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PHIUS+ 2015: Passive Building Standard -- North America

Introduction to PHIUS+ 2015 Webinar Series

Zero Energy Ready Home -- US DOE



  • Based on U.S. DOE-funded research conducted in partnership with Building Science Corporation

  • Peer-reviewed by U.S. DOE and vetted through public comment

  • Qualifies for U.S. DOE Zero Energy Ready Home program

Each point on the map lists the following criteria:

Location of climate station (when available)
ASHRAE Climate Zone

Annual Heating Demand (kBTU/sf-iCFA.yr)
Annual Cooling Demand (kBTU/sf-iCFA.yr)
Peak Heating Load (BTU/
Peak Cooling Load (BTU/
Manual J Peak Heating Load (BTU/
Manual J Peak Cooling Load (BTU/

(iCFA= Interior Conditioned Floor Area)


Find your PHIUS+ 2015 climate specific performance targets

PHIUS + 2015 provides the climate-specific the sweet spot where aggressive energy and carbon reduction overlap with cost effectiveness. It accounts for a full range of variables including climate zone, source energy, and costs. 

Use the clickable map above to find the PHIUS+ 2015 performance metric for your climate. The map includes more than 1000 locations for which performance metrics were calculated based on TMY3 locations. Use the nearest point available. In some cases, when there are no nearby or similar locations mapped, it may be worthwhile to have a custom climate data set generated. 



How PHIUS+ 2015 was developed

In cooperation with Building Science Corporation under a U.S. DOE Building America Grant, the PHIUS Technical Committee has developed passive building standards that account for the broad range of climate conditions, market conditions, and other variables in North American climate zones. Here's what passive designers and builders need to know: 

  • The new standard—PHIUS+ 2015: Passive Building Standard - North America—will be used as criteria for PHIUS+ project certification and quality assurance beginning March 16, 2015. (To accommodate teams that have already embarked on certifying to the old standard, PHIUS will offer both certification paths until September 15, 2015. If you choose this path, a PHIUS+ Contract and certification payment must be submitted before this date.)
  • The three-year study yielded a formula that has been used to generate cost-optimized performance targets for more than 1,000 locations. These metrics represent the "sweet spot" where aggressive carbon and energy reduction overlap with cost-effectiveness. (Use the accompanying map to find performance targets in your area.) 
  • PHIUS+ 2015 provides a cost-effective platform for attaining Net Zero and Net Positive buildings, and certified projects also earn U.S. DOE Zero Energy Ready status. 
  • The research has been refined based on U.S. DOE peer review and public comment. The PHIUS Technical Committee will update the formula in three to five-year cycles to reflect changing economic, climate, and other variables. READ THE FINAL REPORT.
  • Read PHIUS Senior Scientist Graham Wright's blog for more on the development of the standard--you can comment and ask questions there, too. 

Additional recognition will be given to project designs that meet the regular requirements and also achieve any of the following performance goals:

  • Supply Air Heating and Cooling Sufficient
    The design is supply air heating and cooling sufficient per WUFI Passive / PHPP static calculation, with average design ventilation rate no more than 0.4 ACH. This is accomplished with low peak load design.

  • Source Net Zero
    Onsite renewable electricity generation above any that was already credited as coincident-production-and-use, counts toward source net zero with the same source energy multiplier for electricity, e.g. 3.16.   

PHAUS members: You can use the discussion board to post questions and continue the discussion of the new standard. (Posts are visible to the general public, but only members can log in to post questions and comments.)


What's New in PHIUS+ 2015

The adjusted passive building standard has the same high-level organization as before: adaptations have been made to all three main pillars of the passive building approach:

  1. The air-tightness requirement was reconsidered on the basis of avoiding moisture and mold risk, using dynamic hygrothermal simulations to be published elsewhere. The change is from a limit of 0.6 ACH50 to 0.05 CFM50 and 0.08 CFM75 per square foot of gross envelope area. This allows the airtightness requirement to scale appropriately based on building size. Before, a larger building that met the 0.6 ACH50 requirement could be in actuality up to seven times more leaky in terms of air leakage per unit area through the walls than a small single family home that tested the same by volume air change rate. The logic is that the moisture risk is correlated with the leakage rate per unit area of surface rather than the volume rate. This change of scaling aligns with commercial building code and US Army Corps of Engineers practice.

    Note: If the air tightness criterion is missed and the extra leakage can be proven to be due to a non-assembly-threatening leakage element such as a vent damper, certification staff (with approval of the Technical Committee) may allow that element to be taped off for the purpose of passing the air tightness criterion. The un-taped test result must be used for energy model.
  2. The source energy limit was reconsidered on the basis of the global CO2 emission budget. The following changes are proposed to make the scoring more fair and the calculation more accurate:
    • Change to a per-person limit rather than per square foot of floor area, at least for residential projects. This follows the fair share principle and removes the penalty for those who seek to reduce their carbon footprint by building small homes. 
    • Use the source energy factor for grid electricity of 3.16, in line with the U.S. national average according to NREL data and consistent with the value used in the IECC.
    • Increase the lighting and miscellaneous plug load defaults to 80% of the RESNET defaults to better reflect actual US usage, and make the internal heat gain calculations consistent with those assumptions.
    • To absorb the “shock” of the large increase in lighting and plug load defaults, temporarily relieve the source energy limit to 6200 kWh per person per year, tightening to 4200 again in the future as is practical.
    • Apply the limit to: the source energy calculated net of the estimated fraction of onsite PV or other renewable electricity generation that is used onsite as it is produced. This puts PV on a similar footing to how solar hot water is currently treated. (For a typical residence, most of the output of a 2 kW PV array would “count”, depending on the climate.)
  3. The space conditioning criteria were reconsidered on the basis of economic feasibility. The proposed change is to:
    • Shift to mandatory, climate-specific thresholds on specific annual heating and cooling demands and peak heating and cooling loads. These are set at cost optimal “sweet spot” slightly beyond BEopt’s cost optimum for project’s climate for increased resilience benefits. This ensures efficiency measures will have reasonable payback relative to operational energy savings. The peak load thresholds may be adjusted to ensure hourly comfort or the ability of the home to thermally coast through power outages. 
    • Establish the reference floor area iCFA, an inclusive simplified interior-dimension floor area. This eliminates incompatibilities and confusion created by the German-centric treated floor area (TFA). 

PHIUS+ 2015 presents three optimizing steps to Net Zero Source:

  1. The designer focuses first on reducing heating and cooling energy use by passive means (envelope improvement and including some mechanical devices) and is guided in doing so cost-competitively by meeting the pass/fail energy metrics set by climate as presented in this report.
  2. Next priority: reducing total energy demand by efficient equipment (and some renewables), guided in doing so by meeting the source energy criterion which assures meeting the fair share global carbon limit,
  3. Finally, achieving zero source by more renewable generation. This can be done at construction or, consistent with the 2030 Challenge, by 2030.  

Additional Notes

  • The heating and cooling criteria are determined from formulas based mainly on local climate factors including degree-days, outdoor design temperatures and design humidity, and annual solar radiation.
  • The formulas were developed from life-cycle cost optimization studies.  As a result the heating criteria also depend secondarily on energy prices (on a state-by-state average basis), because higher electricity prices justified more investment in heat-saving upgrades.
  • The energy price effect was not statistically significant for cooling, thus the cooling criteria depend only on climate factors. 
  • For now, there is an option to calculate the project peak loads in WUFI Passive/PHPP, or Manual J, and both options are listed for each location.


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