Incorporating precast concrete into a LEED building’s design can contribute to several points required for LEED certification. Precast concrete has the potential to help earn points in a range of categories: site development, heat island effect, energy performance, building reuse, construction waste management, recycled content, regional materials, IAQ management plan during construction, low-emitting materials and innovation in design.
SUSTAINABLE SITES
SS5 Site Development
SS5.1 Site Development: Protect or Restore Habitat (1 point)
Conserve existing natural areas and restore damaged areas.
On Greenfield sites, limit all site disturbance to 40 feet beyond the building perimeter. On previously developed or graded sites, restore or protect a minimum of 50% of the site area.
SS5.2 Site Development: Maximize Open Space (1 point)
Provide a high ratio of open space.
Reduce the development footprint and/or provide vegetated open space within the project boundary to exceed the local zoning’s open requirement for the site by 25%.
Design the building to minimize its footprint by stacking the building program, tuck-under parking. A total precast structure reduces site disturbance with a quieter, cleaner and shorter construction period. The use of a total precast concrete system including columns, beams, long-span double tees and spandrels or architectural panels allows a compact, efficient construction schedule with little or no disruption to adjacent properties. Precast concrete can contribute in these two categories when multi-level structures are used and erected from within the building footprint.
SS7 Heat Island Effect
(Thermal gradient differences between developed and undeveloped areas)
SS7.1 Heat Island Effect: Non-Roof (1 point)
Reduce heat islands to minimize impact on microclimate and human and wildlife habitat.
Option 2
Place a minimum of 50% of parking spaces under cover (defined as underground, under deck, under roof, or under a building).
Place a minimum of 50% of parking spaces under cover (defined as underground, under deck, under roof, or under a building).
SS7.2 Heat Island Effect: Roof (1 point)
Reduce heat islands to minimize impact on microclimate and human and wildlife habitat.
Option 2
Install a vegetated roof for at least 50% of the roof area.
Install a vegetated roof for at least 50% of the roof area.
Consider green roofs over underground precast parking garage (park, athletic fields, etc.), green roofs atop above-ground precast parking garage or solar-power canopies to reduce the heat island effect. Precast/prestressed parking structures can be designed to carry the entire loads imposed from canopies on green roofs.
ENERGY AND ATMOSPHERE
Prerequisite 2 Minimum Energy Performance (Required)
Establish the minimum level of energy efficiency for the proposed building and systems.
Design the building project to comply with ASHRAE/IESNA Standard 9.1-2004.
EA 1 Optimize Energy Performance (2-10 points) 2 points min.
Achieve increasing levels of energy performance above the baseline in the prerequisite standard.
The minimum energy cost savings percentage is 14% for the minimum of 2 points. (Add 1 point for every additional 3.5% energy cost savings)
Design the building envelope to maximize energy performance. Precast concrete contributes to a building’s thermal mass, which improves a building’s energy efficiency. The use of thermal mass in exterior precast walls can reduce a building’s peak energy load, which leads to lower utility bills and smaller HVAC systems. In addition, large precast concrete panels have minimal joints, reducing uncontrolled air infiltration (heat sinks).
MATERIALS AND RESOURCES
MR1 Building and Reuse
MR1.1 Maintain 75% of Existing Walls, Floors & Roof (For renovation of an existing building) (1 point)
MR1.2 Maintain 95% of Existing Walls, Floors & Roof (For renovation of an existing building) (1 point)
Extend the life cycle of existing building.
Maintain at least 75% or 95% of existing building structure and envelope.
Precast concrete panels offer exceptional long-term durability, which reduces long-term maintenance costs and extend the life cycle of a building. Precast offers resistance to damage from fires, insects, wind and floods. In addition, a building owner can completely refurbish the interior of a precast concrete structure while leaving the shell intact, which provides a level of flexibility. Also, precast concrete panels can be reused when buildings are expanded. Precast parking structures can be designed for future vertical expansion in mind, with heavy load-bearing framing to accommodate additional parking and/or commercial office space can be added on top of the parking structure.
MR2 Construction Waste Management
MR2.1 Divert 50% from Disposal (1 point)
MR5.165 Divert 75% from Disposal (1 point)
Divert construction and demolition debris from disposal in landfills and incinerators.
Recycle and/or salvage at least 50% or 75% of non-hazardous construction and demolition.
