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## MEMORANDUM To: Margaret Sheppard , U.S. EPA From: Emily Herzog , Veronica Kennedy, Marian Van Pelt, and Mark Wagner, ICF International Date: September 13 , 20 10 Re: Summary of Updates to the Vintaging Model that Impacted HFO - 1234yf Emissions Estimates (Deliverable under EPA Contract Number EP - W - 06 - 008 Task Order 0 38 , Task 0 1 ) This memorandum summari zes the updates made to the Vintaging Model (VM) that impacted the HFO 1234yf emissions estimates u sed in the August 2009 [EPA - HQ - OAR - 2008 - 0664 - 0037] and May 2010 versions of the revised Assessment of the Potential Impacts of HFO- 1234yf and the Associated Production of TFA on Aquatic Communities and Local Air Quality (referred to below as the ” TFA Assessment”) . The emissions estimates used in the revise d versions of the TFA Assessment varied slightly , as summarized in Table 1 below. Table 1 : HFO - 1234yf Emissions Estimates from the 2009 and 2010 TFA Assessments (M etric T on s)

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% Ref rigeration (2009) a 3,484 12,261 18,216 23,379 Ref rigeration (2010) b 3,636 12,748 18,046 20,318 % change 4.4% 4.0% - 0.9% - 13 .1 % Stationary AC (2009) a 617 2,212 3,936 4,467 Stationary AC (2010) b 620 2,221 3,931 4,447 % change 0.6% 0.4% - 0.1% - 0.4% Scenario 2

– Sum of All Ref/AC (2009) a 10,345 42,800 55,349 64,324 Scenario 2 - Sum of 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 May 25, 2010 analysis and run on the U.S. EPA Vintaging Model, Version VM IO File v4.4_12 - 16 - 09 . The s cenarios described in Table 1 are in referen ce to the s cenarios identified in both the August 2009 and May 2010 versions of the TFA Assessment. Scenario 1 and scenario 2 are defined as follows:- 2 -

 Scenario 1: HFO - 1234yf is used in the United States as a new car refrigerant in the MVAC sector. HFO - 123 4yf begins penetrating the market in 2016 reaching 100 percent market penetration by 2020 .  Scenario 2: HFO - 1234yf is used in the United States as a new car refrigerant in MVAC systems, refrigeration, and stationary AC systems. Similar to scenario 1, by 20 20, HFO - 1234yf is used in all new MVAC systems. For refrigeration and stationary AC systems, HFO - 1234yf enters the market in 2010, reaches 30 percent penetration of the market in 2015, and 100 percent by 2020. Refrigeration systems include equipment used in all refrigeration end uses, such as household refrigerators and freezers, retail food refrigeration, cold storage warehouses, and vending machines. Stationary AC systems include equipment used in all air conditioning end uses for stationary equipment, such as chillers, residential air conditioning and heat pumps, and dehumidifiers. 

## Factors that Contributed to a Change in Emissions Estimates Overall, changes from the 2009 estimates to the 2010 estimates were relatively small, equaling less than 6% fo r all Ref/AC end -uses combined for all projected years. The change is driven primarily by changes in the growth rate assumed for the refrigeration end -uses. S pecific ally, the update s that were made to the Vintaging Model that contributed to this change w ere as follows :  For all Ref/AC end -use sectors, the annual growth estimates from 2031 - 2050 were updated to assume a blanket growth rate of 0.8% based on population projection growth from the Census Bureau. Previously, the post - 2030 growth rates were projected from the growth rates from 2010 - 2030. This change had the most significant impact on the refrigeration end-use sector due to the previously assumed average growth rate of roughly 2.4% for all end-uses within the sector. In addition to the VM updates , f or the refrigeration and stationary AC end-use s , the market penetration assumptions were modeled differed slightly :  In the 2009 version of the TFA Assessment, HFO - 1234yf penetrate s 30% of the market from 2010 to 2015 in a linear transition .  In contrast , in the 2010 version of the TFA Assessment , the transition takes two steps. First HFO 1234yf penetrate s 6% of the market instantaneously in 2010 . Then, another 24% transitions linearly from 2011 - 2015, totaling 30% market penetration by 2015. While the text in the 2009 version of the report indicates that the same assumptions were used in both version s of the report , a closer look at the model run uncovered this minor discrepancy. As a result , the emission estimates for years prior to 203 5 for the refrigeration and stationary AC end -use sectors are slightly higher (<5%) in the 2010 version of the TFA Assessment. This minor difference had no impact on emissions estimates post- 2040 and therefore had no significant impact on the outcome of the analysis. G enerally, the Vintaging Model is routinely updated to modify any of the 100+ end-uses as new data are available or new research is conducted into end -uses. Model ed parameters that could change for a given end -use include growth rates, leak, service, and disposal rates, substitution patterns, charge sizes, lifetime, and market size. To perform off - line analyses such as the TFA assessment, ICF builds from the version of the Vintaging Model that was used for the most recent US Greenhouse Gas Emission Invento ry. This Inventory version of the model is updated annually and takes into account the years’ worth of model improvements. Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.