How Far Can Energy Efficiency Go?

New technology and growing consumer demand are increasing the availability of energy-efficient building products and systems. Concerns about rising home energy costs and the environment are stimulating technological advancements and wider dissemination of energy-efficient and other greenbuilding practices. Two recent reports illustrate that although there are great opportunities for improving home energy efficiency, there are also barriers that prevent the widespread implementation of alternative building practices, materials and design strategies.

The first article, "Net-Zero Fossil Fuel Home Case Study," presents research by the National Association of Home Builders (NAHB) Research Center, which demonstrates that homes of traditional design are capable of generating as much power as they consume. The second study, "Breaking Down the Barriers: Challenges and Solutions to Code Approval of Green Building," explores barriers to green building practices.

Together, these articles demonstrate that, although theoretical modeling shows that available technologies can result in dramatic energy savings in homes, there remains a need to address the misperceptions and knowledge deficiencies that stand in the way of their widespread acceptance and adoption.

Advanced Systems, Dramatic Results

According to the NAHB Research Center case study, "Net-Zero Fossil Fuel Home Case Study," it is feasible for a home of traditional design to achieve net-zero fossil fuel use. To attain net-zero fossil fuel use, the average amount of energy used by the house each year must be equal to or less than the amount of energy it can produce using renewable sources, such as solar energy. The NAHB Research Center is one of four teams funded through Zero Energy Homes, an initiative of the Solar Buildings Program of the U.S. Department of Energy (DOE). The initiative focuses on introducing the new home construction industry to buildings that generate power from renewable resources. The NAHB Research Center effort is unique, in that the home in its case study uses widely available products and systems. Unlike other projects that involve custom designs, the study highlights energy-efficient practices that are easy to replicate.

Using sophisticated computer modeling, the study compares estimates of energy use in a home through four iterations of energy-efficient modifications. The comparisons between the amount of energy used in the standard house to the energy consumed after each modification enable a determination of whether a particular renewable energy system is capable of meeting the needs of the modified structure. For this study, the modified design incorporated a rooftop photovoltaic (PV) system, which generates electricity from solar energy. The home in the study included features found in typical single-family homes, such as average floor space and number of bathrooms. It also incorporated common features that can be challenging to combine with solar features, such as a full basement, living space over an unconditioned garage, and cathedral ceilings in portions of the home.

After estimating the home's initial energy use, its design was modified to incorporate technologies that reduce the energy required to heat and cool it. Although the technologies used are typically upgrades from more commonly used products, and may come with a higher cost, they are not so obscure as to be impractical or hard to find. For the most part, the modifications involved using energy-efficient building techniques to construct the building envelope and installing high-efficiency heating and cooling
equipment. Some of the components or systems used in the modifications include:

• Optimum Value Engineering (OVE) framing techniques that reduce the amount of framing materials while increasing the overall quantity of insulation in the wall system.
  
• High levels of blown (or spray-applied) insulation of high-density material.
  
• Additional thermal mass to absorb solar radiant energy in heating seasons.
  
• Component roofing insulation systems, which place the entire attic within the insulated building envelope.
  
• Component foundation systems that incorporate insulation into pre-cast concrete.
  
• Passive solar sunspace to enhance the collection of direct solar energy to be used for heating.
  
• Active solar hot water heating for household use.
  
• Low-emissivity (low-e) windows with argon gas to reduce thermal bridging and increase occupant comfort.
  
• Very high-efficiency heating and cooling systems, including a ground-source heat pump.

After completing the fourth and final modifications, the model home - with the full complement of energy-saving processes and materials - is estimated to consume two-thirds less energy than the standard house. The research also estimated that a 500 square foot PV system could provide adequate energy for the modified house, resulting in a net-zero requirement for non-renewable resources over the course of a year. Overall, these comparisons are an important first step in understanding how building components can substantially reduce a home's energy consumption, while easing our Nation's dependence on non-renewable sources.

Understanding Barriers to Green Building

Embarking on one of the first efforts to gather information about the relationship between building regulations and green-building practices, the Development Center for Appropriate Technology (DCAT) conducted an Internet survey to identify barriers to green building. The survey, "Breaking Down the Barriers: Challenges and Solutions to Code Approval of Green Building," queried people seeking code approval (code users) and code officials to obtain a comprehensive perspective on roadblocks to receiving approval for sustainable building and development approaches and successful strategies for overcoming these barriers. The report suggests that building codes have long been perceived as detrimental to green building, even though most codes contain provisions for alternative designs, materials, and construction methods.

The survey results reveal that both technical and non-technical barriers affect the approval of green building techniques. Officials routinely consider technical factors when evaluating whether a green building alternative meets code requirements. Code officials cited technical factors, including the lack of supporting documentation from code users and their own lack of technical expertise with the alternatives presented, as major reasons for denying green building alternatives. Non-technical factors, such as insufficient time to research the alternative, were also noted as reasons code officials denied a proposed alternative.

The strategies that code officials and code users found to be successful for gaining approval of green building alternatives included providing adequate review time and presenting detailed supporting information. Both code users and code officials stated that starting the approval process early and working with the building department from the outset are worthwhile strategies to pursue. Code users also stated that persistence and patience are needed when navigating the code approval process.

Another important finding from the survey was that even when building codes allow for green building alternatives, most code users indicate that the approval process was difficult. Sixty-five percent of code users reported that they had not submitted a green building alternative in the past because of the additional time they expected it would take to gain approval and because they lacked documentation to support the alternative.

Studies such as the one conducted by the NAHB Research Center may prove futile if the barriers imposed by building codes are not addressed. These challenges may discourage potential green builders from applying for code approval, preventing this and other theoretical designs from reaching the residential home market. However, the initial findings concerning the code approval process show promise for overcoming code-based barriers. By providing code officials with better information and by educating code users on strategies that work, both sides may find the support they need to accept and incorporate energy efficient designs and products.

Note from the Editor