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New Energy Code Helps Inform Home Buyers

Revisions to the International Energy Conservation Code include an Energy Rating Index to guide purchasers of new homes

Posted on Aug 10 2015 by Kim Tanner

The International Energy Conservation Code (IECC International Energy Conservation Code.) 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, ten 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 codes. 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, ten 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?

The biggest changes in the newest version

In terms of airtightness testing, little has changed from the 2012 to the 2015 IECC. Building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials. testing requires air leakage rates of less than 5 air changes per hour (ACHACH stands for Air Changes per Hour. This is a metric of house air tightness. ACH is often expressed as ACH50, which is the air changes per hour when the house is depressurized to -50 pascals during a blower door test. The term ACHn or NACH refers to "natural" air changes per hour, meaning the rate of air leakage without blower door pressurization or depressurization. While many in the building science community detest this term and its use (because there is no such thing as "normal" or "natural" air leakage; that changes all the time with weather and other conditions), ACHn or NACH is used by many in the residential HVAC industry for their system sizing calculations.) in climate zones 1 and 2, and 3 ACH in zones 3 through 8. Duct leakage testing requires air leakage rates of less than 4 cubic feet per minute per 100 square feet 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 home buyers make informed purchases.

Defining how blower door tests should be conducted

The first big change is a defined standard for blower door testing to ensure accurate and repeatable tests. The 2015 IECC cites two formal test standards: ASTMAmerican Society for Testing and Materials. Not-for-profit international standards organization that provides a forum for the development and publication of voluntary technical standards for materials, products, systems, and services. Originally the American Society for Testing and Materials. E779 and ASTM 1827.

ASTM E779, Standard Test Method for Determining Air Leakage Rate by Fan Pressurization, 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 both a pressurization and a depressurizationSituation that occurs within a house when the indoor air pressure is lower than that outdoors. Exhaust fans, including bath and kitchen fans, or a clothes dryer can cause depressurization, and it may in turn cause back drafting as well as increased levels of radon within the home. test.

Under this standard, there are limitations on the conditions under 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, includes directions such as:

  • Choosing between a repeated single-point and a repeated two-point test. The single-point test is performed at 50 Pa, with a baseline before and after, and is repeated five times. The two-point test is performed 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.


The ERI is a new, inclusive term to describe a code-approved residential energy performance rating. One acceptable example of an ERI rating is the HERS Index.

For all intents and purposes, the term "ERI" was invented to allow (in theory) energy raters who aren't RESNET-certified to perform code-approved energy ratings, as long as the rater is using a calculation method that has been approved by the jurisdiction that adopted the code.

A home's ERI number will in almost all cases be identical to a home's HERS Index, and in almost all cases, the most likely way that an ERI will be determined will be by hiring a RESNET-certified rater to calculate the HERS Index.

For more information on the HERS Index, see How Is a Home’s HERS Index Calculated?

— Martin Holladay

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. The ERI score can range from 100 to 0, with 100 equivalent to the 2006 IECC and 0 equivalent to a net-zero home. (For more information on the ERI, see the sidebar at left: “Is ERI the same as the HERS Index?”)

Think of the ERI as the miles per gallon (MPG) rating on a car. The ERI is a simple way for home buyers to compare the energy efficiency of one house to another. The lower the number, the more energy-efficient the home.

Under the ERI path, each home has a goal number based on the climate zone (see Image #1 at the top of the page).

How the ERI helps home buyers

The introduction of the ERI will be particularly beneficial to home buyers. Evaluating home performance and energy efficiency can be very confusing for a typical home buyer. Trying to understand what "building envelope" and "conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. " mean 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 that 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 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 compliance path gives credit for installed high-efficiency items that aren’t covered in the 2015 IECC. These items — such as PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. panels and high-efficiency HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. 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 with energy efficiency in mind. 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.

Kim Tanner is a marketing communication specialist with The Energy Conservatory, a manufacturer of diagnostic equipment used to measure building performance. The company's products include the Duct BlasterCalibrated air-flow measurement system developed to test the airtightness of forced-air duct systems. All outlets for the duct system, except for the one attached to the duct blaster, are sealed off and the system is either pressurized or depressurized; the work needed by the fan to maintain a given pressure difference provides a measure of duct leakage. and the Minneapolis Blower Door.

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Image Credits:

  1. International Code Council

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