International Living Future Institute’s (ILFI) Living Building Challenge 4.1

Background

ILFI’s Living Building Challenge provides a framework for design, construction, and the cooperative relationship between people, the community, and nature. The certification is ingrained with themes of regenerative design, buildings as beacons for local communities, advocacy, and innovation.

The Challenge utilizes seven performance categories, referred to as “petals.” These petals include Place, Water, Energy, Health + Happiness, Materials, Equity, and Beauty. Each petal is further divided into imperatives, which are similar to how credits or points are defined in other green building certification programs. There are a total of twenty imperatives; ten CORE imperatives that address the fundamental tenets of each petal and 10 additional imperatives that further push the performance and regenerative design of the building.

The Challenge also emphasizes the importance of proven and measured performance. All certified projects must demonstrate compliance over at least 12 consecutive months of operation. Certification occurs in two phases, starting with a Ready Audit and a “Ready” designation at the completion of construction followed by a Final Audit and Final Certification after the 12-month performance period is completed.

The Challenge may be implemented for building typologies categorized as a New Building, Building Renovation, Interior, or Landscape + Infrastructure.

There are three different levels of certification that can be achieved within the Challenge, including CORE, Petal, and Living Building.

Core Green Building Certification

A project that successfully implements all 10 CORE Imperatives across the seven petals.

Water Petal, Energy Petal, or Material Petal Certification

A project that successfully implements all 10 CORE imperatives across the seven petals and chooses to focus specifically on the Water, Energy, or Material petal and complete all remaining imperatives within that specific petal.

Living Building Certification

A project that successfully implements all 20 imperatives across all seven petals.

The table below summarizes the ILFI’s Living Building Challenge petals structural engineers can engage in to help their client achieve the target project certification level while reducing the structural system’s embodied carbon.

Summary of Credits

Summary of Embodied Carbon Imperatives for Structural Engineers in ILFI Living Building Challenge 4.1
Petal	Imperative Number and Title	Imperative Required or Optional	Probability of Embodied Carbon Reduction
Energy	07 – Energy + Carbon Reduction	Required for CORE, Energy Petal and Living Building	Almost Certainly
Energy	08 – Net Positive Carbon	Required for Energy Petal and Living Building	Almost Certainly
Materials	12 – Responsible Materials	Required for CORE, Material Petal and Living Building	Sometimes
	14 – Responsible Sourcing	Required for Material Petal and Living Building	Sometimes
	15 – Living Economy Sourcing	Required for Material Petal and Living Building	Usually
	16 – Net Positive Waste	Required for Material Petal and Living Building	Usually

Energy Petal - Core Imperative 7

Energy + Carbon Reduction:

This core imperative requires that New Building or Building Renovation projects demonstrate a 20% reduction in the embodied carbon of primary materials (structural, foundation, and enclosure elements), exterior materials (permanently installed site elements) and interior products when applicable. Compliance is demonstrated relative to an equivalent baseline based on project size, function, and energy performance. For Building Renovation projects, the reuse of on-site primary and exterior materials may be directly counted against the required reduction.

An embodied carbon assessment is required to be performed for the project and to establish a reference baseline, in accordance with ISO 14044. This assessment must consider upfront carbon including construction phase emissions (life cycle stages A1 through A5 as defined by EN 15978). Assessments of embodied carbon need to be completed with an approved tool. ILFI provides a list of approved tools consisting of both WBLCA tools, like Tally, Athena Impact Estimator, and One Click LCA, and also allows for use of Product Data and Embodied Carbon Calculator Tools, like EC3.

ILFI specifically encourages the use of current, product specific, geographically relevant, and third-party-reviewed EPDs, conforming to ISO 14025, whenever possible. ILFI also encourages advocacy for development of product-specific EPDs when data is not available for a project and provides a sample advocacy letter for use.

The project’s baseline should be identical to the initial design except for the claimed material reductions. In particular, ILFI requires that it is similar in project scope and uses material and design parameters based on standard industry practices. ILFI also requires that the implemented reduction strategies be organized into one of three categories: material quantity reduction, material alternatives, and product alternatives. Additional information on establishing a project baseline, product baseline, and embodied carbon assessment scope can be found in the Living Building Challenge Program Manual.

As part of the embodied carbon assessment for the project, structural engineers should either directly perform or advise the team on the portion of the assessment related to their scope. Preliminary embodied carbon assessment results and an understanding of materials’ embodied carbon can help determine high-carbon impact areas and allow the structural engineer to actively provide solutions to meet the 20% reduction requirement.

Early in the design phase, the design team should agree on which consultant should include the various components of the embodied carbon assessment in their scope, including development of the baseline and final calculations. The structural engineer will also need to understand how the required reductions will be achieved, and include requirements in their drawings and specifications as needed, or allow time for design alternative investigations or design optimization. By measuring and utilizing reduction strategies, structural engineers can reduce the building’s embodied carbon footprint to the greatest extent possible.

Energy Petal - Imperative 8

Net Positive Carbon:

For buildings to meet this imperative, projects must account for and offset all embodied carbon emissions associated with the project. This can be achieved by utilizing carbon-sequestering materials and/or a one-time carbon offset purchase through an ILFI approved carbon offset provider. Embodied carbon measurements performed for Imperative 7 can be utilized for this imperative to determine the required quantity of offsets to be purchased by the owner. The larger the reduction and more carbon-sequestering materials used architecturally and structurally, the fewer carbon offsets the owner has to purchase.

