EMBODIED CARBON IN GREEN RATING SYSTEMS

Introduction

Around the 1990s, major green rating systems for buildings were developed and released in North America and Europe. These green rating systems were created to help provide designers a framework for minimizing the impacts their building designs have on the natural environment. Today, many green rating systems approach the built environment’s effects on the natural environment through varying levels of requirements, strategies, and measurements. The purpose of this document is to provide structural engineers a brief background on each rating system and summarize the credits related to embodied carbon that structural engineers can influence to help their clients achieve the project’s targeted green rating. For resources on explaining, measuring, and reducing embodied carbon, see the SE 2050’s Resource page. It is essential to note what version of the green rating system the project uses since green rating systems evolve as the science and knowledge of sustainability, embodied carbon, and their effects on the natural environment mature.

Even if a project is not pursuing certification through a green rating system, structural engineers can still employ strategies contained within each rating system. In addition to green rating strategies, structural engineers can utilize other tactics to reduce the embodied carbon on a project. To be included in the sustainability conversation and positively impact the design profession, engineers should educate themselves on embodied carbon and reduction strategies.

Please select a green rating system’s logo below to learn about the embodied carbon credits available for structural engineers. When comparing different green rating systems, note that some language is redundant. This is due to the similarities of the embodied carbon reduction credit’s goals and strategies to achieve the credit.

Green Rating Systems in North America

GBI Green Globes for NC 2019

ISI Envision, Version 3

ILFI CORE

ILFI Living Building Challenge 4.0

ILFI Zero Carbon Standard 1.0

ILFI ZE Certification

IWBI WELL Building Standard, Version 2.0

PHIUS+ 2018

USGBC LEED BD+C, Version 4.1

CaGBC Zero Carbon Building

Green Rating Systems in Europe

The following systems are based on a study conducted by Bionova Ltd called The Embodied Carbon Review which reviewed around 216 green building systems that were identified as addressing embodied carbon internationally. Of the 216 systems, 105 included direct measures for embodied carbon. All but one of the 20 international and pan-European standards and rating systems target embodied carbon. Northern Europe, comprising the Nordic countries, UK, and Ireland has 24 such systems and Continental Europe has 38 regulations and certifications in use, including the first regulatory programs targeting embodied carbon.

European standards

The following are common European standards referenced by the green rating systems or requirements:

EN 15978: This standard specifies the calculation method, based on LCA, to assess the environmental performance of a building. It also provides guidance on the reporting and communication of the outcome of the assessment. This standard is relevant to all building types, new and existing.
EN 15804: This standard provides core rules for the creation of EPDs for construction products and services.
EN 15643-5: This standard is Part 5 of the Sustainability of Construction Works standards that lay out the framework on specific principles and requirements for civil engineering works for the sustainability assessment of buildings and civil engineering works.

Incentives Identified in European Systems

The systems typically provide some form of an incentive to apply carbon reduction policies. Table below describes the incentives identified in various systems. EPDs are another essential component of the rating systems, under the oversight of European Standards Technical Committee CEN TC350.

Category of Incentives	Description	System Examples
Rating points	Systems that award rating points for the application of LCA or achieving savings quantifiable with LCA	BREEAM International 2016, DGNB 2016
Density Bonus:	Meeting a carbon performance level may make a project eligible for additional gross floor area rights. A density bonus gives developers the incentive to exceed the normally allowed floor-to-area ratio (FAR). In short, they can develop projects that are taller and more densely packed with residential units in exchange for complying with energy efficient building standards	French E+C
Cash Impact	Either carbon offsetting funded by the constructor, thus ensuring carbon emissions lead to real cash cost for project; or a carbon performance payment	Rijkswaterstaat procurement policy
Mandatory	Carbon criterion is a mandatory requirement	Dutch MPG regulation and allowed level of the French E+C-scheme

Embodied Carbon

Table below shows Methods to Address Embodied Carbon

Method	Description	System Examples
Carbon Reporting	Reporting calculated embodied carbon for a construction project	BREEAM International, EN 15978
Carbon Comparison	Design both a baseline and the proposed design, and show improvements against the self-declared baseline value	BREEAM UK
Carbon Rating	Evaluation of carbon performance on a variable scale from best to worst on which a project’s carbon is rated, but no effective maximum value applied.	DGNB, BREEAM NL
Carbon cap	Calculate the project’s embodied carbon and prove it is not exceeding the CO₂e limit	Energie Carbone, MPG
Decarbonization	Reduce carbon to a minimum, then compensate all residual emissions by own energy export or buying offsets	NollCO2

Carbon Thresholds

Table below shows methods for setting Carbon Thresholds

Method	Description	System Examples
Self-declared	End users declare their own baseline performance, typically 10% reduction against a self-declared baseline	Infrastructure rating systems, Miljöbyggnad 3 systems
Methodology	Threshold values are generated using a well-defined baseline calculation method.	FutureBuilt, HS2 (infrastructure)
Fixed scale	Threshold value, or scale, is fixed for the building type and results mechanically from given parameters without judgement being applied.	DGNB (highest scores achieved by reducing impacts by 45% from the reference value), BREEAM NL (highest scores achieved by 60% reduction from reference value), Energie Carbone (mandatory level is set)