LEED is the leading green building rating system in the US for commer­cial, institutional, and mid-rise to high­-rise residential buildings. It is de­veloped, trademarked and owned by the US Green Building Council. At the end of 2006, nearly 5,000 buildings had registered their intention to use the LEED rating system for new buildings, renovations, tenant remod­els and existing buildings, a 50% increase over 2005 year­-end totals. Al­most 650 million square feet of buildings were involved in LEED­-regis­tered projects, representing close to $78 billion worth of construction. By the end of 2006, according to the US Green Building Council, more than 650 projects had already been certified, an increase of 66% over the 2005 year­-end totals. In an industry that grows typically by 5% per year, this in­crease in green building projects is astounding. The stated goal of LEED is to transform the building industry by introducing rating systems that reflect scientific knowledge, leading­-edge architectural and engineering design approaches and best practices in construction and development. LEED is divided into six rating systems:

• LEED for New Construction (and major renovations).
• LEED for Commercial Interiors (remodels).
• LEED for Core and Shell (typically office buildings and other specula­tive projects). 
• LEED for Existing Buildings (the effects of continuing building oper­ations).
• LEED for Homes (custom homes and production homes, including low­-rise apartments).
• LEED for Neighborhood Development (campuses and urban dis­tricts, new subdivisions). 

The dominant rating system at this time is LEED for New Construction (LEED-­NC), comprising 77% of certified projects and 79% of all project registrations. (Registering a project is like getting engaged, declaring your intention to certify when a building is completed and ready for occu­pancy.) In my opinion and experience, LEED­-NC is a very carefully con­structed rating system. It was introduced in March 2000 after a two-­year beta test or pilot program and has seen widespread use and popularity.

LEED for New Construction (LEED-­NC)

The basic and most frequently used LEED rating system contains 32 cate­gories of environmental design and energy concern, with 64 core points and 5 extra credit points, for a total of 69. A basic LEED­-NC certified proj­ect must score at least 26 points in the categories of site, water, energy, ma­terials and indoor environment. There are also Silver (33 points), Gold (39 points) and Platinum (52 points) certification levels. Less than 20 LEED­-NC projects had been certified Platinum by the end of 2006.

Each project requires rigorous documentation that is evaluated by in­dependent auditors. A finished LEED-­NC certified project is well within the top 10% of all buildings constructed each year, in terms of its green at­tributes. LEED­-NC certified projects also tend to be 30% or more energy efficient than their conventional counterparts, use 30% less water and have healthier indoor air, more daylighting and views to the outdoors.

LEED for Core and Shell (LEED-­CS)

The LEED-­NC standard relies on evaluating a completed and fully furnished building. Many commercial buildings are built as “core­-and-­shell” projects, meaning that 50% or more of the project is empty (a “see­-through” building) when construction is completed, and the office spaces are left for tenants to build out. A core-­and-­shell building typically has a lobby, an elevator core, a finished external and interior structure, major HVAC, plumbing and electrical systems, parking garage and little else. These projects are evaluated using the LEED for Core and Shell standard that makes allowances for items that developers do not finish, such as lighting, carpeting, paints and similar items. The original idea was to link the LEED-­CS rating with a LEED for Commercial Interiors rating, so that the entire building would ultimately be certified similar to a LEED-­NC project. In practice, this does not always work out, since even committed green developers are reluctant to impose green tenant improvement stan­dards.  ....read more