The Key Differences Between Homes that Pass and Fail IECC 2021
The 2021 IECC Energy Code represents a major change in energy efficiency requirements. The code addresses energy efficiency on several fronts including cost, energy usage, use of natural resources and the impact of energy usage on the environment.
IECC 2021 was approved and finalized in 2021 and has gradually been adopted by states across the country. Montana, Nevada, Colorado, New Jersey, and a handful of municipalities have already adopted the new code while others such as Minnesota, Michigan, and Massachusetts have plans to adopt the code in some form in 2023.
In this article, we will discuss the current state of homes passing and failing IECC 2021 based on Ekotrope Rating data as well as the building products that have significant impacts on passing rates. For more information about the new code requirements, check out this article.
What is the current state of passing and failing homes in 2022?
We took a look at homes rated in Ekotrope Rater in 2022 to get a better understanding of the differences between passing and failing homes. While this data is not comprehensive, it gives us a sneak peek into how homes will need to be built in the future in order to pass the new requirements.
In our analysis, we found that roughly 45% of all homes rated within Ekotrope RATER exceeded the performance of the IECC 2021. We also discovered that nearly 30,000 homes, 12% of all homes rated in Ekotrope RATER, failed but only by a performance margin of 5% or less.
We took a look at homes rated in Ekotrope Rater in 2022 to get a better understanding of the differences between passing and failing homes. While this data is not comprehensive, it gives us a sneak peek into how homes will need to be built in the future in order to pass the new requirements.
In our analysis, we found that roughly 45% of all homes rated within Ekotrope RATER exceeded the performance of the IECC 2021. We also discovered that nearly 30,000 homes, 12% of all homes rated in Ekotrope RATER, failed but only by a performance margin of 5% or less.
So, with that in mind, what are the key differences between homes that pass and those that don’t pass?
What are the differences between homes within the same climate zones?
First, it’s important to keep in mind that the new IECC 2021 requirements are based on climate zones and, therefore, the differences between homes that pass and those that just barely failed do as well. You can learn more about the climate zones as prescribed by the IECC 2021 code here.
In Climate Zone 6A and 5B, the biggest difference between passing and failing homes was the median ACH50 number. Those that failed had a median ACH50 of 2.8 while those that failed had a median of 2. This tells us that, even though the ACH50 requirement has been rolled back to 5 in the new code, based on this data it appears that it would be prudent to aim for a more stringent score of roughly ACH50 2.0. In addition, while 5 ACH50 is the minimum, the performance evaluation will still be negatively impacted for most homes with an infiltration greater than 3 ACH50.
In Climate Zone 5A, we saw a similar ACH50 change between passing and failing homes. Passing homes had a median ACH50 score of 2.3 while the failing homes had a median of 2.6. But we also saw a small change in median wall cavity R-value as well median ceiling cavity R-value.
In Climate Zone 4A, we saw the same trend in ACH50 values, though less pronounced. In addition we saw a big increase in continuous insulation rates on above grade walls. We found the same trend in continuous insulation rates for Climate Zones 2A, 3A, and 3B. In the colder climates, the usage of continuous insulation appears to be the biggest difference between homes that fail and those that pass.
Key takeaways:
Overall, we found 2 main differences between passing and failing homes:
ACH50 scores on the more stringent end of the spectrum tend to provide a better opportunity for passing the code - even though many may be led to believe that the new minimum requirement of ACH50 5.0 is sufficient, that doesn’t seem to be the case when applied in the real world.
In the colder climates, the usage of continuous insulation in above grade walls tends to have a fairly significant effect on compliance.
We encourage you to take these insights into account when planning your projects in 2023; however, do so while considering all possible tradeoffs to find the best compliance pathway for your builder. In our research, we found that there are a variety of ways to achieve compliance with IECC 2021.
There are many tradeoffs that you can utilize so that you don’t have to rely on better ACH50 scores or the usage of continuous insulation. Our Scenario Modeling tool can actually help you identify those specific tradeoffs and show you the most efficient path to compliance based on your necessary specifications. You can learn more about the tool here.
We hope you found this article helpful. Please reach out if you have any questions about IECC 2021 or any of the tools we have available to help you navigate it by leaving a comment below or by contacting us at info@ekotrope.com. We’re always here to help!
