Help Make Passive Building Mainstream Support PHIUS

Calculators and Protocols

PHIUS and the high-performance building community are continually creating and updating tools that make passive building energy modeling more accurate and efficient. PHIUS has assembled a list of resources below; be sure to check back often for further updates and additions.


Site & envelope

PHIUS Window Comfort & Condensation Risk Assessment (Nov 2018)

The window comfort and condensation risk criterion applies to all projects, regardless of size.

Pathfinder Shading protocols and calculators (2012)

This .zip package includes full instructions for using the Pathfinder tool and calculating site shading inputs.

ISO13788 ASHRAE calculator (Nov 2017)

This calculator is used to determine the minimum critical interior surface temperature to avoid mold risk at a thermal bridge or corner. This value should be used when modeling this particular junction in THERM, and is based on both climate and interior humidity conditions.

ISO13788 Low Thermal Inertia Elements calculator Condensation - Risk Assessment (Dec 2016)

This calculator is used to determine the minimum window frame or glass U-value to avoid condensation risk. This value should be considered when selecting windows, and is based on both climate and interior humidity conditions. PHIUS+ certification requires using windows with no risk of condensation.

Insulation Global Warming Potential Calculator (2014)

This spreadsheet calculates the global warming potential (GWP) of insulation products. PHIUS recommends using this calculator to better understand a product’s GWP prior to making a final selection.


Ventilation & Mechanical

HRV/ERV Modeling Protocol (2015)

This whitepaper describes how to model ERVs and HRVs for passive building projects.

HVI Winter Ratings for PHIUS+ Modeling (September 2018)

This .xls table provides specifications for HVI-rated equipment, with values adjusted for PHIUS+ project modeling.

AHRI-listed ERV Performance Extrapolation Calculator

This calculator generates PHIUS+ modeling input values from available data for AHRI-listed commercial equipment.

Heat Pump Protocol and Calculator (2014)

This .zip package includes a comprehensive Tech Corner article on calculating the performance of heat pumps for passive building modeling, as well as two accompanying .xls calculators.

WaterSense Hot Water Distribution Volume Calculator

This Excel-based tool from the EPA’s WaterSense program can be used for calculating hot water volume in pipes, an aid to design teams in passing the required onsite QA/QC tests of certification.

PHIUS+ 2018 Hot Water Calculator V1.2 (Oct 2018)

This Excel-based tool should be used for residential projects certifying under the PHIUS+ 2018 pilot and final program.

Fastener Correction Thermal Bridge Calculator (Oct 2017)

This calculator generates an adjusted assembly R-value. It should be used when long screws, bolts or other fasteners penetrate insulation layers at multiple locations.


Renewable energy

PV Utilization Calculator v1.0 (May 2017)

An estimate of coincident production-and-use of energy from renewable energy systems (such as PV) may be included in the source energy calculation for PHIUS+ Certification. The amount of source energy that may be offset by a renewable electricity source depends on the utilization factor. This can be calculated by determining the coincident production-and-use fraction of the generation. If using PV without battery storage, use this calculator to determine your climate specific onsite utilization factor.


Interim Cooling demand

Interim Cooling demand protocol (April 2017)

This temporary protocol was developed specifically to provide an alternative calculation methodology and adjusted criteria for projects that are unable to meet their cooling demand limit, despite all reasonable efforts made to reduce this value. This design limitation typically arises for buildings with high occupant density.

Residential lighting adjustment calculator (Jun 2018)

This Excel-based tool calculates a seasonal adjustment to the lighting power as an interim measure for purposes of heating and cooling annual demand calculation for PHIUS+ 2015 project certification, and produces a corresponding hourly lighting profile with daily and seasonal variation, for use in dynamic modeling.



PHIUS+ 2015 Multifamily Calculator (April 2016)

This calculator should be used for PHIUS+ multifamily projects and follows the same protocol as the Multifamily Lighting and Miscellaneous Electric Loads (MEL) document.

PHIUS+ 2015 Multifamily Lighting and Miscellaneous Electric Loads (MEL) (April 2016)

PHIUS has developed protocol for calculating lighting and plug load energy in multifamily buildings for both residential and common spaces. Please refer to this protocol document for details and references. In general, the protocol follows the single-family method on a per unit basis, and includes additional information for common spaces and exterior spaces.

Multifamily Sample Project Input 

PHIUS has created this multifamily sample project showing both methods for the dwelling unit iCFA calculation listed in the protocol. Included here are two variations of the floor plan takeoffs and calculator showing the per floor method and per unit method. Download the sample floor plans and two variations of the calculator here.


General & Legacy support

IP-SI Conversion sheet

A handy inch-pound to metric calculator tailored for CPHCs.

Makeup Air Calculator

This stand-alone calculator is used to simulate the effect of exhaust appliances and associated make-up air systems. The results of these calculations are then input into the building's energy model.

PHIUS+ 2015 Single-Family Calculator

This calculator should be used for PHIUS+ 2015 single-family projects using PHPP. It includes the equivalent allowance for primary energy from the PHIUS+ allowance in kWh/person/yr to kBTU/ft2.yr, the air-tightness equivalence for 0.05 cfm/ft2.envelope to ACH50, as well as the lighting and plug load calculations for single-family residences.

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