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This web-based tool for thermal comfort calculations according to EN 16798-1:2019 Standard is developed at The University of California at Berkeley. Its aim is to provide a free, cross-platform tool that allows designers and other practitioners to perform thermal comfort calculations. See the bottom of the web-page for acknowledgments, contact information, and citation.
This guide aims to explain the main features of the tool, and demonstrate how best to use it. In most cases, the interface is intuitive and does not require explanation. To get information quickly, click on the input headers to be directed to a Wikipedia article relevant to that input.
The tool has three main parts:
Left-hand side: This section is the user interface. It contains the input fields containing values that drive the comfort calculations and visualizations. To change these input values, you can type directly in the boxes or click on the up and down arrows. There are also several other buttons, their functionality is explained in detail below.
Top-right: This section contains the results of the calculations. The raw output of the comfort model calculations (such as PMV, PPD, etc. for the PMV method) as well as compliance information.
Bottom-right: This section contains a visualization of the thermal comfort conditions in the input. There are currently three types of charts visualizing the thermal comfort region, as follows:
Psychrometric (plotted using either the dry-bulb air temperature or the operative temperature)
Relative humidity vs. dry-bulb air temperature.
Operative indoor air temperature vs. prevailing mean outdoor temperature (Adaptive comfort region).
At the top of the user interface you can choose between the two methods allowed by the standards, which are the PMV/PPD method and the Adaptive method. For more information about the comfort models, you can follow the link to Wikipedia by clicking on 'select method'.
For more information about the PMV model visit this page.
By choosing the Adaptive method at the very top of the user interface, the chart changes and the input variables include air temperature, mean radiant temperature and outdoor running mean temperature. This is because the personal factors and humidity are not significant in this method since adaptation is considered, and the only variable is the outdoor temperature. See above for explanation of the first two variables, air and mean radiant temperature.
Here you can type the outdoor temperature averaged as explained on the standard. See the Wikipedia link for a brief explanation. Changing this variable makes the dot representing the current condition move horizontally. The meaning of this chart is that certain conditions of indoor-outdoor temperature fall inside the comfort zone, which in this case is static.
In the Adaptive method air movement can be used under certain conditions to widen the comfort zone, allowing higher indoor operative temperatures. You can select the value and see how it changes the upper boundaries of the 80% and 90% acceptability zones.
At the bottom of the input section of the tool, you can find more clickable buttons to set more parameters and open some dialogs.
Clicking on this button, a new window pops up, letting you type the following inputs: air temperature, air speed, globe temperature, globe diameter, globe emissivity, to calculate the correspondent Mean Radiant Temperature, that can be set as the current value by clicking the 'set' button. This feature allows you to have a more precise evaluation of the MRT by taking measurements with a globe thermometer. The button is disabled when the operative temperature is used.
You can change the barometric pressure to account for changes in altitude. The standard atmospheric pressure is 1 atm = 101.325 kPa = 101325 Pa. Remember to input the value in Pascals!
This button sets some default values for all the input variables, to restart the calculation and visualization.
Click on this button to switch between the International System of Units (SI) and the Inch-Pound system.
Even though the comfort model based on PMV/PPD describes compliance to thermal comfort for the body as a whole, thermal dissatisfaction may also occur just for a particular part of the body due to local sources of unwanted heating, cooling or air movement. This feature allows you to verify the compliance of the space to the Standard as regards local thermal discomfort. By feeding the tool with measurements of air temperature in particular zones surrounding the occupant, you can see whether the discomfort effect in the space is likely to exceed the ISO 7730 acceptability limits. Change the values in the input boxes according to your measurements. A checkmark will appear next to each section, while a general compliance message will be shown at the bottom of the dialog. Remember that to comply with the Standard all the sections must respect the limits.
This web-based tool for thermal comfort calculations according to is developed at the University of California at Berkeley. Its aim is to provide a free, cross-platform tool that allows designers and other practitioners to perform thermal comfort calculations.
This guide aims to explain the main features of the tool and demonstrate how best to use it. In most cases, the interface is intuitive and does not require explanation. To get information quickly, click on an input header to be directed to a Wikipedia article relevant to that specific input.
