The LEED (Leadership in Energy and Environmental Design) rating system is multifaceted and holistic.  It is not a singular product that is given the rating ‘green’ but the cumulative abilities of several ‘green’ implementations working together that comprise the energy strategy of the building. The LEED rating system seeks to stimulate sustainable building practices within each sector of today’s economy.

 

Prior to the creation of LEED, many only focused on the air quality on health, the need for renewable resources and other singular ‘green’ efforts such as water conservation and recycling. After the US Oil Crisis in the 1970’s, environmental concerns began to heavily surface and the issue gained awareness. This movement in turn prompted the need for a large consortium to integrate and best define environmental parameters.

 

In 1995 the USGBC (United States Green Building Council), with cooperation from the U.S. Department of Energy, developed the LEED rating system to define the term “green building” and to stimulate energy conservation design.  Since then, LEED has become a heralded achievement of environmental sustainability among construction projects across the United States and Canada. 

 

There are six different LEED rating systems: NC (new construction and major renovations), EB (existing buildings and on-going improvements), CI (commercial interiors with tenant finishing), CS (core and shell for buildings reusing the shell of the building, but not the interior), H (for residential homes), and ND (neighborhood development). Each rating system provides a set of performance standards for certifying different project types.  LEED has strived to take an inclusive approach to the interpretation of credits, but point values must be tangible, quantifiable and documented accordingly in order to be achieved. 

 

 

·        Innovation and design process

 

Every rating system has its own set of point credits in each category, their own prerequisite requirements, as well as their own point system for rating the project Certified, Silver, Gold, or Platinum LEED projects. For LEED-NC, there is a maximum of 69 points that can be accrued, with the certification levels defined as below. 

So how does polished concrete fit into this? Polished concrete benefits align with the economic benefits of green building through reduced operating costs (maintenance), optimized life cycle, and reduced first costs (polished concrete is much cheaper to install than terrazzo, granite, or marble, yet sustains the polished stone aesthetic.) Below is a listing of points polished concrete may contribute to according to the standards outlined in LEED-NC v 2.2 (new construction).

 

One of the major points of focus for sustainable building is to extend the lifecycle of materials to prevent waste and reduce the environmental impact that is caused by harvesting and manufacturing new material. Reusing the concrete slab as part of the structure of the building will help to achieve this point if the total amount of reused materials in the project meets or exceeds 75% as calculated by the square footage. It is important to note, however, that if the new construction design increases the square footage more than two times the original, these points cannot be achieved.  

If the total amount of reused material meets or exceeds 95% on the project, the building can achieve an additional point (in addition to MR 1.1). The reused components, including flooring, framing, roof, and the exterior structure of the building, can all be used to calculate this percentage.

Polishing the slab of the concrete, instead of harvesting additional materials to cover the slab prevents waste and reduces the impact on the earths finite resources. Reusing the slab as a floor finish, instead of covering it with carpet, tile, or other materials helps to meet this objective.

 

How does polished concretes contribution to points MR 1.1 and MR 1.2 differ from MR 3.1? MR 1.1 and 1.2 refer to the reuse of the slab as a structural element remaining in the building. Credit MR 3.1 was designed with the intention of reducing the amount of waste, energy, and materials required in the completion of the project (i.e. finishes). With polished concrete, the slab is the floor finish.   For carpet, tile, and other coverings, the material must be harvested, manufactured, shipped, then installed in the building it is intended for. The beauty of polished concrete as a green product is its simplicity. There is no material sitting on top of the slab that will end up in a land-fill when it comes time to replace it. 

If the amount of materials reused in the project exceeds 5%, and meets or exceeds 10%, this point can be attained in addition to MR 3.1. This percentage is determined by comparing the replacement value of items compared to the total cost of the construction project. 

Indoor air quality effects the comfort and well-being of occupants of a building. When each of us consider how much time we spend indoors, this becomes an even greater concern! Materials that emit odorous or harmful VOCs should be avoided whenever possible, and this LEED point was designed with existing building standards (such as the South Coast Air Quality Management District Rule 1113) in mind. By using a low VOC sealer on the floor (or by omitting the sealer entirely), polished concrete will assist in meeting this requirement. 

 

Before any project can even apply to be LEED Certified, it must meet certain prerequisites to qualify. Buildings must comply to a minimum energy efficiency level overall as established by standards in their local building codes, the Department of Energy Standards, or by complying with ASHRAE / IESNA 90.1-2004 regulations. 

 

The reflective nature of polished concrete can assist with this credit as the added ambient lighting provided will reduce the amount of artificial illumination needed. This will help to maximize the natural and artificial lighting already in use, thus improving energy efficiency of the lighting system as a whole.

 

The insulation gained from the thermal mass of constructing with concrete, including walls and exposed slabs, used in conjunction with passive solar design principals, will help retain the internal temperature of the building. Using thermal mass as a design element will moderate the daily temperature fluctuations, and reduce the load on HVAC systems.

 

1-10 points: Energy and Atmosphere 1 - Optimize Energy Performance:
If the energy efficiency threshold exceeds the energy savings baseline required for the prerequisite (EA P2), up to ten points can be achieved through credit EA 1.

Again, polished concrete can assist through increased ambient lighting and thermal mass for these items. One point is achieved for new construction projects if at least 10.5% improvement can be demonstrated by comparing increased energy optimization to the baseline performance, with additional points accumulating for each 3.5% improvement thereafter. For existing buildings, the initial rating is 3.5% with additional points still accruing at each 3.5% improvement. 

 

LEED-NC version 3.0 is not expected to be published until 2010, but it is anticipated to include more stipulations in the reduction of green house gas and carbon footprint. As LEED evolves, it will continue to shepherd building construction toward designing for a sustainable future.