June 26, 2018

PHIUS+ 2018: What’s New?

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In 2014, under a grant from the U.S. Department of Energy and in partnership with Building Science Corporation, the Passive House Institute US (PHIUS) set out to develop the first and only climate-specific passive building standard. The resulting PHIUS+ 2015 standard accounted not only for substantial differences between climate zones, but also for market and other variables, retaining rigorous conservation goals while making passive building more rational and cost effective. PHIUS+ 2015 helped dramatically accelerate adoption.

The PHIUS+ 2018 Pilot is now open for use. PHIUS developed the draft 2018 PHIUS+ Standard to more accurately reflect the nuance of project types and size across climate zones and the relationship between envelope and floor area. PHIUS+ 2018 is the first updated revision, and PHIUS will phase it in through 2018, eventually replacing PHIUS+ 2015. PHIUS recognized that technologies, market conditions, carbon reduction goals and even climates could change over time. Consequently, PHIUS committed to revising the standard to reflect such changes.

What’s new in PHIUS+ 2018?

  • Under the pilot release of PHIUS+ 2018, the space-conditioning targets are less granular in terms of climate. They are instead set zone by zone, using the 17-climate-zone system referenced in the International Energy Conservation Code (IECC).
  • Because size and occupant density influence the optimal path to a low-energy building, the new space-conditioning criteria implement adjustments for a range of building sizes and occupant densities.
  • In PHIUS+ 2018, the source energy criterion is tightened, with a view toward zero, but there are more options for meeting it. There is no cap on total source energy use as long as the predicted annual net source energy use meets the new (lower) target. This “net” source energy use is the remaining source energy use after what is offset by qualified renewable energy measures, both on-site and off-site.

The rollout timeline for PHIUS+ 2018 is:

  • Pilot Phase | open until September 2018
  • Full release of PHIUS+ 2018 | September 2018
  • Certify under either PHIUS+ 2015 or PHIUS+ 2018 | September 2018 – March 2019
  • PHIUS+ 2015 no longer accepted; projects must certify under PHIUS+ 2018 | March 2019

The pilot program of PHIUS+ 2018 is intended to assess how the new performance requirements fit for a variety of projects. The climate and occupant sensitivity may be revisited and refined for the final program.

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