The 2021 IECC, or International Energy Conservation Code, will be the most up-to-date code focused on energy-efficient building, when published and ready for adoption later this year. 

Designed to reflect today’s energy-conscious building standards while also challenging builders to push for greater efficiency, the 2021 IECC could certainly lead to the most energy-efficient housing stock in our country’s history.

One of the biggest changes to the 2021 IECC compared to previous versions of the code is how builders will be able to comply with its requirements using the Energy Rating Index (ERI).

What is the Energy Rating Index?

The ERI is a scale with numbers that range from 0 (to represent net zero energy) to 100 (to represent the approximate efficiency of a home built to the 2006 IECC). Each number on the ERI scale represents a 1% change in the relative energy efficiency of the building. Each point higher is 1% less efficient, and each point lower is 1% more efficient.

The ERI became a compliance pathway for builders wanting to meet the 2015 energy code. Many professionals noticed that the ERI at that time used the same numbers as the RESNET HERS Index, largely due to using the same energy rating software. As a result, these professionals (called Home Energy Raters) entered the discussion and looked for ways to capitalize on the new building code option.

In our post on the 2015 IECC code, we looked at the three compliance pathways that builders have for meeting code. It was an exciting time because the 2015 IECC introduced the ERI compliance pathway and listed requirements for blower door and duct testing. All these concepts resonated with the Home Energy Raters, due to their specialty knowledge in home energy rating and air leakage testing. 

Flash Forward to 2018 IECC

The next iteration of the IECC came out in 2018. Although this version referenced the same underlying standard to calculate the ERI score, the resulting number varied slightly from the “equivalent” HERS Score. A modification made to the 2018 IECC concerning modeled ventilation rate caused this difference. Since then, the HERS Score and ERI Score have been slightly out of sync.

Looking Forward to 2021 IECC

The aforementioned blower door testing requirements remain intact, and, actually, the 2021 IECC takes duct testing even further. According to Ryan Meres, the RESNET Program Director, “the 2021 IECC eliminates the exception that allows HVAC equipment located entirely in conditioned spaces to not be tested. Under the 2021 IECC, all ducts will be required to be tested, regardless of location.”

So What’s New With ERI in the 2021 IECC?

• Proposal RE192 makes the ERI target scores more stringent in each climate zone. The target score could be as low as 55 in some climate zones.
• Proposal RE184 limits renewable energy production to reduce no more than 5% of total energy use. 
• Proposal RE209 applies additional efficiency improvements to all compliance paths, meaning that anyone who uses the ERI pathway will have to further lower their HERS Score target by 5%.

All these changes mean a builder would need to achieve a HERS Score somewhere between 40 and 50, depending on climate zone, and can only claim a 5% reduction in energy use for renewable energy.

What Role do HERS Raters Play Now?

Initially, there was a belief that the ERI compliance pathway would be the path of choice for meeting IECC requirements, due to the index being so similar to the well-established Home Energy Rating System (HERS). There’s already a network of trained and experienced HERS Raters who rely on the HERS Index with their daily work, so it made sense that builders would seek guidance from HERS Raters about meeting ERI.

But that was in 2015, and the 2018 differences between ERI and HERS led to more Raters thinking critically about the guidance to provide to their builder clients.

Because HERS Raters have an exceptional understanding of building science principles, they are viewed in the building industry as the go-to resource for energy code compliance. And with that knowledge, HERS Raters can make their own educated decisions on the best compliance pathway for their builder clients. Ironically, that often means that HERS Raters tend to choose the Performance Path as the best choice.

Compliance with both the ERI and Performance paths is demonstrated using RESNET-accredited software, so HERS Raters are already familiar with the building science and technology required, regardless of which pathway gets chosen. 

Furthermore, the ERI will effectively require target scores to hit the same level of stringency as the net-zero appendix, without renewable energy, which is a stringency level far beyond the prescriptive and performance paths. HERS Raters, therefore, are more likely to choose the easier, and more cost-effective, compliance path for their builder clients. 

If builders use the ERI pathway to meet the 2021 IECC, they will be expected to hit very low HERS Score targets. If builders choose to hire a HERS Rater, they can still achieve energy-efficiency goals, while making smart money choices and keeping their sanity. 

What to Expect

The 2021 codes should be published around October 2020, but most states will likely not adopt the code for years to come. The U.S. Department of Energy will also be releasing its final savings analysis of the 2021 IECC later this year, though Christopher Perry of the American Council for an Energy-Efficient Economy estimates that the new code will provide 10% or more in annual energy savings for residential and commercial buildings that use it.

At the end of the day, net-zero energy homes are the future. It’s clear that the building codes will push us to get there, no matter how long it takes for the states to adopt and implement the policies. 

If you’re considering a career in home performance, look into becoming a RESNET HERS Rater. We expect to see continued growth and demand for HERS Raters in the building industry.

Start online today with RESNET HERS Rater Training and you’ll be well on your way to being a home energy professional!