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PHIUS+ 2015: Passive Building Standard -- North America

Introduction to PHIUS+ 2015 Webinar Series

Co-Requisites for PHIUS+ 2015 Certification

PHIUS+ 2015 certified projects earn U.S. DOE Zero Energy Ready Home (ZERH) status.



PHIUS+ 2015 certified projects earn U.S. EPA Indoor airPLUS label.


  • 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

  • Meets the requirements of the U.S. EPA Indoor airPLUS 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 Cooling Load (BTU/

(iCFA = Interior Conditioned Floor Area)

Find your PHIUS+ 2015 Climate-Specific Performance Targets

The PHIUS+ 2015 Passive Building Standard provides the climate-specific 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 performance metrics (calculated based on TMY3 locations) for more than 1,000 locations in North America. Use the nearest point available. In some cases, when there are no nearby or similar locations mapped, it may be necessary 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 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 PHIUS+ 2015: Passive Building Standard - North America was released on March 16, 2015 and is used as criteria for PHIUS+ project certification and Quality Assurance/Quality Control (QA/QC) measures. All projects pursuing PHIUS+ certification must certify to the PHIUS+ 2015 standard as of September 15, 2015.
  • The three-year study to develop PHIUS+ 2015 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 map shown above 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 Home (ZERH) status. 
  • PHIUS+ 2015 projects meet industry-leading standards for healthy indoor air quality, and certified projects also earn U.S. EPA Indoor airPLUS 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 2015 REPORT
    • Read the 2018 update report ($6 to $15 on TECHSTREET or email to get a legal copy sent to you)
  • Read PHIUS Senior Scientist Graham Wright's blog for more on the development of the standard. You can also comment and ask questions here as well. 

Additional recognition will be given to projects that meet the PHIUS+ 2015 certification 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 Forum to post questions and discuss the PHIUS+ 2015 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 using dynamic hygrothermal simulations with the aim of avoiding moisture and mold risk in wall assemblies. The airtightness requirements have been adjusted 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. Previously, a larger building that met the 0.6 ACH50 requirement could in actuality be 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 amount of volume air change rate. The logic is that 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 U.S. Army Corps of Engineers practice.

    Note: If a building does not pass the initial airtightness test and the extra leakage can be proven to be due to a non-assembly-threatening leakage element such as a vent damper, then PHIUS certification staff (with approval of the Technical Committee) may allow that element to be taped off for the purpose of passing the airtightness criterion. The un-taped test result must be used for the energy model.
  2. The source energy limit was reconsidered on the basis of the global CO2 emission budget. The following changes have been implemented to make the scoring more fair and the calculation more accurate:
    • Source energy limit now based on 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. 
    • Source energy factor for grid electricity is 3.16, in line with the U.S. national average according to NREL data and consistent with the value used in the IECC.
    • Lighting and miscellaneous plug load defaults increased to 80% of the RESNET defaults to better reflect actual U.S. 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, the source energy limit was relieved to 6200 kWh per person per year, and can be tightened back to 4200 kWh in the future as is practical.
    • Source energy limit is applied to the 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 instance, in 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 following changes were implemented:
    • Shift to mandatory, climate-specific thresholds on specific annual heating and cooling demands and peak heating and cooling loads. These are set at a cost optimal “sweet spot” slightly beyond BEopt’s cost optimum for the project’s climate in order to provide 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. 
    • Establishment of 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 achieving Source Net Zero:

  1. The designer focuses first on reducing heating and cooling energy use by passive means with envelope improvement and including some mechanical devices. In so doing they are guided by cost-competitively meeting the pass/fail energy metrics per the given climate.
  2. Next, the designer must reduce the total energy demand of the project by selecting efficient equipment and adding some renewables. In so doing, they are guided to meet the source energy criterion which assures meeting the fair share global carbon limit.
  3. The project must finally achieve source zero with more renewable generation. This can be done at the time of 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 lifecycle 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 the option to calculate the peak cooling load in WUFI Passive/PHPP or Manual J, and both peak cooling load options are listed for each location.

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