Toward a Zero Energy Home: Applying Swiss Building Practices/Attitudes to U.S. Residential Construction

This project evaluated typical U.S. and Swiss homes to identify construction practices that are most energy efficient and have economic payback. A net zero energy home (ZEH) produces as much energy as is consumed in it over time. Students in a College of Technology in a Midwest Indiana State University and a technical University in Switzerland resulted in developing models of homes that combined U.S. and Swiss standards. The project was completed in two phases: during the first phase of this project, construction costs, energy use, and economic payback was calculated for six homes that were designed using both Swiss and U.S. standards. During the second phase of the project, cultural norms that influence energy use were explored. A survey was used to compare U.S. and Swiss college students’ lifestyles and energy habits. All homes had the same basic size and layout, but some used construction practices typical for the United States and others were designed according to Swiss guidelines for residential construction. The results of the study showed that a Swiss-style low-energy home is not cost effective for the Midwestern United States if energy costs remain low, but it could become attractive if energy rates escalate significantly. It was also recognized that technology by itself will not minimize energy consumption, a result of the second part of the project that explored cultural norms that influence energy use. From the survey of both U.S. and Swiss college students’ lifestyles and energy habits, it was revealed with a high level of confidence that Swiss students are more energy conscious than their U.S. counterparts. Introduction This project evaluated typical U.S. and Swiss residential design to identify construction practices that are most energy efficient. The analysis reviewed current best practices in both countries along with an evaluation of attitudes toward energy use by individuals. In the United States an Energy Star system is being used to model homes. Energy Star is an umbrella of voluntary programs started in 1992, which ran as a joint program since 1996 with the U.S. Environmental Protection Agency (EPA) and the DOE to improve energy efficiency of homes (Banerjee & Solomon, 2003). The Swiss method of building a sustainable home is the Minergie System (Minergie, 2010). Zero Energy Homes (ZEH) have been built in Japan, Sweden, Germany, Norway, Austria, and the United States. Unfortunately, there is no real database to centralize information to globalize the adoption of successful homes worldwide (Charron & Athientitis, 2005). To add to the existing body of knowledge, this project reviewed the importance of moving toward ZEH homes, and the current practices and attitudes of the United States and Switzerland toward energy efficiency. The research modeled six variations of designs that incorporated the Energy Star and Minergie systems. T h e J o u rn a l o f Te c h n o lo g y S tu d ie s Toward a Zero Energy Home: Applying Swiss Building Practices/Attitudes to U.S. Residential Construction Daphene C. Koch, William J. Hutzel, Jason M. Kutch and Eric A. Holt 78 Figure 1. Energy Usage by Sector Including Detail for Residential (Energy Star, 2010; Perez-Lombard, Ortiz, & Pout, 2008) T h e J o u rn a l o f Te c h n o lo g y S tu d ie s Significance of Energy Consumption The International Energy Outlook (IEO) report projects that the world energy consumption is expected to expand by 50% in 2030 (Energy Star, 2010). Residential buildings account for 22% of the primary energy use according to the Energy Information Administration (EIA, 2008). Within residential buildings, space heating and water heating (both natural gas and electric) are the biggest opportunities for energy savings. Figure 1 details the exact usage of electricity in the home. It shows that most energy is used for heating (home and water), lighting, and cooling. These should be the initial targets to better design a home. The Department of Energy (DOE) started a program, “Build America,” with a goal of reducing whole-house energy use for new home by 50% by 2015 and 95% by 2025 (Anderson & Horowitz, 2006). The Build America initiative targets significant improvements to the building envelope (the makeup of the walls, roof, and floor) through better insulation and sealants, and major reductions in electricity through using highly efficient appliances, lighting, and mechanical systems. The remaining energy for achieving net-zero will be supplied by a renewable energy source, such as solar or wind. Residential Construction Standards in the United States and Switzerland A detailed inspection of the Swiss and U.S. homes showed fundamental differences in construction techniques. Figure 2 shows photos taken by the students to document the typical systems used in each country. The Swiss building standards are more similar to U.S. commercial standards of building with heavy use of a thick masonry brick-type component. This creates more thermal mass than the typical U.S.