Executive Summary

Towards a Climate-Friendly Built Environment

The energy services required by residential, commercial, and industrial buildings produce approximately 43 percent of U.S. carbon dioxide (CO2) emissions. Given the magnitude of this statistic, many assessments of greenhouse gas (GHG) reduction opportunities focus principally on technologies and policies that promote the more efficient use of energy in buildings. This report expands on this view and includes the effects of alternative urban designs; the potential for on-site power generation; and the life-cycle GHG emissions from building construction, materials, and equipment. This broader perspective leads to the conclusion that any U.S. climate change strategy must consider not only how buildings in the future are to be constructed and used, but also how they will interface with the electric grid and where they will be located in terms of urban densities and access to employment and services. The report considers both near-term strategies for reducing GHGs from the current building stock as well as longer-term strategies for buildings and communities yet to be constructed.

The United States has made remarkable progress in reducing the energy and carbon intensity of its building stock and operations. Energy use in buildings since 1972 has increased at less than half the rate of growth of the nation's gross domestic product, despite the growth in home size and building energy services such as air conditioning and consumer and office electronic equipment. Although great strides have been made, abundant untapped opportunities still exist for further reductions in energy use and emissions. Many of these-especially energy-efficient building designs and equipment-would require only modest levels of investment and would provide quick pay-back to consumers through reduced energy bills. By exploiting these opportunities, the United States could have a more competitive economy, cleaner air, lower GHG emissions, and greater energy security.

GHG Emissions: Sources and Trends

GHG emissions from the building sector in the United States have been increasing at almost 2 percent per year since 1990, and CO2 emissions from residential and commercial buildings are expected to continue to increase at a rate of 1.4 percent annually through 2025. These emissions come principally from the generation and transmission of electricity used in buildings, which account for 71 percent of the total. Due to the increase in products that run on electricity, emissions from electricity are expected to grow more rapidly than emissions from other fuels used in buildings. In contrast, direct combustion of natural gas (e.g., in furnaces and water heaters) accounts for about 20 percent of energy-related emissions in buildings, and fuel-oil heating in the Northeast and Midwest accounts for the majority of the remaining energy-related emissions. Based on energy usage, opportunities to reduce GHG emissions appear to be most significant for space heating, air conditioning, lighting, and water heating.

Mechanisms of Change

Because the building industry is fragmented, the challenges of promoting climate-friendly actions are distinct from those in transportation, manufacturing, and power generation. The multiple stakeholders and decision-makers in the building industry and their interactions are relevant to the design of effective policy interventions. Major obstacles to energy efficiency exist, including insufficient and imperfect information, distortions in capital markets, and split incentives that result when intermediaries are involved in the purchase of low-GHG technologies. Many buildings are occupied by a succession of temporary owners or renters, each unwilling to make long-term improvements that would mostly benefit future occupants. Regulations, fee structures in building design and engineering, electricity pricing practices, and the often limited availability of climate-friendly technologies and products all affect the ability to bring GHG-reducing technologies into general use. Some of these obstacles are market imperfections that justify policy intervention. Others are characteristics of well-functioning markets that simply work against the selection of low-GHG choices.

Numerous individual, corporate, community, and state initiatives are leading the implementation of "green" building practices in new residential development and commercial construction. The most impressive progress in residential green building development and construction is the result of communities and developers wanting to distinguish themselves as leaders in the efficient use of resources and in waste reduction in response to local issues of land-use planning, energy supply, air quality, landfill constraints, and water resources. Building owners and operators who have a stake in considering the full life-cycle cost and resource aspects of their new projects are now providing green building leadership in the commercial sector. However, real market transformation will also require buy-in from the supply side of the industry (e.g., developers, builders, and architects).

Affordability, aesthetics, and usefulness have traditionally been major drivers of building construction, occupancy, and renovation. In addition to climatic conditions, the drivers for energy efficiency and low-GHG energy resources depend heavily on local and regional energy supply costs and constraints. Other drivers for low-GHG buildings are clean air, occupant health and productivity, the costs of urban sprawl, electric reliability, and the growing need to reduce U.S. dependence on petroleum fuels.

Technology Opportunities in Major Building Subsectors

The technical and economic potential is considerable for technologies, building practices, and consumer actions to reduce GHG emissions in buildings. When studying the range of technologies, it is important to consider the entire building system and to evaluate the interactions between the technologies. Thus, improved techniques for integrated building analyses and new technologies that optimize the overall building system are especially important. In this report, homes and small commercial buildings and large commercial and industrial buildings are analyzed separately for their energy-saving and emission-reduction potential, because energy use in homes and small businesses is principally a function of climatic conditions while energy use in large buildings is more dependent on internal loads. 

