Mass Timber Tool Reveals Hidden Carbon Emissions

Corgan, a leading architecture and design firm, has introduced new research alongside a free analytical tool aimed at improving carbon accounting in mass timber construction. The company hopes to  address a knowledge gap in sustainable building practices and offers professionals in architecture, engineering, and construction a more thorough understanding of mass timber’s full environmental impact.

Uncovering the Overlooked Emissions in Mass Timber Use

Mass timber is widely recognized for its renewable qualities and lower embodied carbon when compared to traditional materials such as steel and concrete. Recent findings from Corgan’s sustainability division (Echo) and research arm (Hugo) highlight emissions not typically included in standard life-cycle assessments.

About 35% of a harvested tree contributes directly to construction. The remaining 65%—known as "slash," which includes bark, branches, and roots—typically decomposes or is burned, releasing biogenic carbon back into the atmosphere. These emissions have historically been excluded from common environmental impact calculations.

Addressing Gaps in Carbon Accounting Practices

Prompted by a 2023 World Resources Institute report that questioned mass timber’s assumed carbon neutrality, Corgan conducted a detailed analysis to offer a more accurate emissions profile. This research identifies biogenic carbon emissions from slash material as a substantial, previously underreported factor in carbon accounting.

To support early-stage decision-making, Corgan developed the Mass Timber Carbon Calculator—a free, publicly accessible tool designed for architecture, engineering, and construction (AEC) professionals. The calculator helps estimate project-specific emissions by incorporating key variables:

1. Tree species: Includes analysis for seven commonly used species in U.S. mass timber construction
2. Slash management techniques: Accounts for scenarios including mastication, on-site composting, and pile burning
3. Transport emissions: Considers distances from forest harvest to building sites

These variables provide a more comprehensive view of mass timber’s carbon impact across a building’s life cycle.

Using a hypothetical six-story office building, Corgan demonstrated that, even with slash-related emissions accounted for, mass timber still results in significantly lower embodied carbon than steel or concrete alternatives. This reinforces its value as a lower-carbon material choice, while also underlining the importance of accurate emissions reporting.

Supporting Smarter, More Transparent Material Choices

Material selection during the design phase can account for up to 20% of a building’s total energy usage over its lifetime. By allowing teams to compare species, management practices, and transport logistics, the calculator enhances transparency and supports better-informed decisions from the earliest stages of design.

As demand for wood-based construction materials is expected to increase fourfold by 2050, the industry must prepare for more nuanced and accountable sustainability practices. Tools like Corgan’s calculator aim to equip professionals with the data they need to meet both performance and climate goals.