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Pillar
Tier
Project
Materials & Environmental Impact Required from Certified New construction only GHI Zero Carbon Certified Foam-free Sustainable Materials

Embodied Carbon Reduction

Reduction in upfront embodied carbon below the 154 kg CO₂e/m² baseline. Approved tools: Beam Estimator, EC3, PHPP (PH Ribbon). Alternative pathways available at Silver (no concrete, RECs, solar offset, small home).

Spec by tier

This requirement steps in stringency by tier. Each tier inherits and tightens the value.

Tier Spec
Certified Embodied-carbon evaluation required
Silver 10% reduction from baseline
Gold 15% reduction from baseline
Platinum 30% reduction from baseline

Scope

Upfront embodied carbon (A1-A5 life-cycle stages) of new construction or major addition. Existing structure being kept in place is exempt by definition (zero new embodied carbon).

Requirements

Performance targets

  1. 01.

    At Certified: complete an embodied-carbon evaluation using an approved tool (Beam Estimator, EC3, PHPP / PH Ribbon). The evaluation must report total upfront kg CO₂e/m² for the project.

  2. 02.

    At Silver: reduce embodied carbon by at least 10% below the GreenStar baseline of 154 kg CO₂e/m².

  3. 03.

    At Gold: reduce by at least 15% below baseline.

  4. 04.

    At Platinum: reduce by at least 30% below baseline.

  5. 05.

    Alternative pathways accepted at Silver: build without concrete, OR purchase renewable energy credits equal to project embodied carbon, OR install solar PV offsetting embodied carbon over 30 years.

  6. 06.

    Small-home exemption: single-family ≤ 800 sf and multifamily units averaging ≤ 600 sf are exempt from the Silver+ percentage-reduction requirements (still complete the evaluation at Certified).

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Embodied-carbon report from an approved tool (Beam, EC3, PHPP) showing the project's upfront kg CO₂e/m² and the comparison to baseline.

  2. 02.

    Bill of materials including quantities (cubic yards of concrete, board feet of lumber, etc.) used in the calculation.

  3. 03.

    For alternative pathways at Silver: REC purchase certificate, solar system sizing calculation, or no-concrete design documentation.

Guidance

Why embodied carbon matters now

For a new high-efficiency home, embodied carbon (the carbon emitted to make the building materials) typically exceeds the operational carbon (heating/cooling/electric) for the first 30 years of the building's life. As the grid decarbonizes and homes become more efficient, embodied carbon becomes a larger share of total lifecycle impact. Choosing low-carbon concrete, wood-frame vs steel-frame, and reused materials makes a measurable difference.

The biggest reduction levers

Concrete is typically 30-50% of a home's embodied carbon. Switching from standard Portland cement concrete to a low-carbon mix (Type IL cement, fly ash or slag replacement at 30-50%, or specifying max OPC content) can cut concrete EC by 30-60% with no structural impact. Wood framing has dramatically lower EC than steel; insulation choice (mineral wool vs XPS foam) varies by 10x.

Resources