Precast aids that 50% or 75%, as it provides no on-site waste. Precast components are made in manufacturing facility and shipped for immediate installation reducing congestion and waste on the site.
MR4 Recycled Content
MR4.1 10% (Post Consumer + ½ Pre-Consumer) (1 point)
MR4.2 20% (Post Consumer + ½ Pre-Consumer) (1 point)
Increase demand for building products that incorporate recycled content materials.
Use materials with recycled content such that the sum of post-consumer recycled content plus one-half of the pre-consumer content constitutes at lease 10% or 20% (based on cost) of the total value of the materials in the project.
Precast concrete can contain fly ash, a recycled material from fossil-fuel power plants that replaces some of the cement, the cement is the material in concrete which takes the most energy to produce. Fly ash can replace up to 30% of the cement in concrete. Precast concrete also contains rebar, strand and mesh, which is manufactured from 100% recycled steel.
MR5 Regional Materials
MR5.1 10% Extracted, Processed & Manufactured Regionally (1 point)
MR5.2 20% Extracted, Processed & Manufactured Regionally) (1 point)
Increase demand for building materials and products that are extracted and manufactured within the region.
Use 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% or 20% (base of cost) of the total materials value.
Most plants are within close proximity to the project, and the raw materials used to produce the precast concrete components (cement, aggregate, rebar) are usually obtained from sources within the vicinity of the precast plant. “Verify that required distances are met to qualify.” This advantage leads many designers to replace granite, stone and other imported products with precast concrete panels. By using precast concrete rather than marble or granite, not only does it save significant shipping costs, but also results in environmental savings.
INDOOR ENVIRONMENTAL QUALITY
EQ3.1 Construction IAQ Management Plan(Interior Air Quality): During Construction (1 point)
Reduce indoor air quality problems resulting from construction process.
During construction meet or exceed the recommended control measures of the sheet metal and air conditioning contractor’s national association (SMA CNA).
Using precast concrete can help meet the requirements because it is delivered to the site in finished pieces that do not require jobsite fabrication, processing, or cutting thereby reducing dust and airborne contaminants on the construction site. Concrete is not damaged by moisture and does not provide nutrients for mold growth.
EQ4.2 Low-Emitting Materials: Paints & Coatings (1 point)
Reduce the quantity of indoor air contaminants that are odorous, irritating and/or harmful to the comfort and well being of installers and occupants.
Specify low-VOC paints and coatings.
Precast concrete contains low to negligible amounts of VOC’s. Precast concrete does not need to be sealed or painted and integral color can be used. Precast concrete products can provide both the building structure, and the interior and exterior finishes. Structurally efficient columns, beams, and slabs can be left exposed with natural finishes. Interior and exterior concrete walls offer a wide range of profile, texture, and color options that require little or no additional treatment to achieve aesthetically pleasing results. Exposed ceiling slabs and architectural precast panels are some examples of this environmentally efficient approach. The structure/finish combination reduces the need for the production, installation maintenance, repair, and replacement of additional finish materials. It also eliminates products that could otherwise degrade indoor air quality; like paints, coatings, primers, anti-corrosive and anti-rust paints, clear wood finishes, floor coatings, stains, sealers and shellacs applied to interior elements.
INNOVATION IN DESIGN PROCESS
ID 1.1 TO 1.4 Innovation in Design (1- 4 points)
To provide design teams and projects the opportunity to be awarded points for exceptional performance above the requirements set by the LEED for New Construction Green Building Rating System.
Identify the intent of the proposed innovation credit, the proposed requirement for compliance, the proposed submittals to demonstrate compliance, and the design approach (strategies).
SS7.1 Heat Island Effect Non Roof (1 Point)
100% of the onsite parking spaces have been located under cover.
SS7.2 Heat Island Effect Roof (1 Point)
100% of the project’s roof area is comprised of a green roof system.
MR 4 Recycled Content (1 Point)
The total recycled value must be 30% or greater.
MR 5 Regional Materials (1 Point)
For regionally harvested, extracted and manufactured materials, the credit calculation must be 40% or greater. By using structural and architectural precast components in a total precast building can be accounted for almost 40% of the materials used to calculate the local/regional content of the entire building.
ID 2 LEED Accredited Professional
To support and encourage the design integration required by a LEED for New Construction Green Building Project.
The precast industry has LEED AP available to assist teams with concrete applications and help maximize points for precast concrete.
