Why the humble truss now matters in carbon bids
Steel, concrete and insulation usually hog the spotlight, yet roof and floor trusses can represent 8 to 12 % of a low-rise building’s cradle-to-gate footprint. New public procurement rules in New York City and California cap GWP on structural packages, so bidders must defend every pound of metal or lumber they ship.
The carbon scoreboard: three brands, one metric
- Clark Dietrich LEC cold-formed steel framing reports 1.66 kg CO₂e per kilogram at A1–A3 (Clark Dietrich EPD, 2024).
- The Canadian industry EPD for wood trusses shows 111 kg CO₂e per cubic metre, equal to roughly 0.24 kg CO₂e per kilogram after biogenic storage is counted (CWC, 2025).
- Trussway and UFP have no public EPDs today; in the absence of product-specific data, owners default to the industry average above. That gives timber suppliers a head start, but only if they publish soon.
Converting lab data to the jobsite
A typical cold-formed steel roof truss weighs about 5 lb / ft² (2.3 kg). Multiply by Clark Dietrich’s 1.66 kg CO₂e / kg and designers face ~3.8 kg CO₂e per square foot of roof area. A comparable timber truss comes in closer to 2 lb / ft² (0.9 kg). Using the industry GWP, that is just 0.22 kg CO₂e per square foot—roughly a 17-to-1 delta. Even if Clark Dietrich’s LEC claim of a 30 % improvement over its legacy steel is applied, wood still holds a tenfold margin.
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Independent research backs the spread
A 2025 Chalmers University LCA found that a 12-metre steel truss emitted 842 kg CO₂e, while five nail-plate timber trusses covering the same span emitted 179 kg CO₂e, an 79 % cut (Chalmers Univ, 2025). The pattern held across all span lengths tested.
Prefabrication flips the waste script
On-site stick-built roofs can waste up to 15 % of purchased lumber off-cuts. Off-site automated saws trim that to under 3 %, according to the Structural Building Components Association’s 2024 audit. EPA data show the US generated 600 million tons of construction debris in 2018, more than double municipal trash (EPA, 2025). Every pound saved in teh factory stays out of that pile.
ROI beyond carbon counters
- Lighter timber trusses trim crane time and fastening hardware, slicing install labor by 10–15 % in multifamily walk-ups.
- Steel still rules long spans above 80 ft, so mixed-material portfolios let manufacturers chase both markets.
- Early EPD publication locks in spec loyalty; once an engineer drops a product into a BIM model, switching later is painful.
Read the small print on any EPD
Check the declared unit: Clark Dietrich reports per metric ton, the wood EPD per cubic metre. Always normalise to area or linear foot before comparing. Scrutinise the system boundary too; some steel declarations bury recycling credits in module D, which does not help an A1–A3 cap.
Bottom line for manufacturers
Publish a truss-specific EPD before your competitor does. Pair it with a clear pounds-per-square-foot table that specifiers can drop straight into their calculators. Prefabbrication cuts waste, but only transparent data wins the bid.
