Embodied carbon tools compared: One Click LCA vs Tally vs EC3 and alternatives

Why It Matters

Embodied carbon now represents up to 50 percent of a new building's whole-life emissions, a share that grows as operational energy is decarbonised through electrification and grid greening (WGBC, 2025). Regulations are catching up: the EU Level(s) framework, California's Buy Clean Act, the Greater London Authority's Whole Life Carbon requirement, and the forthcoming updates to EN 15978 all mandate or incentivise embodied carbon assessment. Yet a 2025 benchmarking study by the Carbon Leadership Forum found that the same building modelled in three different tools could produce whole-life carbon results that vary by 20 to 40 percent, depending on database selection, system boundaries, and methodology assumptions (CLF, 2025). For practitioners, choosing the right tool is not a software preference; it is a decision that shapes data quality, regulatory compliance, and the credibility of reduction claims. This guide provides a structured comparison of the three most widely adopted platforms and their leading alternatives.

Key Concepts

Whole-life carbon assessment (WLCA) evaluates greenhouse gas emissions across a building's full lifecycle: product stage (A1 to A3), construction (A4 to A5), use stage (B1 to B7), and end of life (C1 to C4). Module D captures benefits from reuse, recovery, and recycling beyond the system boundary.

Environmental Product Declarations (EPDs) are third-party-verified documents that report the environmental impact of a specific product. EPD-based tools draw on manufacturer-specific data and deliver higher accuracy than those relying on generic industry averages.

BIM integration refers to a tool's ability to extract material quantities directly from Building Information Models, eliminating manual take-offs and reducing human error. The depth of integration varies: some tools operate as native plugins within Autodesk Revit, while others require data export in IFC or spreadsheet format.

Database coverage describes the number and geographic spread of materials, EPDs, and generic datasets a tool can access. Larger databases improve accuracy for global projects; regionally focused databases provide better precision for local material sourcing.

System boundaries define which lifecycle stages a tool includes by default. Inconsistent boundaries are a leading cause of result divergence across tools, and practitioners must verify that comparisons use aligned boundaries (RICS, 2024).

Head-to-Head Comparison

One Click LCA offers the broadest geographic coverage and the deepest certification alignment, making it the default choice for multinational practices. Buro Happold and Arup both use One Click LCA across their global portfolios, citing its database breadth and regulatory reporting templates (One Click LCA, 2025). The platform added automated CSRD and EU Taxonomy alignment reporting in 2025, positioning it for the incoming European regulatory wave.

Tally excels at design-stage integration because it operates natively inside Revit, allowing architects to see embodied carbon results update in real time as they modify the model. Skidmore, Owings & Merrill (SOM) used Tally during the design of the net-zero Robinson Tower in Singapore, iterating through 14 structural options and reducing embodied carbon by 32 percent before construction began (SOM, 2024). The limitation is that Tally's utility drops sharply for teams not working in Revit and for projects outside North America and Europe where the GaBi database has thinner coverage.

EC3 from Building Transparency is a free, open-access tool that focuses on material-level comparison rather than whole-building LCA. It is invaluable for procurement: specifiers can compare EPDs for concrete, steel, insulation, and other materials side by side, filtering by performance, region, and carbon intensity. Skanska used EC3 to set material carbon limits on over 50 US projects in 2024, achieving an average 18 percent reduction in product-stage embodied carbon versus industry baselines (Skanska, 2025). However, EC3 does not perform whole-building lifecycle assessment, so it must be paired with One Click LCA, Tally, or another WLCA tool for comprehensive reporting.

Alternatives worth considering

eTool is an Australian platform with strong coverage of Australasian materials and compliance with the Green Star rating system. It is widely used by Multiplex and Lendlease for projects in the Asia-Pacific region.

CAALA is a German early-design tool that links parametric modelling with LCA, enabling architects to optimise massing and envelope design for embodied carbon before BIM models exist.

Kaleidoscope by IES integrates operational and embodied carbon modelling in a single platform, supporting whole-life carbon optimisation from concept through operation.

