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Points for Concrete in LEED
Using concrete can facilitate the process of obtaining LEED®
Green Building certification. Leadership in Energy and Environmental
Design (LEED) is a point rating system devised by the U.S. Green
Building Council (USGBC) to evaluate the environmental performance
of a building and encourage market transformation towards sustainable
design. The system is credit-based, allowing projects to earn
points for environmentally friendly actions taken during the
construction and use of a building. LEED was launched in an
effort to develop a “consensus-based, market-driven rating
system to accelerate the development and implementation of green
building practices.”
The program is not rigidly structured; not every project must
meet identical requirements to qualify.
There are numerous LEED rating systems for various project types,
including LEED for New Construction, LEED for Schools, LEED
for Commercial Interiors, and LEED for Homes.
| Five Ways Concrete Helps Build
Green |
| 1. Concrete creates sustainable sites. |
| 2. Concrete enhances energy performance. |
| 3. Concrete contains recycled materials. |
| 4. Concrete is manufactured locally. |
| 5. Concrete builds durable structures. |
The LEED rating system has five main credit categories:
- Sustainable sites
- Water efficiency
- Energy and atmosphere
- Materials and resources
- Indoor environmental quality
Each category is divided into credits. Detailed information
on the LEED program and project certification process is available
on the USGBC Web site, www.usgbc.org.
The program outlines the intent, requirements, technologies,
and strategies for meeting each credit. Credits are broken down
into individual points. Additional points can be earned for
innovation, exceptional environmental performance, and the use
of a LEED accredited professional on the project team.
Points for Certification
| At least 26 points are required for LEED
certification. Silver, gold, and platinum levels are also
available. |
| Credit Category |
Points Available |
| Sustainable Sites |
14 |
| Water Efficiency |
5 |
| Energy and Atmosphere |
17 |
| Materials and Resources |
13 |
| Indoor Environmental Quality |
17 |
| Total Core Points |
64 |
| Innovation and Design Process |
5 |
| LEED Certification Levels |
| Certified |
26 - 32 Points |
| Silver |
33 - 38 Points |
| Gold |
39 - 51 Points |
| Platinum |
52 - 69 Points |
Concrete and LEED
Using concrete can increase the number of points
awarded to a building in the LEED system. The following are
suggestions for earning LEED-NC v2.2 points through the use
of cement and concrete products. The paragraph headings correspond
to the credit categories and the credit numbers in the rating
system for LEED for New Construction, LEED for Core and Shell,
and LEED for K-12 Schools. Points must be documented according
to LEED procedures in order to be earned. The USGBC Web site,
www.usgbc.org,
contains a downloadable ”letter template“ that
greatly simplifies the documentation requirements for LEED
v2.2. The potential available points that can be earned by
using concrete range from 16 to 26.
Brownfield Redevelopment (Sustainable Sites Credit
3).
Cement can be used to solidify and stabilize contaminated
soils and reduce leachate concentrations to below regulatory
levels. Documentation is required indicating that the site
was contaminated and the remediation performed. This credit
is worth 1 point.
 |
| Sustainable Sites Credit 5.1. Concrete
parking garages. |
Site Development: Protect or Restore Habitat (Sustainable
Sites Credit 5.1). Concrete parking garages within
buildings can be used to limit site disturbance and restore
previously developed sites. For previously developed sites,
this credit requires restoring a minimum of 50% of the site
area (excluding the building footprint) with native or adapted
vegetation. Parking garages within buildings help maintain natural
areas that would otherwise be consumed by paved parking. This
credit is worth 1 point.
Site Development: Maximize Open Space (Sustainable
Sites Credit 5.2). Concrete parking garages on the
lower floors of a building can be used to help reduce the
footprint of the development. In this context the development
footprint includes the building footprint, hardscape, access
roads, and parking. Garages within buildings reduce the project's
paved parking areas. This requirement can be met by exceeding
the local zoning’s open space requirement for the site
by 25%. Where the local zoning does not include an open space
requirement, the vegetated open space must equal at least
20% of the project’s site area. This credit is worth
1 point.
 |
| Sustainable Sites Credit
6.1. Water flows freely through a section of pervious
pavement. |
Stormwater Design: Quantity Control (Sustainable
Sites Credit 6.1). The intent of this credit is to
limit disruption of natural water hydrology by reducing impervious
cover, increasing on-site infiltration, reducing or eliminating
pollution from stormwater runoff, and eliminating contaminants.
Using pervious concrete pavements will reduce the rate and
quantity of stormwater runoff because they increase infiltration
of stormwater. Pervious concrete contains coarse aggregate,
little or no fine aggregate, and insufficient cement paste
to fill the voids between the coarse aggregate. It results
in concrete with a high volume of voids (20% to 35%) and a
high permeability that allows water to flow through easily.