The tool has three main parts:
Left-hand side: The input section allows you to change all the parameters used to calculate the thermal comfort indices. You can either change the value of each parameter by typing a new value in the respective box or by using the up and down arrows. You can click on the Save button to save the current inputs, Reload to reload the inputs that you have previously saved, Share to share the page (as it appears on the screen) via a link, Reset to reset the input values to the default value. The functionalities of the other buttons in the input section are explained in detail below.
Top-right: This section contains the results of the calculations. The raw output of the comfort model calculations (such as PMV, PPD, etc. for the PMV method) as well as compliance information.
Bottom-right: This section contains a visualization of the thermal comfort conditions in the input. There are currently three types of charts visualizing the thermal comfort region, as follows:
Psychrometric (plotted using either the dry-bulb air temperature or the operative temperature)
Relative humidity vs. dry-bulb air temperature.
Airspeed vs. operative temperature.
Thermal heat losses vs. dry-bulb air temperature. This chart shows the total heat losses per unit area as calculated by the PMV method. By default, the chart is showing only the total heat losses of the human body (latent, sensible as well as their cumulative value) and the metabolic rate. The intersection between the metabolic rate line (constant) and the total heat losses line is the neutral temperature at which the human body is in thermal balance with the surrounding environment. You can toggle on and off other lines, depicting different heat loss components, by clicking on the respective label in the legend.
Operative indoor air temperature vs. prevailing mean outdoor temperature (Adaptive comfort region).
At the top of the user interface, you can choose between the two methods allowed by the standards, which are the PMV/PPD method and the Adaptive method. For airspeeds greater than 0.2 m/s (39.4 fpm) the PMV calculations employ the elevated airspeed method, which calculates and reports the cooling effect of the air movement. For more information about the comfort models, you can follow the link to Wikipedia by clicking on 'select method'.
By choosing the Adaptive method at the very top of the user interface, the chart changes and the input variables include air temperature, mean radiant temperature, and prevailing mean outdoor temperature. This is because the personal factors and humidity are not significant in this method since adaptation is considered, and the only variable is the outdoor temperature. See above for an explanation of the first two variables, air and mean radiant temperature.
Prevailing mean outdoor temperature
Here you can type the outdoor temperature averaged as explained on the standard. See the Wikipedia link for a brief explanation. Changing this variable makes the dot representing the current condition move horizontally. The meaning of this chart is that certain conditions of indoor-outdoor temperature fall inside the comfort zone, which in this case is static.
Airspeed
In the Adaptive method, air movement can be used under certain conditions to widen the comfort zone, allowing higher indoor operative temperatures. You can select the value and see how it changes the upper boundaries of the 80% and 90% acceptability zones.
At the bottom of the input section of the tool, you can find more clickable buttons to set more parameters and open some dialogs.
Converts solar gain (i.e. direct, sky-diffuse, and ground-reflected shortwave radiation) to the equivalent delta mean radiant temperature.
According to an addendum of the Standard, clothing insulation can be predicted by knowing the outdoor air temperature at 6 a.m. of the day in question. By opening this tab, you will be able to type such temperature, based on measurements or a weather file, and feed it to an equation that will automatically update the value in the clo input box, and update the comfort zone according to this change.
Clicking on this button, a new window pops up, letting you type the following inputs: air temperature, air speed, globe temperature, globe diameter, globe emissivity, to calculate the correspondent Mean Radiant Temperature, that can be set as the current value by clicking the 'set' button. This feature allows you to have a more precise evaluation of the MRT by taking measurements with a globe thermometer. The button is disabled when the operative temperature is used.
You can change the barometric pressure to account for changes in altitude. The standard atmospheric pressure is 1 atm = 101.325 kPa = 101325 Pa. Remember to input the value in Pascals!
Reset - all inputs to their default values.
Save - the current input values.
Reload - the saved input values.
Share - creates a link that can be used to share the current page.
Click on this button to switch between the International System of Units (SI) and the Inch-Pound system.
For more information about the PMV model visit , below a video explaining how to calculate PMV and PPD using the CBE thermal comfort tool.
