In this podcast episode, writer and sustainable design advocate Lloyd Alter discusses the critical importance of addressing "upfront carbon" (A1-A5 cradle-to-gate emissions), arguing that the term "embodied carbon" is misleading. Alter criticizes the industry's focus on building the "tallest Mass Timber" structures, advocating instead for mass timber’s "sweet spot" of 5 to 15 stories, where it is most cost and carbon efficient. He highlights the need for material moderation, challenging the traditional mindset that celebrating carbon storage volume in buildings justifies using more wood fiber. Alter showcases innovative regional production models, like Timber AGE, that utilize low-value timber from forest thinning for low-rise buildings, and advocates for the increased use of reusable materials like Dowel Laminated Timber (DLT) and wood fiber insulation to maximize resource efficiency.
Key Discussion Points on Upfront Carbon and Mass Timber
3:15 The Problem with "Embodied Carbon": Lloyd Alter explains why he and others advocate for the term "upfront carbon." "Embodied carbon" is inaccurate because the carbon is immediately released into the atmosphere, not "embodied" in the material. Upfront carbon refers specifically to A1-A5 (cradle-to-gate) emissions.
6:35 The Urgency of "Now Emissions": Alter emphasizes that upfront carbon emissions are critical because they immediately impact the finite global carbon budget set by the IPCC. While buildings must balance upfront (now) and operational (later) emissions, current policy and building codes often ignore upfront carbon.
10:08 Policy and Political Challenges: Alter notes that changes in building standards are slow, often taking a decade or more due to political and vested industry interests (like the concrete industry). He suggests Canada is generally ahead of the U.S. in beginning to require upfront carbon calculations (e.g., British Columbia and California).
14:51 Mass Timber’s Sweet Spot (5–15 Stories): Alter argues that the competition to build the "tallest Mass Timber" is counterproductive. Extreme height creates engineering challenges (e.g., needing heavy concrete ballast in lighter wood structures to resist wind). Citing expert consensus (Andrew Waugh), the ideal, efficient range for mass timber construction is 5 to 15 stories.
16:02 Localized and Efficient Production: Alter praises innovative models like Timber AGE (Kyle Hanson in Colorado). This model uses mobile, small factories to process smaller, low-grade wood from forests requiring thinning, improving forest health and creating local economies while minimizing transportation costs.
20:45 Innovative Construction Materials: The conversation highlights alternatives to CLT:
Nail Laminated Timber (NLT): Used in the T5 building because it was code-compliant; offers a "warehouse look" (21:18). The Candida building demonstrated innovative NLT use with recycled wood and served as a job training exercise (22:15).
Dowel Laminated Timber (DLT): Esteemed for its potential reusability (23:27). DLT uses kiln-dried hardwood dowels that expand with moisture, locking the planks together without nails or glues, making the slabs easily deconstructable later.
25:22 Challenging the Carbon Storage Narrative: Alter critiques the historical mindset of being "proud" of storing maximum carbon fiber. He argues that only about half the carbon from a tree makes it into the mass timber product (due to losses from slash, kiln-drying, and root decay). The focus must shift to moderation and using 40% less fiber, as demonstrated by architects like Waugh Thistleton.
28:55 The Future is Wood Fiber Insulation: Alter anticipates a massive increase in wood fiber insulation (like Timber HP in Maine). This product utilizes small, fast-growing, low-value wood (or even agricultural byproducts like straw) to insulate buildings, efficiently storing carbon for the building's life.
33:35 Final Key Takeaway: Lloyd Alter’s "elevator pitch" for addressing upfront carbon is simple: "Use less stuff and make it last."