Cost Analysis

For a mid-sized architecture or engineering firm running 20 to 40 projects annually, the total cost of ownership (tool license plus staff training plus data management) ranges from US$15,000 to US$50,000 per year for One Click LCA and US$10,000 to US$25,000 for Tally. EC3 eliminates license costs but requires additional staff time for manual data integration and does not cover whole-building assessment, meaning most teams use it alongside a paid tool (CLF, 2025).

The return on investment is increasingly tangible. The World Green Building Council (2025) reports that projects using embodied carbon tools during early design achieve 10 to 30 percent reductions in product-stage carbon with minimal or zero cost increase, because substitutions (e.g., shifting from CEM I to CEM III cement, or specifying recycled steel) often carry comparable or lower material costs.

Use Cases and Best Fit

Large multidisciplinary consultancies operating globally benefit most from One Click LCA. Its database covers 90+ countries, supports multiple certification systems, and provides portfolio-level benchmarking. Firms like WSP and Ramboll have standardised on the platform to ensure consistent reporting across jurisdictions.

Design-led architecture practices working primarily in Revit will find Tally's native integration the most efficient path to embedding carbon into design decisions. The real-time feedback loop means carbon data influences form, structure, and material choices before they are locked in, which is when the largest reductions are possible.

Contractors and procurement teams focused on material specification should start with EC3. Its free access, granular EPD data, and filtering tools make it the fastest way to set carbon intensity limits in specifications and evaluate supplier submittals. Hensel Phelps and Clark Construction have both integrated EC3 into their procurement workflows for Buy Clean Act compliance (Building Transparency, 2025).

Early-stage designers and parametric practices exploring massing and envelope options before BIM should consider CAALA, which links geometry directly to carbon outcomes.

Asia-Pacific focused teams should evaluate eTool for its regional database depth and Green Star alignment.

Decision Framework

Step 1: Define scope and regulatory requirements. Identify which lifecycle stages must be assessed (A1 to A3 only, or full WLCA), which certification systems apply, and which jurisdictions are involved. If EU Level(s) or BREEAM compliance is needed, One Click LCA has the most mature templates.

Step 2: Assess BIM maturity. If the team works in Revit and wants design-stage feedback, Tally is the most integrated option. If BIM models are produced in ArchiCAD, Rhino, or other platforms, One Click LCA offers broader plugin support.

Step 3: Evaluate geographic coverage. Check whether the tool's database includes region-specific EPDs and generic data for the project's location. Tools with thin coverage in a given region produce results that rely heavily on proxy data, reducing accuracy.

Step 4: Budget and team size. Small firms and academic institutions may start with EC3 (free) for material comparisons and add a paid WLCA tool as project volumes grow. Enterprise-scale organisations should negotiate multi-year subscriptions with One Click LCA or Tally for volume pricing.

Step 5: Integration and interoperability. Consider how the tool fits into existing workflows: does it connect to cost-estimation software, structural analysis platforms, or ESG reporting systems? One Click LCA's API enables custom integrations; Tally's strength is Revit-native simplicity.

Key Players

Established Leaders

One Click LCA (Bionova) — Market-leading WLCA platform with 150,000+ EPDs, used in 170+ countries. Acquired by Sphera in 2025 to strengthen its construction sustainability offering.

Tally (KT Innovations / Building Transparency) — Native Revit plugin built on the GaBi database, widely adopted by US and European architecture firms.

Building Transparency (EC3) — Non-profit providing the free EC3 tool and the largest open-access EPD database in North America.

Sphera (GaBi) — Provider of the GaBi LCA database that underpins Tally and numerous industry LCA models globally.

Emerging Startups

CAALA — German parametric LCA tool enabling embodied carbon optimisation at the earliest design stages before BIM.

Kaleidoscope (IES) — Integrated operational and embodied carbon platform for whole-life building performance.

2050 Materials — Data platform aggregating sustainability data for construction materials, backed by a growing materials passport database.