Even though the comfort model based on PMV/PPD describes compliance to thermal comfort for the body as a whole, thermal dissatisfaction may also occur just for a particular part of the body due to local sources of unwanted heating, cooling, or air movement. This feature allows you to verify the compliance of the space to the Standard as regards local thermal discomfort. By feeding the tool with measurements of air temperature in particular zones surrounding the occupant, you can see whether the discomforting effect in the space is likely to exceed the ASHRAE-55 acceptability limits. Draft at the lower leg region may occur in the buildings conditioned by thermally stratified systems, such as displacement ventilation and underfloor air distribution, or with cold-dropping airflow along external walls and/or windows. An ankle draft risk model, based on the work of by and , has been implemented in the tool. This model can evaluate the predicted percentage dissatisfied on draft at ankle level (PPD AD) as a function of PMV and airspeed at the ankle. Regarding the usage of the ankle draft risk model, the subject's metabolic rate and clothing level should be kept below 1.3 met and 0.7 clo, respectively. The airspeed on the upper body is fixed as 0.2 m/s for PMV calculation in the ankle draft risk model since a condition of airspeed higher than 0.2 m/s should refer to the elevated air speed model instead. Change the values in the input boxes according to your measurements. A checkmark will appear next to each section, while a general compliance message will be shown at the bottom of the dialog. Remember that to comply with the Standard all the sections must respect the limits.
Modeling the comfort effects of short-wave solar radiation indoors
Exposure to sunlight indoors produces a substantial effect on an occupant’s comfort and on the air conditioning energy needed to correct for it. It can be used to determine the allowable transmittance of fenestration in a perimeter office. Read the original research paper here
SolarCal, a simplified whole-body model for the thermal comfort effects of shortwave solar radiation.
SolarCal’s ability to predict the impact of solar radiation on occupant thermal comfort verified against lab study.
The solar heat absorbed and liberated in clothing and skin must be offset by cooler air and surface temperatures around the body for the occupant to remain comfortably in thermal balance. The SolarCal model is based on the effective radiant field (ERF), a measure of the net radiant energy flux to or from the human body. ERF is used to describe the additional (positive or negative) long-wave radiation energy at the body surface when surrounding surface temperatures are different from the air temperature. It is in W/m2 , where area refers to body surface area. The surrounding surface temperature of a space is commonly expressed as mean radiant temperature (MRT).
The angle between the sun’s rays and a horizontal plane. See Figure below.
The solar horizontal angle is symmetrical on both sides and ranges from 0 to 180 degrees in relation to the front of the person. Direct-beam radiation from the front is represented by zero (0) degrees, direct-beam radiation from the side is represented by 90 degrees, and direct-beam radiation from the back is represented by 180 degrees. The only angle between the sun and the human is SHARP. See Figure above.
The ratio of incident shortwave radiation to the total shortwave radiation passing through the glass and shades of a window system.
It ranges between 0 and 1.
The percentage of the body not shaded by the window frame, interior or outside shading, or interior furnishings.
The occupant's short-wave absorptivity will vary greatly based on the color of his or her skin, as well as the color and amount of clothing covering his or her body. Approximately equal to 0.67 for (white) skin and average clothing.
Analytical determination and interpretation of heat stress using calculation of the predicted heat strain
The ISO 7933 specifies a method to determine the thermal heat strain experienced by a subject working in a hot environment. It provides a method to calculate the sweat rate and estimate the core temperature. This allows the user to determine how each input parameter affects the above mentioned variable. [1]
The ISO 7933 International Standard allows for the determination of which parameter or collection of parameters should be modified, and to what extent, to reduce the risk of physiological stresses. The following are the key goals of this International Standard:
the assessment of thermal stress in situations that are likely to cause an excessive increase in core temperature or water loss in the standard subject;
determining the maximum exposure time for which the physiological strain is tolerable (no physical damage is to be expected). These exposure times are referred to as "maximum permitted exposure times" in this forecast mode.
The rectal temperature increase must be limited at a maximum value, in the case of non-equilibrium of the thermal balance, such that the likelihood of any harmful impact is extremely low. Finally, regardless of the thermal balance, water loss should be limited to a number, that is compatible with the body's hydromineral equilibrium.
Consequently, our tool reports the maximum allowable exposure times within which the physiological strain is acceptable (no physical damage is to be expected) calculated as a function of:
rectal temperature;
water loss of 5% of the body mass for 95% of the population;
water loss of 7.5% of the body mass for an average person.
The PHS can only be used for:
dry-bulb temperatures between 15 and 50°C,
air speeds between 0 and 3 m/s,
metabolic rates between 1.7 and 6.8 met,
total clothing insulation between 0.1 and 1.0 clo, and
when the difference between the mean radiant temperature and the air temperature is between 0 and 60°C.
