LEED v4 Rating System

Introduction

• LEED (Leadership in Energy and Environmental Design) provides a way to quantify benefits and promote sustainable alternatives in the building industry.
• LEED has put energy and water efficiency, green materials, and indoor air quality on the radar for building projects.
• The point allocation process in the LEED Rating System simplifies complex issues for building project teams globally.
• Key issue involves the relative weight given to different sustainability strategies across building systems and disciplines.
• USGBC has focused on relative weighting and sophistication, which has continually evolved.
• The document reviews the weighting structure and process for LEED version 4.
• The document highlights key findings based on statistical analysis.

Background

• Early LEED versions allocated points based on Technical Advisory Committee members' professional judgments.
• LEED 2009 introduced a weighting system that allocated points based on the ability to reduce environmental problems.
• The new approach added an analytical framework with a focus on performance.
• Impact categories for LEED 2009 derived from the Environmental Protection Agency’s TRACI categories, widely used for Life Cycle Assessments.
• TRACI categories were designed for individual materials, not whole buildings and they were modified to include human health issues and ranked by applicability to the built environment.
• LEED v4 uses the analytical framework and a new set of criteria developed for the built environment.
• The LEED Steering Committee approved Impact Categories focusing on social, environmental, and economic goals.
• LEED v4 asks: “What should a LEED project accomplish?”
• LEED v4 introduces a web-based tool for associations between strategies and impacts, called the LEED Weightings Tool.
• The LEED Weightings Tool enables statistical analysis.

Overview of LEED Structure

• The LEED Rating System is a voluntary, consensus driven, internationally recognized green building certification.
• LEED provides third-party verification that projects were designed and built with sustainable strategies.
• Strategies aim to improve performance across metrics, including energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality, and resource stewardship.
• LEED provides a framework for identifying and implementing practical and measurable green solutions.
• Project teams utilize LEED as both a design guide and verification system to measure progress.
• LEED encourages interdisciplinary project teams and integrated project delivery.
• Rewards successful projects with third-party certification.
• Motivates project teams to take action for higher performing buildings.
• LEED promotes action in 6 key areas, known as credit categories:
  • Location and Transport
  • Sustainable Sites
  • Water Efficiency
  • Energy and Atmosphere
  • Materials and Resources
  • Indoor Environmental Quality
• Credit categories include mandatory and optional strategies, where mandatory strategies are prerequisites.
• Achieving certification requires documenting compliance with all prerequisites and enough credit requirements to reach 40 of 100 available points.
• Higher achievement levels are rewarded with higher levels of certification.
  • 40 points - LEED Certified
  • 50 points - LEED Silver
  • 60 points - LEED Gold
  • 80 points - LEED Platinum

LEED System Goals

• LEED engages building project teams to connect strategies to a defined set of goals, known as "Impact Categories."
• There are seven Impact Categories developed and approved by the LEED Steering Committee for LEED v4.
• The Impact Categories answer the question: “What should a LEED project accomplish?”
  • Reverse Contribution to Global Climate Change
  • Enhance Individual Human Health and Well-Being
  • Protect and Restore Water Resources
  • Protect, Enhance and Restore Biodiversity and Ecosystem Services
  • Promote Sustainable and Regenerative Material Resources Cycles
  • Build a Greener Economy
  • Enhance Social Equity, Environmental Justice, and Community Quality of Life
• The Impact Categories set out an agenda that is only actionable within a framework of prerequisites and credits.
• Projects that meet credit and prerequisite requirements can deliver performance outcomes that address the Impact Categories.
• The certification structure incentivizes higher credit achievement and compliance with credits that accomplish system goals.

Point Allocation Methodology

• Designed to be flexible, LEED allows building project teams to select credits.
• There are roughly 50 credits in the proposed draft of LEED for New Construction.
• Credits that significantly contribute to accomplishing the system goals of the seven impact categories are assigned more points.
• Achieved using a multi-criteria analysis approach, where credits are evaluated based on their expected outcome on each of the impact categories.
• Each LEED credit is independently measured along seven impact categories using a matrix format.
• Associations between credits and Impact Categories are given a weight based on the strength of association.
• A cell with "0" indicates no association between credit and impact category.
• Each Impact Category is weighted relative to each other.
• The weights are layered, normalized to deliver the point scorecard.

Impact Category Weighting Layer

• Applied due to the variation in scale, scope, severity, and contribution of LEED’s Impact Categories.
• Shown as impact weight.
• A consensus driven process was used to weight these impact categories.
• Severe, global problems are given a larger percentage of the 100 points.
• Impact Categories that may be less severe, less certain, operate at a smaller scale, or that the built environment has less of an ability to solve are assigned small proportion of the 100 total points.

