As an independent judge of the efficacy of energy codes, BCAP strives to use data to address energy code barriers, including the real or perceived construction costs incurred by code changes. One major barrier to energy code adoption is the concern in the building community that upgrading to the latest version of the residential energy code, the 2009 IECC, will result in cost prohibitive increases in construction cost for new single-family homes. In an effort to address this concern, BCAP undertook a study to quantify the incremental construction cost of upgrading to the 2009 IECC in each state where such analysis was feasible. BCAP’s incremental construction cost analysis indicates that for states to move from their current residential energy code to the 2009 IECC would result in a weighted average incremental cost of $840.77 per new home. On average, the annual energy savings per home are $243.37, meaning the simple payback for homeowners would occur, on average, in 3.45 years. We believe these cost estimates are conservative and represent an upper bound on incremental cost, as they utilize only traditional building techniques, and do not take advantage of technologies or performance tradeoffs that would lower those costs, as well as improve energy performance.