T3 Minneapolis
The first modern tall wood building in the United States. Seven storeys, 220,000 square feet of office and retail in the North Loop. Completed September 2016. Largest mass timber building in North America at the time of completion. No EN 15978 life cycle assessment has been published.
- Developer
- Hines
- Architect
- Michael Green Architecture (design)
- Architect of record
- DLR Group
- Structural engineer
- Magnusson Klemencic Associates
- Design assist + build
- StructureCraft Builders Inc.
- Storeys / GFA
- 7 / ~20,440 m² (220,000 sf)
- Use
- Office and retail
- Completion
- September 2016
- Certification
- LEED Gold
- LCA standard
- None published. Public figures derived from WoodWorks Wood Calculator.
- Wood source
- Mountain pine beetle-killed BC interior softwood
- Awards
- WoodWorks U.S. Wood Design Award; AIA Minnesota; multiple citations as the breakthrough modern North American mass timber project
The published numbers — and the source they come from
This building's most-cited carbon figures do not come from a life cycle assessment. They come from a vendor sustainability calculator. The distinction is consequential and is documented here.
The standard reference point for T3's environmental performance, repeated across the design firm's project page, the developer's marketing materials, the architectural press, and trade publications, is a set of three numbers attributed to the Canadian Wood Council's carbon calculator (formerly the WoodWorks Wood Calculator). The architect's project page is explicit:
"T3 stores 3,646 metric tons of carbon dioxide. According to the WoodWorks Wood Calculator tool's Carbon Summary: using wood to construct T3 generates environmental benefits that are equivalent to taking 966 cars off the road for a year… By using wood, T3 avoided 1,411 metric tons of carbon dioxide emissions." — Michael Green Architecture project page; Architizer T3 project profile
The carbon figures most frequently cited for T3
| Item | Disclosed value | Source |
|---|---|---|
| Volume of wood used | ~3,600 m³ (180,962 ft³) | MGA project page; Metsä Fibre interview |
| Carbon "stored" in wood | 3,646 tCO₂e | WoodWorks Wood Calculator |
| Carbon emissions "avoided" by using wood | 1,411 tCO₂e | WoodWorks Wood Calculator |
| Total claimed "carbon benefit" | 5,057 tCO₂e | Sum of the two figures above |
What does not appear in the public record for this building
- A whole-building life cycle assessment conforming to EN 15978 or ISO 14040/44.
- An Environmental Building Declaration of the type Athena Sustainable Materials Institute prepared for Brock Commons.
- A bill of materials with quantities for non-timber components (concrete, steel, glass, gypsum, finishes).
- An assessment of end-of-life carbon flows.
- A 60- or 100-year reference-period assessment.
The 5,057 tCO₂e "carbon benefit" figure that has circulated since 2016 is, in EN 15978 terms, a single line item — biogenic-carbon storage plus a substitution credit, computed by a vendor tool calibrated to the North American wood industry's accounting conventions.
What is excluded from the disclosure, by virtue of the source tool's methodology
The Canadian Wood Council's WoodWorks Wood Calculator, on whose output the T3 disclosures rest, is documented by its publisher as a screening-level tool calibrated to produce comparative biogenic-storage and substitution figures for wood structures. Its methodology, as published by CWC and reproduced in WoodWorks resources, draws on:
- U.S. and Canadian softwood lumber industry-average emission factors
- The biogenic-zero / carbon-neutral convention of EN 15978 and ISO 21930
- Athena Sustainable Materials Institute's Impact Estimator for Buildings as an upstream data feed
- Substitution credit logic based on comparison to a hypothetical reinforced-concrete equivalent of equivalent function
What the calculator does not produce
The tool does not produce, and the T3 disclosures therefore do not contain, an accounting for:
- Soil organic carbon (SOC) efflux from the harvested British Columbia interior pine stands. The trees were beetle-killed and the wood was salvaged — a point the design team emphasised — but the harvest operation, the road network, and the skidding still disturb soil and trigger SOC oxidation. Beetle-kill salvage does not avoid this flow.
- End-of-life methane. The disclosed "carbon storage" figure of 3,646 tCO₂e assumes the wood permanently stores the carbon. If at the end of the building's service life the wood enters a C&D landfill, a portion of that carbon is released as methane, which has a 100-year GWP of 27.9.
- Foregone sequestration. The substitution credit of 1,411 tCO₂e is calculated as the avoided emissions from concrete the building did not use. It does not subtract the carbon the harvested forest would have continued to sequester had the trees been left standing — a subtraction that, in the case of beetle-kill salvage on otherwise standing forest, becomes site-specific.
A note on beetle-kill salvage
The T3 design team is correct that beetle-killed wood, if not harvested, would eventually decompose and release its carbon. Foregone sequestration for beetle-kill salvage is therefore lower than for live-tree harvest. We retain a foregone-sequestration line in the recomputation but reduce its factor to the low-range value — that calibration is visible in the calculator below and can be set to zero by anyone who wishes to test that assumption.
