Life Cycle Analysis of a St. Louis Flat Roof Residential Retrofit for Improved Energy Efficiency

Forty percent of the global energy consumption is related directly to commercial and residential buildings. Homeowners of energy inefficient housing have an opportunity to reduce energy consumption and to assist in mitigating climate change. This paper reports a study on retrofitting flat roofs of energy inefficient housing in St. Louis, MO. A life cycle analysis was conducted on a 120-year-old house to evaluate two design options: a green roof vs. a white roof (solar reflective paint). Both options were studied at a 10-year-of-roof-maintenance cycle. The study found that the green roof would require more retrofit embodied energy than that of the white roof because the green roof requires soil transportation, soil pan fabrication, roof joist retrofit kit, and the ceiling replacement, while the white roof requires only the manufactured paint. However, the green roof would still outperform the white roof over a 10-year period on total energy consumption. Furthermore, both options would provide energy savings over the no-retrofit option.