[1] ISO, “ISO 7933 - Ergonomics of the thermal environment — Analytical determination and interpretation of heat stress using calculation of the predicted heat strain.” ISO, Geneva, Switzerland, 2004.
Official documentation website
The CBE Thermal Comfort Tool is a free online tool for thermal comfort calculations and visualizations that implements thermal comfort calculations from standards (ASHRAE 55–2023, ISO 7730:2005 and EN 16798–1:2022).
It incorporates the major thermal comfort models, including the ASHRAE and ISO Predicted Mean Vote (PMV), Standard Effective Temperature (SET), adaptive models, local discomfort models, SolarCal, and dynamic predictive clothing insulation. Our tool also provides dynamic and interactive visualizations of the thermally comfortable conditions depending on the models.
In addition, the CBE Thermal Comfort Tool allows users to upload time-series or large sets of input parameters and it automatically calculates PMV, PPD, SET, and CE. This may allow users to perform exceedance predictions (e.g. annual or seasonal) for simulated or real buildings.
The CBE Thermal Comfort Tool has several practical applications and each year is used by more than 49,000 users worldwide, including engineers, architects, researchers, educators, facility managers and policymakers.
Tartarini, F., Schiavon, S., Cheung, T., Hoyt, T., 2020. CBE Thermal Comfort Tool : online tool for thermal comfort calculations and visualizations. SoftwareX 12, 100563. https://doi.org/10.1016/j.softx.2020.100563
The tool is developed by the University of California at Berkeley.
Questions that can be used for thermal comfort research
These questions are based on Appendix L of ASHRAE 55 2023. ASHRAE 55 aims at achieving an 80% satisfied rating, but this is rarely obtained; typical thermal satisfaction levels are around 40%.
According to ASHRAE 55, using occupant thermal environment surveys is an acceptable way of assessing comfort conditions. Surveys should strive for representative sample size and a high response rate. There are two types of thermal environment surveys, right-now and long-term.
Right-now surveys are used to evaluate occupants’ thermal experience at a single point in time. Suggested questions are shown below. They include (a) the thermal sensation scale, which asks occupants to rate their sensation (from “hot” to “cold”) on the ASHRAE seven-point thermal sensation scale. Votes values between –1.5 and +1.5 can be considered as “satisfied”; This is an assumption and directly using thermal satisfaction and preference gives, in our opinion, a more reliable result. (b) the thermal satisfaction scale that directly asks how satisfied an occupant is and (c) the thermal preference scales for temperature and air movement. This scale is very useful for the control of HVAC systems because it directly specifies what people want, this cannot be easily obtained from the thermal sensation scale.
Optional scales, that could be asked in some research context, are shown below:
Clothing and activity levels can be assessed using the following questions:
Long-term surveys are used to assess thermal comfort in most practical applications. These surveys provides “overall” or “average” comfort votes on their environment. They use the thermal satisfaction question (from “very satisfied” to “very dissatisfied”) on a seven-point satisfaction scale. The percentage of occupants satisfied should be calculated by dividing the number of votes falling between +1 and +3, inclusive, by the total number of votes. The percentage of occupants dissatisfied should be calculated by dividing the number of votes falling between -1 and -3, inclusive, by the total number of votes.
The thermal satisfaction survey can be used by researchers, building operators, and facility managers to assess building systems’ performance in new buildings, and to perform periodic post-occupancy evaluations in existing facilities.
According to ASHRAE 55, as the thermal satisfaction survey assesses a long timeframe, it should be administered every six months or repeated in heating and/or cooling seasons. In a new building, the first thermal satisfaction survey may be performed approximately six months after occupancy, late enough to avoid assessing the effects of building commissioning but early enough to help identify long-term building problems that have escaped detection in the commissioning process.
This version complies with the ASHRAE Standard 55-2023.
This version complies with the ASHRAE Standard 55-2020. You can access this version of the tool using . Please note that this version is no longer supported and may contain errors that have been fixed in newer releases.
