The approach in LEEDv5 is lacking a means to reward and incentivize investment in decarbonization of buildings and excludes or penalizes those who have made significant improvements in reducing carbon footprint (which works against investment in decarbonizing building materials).

  1. More specific to the broad category of “Board and Foam Insulation” in Table 1: Embodied Carbon Benchmarks for Assessment, it fails to set a benchmark that recognizes the uniqueness of and major GHG emissions savings investment in specific types of board and foam insulation products that each have different functional attributes beyond just the functional units applied to GWP. Consider the following actual examples:
    1. CASE 1:  Extruded Polystyrene (XPS) Foam Board.  Over the past couple of decades and more recently, changes in product formulations and blowing agents have come from investment of millions of dollars in R&D&I and have resulted in a net reduction in GWP of these products by 100-fold (two orders of magnitude reduction in GWP).  Yet these products remain above the “benchmark” of 4.0 kgCO2e/m2-RSI which evidently uses a broad categorization of differing material types with different functions and attributes, even among different foam insulation types. It also fails to recognize that even with the specific foam board insulation category of XPS, there are different types of XPS with different properties necessary for particular building applications and functions.  For example, higher density (high compressive strength) XPS boards are necessary to support infrastructure and even building foundation loads in applications where this is required.  But, because the benchmark does not acknowledge such distinctions in establishing GWP benchmarks within a given material class or type, these XPS materials and their applications for important building designs will be penalized (or at least not be given credit) even though for these applications significant carbon savings have been realized by continuing industry investments over the past couple of decades and particularly in the last five years.  This will have the opposite effect of encouraging investment in material decarbonization. Modern XPS materials with low GWP now have values ranging from about 5-12 kgCO2e/m2-RSI depending on the density (compressive strength) required for a particular building or infrastructure design application and are widely available and rapidly being specified across the US.  
    2. CASE 2: A similar story can be told for Polyisocyanurate (PIR) foam insulation boards.  In recent years, significant investment also has been made to dramatically reduce GWP of PIR products by many manufacturers, resulting in a 90% reduction GWP.  Yet, the 4.0 kgCO2e benchmark (Table 1) essentially ignores the significant GHG emission saving investment in this type of foam plastic insulation board.  Modern PIR materials with low GWP now have values ranging from about 4.3-6 kgCO2e/m2-RSI depending on product types for different functional applications on buildings.
    3. CASE 3: While Expanded Polystyrene (EPS) foam board have some product types/densities that fall below the 4.0 kgCO2e/m2-RSI , there are many types for specific building and infrastructure applications that are excluded from recognition in LEED even though they have important functional applications necessary for design (similar to concerns raised above for XPS and PIR product variations for different application conditions).
    4. CASE 4: Spray Foam insulation (SPF) is a unique building material that can insulate and air seal with one product, greatly reducing the amount of energy needed to heat and cool a home. Additionally, closed-cell spray foam (cc-SPF) provides a vapor barrier where applied. Over the past few years, the SPF industry has made several critical advancements in reducing the embodied carbon of their products, most notable by shifting from high-GWP HFC blowing agents to ultra-low-GWP HFO blowing agents. Spray foam ranges from 1.68-4.21 kgCO2e/m2-RSI, with open-cell spray foam (oc-SPF) at 1.68 kgCO2e/m2-RSI and cc-SPF at 4.21 kgCO2e/m2-RSI, and a blend of 50/50 oc-SPF/cc-SPF at 2.95 kgCO2e/m2-RSI. CC-SPF has an environmental payback period of as little as 7-8 years and a lifespan of approximately 75 years. The 4.0 kgCO2e/m2-RSI threshold narrowly excludes cc-spf and ignores the significant carbon savings that cc-SPF provides during the operational phase by providing thermal resistance, an air barrier, and a moisture barrier. Additionally, cc-spf provides racking strength when used in wall cavities, creating more durable buildings.
    5. SOURCES FOR CASES 1, 2, 3, and 4: 
      1. See ACC/ICF report: Schmidt, A. and Chertak, A. (2023). Unlocking Carbon Savings with Plastic Insulation Materials. 2023 Polyurethanes Technical Conference, American Chemistry Council, Center for the Polyurethanes Industry, Washington, DC, https://www.americanchemistry.com/better-policy-regulation/plastics/resources/unlocking-carbon-savings-with-plastic-insulation-materials
      2. See ICF report: ICF. 2023. Determination of Total Carbon Impact of Plastic Insulation Materials. Prepared by ICF, Reston, VA for the American Chemistry Council (ACC), Washington, DC, https://www.americanchemistry.com/better-policy-regulation/plastics/resources/determination-of-total-carbon-impact-of-plastic-insulation-materials
      3. See ABTG report: “Decarbonization of Buildings: A Review of Climate Science, Policies, Practices, Data, and Recommended Actions for Buildings and Building Materials” (Section 4.7.4 and particularly Tables 18, 19 and related data), https://www.appliedbuildingtech.com/rr/2312-01
    6. NOTE:  This list of example cases above could be expanded to include similar concerns with the treatment of other “board and foam insulation” materials (as vaguely and broad as this category is defined in Table 1). 

The approach disconnects embodied carbon from operational GHG emissions of buildings.  They are related and this is especially the case for insulation materials and particularly insulation materials that have multi-functional capabilities that are ignored or even discouraged from employing to result in overall building enclosure assemblies and building systems that may result in both a system-based embodied carbon reduction together with reductions in operational GHG emissions from a “total carbon” perspective. But LEEDv5 prohibits the consideration of operational carbon when assessing embodied carbon implications (See Option 1. Whole Building LCA).  This is counterproductive for a number of reasons that follow, especially for building insulation materials and particularly those that have multi-functional capabilities affecting overall design of building assemblies and systems and the net or “total carbon” outcome.

  1. Essentially all major insulation products (including modern foam plastics) in the US are now in a “low carbon” status in comparison to their role to reduce building energy use and operational GHG emissions.
  2. Essentially all major insulation products (including modern foam plastics) have operational emission paybacks within the first year (or 1.5 years at most) after building completion (rapidly offsetting the insulation package’s initial embodied carbon “investment”).
  3. Essentially all major insulation products (including modern foam plastics) have GHG avoidance ratios ranging from roughly 100:1 to 300:1 depending on the type of heating energy used and rate at which future electric grid decarbonizes.
  4. Some insulation materials, like foam plastics, also have multifunctional capabilities as benefits that affect operational carbon savings and also embodied carbon savings of building enclosure systems.  For example, foam plastics can be used to (1) control water intrusion into buildings when used as the WRB (also eliminating the embodied carbon of a separate building material layer and improving the long-term service life and durability of the building which also reduces embodied carbon consequences), (2) control water vapor and protect structural materials from effects of moisture exposure including corrosion and mold (also eliminating the embodied carbon of a separate building material layer to control water vapor), (3) be used to protect foundations against frost heave damage and allowing the use of significantly reduced amounts of concrete in foundation construction (major embodied carbon savings for the structure) while providing for significantly improved operational energy and GHG emission savings.
  5. All of the above benefits and design optimization possibilities are essentially eliminated from consideration when embodied carbon accounting is disconnected from operational GHG emissions accounting in the design (or rating) of building systems.  At worst, this creates a huge missed opportunity.

SOURCES:

See ACC report (referenced above)

See ICF report (referenced above)

See ABTG Report (referenced above, particularly Sections 4.8 and 4.9)