The National Association of Home Builders (NAHB) provided a list of 47 code changes to the 2012 International Residential Code (2012 IRC), which were approved for incorporation into the 2015 IRC. NAHB then asked Home Innovation Research Labs to conduct an analysis to estimate the expected cost impact of these code changes on construction practices and materials. A number of the selected code changes were found to be inconsequential (e.g., no cost increase or savings) and are therefore not reflected in this report. Reported as cost variance to the builder, the results are aggregated in cost estimate ranges to estimate a cumulative cost impact on an average house in selected climate zones.
Baseline metrics for four single-family houses built to the 2012 IRC and 2012 International Energy Conservation Code (2012 IECC) building codes were defined in order to determine the cost impact resulting from the revisions approved for the 2015 codes. The houses were selected for their similarity to new home offerings in the six metropolitan areas deemed representative for this study. The metros identified were Miami, Dallas, Los Angeles, Seattle, New York, and Chicago. The reference houses defined a starting point for the analysis of the cost impact to a newly-constructed home resulting from adoption of the 2015 IRC and IECC building codes (relative to a 2012 IRC/IECC baseline). Elevations and floor plans for the reference houses are provided in Appendices C through F.