Public Comment Opportunity: PHIUS+ Certification for Multifamily Performance Requirements (v2.0)

Chris McTaggart, PHIUS+ QA/QC Manager, wants your feedback…

Dear PHIUS/PHAUS community members,

Adoption of Passive House Institute US (PHIUS) PHIUS+ certification is growing rapidly. Of particular interest is the application of PHIUS+ certification for multifamily buildings. With several projects already certified or in the process of construction, and several more projects in the design phase, PHIUS expects certification of multifamily buildings to be one of the leading growth sectors for high performance, low-energy buildings moving forward.

With this in mind, PHIUS has created updated draft standards for certifying multifamily projects. These updated standards are intended to replace previous guidance offered by PHIUS for certifying multifamily projects. PHIUS is seeking review and comment from all vested stakeholders on these draft standards with the intent that a finalized version shall be released in Q2 2015.

The updated PHIUS+ Certification for Multifamily Performance Requirements (v2.0) contain several improvements to language regarding the specific performance modeling and testing expectations for certification of multifamily projects, including:

  • Modeled energy performance criteria
  • Infiltration testing requirements/protocol
  • HVAC testing/balancing requirements
  • Sampling protocol for dwelling unit-level testing/inspection
  • Additional onsite testing/inspection requirements

To create these draft guidelines, PHIUS solicited feedback from several constituents who are actively involved in the certification of high performance multifamily projects. These comments helped inform the standard development process, and the goal is that the most fundamental areas of need for clarification and formalization have been addressed.

Please take the time to read the attached PHIUS+ Certification for Multifamily Performance Requirements (v2.0) document below and make comments by June 8, 2015. Use the comments section below or email your input to


Chris McTaggart,  PHIUS+ QA/QC Manager

One thought on “Public Comment Opportunity: PHIUS+ Certification for Multifamily Performance Requirements (v2.0)

  1. 1. Note 8: The RESNET sampling protocols are not optimized for multifamily buildings. The RESNET Multifamily working group tried to tackle this issue, but could not come to a consensus within the timeframe of the working group. It would be beneficial to the program to develop a more multifamily specific approach to sampling.
    2. Note #8, Sub bullet #3: The standards should explicitly state that the Rater must repeat the test on 10% of the units that were measured by the third party professional, rather than just 10% of the units.
    3. Note #9, paragraph #4: This testing setup is described as Option #3 under the RESNET Guidelines for Multifamily Energy Ratings, Procedures for Multifamily Dwelling unit/Building Air Tightness Testing. It may be helpful to reference this section in the note.
    4. Note #9, individual zone “unguarded” testing: This setup is Option #1 in the RESNET Guidelines for Multifamily Energy Ratings, Procedures for Multifamily Dwelling unit/Building Air Tightness Testing.
    4a. The discount coefficients listed in the Multifamily Guidelines are very conservative because the results are used in the HERS energy model. For the purposes confirming an exterior air barrier tightness metric, the program may want to consider lower coefficients.
    5. Note #9, guarded testing: I would suggest deleting this option. In my experience guarded testing does not work and is not consistent. The RESNET Multifamily Guidelines does not provide an option for guarded testing. Also, this section is long and could lead to confusion.
    6. The unit compartmentalization target metric is listed under the “Performance Criteria” on page 1, but not listed again under Note 10. I would suggest it be repeated under Note 10. Also, I would urge PHIUS to consider a tighter compartmentalization metric. Passive House was a leader in advancing building air tightness and should do the same with unit compartmentalization. The Massachusetts’s utility incentive program has three tiers of rebates for unit compartmentalization in residential high-rise construction: 0.30, 0.225, and 0.135 cfm50/sq ft.
    7. Note #10, paragraph #3: The RSNET Multifamily Guidelines defines the surface area of a unit under Option #1 in the Procedures for Multifamily Dwelling unit/Building Air Tightness Testing section (1, c, i). I would suggest referencing this section. In the current language, it is unclear which unit is the “lower dwelling unit”.
    8. Note 11: It is interesting that the standard exclude testing ventilation ductwork. The ENERGY STAR High-rise program has a requirement under the prescriptive option for testing central exhaust ductwork – Central exhaust duct leakage not to exceed the sum of 2.5 CFM50 per register per shaft and 2.5 CFM50 per floor per shaft during testing.
    9. Note 11, Common Spaces: what is the value of the first bullet point? Unless the standard specifically calls out specific items for the Rater to check, the work under this bullet is carried by the code official. I have the same comment for the second bullet point. Unless we pull out specific, critical items for the Rater to look at, referring to the general SMCNA requirements is a token gesture that does not add value to the standards. I think there is value in calling out specific section of codes and standards that are not well enforced, but realize this adds complexity to the program.
    9a. Can you list the SMACNA HVAC Air Duct Leakage Test Manual tightness limits? I would guess few Raters have this manual
    10. Note 12, Common Spaces: The -3 Pa limit is for the zone the exhaust fan is serving, correct?
    11. Ventilation: I would strongly suggest there is explicit language that requires that make up air is directly supplied to each individual unit.

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