and will also be used in the revised report.

2

For this analysis, Papasavva et al. assumed cars and trucks leak identically but point out that trucks likely leak 

more than cars because they have larger refrigerant charges and their MAC systems commonly have more 

connection joints.
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Based on their findings, Papasavva et al. (2009) then estimated total HFO-1234yf emissions for the year 

2017. Papasavva et al. (2009) developed two scenarios, a low leak scenario and a high leak scenario, both 

of which are described in Table 3 below.

Table 3: Emission Estimates of HFO-1234yf in 2017

Assumption Low Leak Scenario High Leak Scenario Units

Vehicle lifetime 9 9 years

Number of services 1 1 Services/lifetime

Percent of fleet serviced per year 10 15 %

Percent of vehicles serviced by a DIYer 0 25 %

Percent of fleet retired 5 10 %

Regular leaks 13.6 13.6 – 15ag/vehicle/year

Irregular leaks 17 17 g/vehicle/year

Professional servicing leaks 40 40 g/vehicle/service

DIY servicing leaks 160 160 g/vehicle/service

End-of-life emissions 100 450 g/vehicle

Total Emissions 11.4 24.7 thousand MT

a Assumes older vehicles have a leak rate that is 10% higher

3) PROPOSED SENSITIVITY ANALYSIS ASSUMPTIONS

To accommodate for the findings of Papasavva et al. (2009), ICF will additionally run the HFO-1234yf 

emissions scenarios in the Vintaging Model (VM) using revised annual leak rate assumptions. No 

changes will be made to the estimated vehicle fleet, the charge sizes of either LDV or LDT, or percent of 

fleet retired each year. Additionally, no changes will be made to the end-of-life emission assumptions 

since the loss rate assumed in the VM (42.5%) falls within the range estimated by Papasavva et al. (2009)

(100 – 450 g/vehicle or 18 – 81%). 

As stated above, Papasavva et al. (2009) estimated annual regular, irregular, and servicing leaks to be 35 -

48.4 g/yr or 6 - 8.8% of the original charge. Therefore, ICF proposes to use the following annual leak rate 

assumptions for the sensitivity analysis, as summarized in table 4 below. Leak rate assumptions for the 

baseline scenario are also provided for comparison.

Table 4: Proposed Refrigerant Loss Assumptions for Baseline and Sensitivity Analysis

Assumption

Emission Rate as a 

Percentage of Charge Size

Equivalent Emission Rateb

(g/vehicle/yr)

Baselinea

Sensitivity 

Analysis

BaselineaSensitivity 

Analysis

Leak rate 8% 5.6% 44 30.8

Servicing leaks (annualized) 10% 3.2% 55 17.6

 Subtotal, annual leaks 18% 8.8% 99 48.4

End-of-life loss rate 42.5% 42.5% 234 234

a HFC-134a MVAC assumptions

b Assuming an average charge of 550 g/vehicle.

4) CHANGES IN EMISSION ESTIMATES
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ICF has updated the Vintaging Model since 2009 to include the most up-to-date projects of growth and 

trends in transitions to alternatives in all industrial sectors. The baseline values will be calculated using 

the updated version of the Vintaging Model. Depending on the year and scenario, these values may be 

higher or lower than those used in ICF’s 2009 analysis. The comparison below shows how emission 

values will be affected by these changes. Overall, changes were relatively small, being less than 6% 

different from the earlier analysis.

Table 5: Comparison of Emissions using Vintaging Model Outputs (in Metric Tons)

2009 Analysis vs. 2010 Analysis

Scenarios 2020 2030 2040 2050

Scenario 1- MVAC (2009)a 6,244 28,327 33,196 36,478

Scenario 1- MVAC (2010)b 6,244 28,327 33,093 35,851

% change 0.0% 0.0% -0.3% -1.7%

Scenario 2 - All Ref/AC 

(2009)a

10,345 42,800 55,349 64,324

Scenario 2 – All Ref/AC

(2010)b

10,501 43,296 55,070 60,616

% change 1.5% 1.2% -0.5% -5.8%

a

ICF projected emissions of HFO-1234yf using special scenarios designed specifically for the August 4, 2009

analysis and run on the U.S. EPA Vintaging Model, Version VM IO File v4.1 5-19-09. 

b

ICF projected emissions of HFO-1234yf using special scenarios designed specifically for the sensitivity analysis 

and run on the U.S. EPA Vintaging Model, Version VM IO File v4.4_12-16-09. 

Specific changes to the Vintaging Model between May 2009 and December 2009 include the following:

1. Historic sales figures of light-duty motor vehicles were updated based on more recent data from 

Ward's Automotive. The updated data showed drops in new vehicle sales over the last few years.

2. Project sales growth rates for new vehicles through 2030 were estimated based on the Energy 

Information Administration's report, An Updated Reference Case Reflecting Provisions of the 

American Recovery and Reinvestment Act as found in EIA’s Annual Energy Outlook. For the 

May 2009 version of the Vintaging Model, projections were estimated using a constant 

compound growth rate

3. Average refrigerant charge sizes for light-duty motor vehicles were updated based on more recent 

information from Ward’s Automotive and from Mobile AC Society (MACS) Worldwide’s Air 

Conditioning Specifications Domestic and Import Cars, APVs, Vans and Light Trucks: 1990 

through 1998 and A/C & Cooling System Specifications: 1996-2007. The average charge size for 

a light-duty truck went down from 910 g to 793 g per truck. The average charge size for other 

light-duty vehicles such as cars and vans went down from 690 g to 555 g per vehicle.

The first two of these changes resulted in reductions in the estimated number of cars and vans, but not 

trucks, in 2020 from 253 million in the May 2009 version of the Vintaging Model to 190 million in 

the December 2009 version.