Economic enhancements to a first-year net zero energy home design project

A half-semester long project has been developed at a major large public university to introduce students to engineering design. The project focuses on the design of a net zero energy home (NZEH) by four-person teams, and was reported on at the 2012 ASEE meeting in San Antonio. This past summer, a significant effort was undertaken to include cost and engineering economics into the design. This paper begins by summarizing that earlier paper, then describes the development of the cost data and economic analysis. This is followed by some parametric studies performed by the authors, and insights into the most viable design features from an economic standpoint. The last section reports on experiences using the enhanced project in class in fall 2012. The plan is to limit each NZEH design to a fixed construction cost budget, and then to have students do tradeoff analysis considering insulation levels, number and types of windows, type of heating/cooling system, solar water heating, and perhaps most importantly, overall size of the house. Construction cost data was developed from RSMeans along with consultations with contractors and equipment suppliers. By constraining the project to be NZEH, the efficiency levels that are economically justified are measurably higher than a more typical house design where current electricity prices are the basis for energy tradeoffs. Another way of saying this is that putting in more insulation in the wall, for example, and reducing the electricity needed for heating and cooling is less expensive than purchasing a larger solar electric system to provide that electricity. Looking at the bigger picture, it is saying that if designers were to include the cost of providing renewable electricity into their designs, they would design differently and houses would use significantly less energy.