Major Changes Overview

Texas is moving from the 2009 IECC/IRC energy code to the 2015 version of these codes. Over the two code cycles that have elapsed since the last statewide code adoption there have been hundreds of changes to these codes. These changes range from minor changes in wording to adding whole new sections to the code. SPEER has compiled what we consider to be the major changes from the 2009 to the 2015 code to help jurisdictions understand the scope of the change in codes as they begin the adoption process. Code officials should still familiarize themselves with the entire code and understand all of the new or revised sections before adoption, but this document will be of use in discussing the new code with policy makers and stakeholders.

The changes in the residential provisions of 2015 IRC/IECC compared to the 2012 IECC are minimal and improve energy efficiency by 1-2% in all of the climate zones in Texas. The changes when comparing the 2015 IRC/IECC to the 2009 code are significant and offer good reason to fully move to the 2015 code.

Savings and costs of the changes in the 2015 residential energy code compared to the 2009 code






* Annual energy cost savings minus annual increase in mortgage payment.
National Cost Effectiveness of the Residential Provisions of the 2015 IECC, June 2015, PNNL

Because there is such a variety of building types and uses covered by the Commercial Provisions of the IECC it is more difficult to provide detailed savings numbers but the Energy Cost Savings Analysis of the IECC for Commercial Buildings, published by PNNL, gives an overall weighted average savings for the transition from the 2009-2015 IECC as 24%. Individual uses vary, with hospitals achieving 25.1% energy savings and small office buildings achieving 27.2%.

One of the most important changes in the residential provisions of the 2015 code is the introduction of the Energy Rating Index (ERI) compliance path. ERI rates homes on a scale of zero-100 with 100 being equivalent to the 2006 IECC and zero being net zero energy. The rating scores can vary by location, by home size and by fuel use (all electric or electric + gas). SPEER has prepared an overview of the Energy Rating Index and a set of charts that demonstrate the difference in ERI scores by city and home size.

A few of the most key changes between the 2009 energy code and the 2015 energy code are:


  • Envelope leakage and duct leakage testing are required
  • Duct and envelope testing requirements are more stringent than in the 2009
  • Improved window performance
  • Wall/ceiling insulation
  • Efficient lighting requirement has gone from 50% to 75%
  • Whole house mechanical ventilation is required
  • Hot water piping insulation is required


  • Commissioning- HVAC, water heating, lighting and envelope commissioning by 3rd party
  • HVAC – new equipment efficiencies, additional requirements for ventilation systems and lighting
  • Water heating – improved efficiency and controls
  • Lighting – occupancy sensors and daylighting controls
  • Additional Efficiency Packages – requires choosing 1 of 6 above code options for compliance

To see a more complete list of major changes in the 2015 energy code go to Major Changes in the 2015 Texas State Energy Code and our Residential High Impact Item Checklist.