LEED v4: What structural engineers need to know


    If you are like most structural engineers, you have realized the importance of sustainability both in your practice and in your life, and have made an effort to learn more about the aspects of sustainable design and construction. However, just like building codes and materials, aspects of the use and enforcement of sustainable practices change over time. As our engineering practices have become busier during the economic recovery, we may not have been focusing as much on the changes in sustainable codes and practices. This article is a primer on some of the changes that are taking place in one of the most popular rating systems for sustainable buildings: Leadership in Energy and Environmental Design (LEED).

    What it is
    Originally developed by the United States Green Building Council (USGBC) and made available in 2000, LEED v4 for new construction rates buildings for sustainability in six primary categories. The initial iteration (LEED 1.0) had 5 primary categories and a possible 69 points; the latest version has 110 points available. Rating categories range from “Certified” (minimum of 40 points) to “Platinum” (80 points or more).

    What’s new
    According to USGBC, changes in LEED v4 are primarily in three areas:

    1. New market sectors
    2. Increased technical rigor, and
    3. Streamlined services

    With new market sectors, LEED has expanded with rating systems in five categories:

    1. Building Design and Construction
    2. Interior Design and Construction
    3. Existing Buildings Operations and Maintenance
    4. Neighborhood Development, and
    5. Homes

    This article focuses only on Building Design and Construction, which now has eight sub-categories:

    • New Construction
    • Core & Shell
    • Schools
    • Retail
    • Hospitality
    • Data Centers
    • Warehouses and Distribution Centers
    • Healthcare

    The expansion in categories was developed to address the fact that different types of buildings may have more or less intensive energy use and material requirements. The basic premises under each of these categories are similar, but have been tailored to meet the specific requirements of the market sector area. Within a rating category, the LEED rating system spells out which sub-categories are included: project teams must select their own sub-category based on project scope and goals.

    What affects structural design
    The biggest changes for most structural engineers are in the section on Materials and Resources (MR). In LEED 2009, the MR section encompassed a total of 14 points under four credits, with one prerequisite for storage and collection of recyclables. The new LEED v4 completely overhauls this section, reduces the number of possible MR points to 13, but expands the credit areas to five and adds a prerequisite of “construction and demolition waste management planning.” Gone are the specific credits related to recycled content and regional materials. The global change to this section is the integration of life-cycle assessment (LCA) methodologies. These are infused in the credit on “building life-cycle impact reduction,” as well as three credits on “building product disclosure and optimization.” The emphasis on adaptive reuse still exists in the LCA credit, so structural engineers may be asked to evaluate existing structures and materials for new applications and loading. This creates some interesting structural challenges when buildings that have performed well for decades must be evaluated and upgraded to meet current codes, or when structural degradation must be evaluated as existing materials are adapted to new uses. The new credits also include concepts and terms that may be new to structural engineers (and other building professionals), such as environmental product declarations (EPDs), product category rules (PCRs), and eutrophication. EPDs are detailed reports outlining a product’s effect on the environment over the course of the product’s life. Some critics of the rating system point out that even EPDs for materials that have a poor environmental performance can count toward this credit, but the intent of USGBC in creating this option is to generate better and more transparent information on construction products and materials, allowing designers (including structural engineers) to make more informed choices.

    Similar to the credit for energy optimization, the LCA credits require designers to model a base building, then model the design building and show reduced life-cycle impacts. Only the building’s structure and enclosure are included. Site work and interior finishes are excluded. Thus, material choices by structural engineers will have greater impacts in this area.

    How does this affect my client base?
    Architects and developers will have to rely more on engineers and others with expertise outside their traditional roles as the LEED requirements become more technical. These aren’t just structural, civil, and mechanical engineers. New requirements for topics such as light pollution and rainwater management require technical specialists that understand terms like “BUG rating” for light fixtures and site hydrology for rainwater management.

    Projects can be registered under LEED v4 since last month. However, LEED 2009 can be used until June 2015. So for 18 months, users will have a choice of which LEED version they use.

    For more information on LEED v4, go to the USGBC website at www.usgbc.org/leed For training on LEED v4, be aware that there are a plethora of courses available, with varying levels of quality.

    Don Allen, P.E, LEED A.P., oversees engineering marketing for DSi Engineering in Norcross, Ga. He is a member of the Structural Engineering Institute’s Sustainability Committee.