Fix:
issue calculation PMV when cooling effect is 0
Fix:
issue with e_max == 0
Fix:
Cooling Effect calculation
Fix:
Updated coefficient of dilation in SET model
Fix:
Hiding globe temperature calculator when operative temp is selected
Fix:
Issue with operative toggle in adaptive model
Fix:
Upload tool was not using dynamic clothing
Calculation of CE was done for a sitting person without using dynamic clothing
Fix:
Fix equation to calculate radiative heat transfer coefficient in SET equation
Features:
Assuming that a person is sitting when calculating SET temperature
Features:
Added PHS model
Added fan heatwaves model
Fix:
Error calculation of PMV in EN tab
Features:
Improved tooltip look
Features:
Improved documentation and made charts responsive
Fix:
Removed old vertical temperature gradient calculator
Fix:
Local discomfort tab the code was broken
Fix:
Spinner behavior compare tab
Units in note under range chart
dilation coefficient in SET equation
Features:
Implemented test for all the major functions
Added bumpversion to track version of the tool
Features:
Changed compliance from ASHRAE 55 2017 to ASHRAE 55 2020
Fix:
Equation to calculate heat transfer coefficient SET equation.
Default value of clo and met dropdown now matches the default input value.
Features:
Wrote testing for ERF, SET and PMV equations
Fix:
Error calculation SHARP and solar altitude supine person.
Features:
Changed limit for elevated air speed calculation from 0.2 m/s to 0.1 m/s.
Features:
Fixed minor issue in the erf equation. Updated fp tables and E_diff equation.
Features:
Fixed issues with calculation of outputs in the Upload tool and removed link to Codelab
Added SET chart, which displays SET outputs as a function of the inout variables selected
Added a note below SET chart
Added a note below PMV heat loss chart
Minor edits to the layout of the comfort tool
Features:
Displaying the relative air speed and dynamic clothing among the outputs.
Fix:
Fixed calculation comfort zone in Ranges
Features:
The Upload tool can be used to calculate LEED compliance.
The Share button now also shares the chart type.
Added notes about relative air speed and dynamic clothing calculation below charts.
Added mean radiant temperature as input in the SolarCal tool.
Fix:
Share fixed the issue with air speed and clothing.
Changes y-label in chart air speed vs operative temperature.
Features:
Fix:
Upload was throwing error for files with more than 1000 inputs.
Improved calculation speed for Upload tool.
Features:
Added Save, Restore and Share button.
Added tooltips to provide additional information to the user.
Fix:
Upload not does not throw an error if the cooling effect cannot be calculated.
Upgraded to new version of pythermalcomfort.
Fixed issue solar gain calculation with IP units.
Features:
Navigation bar responsive.
Created new documentation website.
Fix:
Issue with HeatLoss chart.
The is automatically calculated by the tool.
The is automatically calculated by the tool.
This version complies with the ASHRAE Standard 55-2017. You can access this version of the tool using . Please note that this version is no longer supported and may contain errors that have been fixed in newer releases.
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Olesen, B. W., Scholer, M., & Fanger, P. O. (1979). Discomfort caused by vertical air temperature differences. Indoor Climate, 561-579.
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These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.
Python 3 and Node.js installed on your machine.
If you do not have Python installed on your machine you can follow this guide
If you do not have Node.js installed on your machine you can follow this guide
This guide is for Mac OSX, Linux or Windows.
Get the source code from the GitHub repository
Create a virtual environment using the following command:
On Linux and MAC $ python3 -m venv venv
On Windows py -3 -m venv venv
Activate the virtualenv:
On Linux and MAC $ . venv/bin/activate
On Windows venv\Scripts\activate
Your shell prompt will change to show the name of the activated environment.
Install Python dependencies
The dependencies of the comfort tool are all contained in requirements.txt. Install them all using: $ pip install -r requirements.txt
Install Node.js dependencies
npm install
Run CBE Thermal Comfort Tool locally
Now you should be ready to run the tool locally. python3 comfort.py
Visit http://localhost:5000 in your browser to check it out. Note that whenever you want to run the tool, you have to activate the virtual environment first.
We are using Jest to test the JavaScript functions.
If you want to find out more please read their official documentation or look at how we are testing the ERF functions (file name erf.js) using the test file erf.test.js.
Finally, run npm run test. You should write tests for all the new functions you add and ensure that you get positive results from the tests. Also run tests before deploying a new version of the CBE Thermal Comfort Tool.
