Concrete and LEED® Canada – New Construction (NC) 1.0
The Canada Green Building Council (CaGBC) has released version 1.0 of Leadership in Energy and Environmental Design (LEED) for new construction (NC) in Canada. This version, LEED Canada – NC v.1.0, references relevant Canadian legislation, standards, and government programs.
Using concrete can facilitate the process of obtaining LEED Green Building certification. LEED is a point rating system to evaluate the environmental performance of a building. The system is credit based, allowing projects to earn points for environmentally friendly actions taken during the building process.
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; i.e., not every project must meet identical requirements to qualify. The flexibility in the rating system allows each project team to “select the green strategies that will best meet the project’s goals.”
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 CaGBC website, www.cagbc.ca. 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 use of a LEED-accredited professional on the project team.
Points for Certification
A building requires at least 26 points for certification. Silver, gold, and platinum levels are also available.
Credit Categories Total Available Points
Sustainable Sites 14
Water Efficiency 5
Energy and Atmosphere 17
Materials and Resources 14
Indoor Environmental Quality 15
Total Core LEED Rating System Points 65
Innovation and Design Process Points 5
Concrete and LEED
The following are suggestions for earning LEED points through the use of cement and concrete products. The designations correspond to LEED ratings system credit categories.
Redevelopment of Contaminated Sites
(Sustainable Sites Credit 3)
Cement can be used to solidify and stabilize contaminated soils and reduce leaching concentrations to below regulatory levels. Documentation is required indicating the site was contaminated and the remediation performed. This credit is worth 1 point.
Reduced Site Disturbance: Protect or Restore Open Space
(Sustainable Sites Credit 5.1)
Concrete parking garages on the lower floors of a building can be used to limit site disturbance, including earthwork and clearing vegetation. For example, one criterion is to limit site disturbance to 12m (40 ft) beyond the building perimeter. Parking garages within buildings help maintain existing natural areas that would 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. Parking garages within buildings reduce the building footprint by reducing 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.
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 storm water runoff. Using pervious concrete will reduce the rate and quantity of storm water runoff because it increases 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. On building sites where the existing imperviousness is greater then 50%, the technical requirement for 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.
Heat Island Effect: Non-Roof
(Sustainable Sites Credit 7.1)
Use light-colored/high-albedo materials (reflectance of at least 0.3) for at least 30% of the site’s non-roof impervious surfaces. This requirement can be met by using portland cement concrete, rather than asphalt for 30% of all sidewalks, parking lots, drives and other impervious surfaces. Another option include placing a minimum of 50% of parking spaces underground or covered by structured parking.
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.
Portland cement concrete generally has a reflectance of approximately 0.35, although it can vary. Measured values are reported in the range of 0.4 to 0.5. For “white” portland cement, values are reported in the range of 0.7 to 0.8. New asphalt concrete generally has a reflectance of approximately 0.05, and asphalt concrete five or more years old has a reflectance of approximately 0.10 to 0.15. This credit is worth 1 point.
Minimum Energy Performance
(Energy and Atmosphere Prerequisite 2)
All new buildings must demonstrate energy savings using a whole building energy simulation program. The two compliance paths for new buildings are (1) to show that the building complies with Natural Resources Canada’s Commercial Building Incentive Program (CBIP) requirement by reducing energy consumption by at least 25% relative to the Model National Energy Code for Buildings 1997 (MNECB), or (2) to reduce energy cost consumption of the building by at least 18% relative to ASHRAE/IESNA 90.1-1999.
The two compliance paths for major renovations to existing buildings are to (1) reduce energy consumption by at least 10% relative to the MNECB, or (2) comply with ASHRAE/IESNA 90.1-1999.
Many engineering consulting firms have the capability to perform whole building energy simulations to determine energy consumption and costs as required using computer-based programs such as CBIP-EE4, DOE2 or EnergyPlus. When concrete is considered, it is important to use programs like these that calculate yearly energy use on an hourly basis. Such programs are needed to capture the beneficial thermal mass effects of concrete.
Components constructed of concrete generally are considered “mass.” This means the components have enough heat-storage capacity to moderate daily temperature swings. Buildings constructed of cast-in-place, tilt-up, and insulating concrete forms (ICF) possess thermal mass which helps moderate indoor temperature extremes and reduces peak heating and cooling loads. Thermal mass can make a significant contribution to energy savings; this is demonstrated when mass is incorporated into an energy consumption simulation program. 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.
Optimize Energy Performance (Energy Credit 1)
This credit is allowed if energy cost savings can be shown compared to a base building that meets the requirements of MNECB or ANSI/ASHRAE/IESNA 90.1-1999. Insulated concrete which exhibits the prerequisite thermal mass characteristics noted above, will most likely be eligible for points when used in conjunction with other energy savings measures,. The number of points awarded will depend on the building, climate, fuel costs, and minimum requirements of the standards.
