A Comparative Cost-Benefit Evaluation of a Solar House

July 29, 2015
Poster Session — President’s Hall 2
4:00 pm  -  7:00 pm

“Electrical and thermal performance of a solar house will be discussed using data collected over two years. The house located in mountain climate of Western Maryland has two sections designed and built separately at different times. One section has more solar gain compared to the other, which is more airtight with smaller infiltration and higher insulation values. Thermal characteristics and inside comfort variables for a wide range of external weather conditions are analyzed for each section and compared to determine the cost-effectiveness of the applied concepts.

The house has a grid-tied PV array of total 3640 W rated power. On-site electric generation data has been recorded since its installation. The paper will present monthly electric generation and consumption averaged over two years. The cost-benefit of possible expansions of the PV generation system to make the example house net zero energy or grid independent are compared.

Designers, builders, and homeowners face many energy related issues that must be addressed when planning and constructing a or retrofitting a house. From setting the design requirements to selecting building elements, all decisions affect the initial cost of a construction and its future energy related expenses. Obviously an energy efficient house will have lower energy bills over its economic life. However, how much additional initial cost would be reasonable for an average income family to benefit from a long-term energy saving? The answer depends on many factors such as the type of energy source, energy security, dependency of the house on utilities, and environmental sensibility of the owners. The authors will discuss some of these issues and share their experience, observations, and assessments to help residential construction professionals and their customers in their quest for optimal energy-efficient house design.

BEopt software developed by NREL has been implemented to model each section of the house using actual design parameters and blower test results. EnergyPlus simulations show the effect of changing design parameters and component characteristics on incremental cost and energy saving benefits. Simulation results are evaluated to determine possible improvements to optimize the cost effectiveness of each section.

Passive house standards set by the Passive House Institute (PHI) and US Passive House Institute (PHIUS) or LEED certification criteria of US Green Building Council provide valuable targets for designers and builders but these recommendations may not lead to the optimal cost-effective result. The authors will compare these targets from cost-benefit perspective and discuss certification criteria used by PHI and the climate specific PHIUS-2015 criteria developed for North America.

In addition to analytical evaluations, the owners will share the lessons they have learned throughout the design and construction process as well as the experience they have gained by living in this house.”