Applying currently available technologies can cost-effectively save 30 to 40 percent of energy use and GHG emissions in new buildings, when evaluated on a life-cycle basis. Technology opportunities are more limited for the existing building stock, and the implementation rate depends on the replacement cycles for building equipment and components. However, several opportunities worth noting apply to existing as well as new buildings, including efficiencies in roofing, lighting, home heating and cooling, and appliances. Emerging building technologies, especially new lighting systems and integrated thermal and power systems, could lead to further cost-effective energy savings. All of these potential effects, however, are contingent upon policy interventions to overcome the barriers to change.

Community and Urban Subsystems

Evidence suggests that higher-density, more spatially compact and mixed-use building developments can offer significant reductions in GHG emissions through three complementary effects: (1) reduced vehicle miles of travel, (2) reduced consumption for space conditioning as a result of district and integrated energy systems, and (3) reduced municipal infrastructure requirements. Both behavioral and institutional barriers to changes in urban form are significant. The effect of urban re-design on travel and municipal energy systems will need to be tied to important developments in travel pricing, transportation construction, and other infrastructure investment policies.

Past studies have concluded conservatively that changes in land-use patterns may reduce vehicle miles traveled by 5 to 12 percent by mid-century. More compact urban development could also lead to comparable GHG reductions from efficiencies brought about by district and integrated energy systems, with a small additional decrement from a reduced need for supporting municipal infrastructures. In total, therefore, GHG reductions of as much as 3 to 8 percent may be feasible by mid-century, subject to the near-term enactment of progressive land-use planning policies.

Policy Options

Policy research suggests that public interventions could overcome many of the market failures and barriers hindering widespread penetration of climate-friendly technologies and practices. The mosaic of current policies affecting the building sector is complex and dynamic, ranging from local, state, and regional initiatives, to a diverse portfolio of federal initiatives. Numerous policy innovations could be added to this mix, and many are being tried in test-beds at the state and local level.

In this report, buildings energy research and development (R&D) and six deployment policies are reviewed that have a documented track record of delivering cost-effective GHG reductions and that hold promise for continuing to transform markets.   The six deployment policies include (1) state and local building codes, (2) federal appliance and equipment efficiency standards, (3) utility-based financial incentive and public benefits programs, (4) the low-income Weatherization Assistance Program, (5) the ENERGY STAR(r) Program, and (6) the Federal Energy Management Program. Annual energy savings and carbon-reduction estimates are provided for each of these policies, both retrospectively and prospectively. Summing these values provides a reasonable estimate of the past and potential future impacts of the policies.

Annual savings over the past several years from these R&D and six deployment policies are estimated to be approximately 3.4 quadrillion Btu (quads) and 65 million metric tons of carbon (MMTC), representing 10 percent of U.S. CO2 emissions from buildings in 2002. The largest contributors are appliance standards and the ENERGY STAR Program. Potential annual effects in the 2020 to 2025 time frame are 12 quads saved and 200 MMTC avoided, representing 23 percent of the forecasted energy consumption and carbon emissions of buildings in the United States by 2025. The largest contributors are federal funding for buildings energy R&D (especially solid-state lighting) and appliance standards.

Conclusions and Recommendations

The analysis presented in this report leads to several conclusions:

• An expansive view of the building sector is needed to completely identify and exploit the full range of GHG-reduction opportunities. Such a view needs to consider future building construction (including life-cycle aspects of buildings materials, design, and demolition), use (including on-site power generation and its interface with the electric grid), and location (in terms of urban densities and access to employment and services).

• There is no silver bullet technology in the building sector because there are so many different energy end uses and GHG-relevant features. Hence, a vision for the building sector must be seen as a broad effort across a range of technologies and purposes.

• An integrated approach is needed to address GHG emissions from the U.S. building sector - one that coordinates across technical and policy solutions, integrates engineering approaches with architectural design, considers design decisions within the realities of building operation, integrates green building with smart-growth concepts, and takes into account the numerous decision-makers within the fragmented building industry.

• Current building practices seriously lag best practices. Thus, vigorous market transformation and deployment programs are critical to success. They are also necessary to ensure that the next generation of low-GHG innovations is rapidly and extensively adopted.

• Given the durable nature of buildings, the potential for GHG reductions resides mostly with the existing building stock for some time to come. However, by 2025, newly constructed net-zero-energy homes and climate-friendly designs for large commercial buildings and industrial facilities could begin to generate sizeable GHG reductions by displacing the energy-intensive structures that embody today's standard practices. By mid-century, land-use policies could have an equally significant impact on GHG emissions. This inter-temporal phasing of impacts does not mean that retrofit, new construction, and land-use policies should be staged; to achieve significant GHG reductions by 2050, all three types of policies must be strengthened as soon as politically feasible.

• Similarly, applied R&D will lead to GHG reductions in the short run, while in the long run basic research will produce new, ultra-low GHG technologies. This does not mean that basic research should be delayed while applied R&D opportunities are exploited. The pipeline of technology options must be continuously replenished by an ongoing program of both applied and basic research.

By linking near-term action to long-term potential, the building sector can assume a leadership role in reducing GHG emissions in the United States and globally.