No "equivalency" stated for ASHRAE 90.1-2010 and Title 24-2008?

Drew, if I remember correctly the Title 24 equivalency values came shortly after the release of prior versions of LEED, not in advance of them... I have fond memories of the printed out equivalency chart taped into my Reference Guide. Unless you see language that explicitly forbids an equivalency (have I missed that?) I would hope that USGBC would do this as soon as possible, but given the extent of their work on this new system I'm not surprised that it isn't complete yet.

This is the type of issue/strategy that would best be covered by a Regional Credit, yes?

No, this is the path that most CA projects use to achieve EAc1. It's fundamental to our ability to efficiently (in terms of time and money) pursue LEED.

I understand that. Since we are required by Code to comply with T-24 and it is equal to or exceeds LEED, it seems redundant and complicated to me that we would continue to have to then translate T-24 results into LEED. (...so NOT an engineer, but I am a logical thinker!).

Peggy, the first comment above suggests that T-24 would not be permitted at all, and that separate ASHRAE 90.1 modeling would need to be done. I doubt that will be the case with 2013 but the language (usually a reference guide supplement thing) isn't in place yet. Prior versions of T-24 and 90.1 weren't closely equivalent enough to be treated the same for LEED.

Hi, Mara - Yes, in earlier versions of LEED, there was an equivalency letter or notice that was written after the fact. Usually, long after the fact, and hard to find for many teams. You will notice that in LEED 2009, it is written right in to the language for EA-p2 and EA-c1 at the conclusion of OPTION 1. "Projects in California may use Title 24-2005, Part 6 in place of ANSI/ASHRAE/IESNA Standard 90.1-2007 for Option 1."
hi, Peggy - FYI- Even when CA projects use the Title 24 energu use baseline, it must still be mapped into LEED project energy costs. This has always been true and is not the issue here.

Hello all -
I am the LEED subject matter expert for EA at USGBC, and I just wanted to clarify some of the discussion regarding Title-24 equivalency.

USGBC's information regarding stringency has always been provided by third party studies, such as those commissioned by the DOE. The USGBC does not itself conduct analysis of energy codes to determine relative stringency. The latest comparison provided on the DOE website between T24-2008 and 90.1-2007, indicated that T24 was more stringent that 90.1-2007, but no percentages for relative stringency were provided. (http://www.energycodes.gov/states/state_info.php?stateAB=CA).

DOE has determined that the quantitative analysis of the energy consumption of buildings built to Standard 90.1-2010, as compared with buildings built to Standards 90.1-2007, indicates national source energy savings of approximately 18.2%. (http://www.energycodes.gov/status/documents/Standard_901-2010_Final_Dete...). There have been no studies to suggest that the energy consumption of buildings built to California Title-24 2008, as compared with buildings built to Standard 90.1-2007, indicate average source energy savings up to that level.

Per the DOE website, each state is expected to submit certification that demonstrates that the provisions of the State's commercial building energy code regarding energy efficiency meet or exceed Standard 90.1–2010 and be filed by October 18, 2013 (http://www.energycodes.gov/status/determinations_com.stm). Once the state of California submits this study to the DOE and it is approved, it is probable that an alternative compliance path will be approved that will allow Title-24 2013 to be used in lieu of ASHRAE 90.1-2010 Appendix G to document compliance with EA prerequisite: Minimum Energy Performance and EA credit: Optimize Energy Performance.

The current software developers who offer Title-24 2008 compliance (and the software developers who are preparing software to offer Title-24 2013 compliance) have offered modules that include some ASHRAE 90.1-2007 Baseline modeling functionality. It is expected that the software developers will also update their software to include the capability to model ASHRAE 90.1-2010 Baseline modeling functionality. Therefore, during the interim period before Title-24 2013 takes effect (currently scheduled for January 2014), it is probable that there will be software available that will allow dual compliance to be documented with California Title-24 2008 and ASHRAE 90.1-2010.

I hope that clears things up a bit. It is not USGBC's intention to make compliance with the Energy prerequisite/credit overly difficult, but we also want to make sure that buildings are demonstrating comparable performance. Please feel free to follow up if there are more questions!

Great summary Amy! It is very hard for those who just see the result to understand the discussions and research that goes into these decisions. It is wonderful when USGBC shares the rational behind the decision.

Well, the reason Title 24 2008 was not given a percentage bump compared to ASHRAE 90.1-2004 was the the EA Technical Advisory Group deemed it was too hard to determine a percentage for the bump. The two codes would be equal with no zero bump.

In LEED v2 the USGBC provided an average bump for all Title 24 projects, regardless of type of project. Yes, some types of building would get a percentage bump they did not deserve, and others not enough of a bump.

For LEED v3 (was 2009?) it appears, from meeting minute notes that used to be provided to EA TAG corresponding members, that the EA TAG did not want to use a single percentage for all Title 24 2008 projects. A breakdown by building type seems to have been the desire, and it was deemed too hard to do.

For my LEED v3 projects the energy analyst do a both 2008 and 2005 analysis. Not the intent of saving analysis effort, but that is the best way to efficiently document a California Title 24 project and not leave points on the table.

On one of my projects, nearly 15% more on-site renewables would have been required if the model was not run under the prior code. The added cost was significant to the owner.