A new study has found that timber roof trusses—using nail plate connections —consistently deliver the lowest carbon emissions across all measured span lengths, outperforming concrete, steel, and even glulam.
Led by Zeina Alasadi and Selma Bergström Denizoglu of Chalmers University of Technology, the research highlights timber’s natural edge in structural applications, even when multiple units are needed to match the span of a single steel or concrete truss.
“The issue of climate change is becoming an increasingly relevant and important topic that concerns both companies and individuals,” the authors write. “Within the construction sector, it is therefore especially important to make conscious material choices that can help reduce climate impact.”
The study measured anthropogenic carbon dioxide emissions—one of the main drivers of climate change—across trusses from 6 to 26 metres in span. Using life cycle assessment (LCA) data for the production phase (stages A1–A3), the team compared timber, concrete, steel, and glulam designs, drawing on verified environmental product declarations (EPDs) and manufacturer specifications.
The results were stark. Timber trusses with spans of 6, 8, 12, and 20 metres generated just 59.72 kg, 78.5 kg, 145.15 kg, and 352.5 kg of CO₂, respectively. By contrast, a single 23.14‑metre concrete truss emitted 3,111 kg CO₂e—equivalent to the output of nearly 40 timber trusses. Two timber configurations covering the same span emitted only 396.10 kg and 651.12 kg CO₂e.
Steel performed little better. A 12‑metre steel truss emitted 841.52 kg CO₂e, compared to 178.77 kg for five timber trusses of the same span. For a 20.15‑metre span, one steel truss released 1,577.85 kg CO₂e, while ten timber trusses emitted 403.48 kg. Even with recycled steel, emissions still reached 780.7 kg CO₂e—almost double the timber equivalent.
Meanwhile, glulam trusses, despite being wood‑based, had higher emissions due to larger material volumes and partial steel reinforcement. A 25.63‑metre glulam truss emitted 2,148.32 kg CO₂e, with 1,798.40 kg from steel and 349.92 kg from laminated wood. Timber alternatives using five trusses of the same span emitted between 471.64 kg and 539.34 kg CO₂e.
“The results show that the nail‑plate connected wooden roof trusses have by far the lowest climate impact among the studied alternatives across all span lengths,” the authors conclude. “Even though more timber trusses are required to cover the same roof area.”
The findings challenge industry preferences for concrete and steel, linked to familiarity, design conventions, and perceived limitations of timber. Yet with the ability to span up to 25 metres unsupported—and up to 50 metres with interior wall support—timber trusses offer a scalable, low‑emission option for industrial and public buildings. “The choice of material can have an unexpectedly significant impact on a building’s total climate footprint,” the researchers said, urging architects, engineers, and developers to factor emissions into early‑stage design.
