Unlocking Secret Doors to LEED: New Interpretations and More

This quarter’s LEED Addenda for v4 and v4.1 were released by the U.S. Green Building Council (USGBC) on July 26, 2024.

The addenda deliver four new LEED Interpretations (10511–10514) for residential projects and update one (10480) for California Title 24 2022 equivalency. Updates and corrections were also made to various LEED v4.1 rating systems and beta guides. New calculators and resources were published, and several other tools received updates. 

Healthier Homes + the Energy Rating Index

USGBC issued four new rulings for v4 and v4.1 residential and mixed-use BD+C projects. 

Radon requirements in mixed-use buildings

Radon rules for mixed-use buildings are the same as for residential buildings—with one exception, according to ID# 10511.

When figuring out how many vertical vent pipes you need, you can ignore any slab area that’s purely nonresidential, meaning it has no residential space above or below it. But that’s it: no other exemptions. Just like in fully residential buildings, radon-resistant construction techniques are a must unless there’s a garage under the whole building. 

No paper in the bathtub

Got wallboard around your bathtub or shower? Keep it mold-free and sturdy! There are two ways to reduce the risk of it becoming fungus food:

• Install a non-paper-faced backer.
• Install a paper-faced product that meets the ASTM D 3273 standard.

This applies to every part of the assembly, from floor to ceiling, behind your tub or shower. And the same requirement holds for fiberglass enclosures, whether they are single units or separate from the bathtub.

Navigating newer energy codes

LEED for Homes is tied to the HERS rating, but the International Energy Code has adopted the slightly different Energy Rating Index (ERI).

Different, yes, but not different enough to matter for LEED, according to USGBC. ID# 10513 makes it official.

To opt for ERI instead of HERS, project teams must use approved software that can automatically determine the Energy Star target and ERI for each rated home by following the target procedure specified in the new interpretation. 

Greywater Magic Turning Flushes into Zeroes

When using greywater and rainwater in your project under the Total Water Use credit, here’s the scoop according to ID#10514: manually add greywater as a line item in the Water Reduction Calculator for outdoor use. Indoors, treat greywater as a negative flush rate. So, if you have 1.2 gallons per flush (gpf) toilets fed by greywater, log one as 1.2 gpf and another as -1.2 gpf to zero out the usage. Just remember, you can’t go below zero!

Additional Energy Points Possible for Title 24 Projects

Is your project located in California? Well, good news! Thanks to an update to ID# 10480, you can now document additional energy-performance improvements under Optimize Energy Performance or (for residential projects) Annual Energy Use. This includes Title 24 Building Energy Efficiency Standards from 2016, 2019, 2022, or later for both residential and nonresidential buildings.

To follow this path, project teams must use whole-building simulation, and the Title 24 model must: 

• Include all process energy consumption
• Model all enclosed building spaces, even if space types are not regulated by Title 24
• Use total proposed design and total standard design, including all receptacle, process, and other lighting-energy consumption. 
• Subtract photovoltaics and battery contributions from total proposed design but not from total standard design, to account for additional LEED savings. 

There are a couple of other requirements for mixed-use and core-and-shell projects:

• For mixed use, use a weighted average of Additional Percent Savings based on the gross floor area of each building type. 
• For projects pursuing Core & Shell certification, unfinished spaces not submitted in under CS must still use the CS values for energy savings to get points.

Additional details on percent savings for Title 24 are available in Table 1 of the revised interpretation. 

Popular IAQ Pilot Now Available for ID+C 

The pilot alternative compliance path (ACP) for the EQ prereq Minimum Indoor Air Quality Performance was updated to make it applicable to interior-only projects.

This ACP allows teams, among other things, to rely on air cleaners rather than purely on outdoor air to achieve high IAQ—an approach that is gaining momentum across the industry in the wake of the COVID-19 pandemic.

New Resources for District Energy, LEED for Cities, and More

USGBC is rolling out new tools for projects using district energy, complying with the updated energy-performance requirements for v4, and pursuing LEED for Communities or LEED for Cities.

• The Large-Scale District Energy Calculator provides a streamlined way to document district energy for EA credits.
• A new version of the LEED Minimum Energy Performance Calculator (applicable under the 2024 update only) was published to align with recent updates to the prerequisite.
• Forms for LEED for Cities and LEED for Communities are now published under the Resources tab.

New Calculators for Transit, Renewable Energy, and Title 24 Energy Performance

• Modifications to Option 2 of the LEED v4 O+M LT credit Alternative Transportation are now reflected in the Alternative Transportation Calculator. 
• New alternative compliance paths are now accounted for in the LEED v4.1 Renewable Energy Calculator. 
• The LEED Interpretation 10480 Title 24 Calculator now aligns with the Title 24 Interpretation discussed above.