For full details, please refer to Phius’ formal announcement here: DOE Efficient New Homes Requirement Paused for Multifamily Phius Projects
At RDH Building Science, we believe that high-performance building standards must offer consistency and a reliable roadmap for delivery. Recently, a significant technical challenge emerged regarding the alignment between Phius and the U.S. DOE’s Efficient New Homes (ENH) Version 2 program, which was adopted in 2025. As a required corequisite for Phius certification, along with Energy Star and EPA Indoor airPLUS, the ENH program represents a critical hurdle. This recent shift has specifically impacted the market-rate multifamily sector, where “moving goalposts” in federal requirements have complicated the path to certification.
The Challenge: The Modeling Disconnect
The core of the issue lies in a misalignment between two different performance-based modeling paths. Many current projects have achieved Phius-compliant designs through WUFI Passive modeling, yet these same designs are struggling to meet the ERI targets required by the DOE ENH v2 corequisite.
This friction is particularly acute for market-rate multifamily developments utilizing decentralized mechanical schemes. Electric resistance domestic hot water (DHW) has been a standard, cost-effective solution in the recent past, which can comply with Phius performance requirements if balanced among other key levers in the WUFI Passive modeling. However, this same strategy often triggers a compliance failure under the ERI modeling used for ENH v2. This is largely because the two systems evaluate performance through different lenses: Phius WUFI Passive modeling takes a “whole building” approach to energy balance, whereas ERI modeling evaluates the energy use of individual dwelling units within the building.
While heat pump water heaters can remedy the ERI modeling compliance issue, it is not a universal solution that fits every project, or every owner’s specific operational requirements and preferences. Because ERI modeling is traditionally performed at the end of the design phase, many teams do not realize a project is at risk until the design is complete and contractor pricing is locked in. At that late stage, the design modifications required to reach ERI path compliance for the ENH program can be catastrophic to a project’s budget and overall viability.
Advocacy Through Technical Insight
Recognizing this as a systemic threat to the housing pipeline, RDH collaborated with Alexander Gard-Murray and the team at PHMass to advocate for certification certainty.
Because our team handles both the CPHC and Verifier scopes in-house, we have been able to witness these modeling conflicts as they consistently emerge across market-rate multifamily projects. Historically, since the original Phius 2015 standard, a Phius-compliant design would seamlessly satisfy the requirements for all corequisite programs without issue. ERI modeling remains a useful tool in creating a data point of a project’s performance that can be compared to non-Phius projects nationally.
However, we have encountered a technical inversion where the secondary ENH benchmarks began to exert more influence over the design than the primary Phius performance targets. We saw the ENH corequisite beginning to “wag the dog,” forcing design decisions that prioritized ERI compliance over the whole-building energy balance established by the Phius WUFI Passive model.
The Result: An Indefinite Suspension of the DOE ENH MF v2 Certification Requirement
Following industry feedback, Phius has announced an indefinite suspension of the requirement to earn DOE Efficient New Homes Multifamily Version 2 certification as a co-requisite for eligible multifamily projects. This suspension applies to multifamily, dormitory, residence hall, supportive housing, senior housing, and the residential portions of mixed-use projects that meet Phius eligibility criteria; single-family and townhouse projects remain subject to the DOE Efficient New Homes certification requirement. Importantly, Phius will continue to require the majority of DOE Efficient New Homes checklist items; the suspension applies only to proof of certification within the Phius process, not to the underlying quality-assurance measures. Phius has also indicated it is working with DOE on a longer-term alignment, with a more permanent resolution anticipated in the Phius 2027 standard update.
While long-term alignment between these programs is still being negotiated, this immediate stay allows the industry to maintain its momentum toward better building performance without sacrificing project feasibility.
Let’s Connect
Successfully navigating the shifting landscape of certification requirements requires a proactive approach to both design and verification.
If you have questions about how these changes impact your current design pipeline, or if you would like to discuss the nuances of Phius and DOE corequisite programs, please contact us.
Credit and thanks to Andrew Steingiser, Michael Browne, and the rest of the RDH team.
We also extend a special thanks to Phius for their prompt response and continued efforts to address this issue and support project teams navigating these evolving requirements.