2015 IECC Updates Help Homebuyers Make Informed Purchases

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Categories: Article, Codes and Compliance

by Kim Tanner
Marketing Communications Specialist at The Energy Conservatory

The International Energy Conservation Code (IECC) constantly evolves to meet current energy efficiency needs. Over the years new requirements have been added to the IECC to make it stricter and increase overall energy efficiency of buildings. Some states are resistant to these changes, and some choose not to adopt an IECC at all. In fact, of the 50 states and the District of Columbia, 10 either haven’t adopted an IECC, or are operating under a code older than the 2006 IECC, according to the Online Code Environment and Advocacy Network.

However, the majority of the 50 states have embraced the energy codes and are slowly, but surely, updating the energy related portions of their statewide building code. As of July Vermont and Maryland have already adopted the 2015 IECC and implemented the updates into their building code.

In addition, 11 states are currently operating under the 2012 IECC; 22 are operating under the 2009 IECC; six are operating under the 2006 IECC; and as previously mentioned, 10 either haven’t adopted an IECC or are operating under a code older than the 2006 IECC.

So, what does the new 2015 IECC mean for contractors?

Biggest Changes from the 2012 IECC to the 2015 IECC
In terms of airtightness testing, little has changed from the 2012 to the 2015 IECC. Building envelope testing requires air leakage rates of less than five Air Changes per Hour (ACH) in climate zones 1 and 2, and 3 ACH in zones 3 through 8. Duct leakage testing requires air leakage rates of less than four percent of conditioned floor area.

However, there are a couple of noteworthy updates, such as an industry-wide standard for blower door tests and the introduction of an Energy Rating Index, which helps homebuyers make informed purchases.

Blower Door Test Standards
The first big change is a defined standard for blower door testing, which ensures accurate and repeatable tests. The 2015 IECC cites two formal test standards: ASTM E779 and ASTM 1827.

  • ASTM E779 – Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
    The ASTM E779 test standard includes directions such as:

    • Test at a minimum of five data points between 10 and 60 Pascals (Pa), in increments between 5 and 10 Pa.
    • Complete a pressurization and depressurization test.

Under this standard, there are limitations on the conditions in which the test can be performed. These limitations are based on the difference between indoor and outdoor temperatures and the height of the building.

  • ASTM 1827 – Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door
    The ASTM 1827 test standard includes directions such as:

    • Choosing between a repeated single-point and a repeated two-point test.
      • Single-point is tested at 50 Pa, with a baseline before and after, and is repeated five times.
      • Two-point is tested at 50 Pa and 12.5 Pa, with a baseline before and after, and is repeated five times.
    • Testers can choose to pressurize, depressurize or both.

These standards are a welcome update to the IECC. Requiring that testing is done to a specific standard 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.

Energy Rating Index
With the 2015 IECC comes the introduction of a new Energy Rating Index (ERI). The ERI provides flexibility for builders by allowing them to bring in a third-party rater, such as a Home Energy Rating System Rater (HERS Rater), to give the home a numerical score based on climate zone. Think of the ERI as the miles per gallon (MPG) rating on a car. The ERI allows a simple way for homebuyers to compare the energy efficiency of one house to another. The lower the number, the more energy efficient the home, with zero being a net zero home. On the opposite end, a home with an ERI of 100 is about as efficient as a home built to the 2006 IECC standard.

Under the ERI path, each home has a goal number based on the climate zone. (Climate zone map courtesy of the IECC)



  • Climate zone 1 = ERI 52
  • Climate zone 2 = ERI 52
  • Climate zone 3 = ERI 51
  • Climate zone 4 = ERI 54
  • Climate zone 5 = ERI 55
  • Climate zone 6 = ERI 54
  • Climate zone 7 = ERI 53
  • Climate zone 8 = ERI 53


How the ERI Helps Homebuyers
The introduction of the ERI will be beneficial particularly to homebuyers. Evaluating home performance and energy efficiency can be very confusing for a typical homebuyer. Trying to understand what building envelope and conditioned space means is like trying to understand the inner workings of a car with no prior experience. In short, it takes specialized education and training.

One concept many car buyers can understand is MPG. The higher the number, the better the gas mileage and the more money that stays in your pocket. The ERI will work the same way, only in the opposite direction. The lower the number, the more energy efficient the home and the less money you’re paying to utility companies.

Builders will benefit from this as well because they now have three compliance paths to choose from: the ERI compliance path, the prescriptive path and the performance path. If builders choose the ERI path, which includes bringing in a third party rater, such as a HERS Rater, then the home they built will receive an ERI score. Choosing this path will not only help a potential buyer understand how energy efficient a home is, but it could increase the likelihood of selling the home quickly.

A Caveat within the ERI Compliance Path
While the ERI can make home buying decisions simpler, it also has the potential for builders to cut corners.

The ERI path of compliance gives credit for installed high efficiency items that aren’t covered in the 2015 IECC. These items, such as solar panels, high efficiency HVAC systems and appliances can compensate for decreased efficiency in the building envelope.

The ERI option only requires the building envelope of a home meet the 2009 IECC requirements, whereas other IECC compliance paths – the prescriptive path and the performance path – require the building envelope to meet the 2015 IECC requirements. This is where the problem lies. The ERI score could be based primarily on these high-efficiency items instead of the building envelope. When equipment wears out in the future, the homeowner might replace it with lower-efficiency equipment. This means the home would no longer meet the 2015 code as it originally did, but instead meet the 2009 code.

That being said, the ERI goals were set to avoid overall building efficiency issues. As long as those goal numbers aren’t increased in the 2015 code, then homeowners will be protected from unexpectedly high energy bills over the lifetime of their home. This is because a one-point increase in the ERI score means the home will be about one percent less efficient than a home built to the 2015 IECC.

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