In my last post, I explained how the energy conservation provisions found in Chapter 11 of the International Residential Code (IRC) provide options for designers and builders when it comes to energy code compliance.

Since energy codes were introduced in the 1970s, they’ve provided different ways to design and build a home’s thermal envelope to provide for conservation, as well as other methods of creating effective use of energy that are all sufficient to meet the performance goals established by the International Code Council. Though there have always been options, the options have evolved.

The prescriptive methods for energy code compliance (including the R-value alternative, U-factor computation, and UA alternative) were explained in the last post. These straightforward requirements outlined in the IRC are generally simpler methods than the compliance paths I’ll discuss here.

In this post, I will explain the performance path and the Energy Rating Index, or ERI, but only a basic overview. That’s because these methods require third-party evaluations and significantly more detail about the house’s design, location, orientation, equipment, airtightness, on-site energy generation, and more to be evaluated for energy code compliance. While they may require more detailed information and the work of third-party professionals, they also offer much more design flexibility and choice.

No matter which path you take to energy code compliance, the 2021 IRC includes a section of “additional efficiency package options.” Here designers and builders face another set of choices. I will discuss this section of the energy code in this issue as well.

Performance path and energy costs

When measuring the results of something, you need to have a metric for comparison. For my route to the retail store, the metric of success is whether I arrived. But when measuring the path of energy code compliance, there is…