When you release a new version of the tool you should first use bumpversion to update the version of the tool. You can use the following command:
Secondly, you should describe the changes in docs/changelog/changelog.md
We are deploying the tool using Google Cloud Run. The project is automatically deployed when you push to master the commit message includes the word bump version. Check the GitHub action in the folder ./.github/workflows/deploy.yml for more information about how we build and deploy the application.
Alternatively, you can deploy a new version of the tool to Google Cloud Run using the following command. Please note that you have to set a valid account before running the command and add your email in the code below.
Six primary factors affect thermal comfort. These include environmental conditions such as air temperature, and personal factors such as metabolic rate.
By modifying this value, you will notice the output in the upper-right region changing, as well as the red dot on the chart moving. Depending on which specification of humidity is being used, the red dot may follow the lines of constant relative humidity, or move horizontally. This value does not affect the comfort zone itself, since the zone represents a range of air temperature and humidity values. Next to the air temperature box, you can click on the 'use operative temperature' button. When this option is selected, it will be assumed that the air temperature and mean radiant temperature are equal to the value in the operative temperature input field.
MRT represents the mean of the radiant temperatures of the enclosing surfaces of a space, which is determined by the emissivity and the temperature of the surfaces. This value affects the location of the comfort zone, since it may affect the range of acceptable air temperatures. For example, higher radiant temperatures allow the occupant to feel comfortable at lower air temperatures, or vice versa. Thus, an increase in MRT shifts the comfort zone to the left side of the charts.
This is the rate of spatial change of air in a space, which is used to calculate convective heat transfer and thus changes the comfort zone. Higher air speeds allow higher temperatures and humidity, due to the cooling effect that air movement has on an occupant. Local air speed control is the ability for the occupants to modify the local air flow, and if this is not available in their space, limits apply to the range of temperatures that can be covered. Therefore, availability of local control allows wider ranges of air speed that can be used to offset higher temperatures.
The body movement affects the air speed surrounding the human body. Consequently, the sum of the average air speed and the self-generated air speed shall be used as input in the PMV model. In accordance with the ASHRAE 55 and the ISO 7730, if the metabolic rate is higher than 1 met, the self-generated air speed is calculated using the following equation: V_sg = V + 0.3 (MET - 1). Where V is the "Average air speed" and MET is the "Metabolic rate". The CBE comfort tool automatically calculates the self-generated air speed for you in the background and sums it to the average air speed you entered in the tool.
Relative Humidity is the ratio of the partial pressure of the water vapor in the air to the saturation pressure of water vapor at the same temperature. You can also input dew-point temperature, humidity ratio, wet bulb temperature, or vapor pressure, by selecting it through the expandable box. Humidity will change the position of the dot. It doesn't affect the comfort zone boundary since the boundary represents a range of temperature and humidity, but it does affect the PMV/PPD calculations.
Metabolic rate is the rate of energy production of the body, which varies for different activities. A list of common activities and correspondent metabolic rate in met units is available next to the input box. You can either chose one value from the list or type a different and more precise one directly, as preferred. Increasing the metabolic activity means moving the comfort zone significantly towards lower temperatures and vice versa, since higher activities make the body produce more heat and thus be more comfortable in colder environments. Elevated metabolic rate can also result in decreased effective clothing value and increased relative air speed (as air is pumped through clothing).
Clothing is probably the most important variable in terms of adaptation to a thermal environment, and this means that acting on the clothing level may be very effective to reduce energy consumption. This tool allows you to select clo values for common clothing ensembles by the list on the right of the input box, or also to create a custom ensemble by choosing every garment that composes it, by clicking on the button just beneath. This meets the methods provided by the Standard to evaluate the clothing insulation, as you can see in more depth by clicking on the Wikipedia link. It's important not to forget the clo value provided by the chair, that can be found in the list of garments. Once the ensemble has been created, the clo value can be set to the input field.
The body movement affects the insulation characteristics of the clothing and the adjacent air layer. Consequently, the dynamic clothing insulation (I_clo_dynamic) shall be used as input to calculate the thermal comfort indices.
ASHRAE 55 Standard: defines that the following equation shall be used to calculate the dynamic clothing insulation. I_clo_dynamic = CLO (0.6 + 0.4 / MET). Where CLO is the "Clothing level" and MET is the "Metabolic rate" you entered as input in the CBE thermal comfort tool, respectively. The CBE comfort tool automatically calculates the dynamic clothing insulation for you in the background.