The three liabilities added back, with beetle-kill salvage adjustment
The building's own disclosed values for biogenic storage (3,646 tCO₂e) and substitution credit (1,411 tCO₂e) are used as the baseline — we do not silently restate them. We add the three excluded liabilities on top, with the foregone-sequestration window calibrated to 50 years to reflect the beetle-kill salvage adjustment.
| Line | Factor or source | Result | Source |
|---|---|---|---|
| Wood volume | 3,600 m³ | — | MGA project page |
| A1–A3 manufacturing emissions | 0.18 tCO₂e / m³ | +648 tCO₂e | Athena EPDs |
| Biogenic storage (building's own disclosure) | — | −3,646 tCO₂e | MGA / WoodWorks |
| Substitution credit (building's own disclosure) | — | −1,411 tCO₂e | MGA / WoodWorks |
| Disclosed net (using their numbers) | — | −4,409 tCO₂e | A1–A3 minus disclosed credits |
| + DRL liability 1: SOC efflux | 0.12 tCO₂e / m³ | +432 tCO₂e | James & Harrison 2016 |
| + DRL liability 2: EOL methane | 12% biogenic C as CH₄ | +4,439 tCO₂e | Ximenes 2008; IPCC AR6 |
| + DRL liability 3: foregone seq, 50 yr (beetle-kill adj.) | 0.45 tCO₂e / m³ | +1,620 tCO₂e | Stephenson 2014; reduced for salvage |
| Full-boundary total (wood-attributable) | — | +7,139 tCO₂e | Recomputed |
| Delta vs. disclosed | — | +11,548 tCO₂e | From −4,409 to +7,139 |
The publicly cited "carbon benefit" of building T3 in wood is reported as 5,057 tCO₂e of avoided emissions and stored carbon. Under full-boundary accounting, applied with the beetle-kill salvage adjustment (50-year foregone-sequestration window — half what would apply to live-tree harvest) and mid-range factor values for the other liabilities, the wood-attributable contribution becomes a 7,139 tCO₂e liability. The swing is approximately 11,548 tCO₂e — more than twice the size of the original disclosed benefit. At the EPA average of 4.6 tCO₂e per passenger vehicle per year, this is approximately 2,510 vehicle-years of emissions.
What this recomputation does not say. It does not say wood is worse than concrete or steel. The concrete and steel alternatives also have uncounted liabilities — those will appear in the corresponding ledger entries on this site. The point of this recomputation is narrower: the published headline for T3 — a five-thousand-tonne carbon benefit — rests on a vendor-calculator output that does not consider any of the three flows added here. The flows are documented in peer-reviewed literature. They are not contested in the science. They are simply outside the boundary of the calculator the disclosure relied on.
Run the math yourself
The calculator below loads with T3's 3,600 m³ timber volume and the low-range foregone-sequestration factor (50-yr window) reflecting the beetle-kill salvage adjustment. Change any input and watch the answer move.
Sources cited on this page
- Michael Green Architecture. T3 — project page. mg-architecture.ca/project/t3-minneapolis
- Architizer. T3 Minneapolis by MGA. Project profile with "T3 Green Facts." architizer.com/projects/minneapolis-t3
- Dezeen (2016). Michael Green Architecture completes largest mass timber building in United States. dezeen.com
- Metsä Fibre / Metsä Group. Architect Michael Green is an advocate for timber building. Interview confirming 3,600 m³ wood volume and 3,200 t carbon sequestration claim. metsagroup.com
- WoodWorks | Wood Products Council. T3 Minneapolis project profile. woodworks.org
- WoodWorks Wood Calculator (methodology). Canadian Wood Council / WoodWorks. The Carbon Calculator tool referenced in the disclosed figures uses Athena Sustainable Materials Institute Impact Estimator data as upstream feed, configured to the biogenic-zero convention of EN 15978 and ISO 21930.
- Stephenson, N. L., et al. (2014). Rate of tree carbon accumulation increases continuously with tree size. Nature, 507(7490), 90–93.
- James, J. & Harrison, R. (2016). The effect of harvest on forest soil carbon: a meta-analysis. Forests, 7(12), 308.
- Ximenes, F. A., et al. (2008). Greenhouse gas balance of native forests in New South Wales, Australia. Carbon Balance and Management, 3(1), 1–13.
- IPCC (2021). Sixth Assessment Report, WG1, Ch. 7, Table 7.15 — methane GWP₁₀₀ = 27.9.
- Searchinger, T. D., Peng, L., et al. (2023). Re-evaluating the climate effects of biofuels and bioenergy and the role of land use. Nature, 619, 64–73.