Similar results can be achieved by using concrete grid pavers
that have large voids where vegetation can grow. On building
sites where the existing imperviousness is greater then 50%,
this credit requires reducing the quantity of stormwater runoff
by 25%. On building sites where the existing imperviousness
is less than 50%, the requirement specifies that the post-development
discharge rate and quantity from the site shall not exceed
the pre-development rate and quantity. This credit is worth
1 point.
Stormwater Design: Quality Control (Sustainable Sites
Credit 6.2). The intent of this credit is to limit
disruption and pollution of natural water flows by managing
stormwater runoff. Using pervious concrete pavements or concrete
grid pavers promotes infiltration thereby reducing pollutant
loadings. Increased infiltration also reduces the size and
cost of Best Management Practices (BMPs) used to treat runoff.
The credit is worth 1 point.
 |
| Sustainable Sites Credit 7.1. Light
colored concrete pavement |
Heat Island Effect: Non-Roof (Sustainable Sites Credit
7.1). This credit requires shade (within 5 years of
occupancy), materials with a Solar Reflectance Index (SRI) of
at least 29, and/or open-grid pavement for at least 50% of the
site’s non-roof impervious surfaces such as roads, sidewalks,
courtyards, and parking lots. It can be met by using concrete,
light colored pavers, or open-grid pavers rather than asphalt
for 50% of the impervious surfaces. A second option requires
placing a minimum of 50% of parking spaces underground or under
a deck, a roof, or a building. Any roof used to shade or cover
parking must also have a SRI of at least 29. Generally, light-colored
surfaces have a high SRI, but this is not always the case. Surfaces
with lower SRI’s absorb more solar radiation. The absorbed
radiation is converted into heat and the surface gets hotter.
Where paved surfaces are required, using materials with higher
SRI’s will reduce the heat island effect—consequently
saving energy by reducing the demand for air conditioning—and
improve air quality. As the temperature of urban areas increases,
so does the probability of smog and pollution. Smog episodes
rarely occur when the temperature is below 21°C (70°F).
The Solar Reflectance Index (SRI) is a measure of the constructed
surface’s ability to reflect solar heat, as shown by a
small temperature rise. It is defined so that a standard black
(reflectance 0.05, emittance 0.90) is 0 and a standard white
(reflectance 0.80, emittance 0.90) is 100. The SRI for a given
material is calculated according to ASTM E 1980-01, from the
reflectance value and emittance value for the material. Most
opaque non-metallic materials encountered in the built environment
(including concrete and asphalt) have an emittance between 0.85
and 0.95, and a value of 0.90 is usually assumed. Therefore,
for these materials, SRI is mostly a function of solar reflectance.
Concrete constructed using ordinary portland cement generally
has a reflectance of approximately 0.35, although it can vary.
Measured values are reported in the range of 0.35 to 0.5. For
concrete made with ”white“ portland cement, values
are reported in the range of 0.7 to 0.8. New asphalt generally
has a reflectance of approximately 0.05, and asphalt five or
more years old has a reflectance of approximately 0.10 to 0.15.
This credit is worth 1 point.
Project
Checklist: LEED— New Construction (NC) v2.2
|
How Concrete
Can Contribute to Points |
| Credit Categories |
| Sustainable Sites |
Possible Points |
| Credit 3 |
Brownfield Redevelopment |
1 |
| Credit 5.1 |
Site Development: Protect or Restore Habitat |
1 |
| Credit 5.2 |
Site Development: Maximize Open Space |
1 |
| Credit 6.1 |
Stormwater Design: Quantity Control |
1 |
| Credit 6.2 |
Stormwater Design: Quality Control |
1 |
| Credit 7.1 |
Heat Island Effect: Non-Roof |
1 |
| Energy and Atmosphere |
| Prerequisite 2 |
Minimum Energy Performance |
Required |
| Credit 1 |
Optimize Energy Performance |
1-10 |
| Materials and Resources |
| Credit 1.1 |
Building Reuse: Maintain 75% of Existing Walls, Floors
and Roof |
1 |
| Credit 1.2 |
Building Reuse: Maintain 95% of Existing Walls, Floors
and Roof |
1 |
| Credit 2.1 |
Construction Waste Management: Divert 50% from Disposal |
1 |
| Credit 2.2 |
Construction Waste Management: Divert 75% from Disposal |
1 |
| Credit 4.1 |
Recycled Content: 10% (post-consumer plus 1/2 pre-consumerl) |
1 |
| Credit 4.2 |
Recycled Content: 20% (post-consumer plus 1/2 pre-consumer) |
1 |
| Credit 5.1 |
Regional Materials: 10% Extracted, Processed and Manufactured
Locally |
1 |
| Credit 5.2 |
Regional Materials: 20% Extracted, Processed and Manufactured
Locally |
1 |
| Innovation and Design Process |
| Credit 1.1 |
Innovation in Design: Reduce Cement Content |
1 |
| Credit 1.-1.4 |
Apply for other credits demonstrating exception performance
|
3* |
| Credit 2 |
LEED Accredited Professional |
1 |
| Project Totals |
26 |
| *Up to 3 additional points can be earned,
must be submitted and approved (not included in total) |
 |
| Solaire, Battery Park City, NY. The
nation’s first green residential high-rise building |
Minimum Energy Performance (Energy and Atmosphere
Prerequisite 2). All buildings must meet both the
mandatory provisions and the prescriptive requirements as
required by ASHRAE/IENSA Standard 90.1-2004 (without amendments).