This page explains how to use the ranges tool. In most cases, the interface is intuitive and does not require explanation. To get information quickly, click on the input headers to be directed to a Wikipedia article relevant to that input. In addition the video-tutorial below explains how to use the Ranges tool.
The tool has three main parts:
Left-hand side: This section is the user interface. It contains the input fields containing values that drive the comfort calculations and visualizations. To change these input values, you can type directly in the boxes or click on the up and down arrows. There are also several other buttons, their functionality is explained in detail below.
Top-right: This section contains the results of the calculations. The raw output of the comfort model calculations (such as PMV, PPD, etc. for the PMV method) as well as compliance information.
Bottom-right: This section contains a visualization of the thermal comfort conditions in the input. There are currently three types of charts visualizing the thermal comfort region, as follows:
Psychrometric (plotted using either the dry-bulb air temperature or the operative temperature)
Relative humidity vs. dry-bulb air temperature.
Operative indoor air temperature vs. prevailing mean outdoor temperature (Adaptive comfort region).
For more information about the PMV model visit this page.
At the bottom of the input section of the tool, you can find more clickable buttons to set more parameters and open some dialogs.
Clicking on this button, a new window pops up, letting you type the following inputs: air temperature, air speed, globe temperature, globe diameter, globe emissivity, to calculate the correspondent Mean Radiant Temperature, that can be set as the current value by clicking the 'set' button. This feature allows you to have a more precise evaluation of the MRT by taking measurements with a globe thermometer. The button is disabled when the operative temperature is used.
You can change the barometric pressure to account for changes in altitude. The standard atmospheric pressure is 1 atm = 101.325 kPa = 101325 Pa. Remember to input the value in Pascals!
This button sets some default values for all the input variables, to restart the calculation and visualization.
Click on this button to switch between the International System of Units (SI) and the Inch-Pound system.
This page explains how to use the compare tool. In most cases, the interface is intuitive and does not require explanation. To get information quickly, click on the input headers to be directed to a Wikipedia article relevant to that input. In addition, the video-tutorial below explains how to use the Compare tool.
The tool has three main parts:
Left-hand side: This section is the user interface. It contains the input fields containing values that drive the comfort calculations and visualizations. To change these input values, you can type directly in the boxes or click on the up and down arrows. There are also several other buttons, their functionality is explained in detail below.
Top-right: This section contains the results of the calculations. The raw output of the comfort model calculations (such as PMV, PPD, etc. for the PMV method) as well as compliance information.
Bottom-right: This section contains a visualization of the thermal comfort conditions in the input. There are currently three types of charts visualizing the thermal comfort region, as follows:
Psychrometric (plotted using either the dry-bulb air temperature or the operative temperature)
Relative humidity vs. dry-bulb air temperature.
For more information about the PMV model visit this page.
At the bottom of the input section of the tool, you can find more clickable buttons to set more parameters and open some dialogs.
Clicking on this button, a new window pops up, letting you type the following inputs: air temperature, air speed, globe temperature, globe diameter, globe emissivity, to calculate the correspondent Mean Radiant Temperature, that can be set as the current value by clicking the 'set' button. This feature allows you to have a more precise evaluation of the MRT by taking measurements with a globe thermometer. The button is disabled when the operative temperature is used.
You can change the barometric pressure to account for changes in altitude. The standard atmospheric pressure is 1 atm = 101.325 kPa = 101325 Pa. Remember to input the value in Pascals!
This button sets some default values for all the input variables, to restart the calculation and visualization.
Click on this button to switch between the International System of Units (SI) and the Inch-Pound system.
Operative temperature can be selected as an input. This will hide the air temperature and mean radiant temperature input boxes.
You can select this button when the occupants have control of the air movement, e.g. if they can operate a fan and set its intensity.
This project is maintained by a group of researchers at the Center for the Built Environment (CBE), University of California Berkeley (USA). This is a free tool and we have only limited ability to answer questions.
Please check the CHANGELOG page where we have described all the latest changes we have implemented.
If you have a question about the tool, email us at cbecomforttool@gmail.com.
Please report issues and bugs on our GitHub page.
Please suggest new features on our GitHub page.
This page explains how to use the upload tool which can be used to upload a large set of comfort parameters and this tool will automatically calculate the thermal comfort indices.
