HumidAir Excel Add-In

HumidAir for Excel based on real gas formulation (32 bit & 64 bit)

For Excel 2007 / 2010 (32 bit & 64 bit) / 2013 (32 bit & 64 bit) / 2016 (32 bit & 64 bit) / 2019 (32 bit & 64 bit) / 365 desktop (32 bit & 64 bit)

HumidAir Excel Add-In

HumidAir App   BONUS

Each license for the HumidAir Excel Add-In also inludes a free license for the HumidAir Desktop Application ($150 value).

The HumidAir Desktop Application allows calculation of psychrometric properties and the saving and printing of calculated properties.

This offer cannot be combined with any other offer that we might have.

About Humid Air Excel Add-In

The psychrometrics Excel Add-In library calculates 35 thermodynamic properties of humid (moist) air in SI and English units.

It allows 21 different combinations of input variables to be used for calculations.

Input variables that can be used are:

  •  1 Pressure
  •  2 Dry bulb temperature
  •  3 Wet bulb temperature
  •  4 Dew bulb temperature
  •  5 Relative humidity
  •  6 Humidity ratio
  •  7 Enthalpy
  •  8 Entropy
  •  9 Volume

The library is fully integrated in Excel, and available functions can be used in the same way as any other Excel function.

Main features of the library:
  • Professional quality, industrial strength software, proven in real world applications
  • Based on the most accurate formulation (Hyland and Wexler)
  • License includes 32 bit and 64 bit version of the library
  • Developed in C++ for maximum speed, thoroughly tested for accuracy
  • Create User Defined Functions (UDF) which use HumidAir functions
  • Call HumidAir functions from VBA (samples are included in the release version)
  • Easy to install and easy to use
  • One year free technical support

The following figure shows a sample spreadsheet included in the download package.

HumidAir Excel Add-In

HumidAir Excel Add-In - Sample calculations in Excel

Used Formulations

The psychrometrics library uses the most accurate formulations of thermodynamic properties of moist air.

Formulations are based on the study performed by Hyland and Wexler, and approved by ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers) as documented in the 1997 ASHRAE Handbook "Fundamentals". They presented the equation of state in:

  • Formulations for the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K, W. Hyland and A.Wexler, ASHRAE Transactions, 89(2A) 500-519, 1983.
  • Formulations for the thermodynamic properties of dry air from 173.15 K to 473.15 K, and of saturated moist air from 173.15 K to 372.15 K, at pressures to 5 MPa, R. W. Hyland and A. Wexler, ASHRAE Transactions, 89(2A) 520-535, 1983.

System Requirements

Operating system Windows 7 / Windows 8 / Windows 8.1 / Windows 10.

Excel 2007 / 2010 (32 bit & 64 bit) / 2013 (32 bit & 64 bit) / 2016 (32 bit & 64 bit) / 2019 (32 bit & 64 bit) / 365 desktop (32 bit & 64 bit).

User privileges
Installation and use of the library requires standard user privileges or better.

Psychrometric Functions

Compact Design   IMPORTANT

This software is designed to be easy to use. There are 42 functions (21 for SI units and 21 for English/Imperial units). Each function can calculate 35 properties. As a concesquence the library covers 21*2*35 = 1470 combinations.

Instead of creating hundreds of functions, the library provides access to psychrometric properties covering 1470 combinations in only 42 functions. This significatly reduces the learning curve and simplifies the use of the library.

The following functions are available in the HumidAir Excel Add-In:

Function List in SI and E units - HumidAir Excel Add-In v3.1
  # Function Name
 SI Units
 Function Name
 English Units
 Argument 1
 Argument 2
 Argument 3
 Argument 4
  1 HumidairTdbRHPsi HumidairTdbRHPe Tdb RH P propertyID
  2 HumidairTdbTwbPsi HumidairTdbTwbPe Tdb Twb P propertyID
  3 HumidairTdbTdpPsi HumidairTdbTdpPe Tdb Tdp P propertyID
  4 HumidairTdbWPsi HumidairTdbWPe Tdb W P propertyID
  5 HumidairTdbHPsi HumidairTdbHPe Tdb H P propertyID
  6 HumidairTdbSPsi HumidairTdbSPe Tdb S P propertyID
  7 HumidairTdbVPsi HumidairTdbVPe Tdb V P propertyID
  8 HumidairTwbRHPsi HumidairTwbRHPe Twb RH P propertyID
  9 HumidairTwbTdpPsi HumidairTwbTdpPe Twb Tdp P propertyID
 10 HumidairTwbWPsi HumidairTwbWPe Twb W P propertyID
 11 HumidairTwbHPsi HumidairTwbHPe Twb H P propertyID
 12 HumidairTwbSPsi HumidairTwbSPe Twb S P propertyID
 13 HumidairTwbVPsi HumidairTwbVPe Twb V P propertyID
 14 HumidairTdpRHPsi HumidairTdpRHPe Tdp RH P propertyID
 15 HumidairRHWPsi HumidairRHWPe RH W P propertyID
 16 HumidairRHHPsi HumidairRHHPe RH H P propertyID
 17 HumidairRHSPsi HumidairRHSPe RH S P propertyID
 18 HumidairRHVPsi HumidairRHVPe RH V P propertyID
 19 HumidairWHPsi HumidairWHPe W H P propertyID
 20 HumidairWSPsi HumidairWSPe W S P propertyID
 21 HumidairWVPsi HumidairWVPe W V P propertyID

