Life-Cycle Energy, Costs, and Strategies for Improving a Single-Family House

The life-cycle energy, greenhouse gas emissions, and costs of a contemporary 2,450 sq ft (228 m³) U.S. residential home (the standard home, or SH) were evaluated to study opportunities for conserving energy throughout pre-use (materials production and construction), use (including maintenance and improvement), and demolition phases. Home construction and maintenance materials and appliances were inventoried totaling 306 metric tons. The use phase accounted for 91% of the total life-cycle energy consumption over a 50-year home life. A functionally equivalent energy-efficient house (EEH) was modeled that incorporated 11 energy efficiency strategies. These strategies led to a dramatic reduction in the EEH total life-cycle energy; 6,400 GJ for the EEH compared to 16,000 GJ for the SH. For energy-efficient homes, embodied energy of materials is important; pre-use energy accounted for 26% of life-cycle energy. The discounted (4%) life-cycle cost, consisting of mortgage, energy, maintenance, and improvement payments varied between 426,700 and 454,300 for a SH using four energy price forecast scenarios. In the case of the EEH, energy cost savings were offset by higher mortgage costs, resulting in total life-cycle cost between 434,100 and 443,200. Life-cycle greenhouse gas emissions were 1,010 metric tons CO₂ equivalent for an SH and 370 metric tons for an EEH.