While renewable energy is rapidly growing in worldwide adoption, approximately 89 percent of the energy consumed in the United States comes from non-renewable sources like coal, gas, and nuclear power. Of that energy produced, the residential sector accounts for approximately 21 percent of consumption. Simultaneously, almost half of all renter households are cost-burdened due to poverty and rapidly rising housing prices in metro areas. The residential sector in the U.S. is clearly in need of comprehensive policymaking reforms that address sustainable residential development to reduce risks and uncertainties around the national economy, energy security, declining natural resources, and climate change.
Despite its significance as an opportunity to drive innovative solutions to address environmental sustainability and economic development through affordable housing in the U.S., zero-energy affordable housing has received little attention in literature, policy, and practice. If proved to be cost-effective, zero-energy developments can benefit residents and society as a whole by increasing housing affordability, environmental sustainability, and distribution efficacy of limited federal financial incentives.
“Feasibility of Zero-Energy Affordable Housing” is the title of a recently published paper in the Journal of Energy and Buildings. In this article Drs. Andrew McCoy, Philip Agee, Xinghua Gao, and Armin Yeganeh explore the existing gap to zero energy in the context of the Low Income Housing Tax Credit (LIHTC) program: how much should state housing agencies raise energy efficiency and renewable energy requirements to bridge the gap to zero-energy LIHTC units?; how much does a zero energy LIHTC building cost to developers?; is a zero-energy LIHTC building more cost-effective than a conventional building over its lifecycle?; and what types of additional support does the construction industry need to bridge the gap to zero energy? The main hypothesis examined is the net present cost of the implementation of rooftop solar systems to achieve zero-energy affordable housing is lower than the discounted present cost of energy of otherwise identical buildings that run without renewable energy generation systems.
Based on statistical regression analysis, energy simulation, and simulation-based risk analysis, the authors find that the net present cost of the implementation of rooftop residential solar systems to achieve zero-energy units in Virginia can be lower than the discounted present cost of energy of otherwise identical units that have no renewable energy generation systems, and the value of cost savings can be statistically significant. The results imply that the affordable housing sector in most southern U.S. states is capable to become zero energy; zero-energy affordable housing is feasible from both energy and financial standpoints; energy efficiency improvements have significantly reduced residential energy use and emissions, and zero-energy affordable housing can yield high financial returns on investment.
The investment value often depends on the zero-energy building definition, weather characteristics, the retail price of electricity, and the incentive rate. The annual electricity generated using the PV system in the 60-unit study case is ~146,060 kWh/yr. The estimated savings from switching to a photovoltaic system would exceed $120,000 in a 30-year period with a zero risk of loss of investment. The greenhouse gas emissions avoided by the PV system per year equal ~103 metric tons of carbon dioxide. This avoided carbon dioxide in 30 years amounts to nearly 348,600 gallons burnt of gasoline or 7,687,620 miles driven by an average passenger vehicle, suggesting the presence of great potentials for emission reductions and contributions to economic, environmental, and equitable developments in Virginia through promoting zero-energy affordable housing in the 2020s.
The annual balance partially restores the energy loss in the grid infrastructure system, but to restore all the grid energy loss (~32.31 percent), each unit’s array size must increase from 6.5 kW(dc) to 7 kW(dc), which would increase each module’s area from 28 to 42 square meters. Low-rise developments are the dominant building configuration (~68 percent) among the funded LIHTC projects (2011-2018) in Virginia, which means that most LIHTC projects can easily adopt solar systems to become zero-energy. Achieving an annual balance of primary energy is a required step toward performance improvement, but zero-energy design and upgrade considerations can include an optimized combination of power storage systems, mechanical and electrical operation control systems, and additional energy-efficiency measures that help buildings achieve the balance in all individual months, reduce stress on existing power infrastructure, reduce greenhouse gas emissions, and increase the building’s economic value.
To read or cite the full article: Yeganeh, A., Agee, P. R., Gao, X., & McCoy, A. P. (2021). Feasibility of Zero-Energy Affordable Housing. Energy and Buildings, 110919.
Image from waste360.com