When using MNECB, from 1 to 10 points are awarded for energy cost savings of 24% to 64% for new buildings and 15% to 55% for existing buildings. When using ASHRAE/IESNA 90.1-1999, 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.
Building Reuse (Materials 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 skin and framing but excludes window assemblies, interior walls, floor coverings, and ceiling systems. This credit should be obtainable when renovating buildings with a concrete skin, 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, 2 points if 95% is left in place, or 3 points if 50% of non-shell areas are maintained.
Construction Waste Management (Materials 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 or volume of the above listed materials. Since 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%.
For concrete, either the credit for building reuse or the credit for construction waste management can be applied for, but not both, because the concrete structure is either reused or recycled into another use.
Materials Credit 2. This picture shows a machine crushing portions of concrete walls, columns, and floors. The crushed concrete was reused as fill material.
Recycled Content (Materials 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 7.5% 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 (SCMs), such as fly ash, silica fume, and slag cement, are considered post-industrial materials. LEED Canada – NC makes special provisions for SCMs due to their light weight and environmental impact. Instead of using the weight of the concrete to determine recycled content, the weight of the SCMs is divided by the weight of the total cementitious material, then multiplied by two, and that number is multiplied by the cost of the concrete and formwork. The intent is that a concrete building with 25% of the portland cement replaced with fly ash should be able to achieve 1 point and a concrete building with 40% replacement of portland cement with fly ash should be able to achieve 2 points. Using fly ash replacement levels for portland cement greater than 25% are not routine. Actual limits are based on experience and concrete performance in the field or laboratory. Contact your local ready-mix concrete supplier to determine what fly ash is available and to verify its performance in quality concrete.
Using recycled concrete or slag as aggregate instead of extracted aggregates would also qualify as post-consumer.
Although most reinforcing bar is manufactured from recycled steel, and would probably qualify, it would not be considered as part of concrete. This credit is worth 1 point for the quantities quoted above and 2 points if the quantities are doubled to 15% combined post-consumer plus one-half post-industrial recycled content.
Regional Materials (Materials Credit 5)
This credit supports the use of indigenous materials and reduced transportation distances. It also recognizes the reduced impacts of rail or ship compared to truck. The requirements of this credit state: “Specify a minimum of 10% of building materials that are extracted, processed, and manufactured within a radius of 800 km (500 miles) OR specify a minimum of 10% of building materials that are extracted, processed, manufactured, and shipped primarily by rail or water within a radius of 2400 km (1500 miles).” Combinations of the first criterion (for trucks) and the second (for rail or water) can also be used.
Ready-mix plants generally use aggregates that are extracted within 160 km (100 miles) of the plant. Cement and supplementary cementitious materials used for buildings are often manufactured within 800 km (500 miles) of a job site. Concrete made with regional cementitious materials and aggregates will often qualify since ready-mix plants are generally within 160 km (100 miles) of a job site. Reinforcing steel is also often manufactured within 800 km (500 miles) of a job site, and is typically made from recycled materials from the same region. The percentage of materials is calculated on a cost basis. This credit is worth 1 point.
An additional point is earned if the above quantities are doubled to 20%.
Durable Building (Materials Credit 8)
LEED Canada – NC provides an incentive for durable buildings and recognizes resources required to replace materials with a short service life. This credit requires that a Building Durability Plan be developed and implemented in accordance with portions of CSA S478-95 (R2001) – Guidelines on Durability in Buildings for the construction and preoccupancy phases of the building. The guidelines require (1) an appropriate design service life for components and assemblies, (2) appropriate materials and designs so the design service life is exceeded, (3) documentation, and (4) quality assurance. This credit is worth 1 point.
In addition to the points discussed above, 4 points are available under Innovation & Design Process. 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. One point is also 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.
Points must be documented according to LEED procedures in order to be earned.
Using concrete can increase the points awarded to a building under the LEED system. The potential available points that can be earned through the use of concrete range from 13 to 23.
Benefits of LEED Certification
LEED certification is solely 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 plenty 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—which are about ten times higher than rent, utilities, and maintenance combined—are the largest expense for most companies occupying office space. Students in these environments have higher test scores and lower absenteeism.
Many cities and government agencies require LEED green building certification for new public buildings. These include Greater Vancouver Regional District, City of Vancouver, Alberta Infrastructure, City of Calgary Sustainable Buildings Policy, Manitoba Hydro, Public Works and Government Services Canada, BC Buildings Corporation and La Societe Immobilliere du Quebec. Support for green buildings has increased rapidly each year over the last five years.
LEED Canada – NC promotes environmentally conscious buildings for the improvement of outdoor and indoor building quality and the reduction of waste during the building process. Concrete can be used in conjunction with the LEED program to earn a LEED certification.