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PHIUS+ 2018: Getting to Zero

PHIUS+ 2018: Pilot & Target Setting Documentation

PHAUS Member Forum - Informal Discussion of PHIUS+2018

PHIUS+ 2018 Pilot Energy Modeling Protocol

PHIUS+ 2018 Roll-Out

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

 

In 2014, under a grant from the U.S. Department of Energy (DOE), and in partnership with Building Science Corporation, 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.

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. PHIUS+ 2018 is the first updated revision, and it will be phased in through 2018 and will eventually replace PHIUS+ 2015. This update focuses on adding more nuance for different building types, and supporting an overall transition to renewable energy.

What’s the same

PHIUS+ 2018 remains a pass/fail passive building standard, serving as an update to replace PHIUS+ 2015. It remains a “performance-based” energy standard that includes prescriptive quality assurance requirements.

The performance standard relies on three pillars:

  • Limits on heating/cooling loads (both peak and annual)
  • Limit on overall source energy use
  • Air-tightness and other prescriptive quality assurance requirements

PHIUS+ 2015 recognized that there are diminishing returns on investment in energy-conserving measures, and an optimum level in a life-cycle cost sense.. Climate plays a large role in determining where that point is. For PHIUS+ 2015, researchers studied optimization in 110 cities, and developed interpolation formulas to set heating and cooling (space-conditioning) energy targets for 1000+ cities across the US and Canada. The same criteria applied to buildings of all sizes.

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).

New in PHIUS+ 2018

Because size and occupant density influence the optimal path to a low energy building, the new space-conditioning criteria implement continuous adjustments for a range of different building sizes and occupant densities.


Select your ASHRAE Climate Zone, Floor Area (iCFA), and Total Occupancy to estimate your project's space conditioning target criteria. Exact certification criteria can be determined using the project's envelope to floor area ratio and square feet per person calculator found in the 'PHIUS+ 2018 Pilot Phase' document linked at the top of this page. Estimates from this calculator should closely reflect 'exact' targets.
 

What’s the same

The overall energy limit under PHIUS+ 2018 is based on source energy, rather than site energy, as it is a better proxy for resource consumption and emissions associated with the site’s energy use. The optional add-on badge for Source Net Zero, whereby all of the building’s energy use is offset by on-site renewable generation, remains available.  

 

New in PHIUS+ 2018

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, on-site and off-site.

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.

 

Passive House Alliance US Members: An online discussion forum is available to all members.

  • The forum discussion will be visible to the general public, but only PHAUS members can make comments.
  • Comments on the discussion forum are not guaranteed to be reviewed by the Technical Committee.

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