Key Investors/Funders

Breakthrough Energy Ventures — Backing construction decarbonisation technologies including low-carbon materials and digital tools.

Laudes Foundation — Major funder of Building Transparency and embodied carbon data infrastructure.

ClimateWorks Foundation — Supporting open-source carbon data standards and tool development for the built environment.

FAQ

Why do different tools produce different results for the same building? Divergence stems from three main sources: database selection (manufacturer-specific EPDs versus generic industry averages), system boundary definitions (which lifecycle stages are included), and methodology choices (allocation rules, biogenic carbon accounting, end-of-life scenarios). The Carbon Leadership Forum (2025) recommends that practitioners document tool, database version, and boundary assumptions alongside any published result to enable fair comparisons.

Is EC3 sufficient on its own for regulatory compliance? EC3 covers product-stage emissions (A1 to A3) and is well suited for Buy Clean Act compliance and material specification. However, regulations such as the GLA Whole Life Carbon requirement and EU Level(s) mandate assessment of lifecycle stages A1 through C4, which requires a whole-building LCA tool like One Click LCA or Tally. Most compliant workflows use EC3 for material selection and a WLCA platform for building-level reporting.

How accurate are embodied carbon assessments in practice? Accuracy depends on data quality. Assessments using project-specific EPDs can achieve uncertainty ranges of plus or minus 10 to 15 percent. Those relying on generic data may see uncertainty of plus or minus 30 to 50 percent (RICS, 2024). Accuracy improves as the design progresses from concept (generic data) to detailed design (specific product selections). Running the assessment at multiple design stages and updating data as specifications are finalised is considered best practice.

What is the cost of not measuring embodied carbon? Beyond regulatory non-compliance risk, failing to measure embodied carbon means missing reduction opportunities that are often cost-neutral. The WGBC (2025) documents cases where material substitutions identified through LCA tools reduced embodied carbon by 20 to 40 percent with no construction cost increase. As carbon pricing mechanisms expand to cover materials (e.g., the EU Carbon Border Adjustment Mechanism), unmeasured embodied carbon will increasingly translate to unmanaged financial exposure.

How should teams handle data gaps when EPDs are unavailable? Use conservative generic data from recognised databases (e.g., ICE Database from the University of Bath, Oekobaudat for Germany, AusLCI for Australia) and flag the data quality level in the assessment. Engage suppliers early to request EPDs; the number of construction EPDs globally has grown from 30,000 in 2020 to over 150,000 in 2025, so availability is improving rapidly (One Click LCA, 2025). Where gaps persist, sensitivity analysis showing the impact of data uncertainty on results is essential.

Sources

• WGBC. (2025). Bringing Embodied Carbon Upfront: 2025 Status Update. World Green Building Council.
• CLF. (2025). Embodied Carbon Benchmark Study: Tool Comparison and Data Quality Assessment. Carbon Leadership Forum, University of Washington.
• RICS. (2024). Whole Life Carbon Assessment for the Built Environment (2nd Edition). Royal Institution of Chartered Surveyors.
• One Click LCA. (2025). Platform Impact Report: 150,000 EPDs and 10,000 Building Benchmarks. Bionova Ltd.
• SOM. (2024). Robinson Tower: Designing for Net-Zero Embodied and Operational Carbon. Skidmore, Owings & Merrill.
• Skanska. (2025). Buy Clean Implementation: EC3-Driven Material Carbon Limits Across 50+ US Projects. Skanska USA.
• Building Transparency. (2025). EC3 Annual Report: Database Growth, User Adoption, and Policy Impact. Building Transparency.
• IEA. (2024). Global Status Report for Buildings and Construction 2024. International Energy Agency.
• Laudes Foundation. (2025). Funding Open Data for Building Decarbonisation. Laudes Foundation.
• BPIE. (2025). Embodied Carbon in Building Renovation: Quantifying the Benefits of Retention. Buildings Performance Institute Europe.