-style wood-frame home. Significant attention in optimizing the building envelope in terms of insulation, air sealant, and efficient windows is a component of the Swiss system. The highly efficient mechanical systems included air-to-air heat recovery, radiant slab heating and cooling, and solar domestic hot water in Swiss homes, which is currently utilized in more commercial applications in the United States. Typical Swiss home are built using a masonry type of material, which does not exist in the United States. A Swiss home also typically costs more than $600,000 (U.S.) to purchase, and in Switzerland, most people do not own homes, but rather inherit them. The U.S. has produced affordable housing using wood-frame construction. This vast difference in materials used for homes resulted in the development of a typical midrange U.S. home layout that was developed to be used for modeling the standards of Minergie and Energy Star. Figure 3 shows the standard home layout 79 Figure 2. Swiss Masonry Walls (left) and U.S. Wood-frame Walls (right) (photos by authors) Figure 3. Floor Plan of Typical Midrange U.S. Home (plan produced for research project) T h e J o u rn a l o f Te c h n o lo g y S tu d ie s that was developed to standardize comparisons of different characteristics of homes. A single-family home with one story and a conditioned unfinished basement was used because this type of construction is found in both countries. The floor plan included three bedrooms, two bathrooms, one walk-in closet, a living room, a dining room, a kitchen, a sunroom, a screened-in porch, and a front porch: it totaled 1,504 ft2 (139.7m2). Four exterior doors account for approximately 100 ft2 (9.3 m2) of surface area and the windows equaled approximately 237 ft2 (22 m2); the majority of the windows face south, which provides additional heating during the winter. The above-grade wall surface area is approximately 1400 ft2 (130 m2). The basis of the project was to differentiate the Energy Star and Minergie building standards, but it was found that in the United States not all of the Swiss standards were realistically applied. Table 1 identifies six different combinations of residential construction identifying the wall and attic insulation, heating, and application of solar hot water heating. These are the major characteristics of the home that were modeled to evaluate using the standardized floor plan. The combinations range from the least energy efficient design, standard U.S. home, to the standard Minergie home of Switzerland. The insulating value of the walls and attic in Table 1 is expressed in terms of an R-value. Two systems of units are shown. The U.S. customary R-value has units of ft2-°F-hr/Btu. The conversion to comparable SI units is 5.68 ft2-°F-hr/Btu equals 1.0 m2-°C/W. Table 1 shows the U.S. R-value first, with the SI version (labeled RSI) in parentheses. The exterior walls of the “Standard U.S.” home have R-11 (1.94 RSI) insulation, whereas the attic has an R-30 (5.28 RSI). Heating is provided by a natural gas furnace rated at an annual fuel utilization efficiency (AFUE) of 80% with a capacity of 80 MBtuh (23.4 kW). Modeling U.S. and Swiss Homes A software tool, RemRate, was used to analyze energy use. RemRate is an easy-to-use computer program for residential construction that calculates heating, cooling, hot water, lighting, and appliance loads. Certified energy auditors use the program to determine whether a new home design meets the requirements for 80 Construction Category Wall R-value (RSI) Attic R-value (RSI) Heating Solar for Hot Water Standard U.S. 11 (1.94) 30 (5.28) Gas 80% AFUE 80 MBtuh (23.4 kW) No Energy Star 19 (3.35) 50 (8.81) Gas 92% AFUE 80 MBtuh (23.4 kW) No Standard Swiss 19 (3.35) 38 (6.69) GSHP 5.0 COP 40 MBtuh (11.7 kW) No Minergie 30 (5.28) 50 (5.28) GSHP 5.0 COP 36 MBtuh (10.5 kW) Yes Hybrid Energy Star 19 (3.35) 50 (8.81) GSHP 5.0 COP 40 MBtuh (11.7 kW) Yes Hybrid Minergie 30 (5.28) 50 (8.81) Gas – 92% AFUE 80 MBtuh (23.4 kW) No Table 1. Major Specifications for Six Residential Construction Models Figure 4. HERS Index Ratings for Research Model Homes (developed by researchers) T h e J o u rn a l o f Te c h n o lo g y S tu d ie s U.S. Energy Star certification. RemRate includes climate data for cities and towns throughout North America. The analysis for this project was conducted in a Midwestern city, which is classified as a cold climate according to DOE’s Building Technologies Program (Polly et al., 2011). The winter design temperature used was -5 °F (-20.6 °C) and a summer design temperature is 93 °F (-33.9 °C). The RemRate software also predicts annual utility costs when rates are provided. This project assumed utility rates that are typical for an area, but low compared to the rest of the United States. Electricity was $0.10 / kilowatt-hour (kWh). Natural gas was $1.50 / hundred cubic feet (CCF). During the economic analysis, an energy escalation rate of 3% annua