How Green Is Your Building?
The United States accounted for 20 percent of global energy consumption in 2008, which is the largest share of world energy consumption by any country. And buildings account for 40 percent of all energy use, consuming more energy than the industrial or transportation sectors. The U.S. is also responsible for 20 percent of the world’s carbon dioxide emissions, with energy use in buildings responsible for 8 percent. With increasing focus on the energy, carbon and environmental footprint of buildings, new methods of construction are being considered. Due to their potential to reduce energy consumption, decrease greenhouse gas emissions, reduce water usage, and add to the building value, green buildings have been gaining attention in the United States.
Green buildings have been defined by the Environmental Protection Agency as structures that are built using processes that are environmentally responsible and resource-efficient throughout a building’s lifecycle from siting to design, construction, operation, maintenance, renovation and deconstruction. These buildings embody increased efficiencies in resource utilization, sustainable site planning, reduced wastage and environmental impacts, enhanced economic performance, and an overall positive impact on quality of inhabitance of such spaces and on its occupants. Green buildings thus address design concerns of economy, utility, durability and comfort.
The U.S. Green Building Council (USGBC) has led the movement toward high-performance buildings. In 1998, the Council undertook the task of developing and subsequently administering the Leadership in Energy and Environmental Design (LEED) suite of certification systems, focused on evaluating sustainable building achievements with an integrated, whole building approach. This approach combines the design, construction, and operation aspects of a building to get an aggregate performance quotient that would make it a sustainable building or project. LEED promotes a whole-building approach to sustainability by focusing on the key performance areas:
Sustainable sites, water efficiency, energy and atmosphere, materials and resources, indoor environmental quality, locations and linkages, awareness and education, innovation in design and regional priority
Since the first version was introduced in 2000, the LEED system has become synonymous with sustainable design, not only in the United States, but in many other countries that have developed regional chapters of the Green Building Council to represent local dynamics, including Canada, Brazil, Mexico and India. While LEED was originally based on design and construction requirements and benchmarks rather than performance, the USGBC has taken steps to move closer to a performance-based system.
The latest version of LEED places more focus on energy efficiency and reduction of carbon dioxide; identifies existing credits for bonus points based on specific regional issues to reflect local priorities; and tightens the energy savings requirements to 10 percent over the American Society of Heating, Refrigerating and Air-Conditioning Engineers standard for 2007 for new buildings, and 5 percent for renovations. In addition, LEED 2009 was designed to help the USGBC obtain a better understanding of the relationship between credits and building performance. With this goal in mind, LEED 2009 requires that teams agree to report post-occupancy energy and water use as part of project registration. By monitoring energy and water usage, the USGBC is attempting to ensure energy savings goals are being met and to determine ways to constantly make the standard more effective.
Due to constant improvement to the rating system and the increasing trend toward sustainable building practices, LEED certifications have been on the rise.
While the number of LEED certifications has steadily increased and many buildings strive to attain LEED certification, LEED certification is voluntary and, as a result, many buildings are not LEED certified. Even when buildings are certified, under LEED, building owners may choose to address certain aspects of energy efficiency, such as lighting, but leave other aspects out. Furthermore, when given a choice, some building owners are choosing not to follow these guidelines at all in order to reduce their initial investment, without considering the total cost of ownership and the building’s impact on the environment.
To address this issue, the U.S. has approved its first national green building code. The International Green Construction Code (IgCC) was passed after two years of development. The code applies to all new and renovated commercial buildings and residential buildings higher than three stories. The goal of IgCC is to set enforceable minimum standards for all aspects of building design and construction, including energy efficiency, water efficiency, site impacts, building waste and materials. The code also gives voluntary certifications more flexibility to set the high-performance requirements even higher so that buildings are awarded for going above the minimum standards of performance, instead of being awarded for meeting what have increasingly become expected standards.
One of the mandatory requirements is related to site development and land use. The IgCC eliminates greenfield development, with some exceptions based on existing infrastructure. It also provides guidelines for site disturbance, irrigation, erosion control, transportation, heat island mitigation, graywater systems, habitat protection and site restoration. In terms of materials conservation and efficiency, the IgCC requires that at least 50 percent of construction waste be diverted from landfills, and at least 55 percent of building materials be salvaged, recycled content, recyclable, bio-based or indigenous.
Regarding energy conservation and efficiency, a building’s total efficiency must be 51 percent of the energy allowable in the 2000 International Energy Conservation Code (IECC), and building envelope performance must exceed that by 10 percent. It also sets minimum standards for lighting and mechanical systems, and requires certain levels of submetering and demand-response automation. The IgCC also sets standards for maximum consumption of fixtures and appliances, as well as for rainwater storage and graywater systems. Regarding indoor air quality, it addresses radon, asbestos, VOCs, sound transmission, and daylighting. In addition, the IgCC requires extensive pre and post-occupancy commissioning, as well as education of building owners and maintenance employees.
Local governments and states have the choice of adopting the code, but if adopted, it becomes enforceable. Local governments and states can also add their own requirements, on top of the code, that address local concerns. Although many jurisdictions have already adopted IgCC, the final code was to be published in March 2012. The new enforceable requirements are thus expected to support growth in the green building market.
Because it significantly reduces or eliminates the negative impact of buildings on the environment and on the building occupants, the green building sector has been gaining momentum in the Unites States. This sector is expected to continue to grow further given the increasing adoption of the LEED certification and the new national green building code.
Alejandra Lozano is an environmental and building technologies researc