This imperative does provide scope clarifications for the embodied carbon assessment including the following:

As noted above, biogenic carbon may be included in the analysis, provided the Living Building Challenge’s strict sustainable sourcing requirements are met. Project teams are encouraged to report structural embodied carbon intensity both with and without biogenic carbon to illustrate its impact on the results. Projects electing to include biogenic carbon must coordinate applicable sourcing and documentation requirements early in design and incorporate them into the project specifications.
Embodied carbon intensity per floor area must account for the project floor area plus all exterior areas of the site that are disturbed as part of the project scope of work.
Offsets must consider primary material assemblies, interior material assemblies and exterior material assemblies.
Building renovation projects must consider embodied carbon associated with the refurbishment, transport, and installation of salvaged or reused materials (A3-A5) and the embodied carbon of any new materials. Existing materials are not considered relative to carbon offsets.

This imperative also requires the project to be within a maximum embodied carbon threshold of 350 kgCO2e/m2 for A1-A5 scope considering primary material assemblies, interior material assemblies, and exterior material assemblies. For some projects this requirement may result in additional effort for embodied carbon reductions beyond those of Imperative 7. Pathways are provided to provide a narrative documenting reduction efforts and specific constraints that prevent the threshold from being attainable if applicable.

Materials Petal - Core Imperative 12

Responsible Materials:

Although Core Imperative 12 is not focused exclusively on embodied carbon, many of its requirements promote material selection and procurement strategies that align with embodied carbon reduction efforts. Product transparency, responsible sourcing, regional procurement, and construction waste diversion can support broader project sustainability goals while encouraging more informed material selection.

Core Imperative 12 includes requirements related to:

Product transparency through Declare labels and manufacturer disclosure.
Living Product Challenge certified products.
Forest Stewardship Council (FSC) certified or other qualifying timber.
Regional material sourcing.
Construction and demolition waste diversion.
Low-VOC wet-applied products.

Structural engineers may contribute to these requirements through project specifications, supplier coordination, and material procurement discussions. Collectively, these strategies often complement embodied carbon reduction efforts by improving supply chain transparency, supporting responsible forest management, reducing transportation distances where feasible, and minimizing construction-related waste. Readers should refer to the current Living Building Challenge documentation for complete compliance requirements and implementation guidance.

Materials Petal - Core Imperative 14

Responsible Sourcing:

Imperative 14 builds upon the framework established in Core Imperative 12 by establishing more stringent requirements for responsible material procurement and supply chain transparency. The same general strategies remain applicable but with higher performance thresholds for product transparency, responsibly sourced timber, manufacturer participation, and project advocacy.

Structural engineers may continue to support compliance through project specifications, supplier coordination, and material procurement discussions, although successful implementation will typically require increased collaboration among the broader design team, contractors, manufacturers, and suppliers. Readers should refer to the current Living Building Challenge documentation for complete compliance requirements and implementation guidance.

Materials Petal - Imperative 15

Living Economy Sourcing

This imperative builds upon the requirements outlined in Imperative 12 (Responsible Materials). Specific requirements of this imperative include the following:

1) Manufacturer location for materials must adhere to the following restrictions:

20% or more of the materials construction budget must originate within 310 miles (500 kilometers) of the project site.

30% of the total materials construction budget must come from within 620 miles (1000 kilometers) of the project site.

An additional 25% of the materials construction budget must come from within 3100 miles (5000 kilometers) of the project site.

The remaining 25% of materials may be sourced from any location.

This provision increases the reporting and investigation requirements for supplying products locally or regionally. Sourcing of all structural materials should be considered and requirements included in the specifications. North American sourcing is feasible for most or all primary structural products and can be used to meet the requirements of this provision. Manufacturer location for steel and cold formed elements is not generally considered to be the fabricator’s facility.

Materials Petal - Imperative 16

Net Positive Waste:

This imperative strives to have projects reduce or eliminate the production waste during design, construction, operation, and end of life. To achieve this, the design team is required to implement a variety of material conservation and waste reduction strategies, including completion of a pre-building audit (where applicable), development of a Materials Conservation Management Plan, incorporation of salvaged materials or adaptive reuse, and achievement of construction and demolition waste diversion rates that exceed those required under Core Imperative 12. Structural engineers may contribute to the Materials Conservation Management Plan by identifying opportunities to optimize material use and reduce waste during the design, construction, operation, and end-of-life phases of the project.

All projects must feature at least one salvaged material per 5,380 sf (500sm) of gross building area, or be an adaptive reuse of an existing structure. Structural engineers can play a key role in meeting this requirement by evaluating opportunities to reuse or salvage existing structural materials and systems. Reusing existing structural materials on a project can help reduce the demand for new materials and the structure’s embodied carbon from the process of extraction and manufacturing. Structural engineers will need to assess and determine the condition and strength of existing structural elements to ensure they will be adequate for the proposed design’s demands. It is paramount that structural engineers are engaged during schematic design when building and material reuse is being considered.

A few strategies structural engineers can investigate and employ when designing for deconstruction include using mechanical fasteners over welding, simplifying connections, utilizing standard details to the maximum extent possible, and avoiding cast-in-place concrete composite systems. A structural system designed for deconstruction can provide a renewable construction material resource that can reduce the demand for new materials and promote a circular economy.

Reference

ILFI. (2025). Living Building Challenge 4.1. Seattle, WA. Accessed January 1, 2026. https://www.manula.com/manuals/living-future/living-building-challenge-4-1/1/en/topic/april-2024-lbc

EMBODIED CARBON IN GREEN RATING SYSTEMS