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. (NOTE: If you're unable to open the link, please right-click on the link and open it in a new window/tab or copy the link and paste it in a new window/tab.)

Energy Modeling

Guidelines for using SketchUp with WUFI® Passive V1.0 (May 2020)

Consider this a guide for beginners and experienced modelers alike. PHIUS' certification team (with a combined 16+ years of using WUFI Passive and SketchUp) put together this outline of helpful modeling tips, tricks and general information on getting the geometry of a building from SketchUp into WUFI Passive.



PHIUS+ 2018 Initial Cost Premium & Source Energy Savings Estimator (2020)

Estimates the capital cost premium and overall energy savings for a certifiable project, depending on building size and climate, relative to a 2009 code baseline.  Based on modeling for the 2018 standard-setting study.  Read the corresponding Tech Corner article for more information.

Site / Shading

Phius Blinds Calculator (2021)

This calculator accounts for occupant control over blinds in passive buildings.  Use this to convert datasheet information to WUFI Passive inputs.  For exterior and interior blinds.

Pathfinder Shading protocols and calculators (2012)

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



Window Installation (Psi-Install) Thermal Bridge Modeling Protocol v1.1 (Sept 2021)

This document outlines the process for modeling a window installation thermal bridge for Phius Certification in lieu of using the default window installation thermal bridge psi-values outlined in the Guidebook. 

Moisture Risk Analysis & Assessment using WUFI (July 2021)

This is a "performance criteria" protocol for assessing moisture risk in opaque assemblies. It is referred to as a compliance path in the Certification Guidebook, section B-1.  The current version mainly pertains to WUFI Pro.

Thermal Bridge Psi-Value Calculator V2.3 (April 2019)

This calculator can be used to determine psi-values for 2-D thermal bridges in combination with THERM.

PHIUS Window Comfort & Condensation Risk Assessment (Nov 2018)

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

ISO13788 ASHRAE calculator (March2020)

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.

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.

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.



E/HRV Outside (June 2021)

This calculator should be used to determine the 'Mechanical Room' temperature when a mechanical ventilation device is located outside of the thermal envelope. (eg. the roof)

HVI Winter Ratings for PHIUS+ Modeling (March 2021)

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

Intermittent Kitchen Exhaust Allowance Calculator v1 (September 2019)

Use this calculator to determine if a building aiming for PHIUS+ Certification is required to provide makeup air when using direct kitchen exhaust hoods. See corresponding Tech Corner article for details.

AHRI-listed ERV Performance Extrapolation Calculator

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

HRV/ERV Modeling Protocol (2015)

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


Hot Water Plumbing

Water Demand Calculator - IAPMO (April 2021)

Sample DHW Distribution Layouts+Entries for WUFI Passive (March 2019)

This document provides guidance on entering various DHW Distribution networks in the new DHW distribution pipe calculator in WUFI Passive.

Sanden CO2 Heat Pump Water Heater Climate-Adjusted EF Calculator V3.1 (Nov 2021)

Use this calculator to calculated a climate-adjusted Energy Factor for the Sanden CO2 Heat Pump Water Heater. This calculator is applicable for Gen 1 through Gen 4.

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

If using V3.2.0.1 of WUFI Passive or later, this calculator is built in to the model. This Excel-based tool should be used for residential projects certifying under the PHIUS+ 2018 pilot and final program.

PHIUS Solar DHW Fraction: BEopt Protocol

Protocol document for BEopt model setup used to determine the solar hot water coverage fraction on a project. This is an alternate path and not required.

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.


Space Conditioning

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.

HSPF De-Rating Calculator

The actual heating efficiency and seasonal performance of a "conventional" air-source heat pump may vary significantly from its rated heating season performance factor (HSPF). This is a procedure for determining an adjusted HSPF for your location for an air-source heat pump that uses only electric resistance heating as the auxillary heat source.


Renewable energy

PV Utilization Calculator v1.1 (Sept 2019)

Only applies to PHIUS+ Core projects. An estimate of coincident production-and-use of energy from renewable energy systems (such as PV) may be included in the Net 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. 

PHIUS Co-Generation Source Energy Factor Calculator

Calculation protocol for determining source energy factor of co-generation depending on operation priority: electrical demand or heating demand.


Interim Cooling demand

Interim Cooling demand protocol (April 2017)

Only applies to PHIUS+ 2015 projects. 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+ 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+ 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 (PHPP only)

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

Makeup Air Calculator (PHPP only)

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 (PHPP only)

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.


Additional Calculators

Walk-In Cooler Calculator V1.0 (February 2019)

This tool can be used to estimate energy use of a walk-in cooler or freezer if annual energy use data is not available.

Indoor Pool Calc

IndoorPoolCalc is an online spreadsheet for estimating the energy use due to evaporation and dehumidification for indoor swimming pools.


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