Credit Outcome Weighting

• The relative strength of the relationship between a credit outcome and goal within an Impact Category contributes to the credit’s point value.
• Methods to establish the relationships vary.
• Determining the relative importance of credit achievement to the system goals is often a quantitative exercise, such as with the Climate Change Impact Category.
• Data drives credit ranking, while other Impact Categories rely on qualitative estimations.

LEED Scorecard Development

• Over 4,000 connections related to the efficacy, duration, and control of the benefit are made.
• Impact categories have defined bounding assumptions to prevent double counting.
• The weights compile a scorecard based on the total points (100 for LEED v4) and minimum points for credit (1 for LEED v4).

Impact Category Definitions

• Impact categories must be well defined and clearly bound.
• The conceptual definition behind each Impact Category is broad. The impact categories are broken down into key indicators, referred to as components for LEED v4.
• The weighting associations are made with the components for direct correlation between credits and outcomes.
• The organization of the impact categories and their components are:
  • Reverse Contribution to Global Climate Change
    • GHG Emissions Reduction from Building Operations Energy Use
    • GHG Emissions Reduction from Transportation Energy Use
    • GHG Emissions Reduction from Materials and Water Embodied Energy Use
    • GHG Emissions Reduction by Embodied Energy of Water Reduction
    • GHG Emissions Reduction from a Cleaner Energy Supply
    • Global Warming Potential Reduction from Non-Energy Related Drivers
  • Enhance Individual Human Health and Well-Being
    • Support Occupant Comfort and Well-Being
    • Protect Human Health from Direct Exposure to Negative Health Impacts
    • Protect Human Health Globally and Across the Entire Built Environment Life Cycle
  • Protect and Restore Water Resources
    • Water Conservation
    • Water Quality Protection
    • Protection and Restoration of Water Regimes and Natural Hydrological Cycles
  • Protect, Enhance and Restore Biodiversity and Ecosystem Services
    • Local Biodiversity, Habitat Protection and Open Spaces
    • Global Biodiversity, Habitat Protection and Land Preservation
    • Sustainable Use and Management of Ecosystem Services
  • Promote Sustainable and Regenerative Material Resources Cycles
    • Reduce Raw Material Resources Extraction
    • Move to Cyclical, Non-Depleting Material Cycles
    • Reduce Negative Environmental Impacts throughout the Materials Life-Cycle
  • Build a Greener Economy
    • Enhance the Value Proposition of Green Building
    • Strengthen the Green Building Industry and Supply Chain
    • Promote Innovation and Integration of Green Building Products and Services
    • Incentivize Long Term Growth and Investment Opportunities
    • Support Local Economies
  • Enhance Social Equity, Environmental Justice, Community Health and Quality of Life
    • Create a Strong Sense of Place
    • Provide Affordable, Equitable and Resilient Communities
    • Promote Access to Neighborhood Completeness Resources
    • Promote Human Rights and Environmental Justice

Association Factors

• Associations between LEED credit requirements and Impact Category measured through lenses.
• Lenses are known as association factors:
  • Relative Efficacy: associates an outcome with an Impact Category, determining the strength of the relationship.
    • Is the credit outcome related to the component?
    • If yes, how strong, weak, or negative is the credit outcome linked to the component relative to other credits?
      • No association
      • Low association
      • Medium association
      • High association
      • Negative association
  • Duration: measures the life span of the benefits or consequences of a credit outcome.
    • 1-3 Years
    • 4-10 Years
    • 11-30 Years
    • 30+ Years (Building/Community Lifetime)
  • Control: indicates which actor ensures proper execution of predicted credit outcome.
    • Occupants
    • Operation and Maintenance Staff (or construction crew)
    • Owner (or Developer)
    • Passive

Scorecard Rules

• Scorecard intended to enable project teams to make complex decisions.
• USGBC has instituted conventions:
  • The base LEED Rating System is a base of 100 points.
  • All credit in the ratings system is worth at least 1 point.
  • Fractional credit values are rounded to the nearest whole point.
• conventions lead to a reasonable LEED scorecard.

Lessons Learned, A more robust and transparent articulation of USGBC goals

• USGBC involved with point allocation for LEED v4.
• Important lessons learned during the process will benefit LEED.
• Development of LEED v4 impact categories provides incentive for organization to explicitly define its goals.

Ability to measure current and future success of the LEED rating system

• Weighting process reveal areas that LEED is no effective with addressing; particularly human health, community, and social equity- as opposed to climate change.
• This is taken into account when weighting Impact Categories against one another, to tackle all of these issues.

Technical Development Agenda

• Focuses research and development agenda for future technical revisions.
• Advances discourse around the evolution of green building rating systems worldwide.

Importance of Prioritization

• Need to prioritizes its goals given the impact that built environment has on outcomes.
• It is possible to maximizes change needed to realize critical goals, key that any new strategy integrated into LEED deeply address one or more of the system goals.