  • The fourth argument "propertyID" specifies which property to calculate, see the "Psychrometric Properties" table below.
  • Since "propertyID" is string type it must be enclosed in quotes, see an example below.

To download a list of all available functions in the PDF format, switch to the "Downloads" tab and go to a section "Quick reference documents".

Functions Notation

In order to easily identify functions to be used, function names are formated using the following rules:

  • All function names start with HumidAir
  • Next follow letters denoting the first, the second and the third input parameter of a function, shown in bold in the function list table above
  • Function names ending with si mark functions to be used for calculations in SI Units
  • Function names ending with e mark functions to be used for calculations in English Units


To calculate enthalpy of moist air in SI Units based on dry bulb temperature, relative humidity and pressure as input, use the following:
  •  1 Tdb = 15.5 °C
  •  2 RH = 95 %
  •  3 P = 1.2 bar
  •  4 the fourth argument is a string which specifies the property to be calculated by suppling the appropriate propertyID (see Psychrometric Properties table below)
Based on the above provided description, the following should be entered into a cell or the formula bar:
=HumidAirTdbRHPsi(Tdb, RH, P, "Hm")

Psychrometric Properties

The following thermodynamic and transport properties can be calculated with HumidAir Excel Add-In:

Calculable properties in SI or E units - HumidAir Excel Add-In v3.1
  # Property Name Property ID SI Units English Units
  1 Dry bulb temperature Tdb °C °F
  2 Wet bulb temperature Twb °C °F
  3 Dew point temperature Tdp °C °F
  4 Pressure P bar psi
  5 Saturation water pressure Ps bar psi
  6 Saturation pressure at wet bulb temperature Pwb bar psi
  7 Saturation pressure at dew point temperature Pdp bar psi
  8 Mole fraction of water Xw - -
  9 Mole fraction of air Xa - -
 10 Weight fraction of water Ww - -
 11 Weight fraction of air Wa - -
 12 Humidity ratio W (kg moisture)/(kg dry air) (lb moisture)/(lb dry air)
 13 Saturation humidity ratio Ws (kg moisture)/(kg dry air) (lb moisture)/(lb dry air)
 14 Degree of saturation DS - -
 15 Relative humidity RH - -
 16 Specific volume of dry air Va m³/(kg dry air) ft³/(lb dry air)
 17 Specific volume of saturated ice Vi m³/kg ft³/lb
 18 Specific volume of saturated water Vw m³/kg ft³/lb
 19 Specific volume of saturated vapor Vv m³/kg ft³/lb
 20 Specific volume of moist air Vm m³/(kg dry air) ft³/(lb dry air)
 21 Specific density of dry air Da (kg dry air)/m³ (lb dry air)/ft³
 22 Specific density of saturated ice Di kg/m³ lb/ft³
 23 Specific density of saturated water Dw kg/m³ lb/ft³
 24 Specific density of saturated vapor Dv kg/m³ lb/ft³
 25 Specific density of moist air Dm (kg dry air)/m³ (lb dry air)/ft³
 26 Specific enthalpy of dry air Ha kJ/(kg dry air) Btu/(lb dry air)
 27 Specific enthalpy of saturated ice Hi kJ/kg Btu/lb
 28 Specific enthalpy of saturated water Hw kJ/kg Btu/lb
 29 Specific enthalpy of saturated vapor Hv kJ/kg Btu/lb
 30 Specific enthalpy of moist air Hm kJ/(kg dry air) Btu/(lb dry air)
 31 Specific entropy of dry air Sa kJ/(kg dry air•K) Btu/(lb dry air•°F)
 32 Specific entropy of saturated ice Si kJ/(kg•K) Btu/(lb•°F)
 33 Specific entropy of saturated water Sw kJ/(kg•K) Btu/(lb•°F)
 34 Specific entropy of saturated vapor Sv kJ/(kg•K) Btu/(lb•°F)
 35 Specific entropy of moist air Sm kJ/(kg dry air•K) Btu/(lb dry air•°F)

To download a list of all available properties in the PDF format, switch to the "Downloads" tab and go to a section "Quick reference documents".