The requirements of the ASHRAE standard are cost-effective
and not particularly stringent for concrete. Insulating to
meet or exceed the standard requirements is generally a wise
business choice. Determining compliance for the envelope components
is relatively straightforward using the tables in the ASHRAE
standard. Minimum requirements are provided for mass and non-mass
components such as walls and floors. Components constructed
of concrete generally are considered ”mass.“ This
means they have enough heat-storage capacity to moderate daily
temperature swings. Buildings constructed of cast-in-place,
tilt-up, precast concrete, insulating concrete forms (ICF),
or masonry possess thermal mass that helps moderate indoor
temperature extremes and reduces peak heating and cooling
loads. In many climates, these buildings have lower energy
consumption than non-massive buildings with walls of similar
thermal resistance. When buildings are properly designed and
optimized, incorporating thermal mass can lead to a reduction
in heating, ventilating, and air-conditioning equipment capacity.
Reduced equipment capacity can represent energy and construction
cost savings. This item is required and is not worth any points.
 |
| Concrete framed buildings provide thermal
mass and have lower energy consumption than non-mass buildings. |
Optimize Energy Performance (Energy and Atmosphere Credit
1). This credit is awarded if energy cost savings can
be shown compared to a base building that meets the requirements
of ASHRAE/IENSA 90.1-2004. The method of determining energy
cost savings must meet the requirements of Appendix G of the
standard. When concrete is considered, it is important to determine
energy savings using a whole building energy simulation program
that calculates yearly energy use on an hourly basis. Such programs
are needed to capture the beneficial thermal mass effects of
concrete. Insulated concrete systems, used in conjunction with
other energy-saving measures, will most likely be eligible for
points. The number of points awarded will depend on the building,
climate, fuel costs, and minimum requirements of the standard.
From 1 to 10 points are awarded for energy cost savings of 10.5%
to 42% for new buildings and 3.5% to 35% for existing buildings.
New buildings must earn at least two points under this credit
(energy cost savings of 14% compared to the baseline building).
Studies show that using concrete walls that are insulated to
exceed minimum code requirements by a modest amount (about the
same as minimum requirements for frame walls) can contribute
to earning 1 to 3 points, depending on the building type, orientation,
and climate.
Building Reuse (Materials and Resources Credit 1).
The purpose of this credit is to leave the main portion of
the building structure and shell in place when renovating.
The building shell includes the exterior walls, roof, and
framing but excludes window assemblies, interior walls, floor
coverings, non-structural roofing material, and ceiling systems.
This credit should be obtainable when renovating buildings
with concrete walls, since concrete in buildings generally
has a long life. This is worth 1 point if 75% of the existing
building structure/shell is left in place and 2 points if
100% is left in place.
 |
| Material and Resources 2. The picture
shows machinery taking portions of concrete walls, columns,
and floors and crushing them to be used as fill material. |
Construction Waste Management (Materials and Resources
Credit 2). This credit is received for diverting
construction, demolition, and land clearing waste from landfill
disposal. It is awarded based on diverting at least 50% by
weight of the above listed materials. Because concrete is
a relatively heavy construction material and is frequently
crushed and recycled into aggregate for road bases or construction
fill, this credit should be obtainable when concrete buildings
are demolished. This credit is worth 1 point if 50% of the
construction, demolition, and land clearing waste is recycled
or salvaged and 2 points for 75%.
 |
| Materials and Resources Credit
4. Supplementary cementitious materials are easily and
widely used in concrete. |
Recycled Content (Materials and Resources Credit 4).
