By Julie Lundin, NCIDQ, LEED AP ID+C, Principal
Emerald Skyline Corporation
As business owners and designers of our renovation project in Boca Raton, there are many decisions and variables involved in the design of both the building and the site. This project is a LEED registered project which impacts our design decisions and materials selected to incorporate sustainable goals. It gave us the opportunity to explore sustainable pavement options rather than the traditional blacktop used in most projects. The size of the project, location, cost, financial incentives to explore alternatives, and local city requirements all impact decisions to be made. When a pervious pavement is used in building site design, it can aid in the process of qualifying for LEED Green Building Rating System credits.
Leadership in Energy and Environmental Design (LEED®) is a rating system developed by the United States Green Building Council (USGBC) to evaluate the environmental performance of a building. LEED is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings.
LEED provides a framework for evaluating building performance and meeting sustainability goals through five credit categories: sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality. It should be noted, however, that LEED points are not gained directly by the use of a product but by meeting a specific sustainability goal of the rating program.
Pervious pavement options can contribute to many LEED categories including: Sustainable Sites, Water Efficiency, Materials and Resources, and Innovation in Design. Pervious pavement choices are unique and innovative ways to manage storm water and as a method of delaying roof runoff from entering city sewers. Considering these gives environmentally conscious business owners options to use in parking lots and walkways. When they are used in the building site design they function like storm water retention basins and allow the storm water to infiltrate the soil over a large area and recharge the groundwater supplies.
Why consider pervious pavement options?
Storm water is polluted
- Oils and greases
- Low-Impact Development
- Pollution Treatment
- Recharging Ground Water
- Tree Protection
- LEED Requirements
- Cool Communities
Meets LEED Requirements
- Reduce Storm Water Runoff
- Improve Storm Water Quality
- Reduce Urban Heat Islands
- Recycled Materials
- Regional Materials
Description of specific credits where pervious pavement can aid the business owner or designer include:
LEED Credit SS-C6.1 Storm Water Design – Quantity Control
LEED Credit SS-C6.2 Storm Water Design – Quantity Control
The intent of these credits is to limit disruption and pollution of natural water flows by managing storm water runoff, increasing on-site infiltration and eliminating contaminants. Pervious pavement can contribute to this credit by reducing storm water flow by allowing water to soak through and infiltrate to the ground below. Pervious choices can also reduce the pollutant loads by filtering contaminants as the water is transferred through the pavement.
LEED Credit SS-C7.1 Heat Island Effect- Non-Roof
Pervious pavement acts to reduce the heat island effect by absorbing less heat from solar radiation than darker pavements. The relatively open pore structure and the light color of pervious pavements store less heat, therefore, reducing the heat reflected back into the environment and helping to lower heat island effects in urban areas. The heat island effect can be further minimized by the addition of trees planted in parking lots. The trees offer shade and produce a cooling effect for the paving. Pervious pavement is ideal for protecting trees in a paved environment (many plants have difficulty growing in areas covered by impervious pavements, sidewalks and landscaping, because air and water have difficulty getting to the roots). Pervious pavements or sidewalks allow adjacent trees to receive more air and water and still permit full use of the pavement.
LEED Credit WE C1.1 Water Efficient Landscaping
The intent of this credit is to limit or eliminate the use of potable water, or other natural surface or subsurface water resources available on or near the project site, for landscape irrigation. The gravel sub-base under pervious pavements can be used to store storm water for irrigation, helping to satisfy this credit. If no irrigation is required for a project, two points may be earned.
LEED Credits MR-C4.1 and MR-C4-2 Recycled Content
The intent of this credit is to increase the demand for building products that have incorporated recycled content material reducing the impacts resulting from the extraction of new material. Almost all ready mixed concrete contains recycled materials in the form supplementary cementitious materials (SCM) such as fly ash, slag, or silica fume. The use of SCMs or recycled aggregate in pervious concrete or base material contributes to recycled content needed for this credit.
LEED Credit MR-C5.1 and MR-C5.2 Regional Materials
The intent of this credit is to increase demand for building products that are extracted and manufactured locally, thereby reducing the environmental impacts resulting from their transportation and supporting the local economy. The majority of materials in pervious concrete and pavements are considered regional materials. In addition to aiding in gaining LEED certification points, pervious concrete can provide a safe and durable surface for most pavement needs. Light colored pervious pavements require less site lighting to provide safe night-time illumination levels, whether on parking lots, driveways, or sidewalks.
Types of Pervious Pavements
- Porous Asphalt (Blacktop)
- Low Cost
- Effective Porosity
- High Maintenance – Biannual cleaning to prevent clogging
- Does not allow for plant growth
- Contributor to heat island effect but better than standard ashphalt
- Alternative for large projects
- Pervious Concrete
- Same concept as porous asphalt, except it is concrete
- Easy to order and have installed
- Light in color and not contribute to heat island effect
- Higher Cost than Asphalt
- Request use of local or reclaimed aggregates
- Use highest amount of Fly Ash and/or Slag (both are reclaimed waste products)
- Requires cleaning to prevent clogging
- Can serve as a retention basin for storing rainwater during a storm
- Pervious Block Pavers
- Many different types on the market
- Can look like traditional pavers for aesthetics
- Filled in with grass or gravel
- Allows for plant growth
- Pavers are pricey
- Installation requires laying of individual small blocks
- May settle or become misplaced after use
- Drivable Grass
- Unique product
- 2” x 2” mats that are more affordable individual pavers
- Good infiltration for grass growth or ground cover
- Plants remain cooler and receive uniform watering
- Greener parking surface than other plantable systems
- Low maintenance
- Plastic Grid Systems
- Made of recycled plastic and fully recyclable themselves
- Low maintenance
- Easy installation
- Can provide a fully sodded surface if desired
- Use only appropriate for light or occasional use parking lots
Decision making is a critical process for any project. Well informed choices and decisions can help keep a project timeline on track. Decisions in all areas including design and specifications need to be clearly and fully described. There should be at least three options to choose from that include how, what, where and how much? All the implications and impact of each option must be considered. Will it delay the project? Will it increase the cost? A LEED project also needs to incorporate the analysis of products and design and their sustainable impacts. We are considering 3 categories of pervious pavement products for our project; pervious concrete, pervious block pavers, and drivable grass. With the ever evolving development of sustainable products, there may also be a hybrid solution available that will meet all of our project goals.