Range of Validity

The entire set of equations used by the Humid Air application, is defined by the following temperature and pressure range:

  • 173.15 K <= T < = 473.15 K
  • 0.000001 MPa <= P < = 5 MPa

Moist Air Properties Limits

The upper limit of the absolute pressure is set at 5 MPa, and the temperature is restricted to the range -100 to 200°C. However, for any given absolute pressure, the highest temperature cannot exceed that temperature at which the saturation vapor pressure equals the absolute pressure.

In other words, moist air properties are valid for any dry-bulb temperatures below or equal to the saturation temperature of water at the same given absolute pressure, above that limit saturated moist air cannot exist.

Reference Point

In the used formulations for calculation of thermodynamic properties of moist air, the reference state (zero enthalpy) is set at 0 °C. On some psychrometric charts (especially in the US) the reference state (zero enthalpy) is set at 0 °F.

As a consequence, enthalpy and entropy values calculated by the library will be shifted on these charts for the difference between the reference points.

Since for any process calculation only enthalpy difference (in and out of a process) is important, the reference point doesn't really matter.

If you want to reproduce enthalpy values from such charts, you should find the enthalpy difference for one point (doesn't matter which one), and then add that value for all calculated enthalpies. The same applies for entropy values.


The following screenshots demonstrate how to use the library, it's a 4 step process.

1.(a) Start Excel and press the "Insert Function" toolbar button.

Insert Function toolbar button

1.(b) Alternatively, start Excel and press the "Insert Function" menu item.

Insert Function menu item

2. Select a HumidAir library (SI or English units).

Select HumidAir library

3. Select a function and press the OK button.

Select Function - HumidAir library

4. Enter input parameters and press the OK button.

Calculate HumidAir properties

NOTE: You don't have to put quotes around the property ID, they are inserted automatically.

That's it, the result will be displayed in the selected cell.


The setup program will automatically install the library in Excel.

To install the library successfully you must have at least standard user privileges on your computer.


The built-in ZIP support on Windows 10 is buggy and sometimes cannot open a valid (not empty) zip file.

Use 7-zip (free and open source) or some other reliable program for zip file processing.

HumidAir Excel Add-In library

For Excel 2007 / 2010 (32 bit) / 2013 (32 bit) / 2016 (32 bit) / 2019 (32 bit) / 365 desktop (32 bit)

- Download HumidAir Excel Add-In version (3.1) - demo (32 bit)

HumidAir Excel Add-In library

For Excel 2010 (64 bit) / 2013 (64 bit) / 2016 (64 bit) / 2019 (64 bit) / 365 desktop (64 bit)

- Download HumidAir Excel Add-In version (3.1) - demo (64 bit)


For the demo version input pressure is fixed to:

  • p = 8 bar in SI Units and
  • p = 116.029 psi in English Units.

These values will be used for calculation regardless of your input value for pressure.

To further evaluate the library (at pressure p = 1 bar or p = 14.5 psi), go to our Psychrometric Calculator web application, it uses the same calculation engine.

Quick reference documents

- List of available properties in the HumidAir Excel Add-In library

- List of available functions in HumidAir Excel Add-In library

Price info

Prices subject to change without notice!

  • A license includes 32 bit and 64 bit versions of the HumidAir Excel Add-In library
  • A license also includes the HumidAir Desktop Application (calculate properties, save calculations, printing...)

HumidAir Excel Add-In version 3.1
1-4 licensesUSD 199.95 per copy
5-20 licensesUSD 174.95 per copy
21 > licensesUSD 149.95 per copy
Company wide licenseUSD 7995.00


Each license also includes the following:

  • One year free e-mail technical support
  • One year free minor version updates if available (for example 3.2, 3.x up to, but not including version 4.0)

If you have any questions, please don't hesitate to contact sales. Contact information is provided on the following page:

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General Information

For quick access to the HumidAir Excel Add-In, you may purchase and download our product using automated and secure online ordering system.
After ordering, you will receive a notification mail with further instructions for how to download and install the software.

The Registration includes a free subscription program. Each Registered user will be receiving bug fixes and technical support for the registered version within one year.

Shipping by the postal mail is not available.

How to order

1. Internet ordering

Available ordering options (open an order form to select):

  • Credit Card (Visa®, Mastercard®, American Express®, Discover®)
  • PayPal
  • Amazon

To buy a specific number of licenses for the HumidAir Excel Add-In click the button: Open order page for the HumidAir Excel Add-In.

To purchase a Company Wide License contact sales. Contact information is provided on the following page:
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2. Bank Direct Payment

If you prefer to pay for the product by "Bank Direct Payment", contact sales. Contact information is provided on the following page:

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