The requirements of this credit are for using materials with
recycled content. One point is awarded if the sum of the post-consumer
recycled content plus one-half of the pre-consumer recycled
content constitutes at least 10% of the total value of the materials
in the project. The value of the recycled content of a material
is the weight of the recycled content in the item divided by
the weight of all materials in that item, and then multiplied
by the total cost of the item. Supplementary cementitious materials,
such as fly ash, silica fume, and slag cement are considered
pre-consumer. Furthermore, using recycled concrete or slag instead
of extracted aggregates would qualify as post-consumer. Although
most reinforcing bars are manufactured from recycled steel,
in LEED, reinforcing is not considered part of concrete. Reinforcing
material should be considered as a separate item. This credit
is worth 1 point for the quantities quoted above and 2 points
if the quantities are doubled to 20% combined post-consumer
plus one-half pre-consumer recycled content.
Regional Materials (Materials and Resources Credit 5).
This credit supports the use of local materials and reduced
transportation distances. The requirements state: Use building
materials or products that have been extracted, harvested or
recovered, as well as manufactured, within 500 miles of the
project site for a minimum of 10% (based on cost) of the total
material value.” The percentage of materials is calculated
on a cost basis. Concrete will usually qualify since ready-mix
and precast plants are generally within 50 miles of a job site.
Ready-mix and precast plants generally use aggregates that
are extracted within 50 miles of the plant. Cement and supplementary
cementitious materials used for buildings are also often manufactured
within 500 miles of a job site. Reinforcing steel is usually
manufactured within 500 miles of a job site, and is typically
made from recycled materials from the same region. This credit
is worth 1 point. An additional point is earned if 20% of
the regionally manufactured materials are extracted, harvested
or recovered and are manufactured within 500 miles.
Others Points
Concrete can also be used to obtain points indirectly. For
example, the Pennsylvania Department of Environmental Protection
building in Harrisburg is LEED-Certified and features a concrete
floor with low-VOC sealant. This allowed the building to obtain
the Low-Emitting Materials: Adhesives and Sealants Credit
(Indoor Environmental Quality Credit 4.1). All other adhesives
and sealants in the building must also meet certain criteria
to obtain this point.
In addition to the points discussed above, 4 points are available
through Innovation Credits. These points can be applied for
if an innovative green design strategy is used that does not
fit into the point structure of the five LEED categories or
if it goes significantly beyond a credit requirement and demonstrates
exceptional environmental performance. For example, the USGBC
has issued a credit interpretation that allows for an innovation
credit if 40% less cement is used than in typical construction,
or if 40% of the cement in concrete is replaced with slag cement,
fly ash, or both. Slag cement is commonly used at replacement
levels up to 60%. However, using fly ash replacement levels
for portland cement greater than 25% is not routine. Actual
limits should be based on compatibility of fly ash with cement,
experience, and concrete performance in the field or laboratory.
Contact your local ready-mix concrete supplier to determine
what fly ash or supplementary cementitious material is available
and to verify its performance in quality concrete.
In addition, one point is provided if a principal participant
of the project team is a LEED Accredited Professional. The
concrete industry has LEED-experienced professionals available
to help maximize the points for concrete.
Benefits of LEED Certification
LEED is a voluntary program; however, obtaining a LEED certification
projects a positive environmental image to the community.
Additionally, meeting many of the green building practices
can result in energy and cost savings over the life of the
structure. Other advantages include better indoor air quality
and increased amounts of daylight.
Studies have shown that workers in these environments have
increased labor productivity, job retention, and days worked.
These benefits contribute directly to a company’s profits
because salaries are the largest expense for most companies
occupying office space—about ten times higher than rent,
utilities, and maintenance combined. In addition, students
in these environments have higher test scores and lower absenteeism.
Retail sales are higher in day-lit buildings.
 |
| Walmart’s experimental green store
in McKinney, Texas features the latest in environmental,
sustainable design including concrete parking lots and
pervious paving. |
Support for green buildings has increased rapidly each year
during the last five years. Many cities and states either provide
tax credits or grants for green buildings, or require green
building certification for public buildings. The U.S. government
is adopting green building programs similar to LEED through
the General Services Administration (which owns or leases more
than 8300 buildings), the U.S. Army, the U.S. Navy, the Department
of State, the Department of Energy, and the Environmental Protection
Agency. Eight states, including California, New York, Oregon,
and Washington, have adopted its use for public buildings. Many
agencies are requiring LEED silver certification as a minimum.
Thirteen countries have expressed interest in LEED including
China and India; these countries have exceptionally high new
building construction. Conditions vary and the list is growing,
so please contact local jurisdictions or USGBC for details.
The LEED Green Building Rating System for New Construction,
Version 2.2, promotes environmentally sustainable buildings
for the improvement of outdoor and indoor building quality,
the conservation of resources, and the reduction of waste during
the building process. Concrete can be used in conjunction with
the LEED program to earn certification.
|