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Max GWP Limits

Last Updated: January 2026; Document Reference: EE-5.1; Downloadable links at the bottom of page

Buy Clean Colorado Act: Maximum Acceptable Global Warming Potential (GWP) Limits

The Buy Clean Colorado (BCCO) Act (C.R.S. 24-92-117) applies to state public projects (C.R.S. 24-92-102 (8)) over $500,000 solicited as of January 1st, 2024.

The BCCO Act targets carbon emissions associated with the production or manufacturing of eligible materials, further defined as asphalt and asphalt mixtures, cement and concrete mixtures, glass, post-tension steel, reinforcing steel, structural steel, and wood structural elements. When used in eligible projects, these materials must have a GWP that does not exceed the limits set by the OSA. The BCCO Act focuses on these materials due to their high carbon emissions impact, and reducing the impact of these materials will provide the greatest greenhouse gas emissions reduction during the construction of Colorado public projects. For further information regarding this program, please refer to the OSA policy and resources available on the OSA Buy Clean Colorado Act webpage. Please refer to the CDOT website for projects under their purview.

The information utilized to determine the eligible material GWP thresholds is subject to change due to background data updates. EPDs, both product-specific and industry-wide, expire after 5 years. Therefore, each industry may improve its data and EPD information within the 5 years, resulting in more accurate EPDs. However, improving the background EPD information may result in increased GWP values as reported in an EPD. The OSA is utilizing current EPD information to determine its GWP thresholds. The OSA takes precautions to set the GWPs as feasible thresholds that incorporate room for improvement in background data sources. However, if background data improvements result in increased GWP reporting above the OSA’s limit, then the OSA will make necessary adjustments to improve the feasibility of the GWP limits for State public projects.

The existing OSA GWP limits for 2026 are the same as the 2025 GWP limits. New eligible material subcategories (with GWP limits) for 2026 include: Concrete Masonry Units (CMU), Steel Roof and Floor Deck, and Open-Web Steel Joist and Joist Girders. OSA is required to review the industry average GWP limits every four years; however, industry data is reviewed, and GWP limits may be reduced on an annual basis.

By January 1st, 2026, OSA reviewed the maximum acceptable GWP limits for each category of eligible materials. Through this review, OSA determined that there is potential to reduce the current GWP limits for the following eligible material subcategories: Asphalt Mixtures, Cement, Flat Glass, Rebar, Cold-Formed Steel Framing and Accessories, and Oriented Strand Board (OSB). However, few projects have been completed. More project completions are needed to ensure these limits are achievable. Therefore, due to insufficient project compliance information available at this time, OSA is maintaining the current GWP limits.

2026 OSA Updated GWP Limits for Eligible Materials

Only consider permanently installed materials. OSA subcategories align with available products, product categories, and building codes.

Asphalt and Asphalt Mixtures

Inclusive of all paving asphalt mixes supplied.

  1. Asphalt Mixtures (in kg CO2e/t or kilograms of carbon dioxide equivalent per 1 metric ton): 85 kg CO2 eq.

Cement & Concrete Mixtures

Subcategories based upon regional compressive strength specifications at 28 days.

  1. ReadyMix Concrete (in kg CO2e/m3 or kilograms of carbon dioxide equivalent per cubic meter) at 28 days:
    1. 2,500 psi: 232
    2. 3,000 psi: 255
    3. 4,000 psi: 301
    4. 5,000 psi: 358
    5. 6,000 psi: 379
    6. 8,000 psi: 440
    7. Lightweight (LW) 3,000 psi: 484
    8. LW 4,000 psi: 532
    9. LW 5,000 psi: 580
  2. Cement (in kgCO2e/t or kilograms of carbon dioxide equivalent per metric ton): 1,112
  3. Concrete Masonry Units (CMU) (1 m3): 395 kg CO2 eq.

Glass

Designs specify processed glass, and flat glass is a component of processed glass assemblies.

  1. Flat Glass (1 metric ton): 1,510 kg CO2 eq.

Post-Tension Steel

No sufficient data to set a valid threshold at this time. Zero post-tension steel subcategories identified at this time.

Reinforced Steel 

Rebar is the only identified subcategory for Reinforced Steel at this time.

  1. Fabricated Steel Reinforcing Bar "Rebar" (1 metric ton): 1,030 kg CO2 eq.

Structural Steel

Structural steel subcategories as defined by AISC Code of Standard Practice (ANSI/AISC 303-16). HVAC units as manufactured do not need to conform.

  1. Fabricated Hot-rolled steel (1 metric ton): 1,220 kg CO2 eq.
  2. Fabricated Plate steel (1 metric ton): 1,730 kg CO2 eq.
  3. Fabricated Hollow Structural Sections (1 metric ton): 1,990 kg CO2 eq.
  4. Cold-Formed Steel Framing and Accessories (1 metric ton): 2,843 kg CO2 eq.
  5. Steel Roof and Floor Deck (1 metric ton): 2,350 kg CO2 eq.
  6. Open-web Steel Joist and Joist Girders (1 metric ton): 1,450 kg CO2 eq.

Wood Structural Elements 

Subcategories based upon available IW-EPDs. Only consider permanently installed wood products. 

  1. Plywood (1 m3): 219.32 kg CO2 eq
  2. OSB Sheathing (1 m3): 242.58 kg CO2 eq
  3. Laminated Strand Lumber
    1. Laminated Strand Lumber (1 m3): 274.90 kg CO2 eq
    2. Laminated Veneer Lumber (1 m3): 361.45 kg CO2 eq
  4. Glued Laminated Timber (1 m3): 137.19 kg CO2 eq

Downloadable Links:

OSA Max. GWP Limits_2026-01

OSA Max. GWP Limits_2025-01

OSA Max. GWP Limits_2024-01