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Points for Concrete in LEED
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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.
Three LEED products are currently available:
- LEED-NC v2.1 for new commercial construction and major
renovation projects
- LEED-EB v1.0 for existing building operations
- LEED-CI v1.0 for commercial interiors projects
| Five Ways Concrete Helps Builds
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. 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 v2.1 points through the use
of cement and concrete products. The paragraph headings correspond
to the credit categories and the credit numbers in the LEED
rating system. Points must be documented according to LEED
procedures in order to be earned. The USGBC Web site, www.usgbc.org,
contains a download-able ”letter template“ that
greatly simplifies the documentation requirements for LEED
v2.1. The potential available points that can be earned by
using concrete range from 11 to 21.
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 |
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. |
Reduced Site Disturbance: Protect or Restore Open Space
(Sustainable Sites Credit 5.1). Concrete parking garages
within buildings can be used to limit site disturbance, such
as earthwork and clearing vegetation. For example, one LEED
criterion is to limit site disturbance to 12m (40 ft) beyond
the building perimeter. Park¬ing garages within buildings
help maintain existing natural areas that would otherwise be
consumed by paved parking. This credit is worth 1 point.
Reduced Site Disturbance: Development Footprint (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 building footprint
includes the building, access roads, and parking. Garages
within buildings reduce the building paved parking areas.
This requirement can be met by exceeding the local zoning’s
open space requirement for the site by 25%. This credit is
worth 1 point.
 |
| Sustainable Sites Credit
6.1. Water flows freely through a section of pervious
pavement. |
Stormwater Management: Rate and Quantity (Sustainable
Sites Credit 6.1). The intent of this credit is to
limit disruption and pollution of natural water flows by managing
stormwater runoff. 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 rate
and 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.
 |
| Sustainable Sites Credit 6.1. Light
colored concrete panels |
Landscape and Exterior Design to Reduce Heat Islands
(Sustainable Sites Credit 7.1). This credit requires
high albedo materials (reflectance of at least 0.3) and/or open-grid
pavement for at least 30% of the site’s non-roof impervious
surfaces such as sidewalks, parking lots, drives, and access
roads. It can be met by using concrete, light colored pavers,
or open-grid pavers rather than asphalt for 30% of the impervious
surfaces. Two other options include placing a minimum of 50%
of parking spaces underground or covered by structured parking;
or using an open-grid pavement system (less than 50% imperviousness)
for a minimum of 50% of the parking lot area. Albedo, which
in this context is synonymous with solar reflectance, is the
ratio of the amount of solar radiation reflected from a material
to the amount that shines on the material. Solar radiation includes
the ultraviolet as well as the visible spectrum. Generally,
light-colored surfaces have a high albedo, but this is not always
the case. Surfaces with lower albedos 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 albedos 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).
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.
|
How Concrete Can Contribute
to Points |
| Credit Categories |
| Sustainable Sites |
|
Possible Points |
| Credit 3 |
Brownfield Redevelopment |
1 |
| Credit 5.1 |
Reduced Site Disturbance, Protect Open Space |
1 |
| Credit 3 |
BReduced Site Disturbance, Development Footprint |
1 |
| Credit 6.1 |
Stormwater Management, Rate & Quantity |
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 Shell |
1 |
| Credit 1.2 |
Building Reuse, Maintain 100% of Existing Shell |
1 |
| Credit 2.1 |
Construction Waste Management, Divert 50% |
1 |
| Credit 2.2 |
Construction Waste Management, Divert 75% |
1 |
| Credit 4.1 |
Recycled Content, Use 5% (post-consumer plus 1/2 post-industrial) |
1 |
| Credit 4.2 |
Recycled Content, Use 10% (post-consumer plus 1/2 post-industrial) |
1 |
| Credit 5.1 |
Regional Materials, 20% Manufactured Regionally |
1 |
| Credit 5.2 |
Regional Materials, 50% Extracted Regionally |
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 |
25 |
| *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 building
energy efficiency and performance as required by ASHRAE Standard
90.1-1999 or the local energy code, whichever is the more
stringent.” The ASHRAE standard is usually more stringent
and applies in most states. 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 Appendix B of 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 90.1-1999. The method of determining
energy cost savings must meet the requirements of Section
11 of the standard. Many engineering consulting firms have
the capability to perform whole building energy simulations
to determine energy savings as required using a computer based
program such as DOE-2 or EnergyPlus. When concrete is considered,
it is important to use a program like these that calculate
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-savings 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
15% to 60% for new buildings and 5% to 50% for existing buildings.
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 post-industrial recycled content constitutes at least
5% 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
post-industrial. 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 10% combined
post-consumer plus one-half post-industrial 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
a minimum of 20% of building materials that are manufactured
regionally within a radius of 800 km (500 miles).“ Concrete
will usually qualify since ready-mix and precast plants are
generally within 80 km (50 miles) of a job site. The percentage
of materials is calculated on a cost basis. This credit is worth
1 point. 
An additional point is earned if 50% of the regionally manufactured
materials are extracted, harvested, or recovered within 800
km (500 miles). Ready-mix and precast plants generally use
aggregates that are extracted within 80 km (50 miles) of the
plant. Cement and supplementary cementitious materials used
for buildings are also often manufactured within 800 km (500
miles) of a job site. Reinforcing steel is usually manufactured
within 800 km (500 miles) of a job site, and is typically
made from recycled materials from the same region.
Others Points
Concrete can also be used to obtain points indirectly. For
example, the Pennsylvania Department of Environmental Protection
building in Harrisburg, is LEED Bronze certified and features
a concrete floor with low-VOC sealant. This allowed the building
to obtain the Low-Emitting Materials Credit (Indoor Environmental
Quality Credit 4.2). All other paints and coatings in the
building must also meet certain criteria to obtain this point.
 |
| Slim and accurate construction is much
easier to realize with self-consolidating concrete. This
83-m high Stockholm Airport tower is decorated with excerpts
from the work of Antoine de Saint-Exupéry. Reduced
noise levels made construction during nighttime hours
possible. |
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% are 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 con
crete 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 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 2.1, 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.
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