The challenge of defining a sustainable roof is similar to the task of blind men describing an elephant. One man mistakes a massive leg for a pillar, another perceives the trunk to be a snake, while others mistake ears for giant fans and tusks for pointed spears. And just as each individual perception fails to grasp the grandeur of the entire elephant, first impressions about sustainable roofing tend to fall short of revealing the true potential of the world’s rooftops.
Words that currently describe sustainable roofs create as much contradiction as clarity. Sustainable roofs may be described as “warm” and “cool.” They may not only be “energy efficient” but also produce “clean energy.” Frequently, sustainable roofs are described by a particular color they exhibit: “white” to reflect the sun, “blue” from captured stormwater, “green” from a living carpet of plants, and “black” from the sheen of solar panels. But behind these descriptions lies the fact that modern roofs serve many functions and impact the environment in many different ways:
• Energy Sustainable roofs can both save and produce energy. The potential energy savings available through the use of properly insulated roofing systems could exceed 700 trillion Btu each year, while the solar energy potential of our nation’s roof surfaces could exceed the power of over one dozen Grand Coulee dams.
• Water For hundreds of cities relying on antiquated combined sewer systems, the capture of rooftop stormwater can play a significant role in reducing the amount of pollution that goes into our waterways. The use of this water for landscaping and other building-related needs also can reduce overall demand on municipal water sources.
• Air and climate In addition to saving energy during the air-conditioning season, cool roof surfaces help mitigate heat-island effects in urban areas, reducing air pollution and global warming.
• Materials Roofing waste accounts for over 40 million tons, or 5 percent of all solid waste generated annually in the United States. Improved use and reuse of roofing materials offers one of the best opportunities to reduce landfill waste throughout the world.
• Service life Far too often, building deterioration starts with a leaky roof that leads to marred interior surfaces, mold growth, and structural damage. Developing new standards of roof system durability and roof asset management may significantly increase a building’s service life.
As public recognition of the complex role of rooftops has grown, limited descriptions of roof system sustainability based on a single characteristic are merging into a more comprehensive approach. An excellent example of this trend is the roof on the Jerry F. Costello National Great Rivers Research & Education Center Confluence Field Station in Alton, Ill., which recently received the Center for Environmental Innovation in Roofing’s 2010 Innovation in Design award for its comprehensive contribution to roofing sustainability. The facility serves as a laboratory and classroom for researchers and students to study the ecology and management of large rivers. Sustainable features on its roof include:
• Rooftop vegetation featuring native plants to minimize the impact on local ecology
• Roof-mounted solar tubes that supply over half of the building’s lighting requirements
• Roof-mounted solar panels for supplemental building power
• A comprehensive stormwater retention system to provide irrigation for the building site
• High-efficiency roof insulation to minimize building heating and cooling requirements
• A high-performance roofing system designed to extend building service life
• Rooftop classroom and meeting facilities to expand the usefulness of the roof space
For the design professional, the multifaceted approach to sustainable roofing exemplified by the Costello Confluence Field Station poses a number of challenges. There are new technologies to understand and harness, and these technologies require new design skills to effectively integrate them into the overall roof design.
In terms of renewable energy, for example, new technologies might include solar energy systems and roof daylighting, which in turn might require skills with solar energy modeling and electrical and lighting system design. New water-retaining roof technologies might require knowledge of climate modeling and landscape design, and examining energy efficiency in light of new high-efficiency materials might require new knowledge of heat, air, and moisture modeling.
With this in mind, effective systems integration emerges as perhaps the most critical challenge. What are the consequences of pursuing many different green strategies within a single building system? Will the use of certain technologies degrade or negate the effects of other technologies? What are the trade-offs and how can the overall sustainable contribution of the roofing system be optimized?
Because of the increasing complexity in sustainable roofing, more sophisticated design and decision tools are needed. In response, the Center for Environmental Innovation in Roofing has developed a voluntary, consensus-based guideline for sustainable roofing systems called RoofPoint. Similar to the goal of whole-building programs such as LEED and Green Globes, RoofPoint’s mission is to serve as a guideline for selecting environmentally innovative roofing systems, as a checklist to identify the ways roofing systems provide economic and environmental benefit, as an assessment system to compare roofing alternatives, and as a platform for a comprehensive certification program to recognize and reward environmentally responsible roofing practices.
RoofPoint is organized into five functional areas representing the primary environmental contributions of modern low-slope roofing systems: energy management, materials management, water management, life-cycle management, and roofing innovation. Each functional area is then broken down into credits such as roof daylighting, recycled content, roof maintenance programs, and innovation in design. Each credit has specific strategic goals and measurable criteria, and points are awarded based on how a system meets these goals and criteria. These points can then be tallied for a final score to help determine the level of sustainability of the overall roofing strategy.
Currently, RoofPoint is being implemented in a pilot program sponsored by the member companies of the Center for Environmental Innovation in Roofing, and we plan on releasing a more robust public version by the end of 2011.
RoofPoint is one step toward showcasing the roofing industry’s vital role in supporting energy security. Commercial rooftops cover over 50 billion square feet of developed space in North America, and if effectively utilized, this vast area of roof surface can deliver enormous benefits, through both energy efficiency and the production of clean energy.