2015 IECC: What’s changed since 2012?


The International Energy Conservation Code (IECC) is the national model energy code adopted by many states and municipal governments in the United States. It establishes the minimum design and construction “requirements for energy efficiency that new buildings – as well as additions and renovations to existing buildings – must meet wherever the code has been adopted into law. These requirements affect the building thermal envelope, lighting systems, and heating and cooling” (Institute for Market Transformation, 2015).

The IECC is updated every 3-years, and the latest version is 2015. “The 2012 IECC raised energy efficiency standards by approximately 30% just over the 2006 edition of the code” (Institute for Market Transformation, 2015). According to an analysis by the Alliance to Save Energy, benefits would include about $40 billion annual energy savings by 2030 and 200 million metric tons of carbon dioxide emissions would be avoided every year if all 50 U.S. states adopted the 2012 edition or higher.

2015 IECC

The 2015 IECC has had mixed reviews. While the code has stayed the same in regards to energy efficiency, the new compliance path gives building professionals a more flexible way to achieve energy efficiency and compliance in a format that is familiar to many. As technological advances continue to open up opportunities for scientific advance, and consumers demand the latest systems, this code is heavily recommended to be embraced because of its ability to incorporate different approaches that achieve robust energy and performance goals (Richardson, 2015).

So what does this mean? By and large the 2015 IECC cleans up language many building professionals found confusing in earlier codes which often led to significant re-work; the 2015 IECC begins the process of documenting for consumers the expected energy performance of their buildings through the Energy Rating Index; it allows in the ERI path, the use of HERS ratings already used by a large number of builders to rate and market their new homes to consumers; and lastly, the 2015 IECC includes several adjustments that will affect new home construction such as new industry-wide standards, and specified required inspections.

Many of the changes made benefit apartment and commercial construction, and taken as a whole these positive changes more than offset the modifications that may increase construction costs. Overall, the 2015 IECC is more user-friendly, and makes it easier to realize the targeted energy savings.

The Introduction of the ERI

According to the Builder Magazine’s blog and other reputable sources, the Energy Rating Index (ERI) compliance path is the biggest code alteration that will affect builders. “The ERI compliance path represents an important evolutionary step toward a code based on whole-house energy consumption and not a debate over specific values of individual components” (Meres, 2014).

This new voluntary path for the 2015 IECC now provides builders with a total of three compliance paths to choose from: the ERI compliance path, the prescriptive path, and the performance path. If builders choose the ERI path, they have the option of complying with the code by attaining a third-party inspection of the home to assess its efficiency using an energy rating index, such as the RESNET Home Energy Rating System (HERS), a tool already being used to rate one-third of all new homes (Waltner, 2013).

“The ERI is a measure of the home’s efficiency on a 0 to 100 scale where 0 is equivalent to a net-zero energy home and 100 is equivalent to a home compliant with the 2006 version of the IECC. Homebuilders choosing this path would have to meet or exceed a specific ERI score, in addition to meeting minimum envelope requirements and other mandatory measures, such as insulating hot water pipes.

… Furthermore, the energy rating index is certified by a third party, reducing the burden on code officials and increasing code compliance which adds to overall energy and cost savings. Finally, many builders will likely highlight their excellent energy ratings to the home buyer as a marketing tool, promoting competition and likely incentivizing some builders to build beyond code” (Waltner, 2013).

An analysis conducted by Pacific Northwest National Laboratory (PNNL) suggests that most homes built using the ERI path, as specified in the 2015 IECC, are likely to be at least as efficient as the homes built to meet the prescriptive requirements of the IECC or the traditional performance path (Taylor & Mendon, 2014).

In addition to builders, the introduction of the ERI in the 2015 IECC will be especially beneficial to home buyers who typically find evaluating home performance and energy efficiency very confusing. Simply put, the lower the ERI number, the more energy-efficient the home. Knowledge of this allows homebuyers to make informed decisions and most importantly, save money on utility bills.

Overall this is a step in the right direction. The Introduction of the ERI gives builders more options and new goals to aim for, and it gives homebuyers an easier way to understand the energy efficiency of houses.

Increased Commissioning

Another major change, according to the Online Code Environment & Advocacy Network, is the scope of increased commissioning that will help improve code compliance. The 2015 IECC applies commissioning to HVAC, all lighting systems, water heating systems, and the entire building envelope using approved third parties for verification. Moreover, the commissioning requirements also includes a detailed list of items needed to complete commissioning (Rhee, 2015).

HVAC, Water Heating, and Lighting is Upgraded

In addition to the mandatory commissioning, “HVAC upgrades include new equipment requirements on minimum efficiency air-conditioners and condensing units serving computer rooms, improved energy recovery ventilation systems, and specifications for motorized dampers to better control outdoor air intakes, exhaust openings, stairway and shaft vents” (Rhee, 2015).

