December 13, 2007

Purdue students' study: U.S. homebuilders can learn from the Swiss

"The goal of our project was to look at ways to make homes more efficient and to examine whether building practices in Switzerland could feasibly be put to use in the U.S.," said Keith Spence, a senior in mechanical engineering technology. "We did a cost analysis and found that it would be significantly more expensive to build this type of house and that the energy savings would not make up for the increased initial cost."

Spence said Switzerland was chosen because that country is a world leader in the area of energy efficiency and environmental concerns.

"The Swiss have a completely different way of building homes and of using energy and natural resources," he said. "Although there are a lot of cultural differences between the Swiss and Americans, U.S. homebuilders can take some of the practices used by the Swiss to make more efficient homes that people can still afford and want to live in."

Students from the departments of Building Construction Management and Mechanical Engineering Technology collaborated on the study with students from HTA Lucerne, a technical school in Switzerland. Purdue students traveled to Switzerland last summer to study homes there, and a group of Swiss students visited West Lafayette to do the same in October.

In addition to Spence, the students involved in the project are Jason Kutch, a graduate student in mechanical engineering technology, and Jamie Metzinger, a senior in building construction management. Daphene Cyr Koch, an assistant professor in building construction management, and William Hutzel, an associate professor of mechanical engineering technology, advised the students.

The students compared four types of homes: a standard American home and an Energy Star home, which is 15 percent more efficient, and a standard Swiss home and a Minergie, which is 20 percent more efficient. Each house was about 2,900 total square feet.

The students compared both the initial construction cost and the cost to heat and cool the home for a year. Energy costs included heating, cooling, water heating and the cost to power lights and appliances.

The students used a software program called REM/Rate to evaluate each of the four homes. This program uses an average energy usage for winter and summer months to determine the total cost of the home over the course of a year.

Each home was evaluated in its natural placement, then the software program relocated the Swiss homes to an Indiana environment. The initial costs of each type of home were based on Indiana construction figures.

The initial cost of the standard American home was $168,000 and $170,000 for the Energy Star home. The standard Swiss home had an initial cost of $219,000, and the Minergie home had a cost of $232,000.

The students said the Swiss homes' greater initial cost has to do with practices such as using only concrete and brick, unlike the wood used in most American homes. Also, the Swiss infrequently use air conditioning, wrap water heaters in insulation and use solar panels to help heat water. And since Swiss homes are built much tighter than U.S. homes, they utilize a mechanical ventilation system to help draw fresh air into the house.

The energy cost for a standard U.S. home for a year was $1,679 and $1,669 for an Energy Star home. The standard Swiss home cost $1,194 to operate for a year, compared to $938 for a Minergie home.

The students found that there was an energy savings of $485 a year on the Swiss standard home compared to the American standard home and $731 a year for the energy-efficient Swiss home compared to the American equivalent. The student calculated that it would take 85-100 years to pay back the extra initial cost of the Swiss homes.

Another evaluation involved hybrid versions of these homes to determine which would be the most energy efficient for the cheapest cost.

The American hybrid used an Energy Star shell (wood construction with added insulation) and a Swiss mechanical system, and the Swiss hybrid used a Minergie shell (brick or concrete) and a standard mechanical system.

Compared to their standard counterparts, the Energy Star home had a yearly $10 savings with a 200-year payback period, the Minergie home had a $256 savings with a 51-year payback and the hybrid Energy Star had a $599 savings with a one-year payback. The hybrid Minergie home had lower initial costs, but had a $363 loss in energy savings the first year.

The students found that among these homes, the best option was the hybrid Energy Star home, because of its large savings and short payback period. This home featured added insulation, a ground-source heat pump and no summer cooling.

"While the Minergie home had a good savings, the 51-year payback period is not suitable for most Americans because people in our country tend not to live in a house that long," Spence said. "The Swiss tend to live in the same house their entire lives. But in order for it to be worth it for Americans, the payback period would have to be less than five years."

The group concluded that although replicating the Swiss homebuilding practices in America may not pay off, there are several practices that U.S. homebuilders can adopt.

"We did prove that it is possible to modify American construction practices to save money," Kutch said. "Having no summer cooling may not be a good option for many Americans, but by adding insulation, lowering the number of appliances in the home and perhaps adding a heat pump, any homeowner can experience significant energy savings."

Kutch plans to do further study on the cultural differences between the Swiss and the Americans on energy and conservation issues.

Writer: Kim Medaris, (765) 494-6998, kmedaris@purdue.edu

Sources:   Daphene Cyr Koch, (765) 496-1734, cryd@purdue.edu

William Hutzel, hutzelw@purdue.edu

Jason Kutch, (219) 608-4841, jmkutch@purdue.edu

Keith Spence, (317) 413-7549, kspence@purdue.edu

Jamie Metzinger, (765) 426-0688, jmetzing@purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

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