Texas FAQ Sheet
With such an active and evolving energy rating landscape in Texas, a few common questions and concerns have arisen to our attention that we want to address. Below you’ll find an FAQ that we hope will provide some clarity.
FAQs
Will Ekotrope release a code compliance path and report to support Texas HB 3215?
Yes! We plan to release this within a month.
Why is the HERS Index different from the ERI in many cases?
The ERI is a generic term that can be used in many ways and refer to various versions and vintages of ANSI 301. The HERS Index is a special RESNET-administered version of the ERI that stays up to date with the latest version of ANSI 301 and includes requirements for quality assurance, training, certification, etc. There are 3 reasons that an ERI might be different from a HERS Index:
The organization adopting the ERI (such as ICC or a state government) has stipulated some change to the ERI such that it does not strictly conform to ANSI 301. This is the case with the 2018 IECC ERI Index, because the 2018 IECC modified the ventilation rate of the reference home in such a way that the infiltration was reduced to zero in the IECC ERI reference home, making 2018 IECC ERI scores much higher than HERS Index scores across the board.
The adopting organization specifies a date to freeze the ERI, whereas the HERS Index and ANSI 301 continue to improve over time. For example, when the 2018 IECC was published, the ERI score used a version of ANSI 301-2014 that did not include the addenda enabling credit for LED lighting. Thus, when ANSI 301-2014 (and therefore the HERS Index) adopted further addenda and then updated to ANSI 301-2019, the up-to-date ERI and the HERS Index became different from the 2018 IECC frozen-in-time ERI.
RESNET Standards make modifications to ANSI 301. This is typically a small, temporary effect - much less significant than the first two items. While the RESNET Standards do include some minor modifications to ANSI 301, they typically have a very small (or zero) impact on the HERS Index and they are usually temporary addenda to more quickly incorporate changes that are already queued up for ANSI 301. The overall divergence between ANSI 301 and the RESNET HERS Index is extremely minor. The temporary allowance of COVID default testing values was one example of this.
Is Texas HB 3215 based on a HERS Index, an ERI, or something else?
The Texas HB 3215 language states compliance will be based on “A home energy rating system index utilizing Standard 301 of the American National Standard for the Calculation and Labeling of the Energy Performance of Dwelling and Sleeping Units using an Energy Rating Index, commonly cited as ANSI/RESNET/ICC 301, as it existed on January 1, 2021.”
This has caused some confusion around whether the bill intends to specify the HERS® Index or a frozen-in-time version of ANSI 301. State Representative Charlie Geren (author of HB 3215) recently addressed this confusion in an official letter dated April 5, 2022, stating that compliance should be based on the “home energy rating system index” commonly referred to - as of January 1, 2021 - as ANSI/RESNET/ICC 301-2019 or a HERS® Index…”
This statement confirms that it is proper to use the HERS® Index as a path to determine compliance with HB 3215.
Texas HB 3215 requires that the thermal envelope efficiency and SHGC be equal to or greater than the levels in Table R402.1.2 or Table R402.1.4 of the 2018 IECC. Does a Total UA Alternative calculation satisfy this requirement?
Yes, a Total UA Alternative calculation satisfies this requirement. State Representative Charlie Geren confirmed this in his letter of intent, stating: “homes that meet the calculation criteria of R402.1.5 (Total UA Alternative) of the 2018 International Energy Conservation Code shall meet the intent of the prerequisite prescriptive envelope references in this bill.”
Why does the thickness of a layer of brick in the Ekotrope assembly calculator matter for code compliance?
In the IECC performance and prescriptive paths, there is a special allowance for “Mass Walls” that provides a higher (more lenient) U Factor requirement and a higher reference home U Factor. Thus, Ekotrope does its best to determine whether each assembly is a “Mass Wall.” The IECC stipulates that a Mass Wall must have one of the following:
Concrete block, concrete, insulated concrete forms (ICF), masonry cavity, brick but not brick veneer, adobe, compressed earth block, rammed earth, solid timber or solid logs.
Heat capacity >= 6 Btu/ft2 F
Because of the specific exclusion of brick veneer, Ekotrope requires that brick layers be 3 inches or thicker to qualify a wall as a high mass wall. Because of this logic, a home with a 2.9” brick layer may see significantly different code compliance results as a home with a 3” brick layer, because the latter is treated as a high mass assembly. A brick veneer is typically thinner than 3”.
Do software tools really have different definitions of heating and cooling loads? And does this impact the HERS Index or ERI?
In early RESNET Standards and ANSI 301 Standards, the definition of building loads (i.e. heating and cooling loads) was not particularly thorough, leading some to question how loads should be calculated by software tools. However, all RESNET Accredited HERS Rating software tools today use the same definition of building loads. This is not a source of confusion or inconsistency between software tools.
Last updated May 23, 2022.