The new water heating section delivers upgraded requirements for electric, oil storage, and pool- water heaters. It also increases the 2012 IECC minimum thickness requirement for water heating pipe insulation. Lighting systems also received an energy efficiency enhancement. The new lighting control section mandates occupant sensor controls for certain types of spaces and offers additional energy efficiency options (Rhee, 2015).

Overall the new 2015 IECC equipment performance requirements will set the foundation for “bigger returns in energy efficiency through improved specifications of equipment efficiencies” (Rhee, 2015).

A Defined Standard for Blower Door Testing

Professional energy auditors use blower door tests to help determine a home’s airtightness. The 2015 IECC has defined a standard for blower door testing to ensure precise and repeatable tests. Two formal test standards are mentioned: ASTM E779, a standard test method for determining air leakage rate by fan pressurization, and ASTM 1827, a standard test method for determining airtightness of buildings using an orifice blower door (Tanner, 2015).

“These standards not only helps ensure that the test is performed correctly, but also that it is accurate and repeatable. While there were test requirements for air leakage testing of the building envelope in the 2009 and 2012 IECC, neither referenced a formal test standard. The 2015 code requires contractors to follow one of the above ASTM test standards” (Tanner, 2015).

Simple Language Change for Roofs

The 2015 IECC includes new language that provides unambiguous direction on how the energy code provisions apply to roof repair, roof recover and roof replacement. “There has been a great deal of confusion given the various terms used to describe roofing projects on existing buildings in both the International Building Code and the International Energy Conservation Code, such as re-roofing, roof repair, roof recover and roof replacement” (Construction Magazine Network, 2014). This clarification to the 2015 IECC makes the code easier to interpret and enforce.

This update also clearly defines the exemption for roof repair, making it easier for building owners and roofing contractors to execute routine upkeep without causing additional costly energy efficiency upgrades (Construction Magazine Network, 2014).

Restrictions removed for Podium/Pedestal Buildings

According to the Backgrounders review, the removal of the restriction limiting the podium or pedestal portion of the building to one story is the most beneficial change. This means that the podium or pedestal portion can go to any height without imposing a limit on the number of stories allowed in the property. In addition, “the restrictions on occupancies allowed in the podium or pedestal portion of the building have also been revised” (Backgrounder, 2014).

Overall Energy Impact

With regards to the overall energy impact, the 2015 IECC is said to be is only marginally different from the 2012 version. A technical analysis by the U.S. Department of Energy (DOE) has determined that buildings built to the 2015 IECC, as compared to the 2012 IECC, would in fact result in improved energy efficiency. The study reveals that “buildings meeting the 2015 IECC would result in national source energy savings of approximately 0.87 percent, site energy savings of approximately 0.98 percent, and energy cost savings of approximately 0.73 percent of residential building energy consumption, as regulated by the IECC” (Energy Department, 2015).

“A few of the more significant residential changes included: revisions to the provisions for existing buildings, changes to how the code treats historic buildings, revisions to the air barrier and insulation installation table, new requirements for combustion closets, revisions to the building envelope and duct leakage testing requirements, new and revised requirements for hot water distribution efficiency, a new requirement for drain water heat recovery, a new Energy Rating Index compliance path, and two new appendices” (Meres, 2015).

As for the commercial buildings, the 2015 IECC is said to improve the energy impact by a little more than 1%, when compared to the 2012 IECC (Kaplow, 2015). According to the PNNL report, 11.5% site energy savings are achieved at the aggregate national level in the 2015 IECC, compared to the 2012 IECC. For all prototypes combined, the 2015 IECC and Standard 90.1-2013 are within 1% for both energy use and energy costs on a national average basis. “Savings from the 2012 to 2015 IECC vary considerably by prototype. This is expected because code requirements are different by building type and by climate.” Notably, a few high impact changes to the building envelope, HVAC systems and lighting will result in significant and quantifiable energy savings (Zhang, et al., 2015).

DOE’s study also indicates that only 6 of the 77 total changes actually increase energy savings, more than 60 of the changes require new materials and methods but are energy neutral, and 3 arguable have a detrimental effect on energy savings (Kaplow, 2015).


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  2. Construction Magazine Network. (2014, Jan. 14). Insulation Levels in Reroofing Projects to Comply with New Construction Requirements. Retrieved from Construction Magazine Network 
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  12. Waltner, M. (2013, Oct. 10). Efficiency Wins Big in Atlantic City, Homeowners Will Benefit. Retrieved Oct. 2015, from Natural Resoures Defense Council Staff Blog