Application of Gagge’s energy balance model to determine humidity-dependent temperature thresholds for healthy adults using electric fans during heatwaves
Electric fans are an affordable, sustainable and effective way to keep people cool. They are the most cost-effective cooling method for most applications. The CBE Thermal Comfort Tool uses the Gagge et al. (1971) two-nodes human energy balance model, to determine under which environmental (air temperature, relative humidity, air speed and mean radiant temperature) and personal (metabolic rate, clothing) conditions the use of fans is beneficial.
Electric fans can safely be used even if the air temperature is higher than 35 °C.
Electric fans cool people even when air temperature exceeds skin temperature.
Our open-source tool calculates humidity-dependent temperature thresholds.
Increasing air movement is a personalized cooling strategy that bypasses the issues associated with refrigerant gases and is more efficient than compressor-based air conditioning [1]. Electric fans are relatively inexpensive, energy-efficient, some (e.g., pedestal and desk) do not have any installation cost, and with direct current motors, they now consume single-digit watts and provide substantial air flows [2]. Electric fans can be used either as an alternative cooling technology or in combination with a reduced level of compressor-based air conditioning [1].
The WHO used to state that if the dry-bulb air temperature (tdb) is higher than 35 °C, fans can make an individual hotter, and "fans should be discouraged unless they are bringing in significantly cooler air". They also mentioned that when tdb is higher than 35 °C, fans may not prevent heat-related illness [4]. The underlying assumption is related to the fact that if tdb exceeds skin mean temperature (tsk) (approximately 35 °C) the gradient for dry heat loss is reversed, and sensible heat is added to the body.
Ready.gov, a national public service campaign of the U.S. Government that aims to "educate and empower the American people to prepare for, respond to and mitigate emergencies, including natural and man-made disasters", still states that electric fans should not be used when outside temperatures are higher than 35 °C [5]. According to Ready.gov, in these conditions, electric fans could increase the risk of heat-related illness, and they create airflow and a false sense of comfort but do not reduce body temperature. The Centers for Disease Control and Prevention (CDC) states that when the temperature is in the high 90’s (°F, i.e., above 32-37°C), fans will not prevent heat-related illness [6]. Similarly, the EPA Excessive Heat Events Guidebook discourages directing the flow of fans towards the body when tdb is higher than 32.2 °C [7].
When the dry-bulb temperature is higher than skin temperature, the aforementioned recommendations undervalue the evaporative cooling impact of electric fans, ignoring empirical evidence showing healthy adults benefit from their use [10, 18, 19, 20]. Based on this evidence, advising healthy adults not to use fans when tdb exceeds tsk or 35 °C could increase their risk of suffering from heat strain and would prevent them from using an effective, energy-efficient, and low-cost cooling technology.
In 2024, the WHO updated the and now reads: "Use electric fans only when temperatures are below 40 ˚C / 104 ˚F."
The CBE Thermal Comfort - Fan Heatwaves tool estimates heat losses and physiological variables as a function of ambient and personal parameters using the human thermoregulatory model proposed by Gagge et al. (1971) [11]. These results are then utilized to calculate humidity-dependent temperature thresholds for healthy persons who use electric fans during heatwaves. The model's interface is depicted in the diagram below. The user can alter the input variables on the left side of the screen, while the results are displayed on the right side.
In the CBE Thermal Comfort tool, we only allow users to change the following variables:
air speed (m/s),
metabolic rate (met), and
clothing level (clo).
We also assume that dry-bulb air temperature is equal to the mean radiant temperature.
The figures are updated in real time using the results, which are derived automatically. We use a red backdrop to indicate when heightened air velocity can be utilized to cool the human body, while we use a green background to depict when electric fans should not be used. While the usage of fans is still advantageous in the dark green area, not all healthy adult individuals will be able to compensate for endogenous and external heat gains, resulting in heat stress. Because the greatest rate of evaporative heat loss from the skin (W/m2) is inversely related to Relative Humidity (RH), the maximum operative temperature at which heat strain is anticipated to occur lowers as the value of RH increases. At low RH, the slope of the heat stress curve flattens. The RH value at which the curve flattens is proportional to the air speed (V). This is because at low RH levels, cutaneous blood flow reaches its maximum, creating heat strain.
The Gagge et al. (1971) heat balance model employs experimentally derived coefficients and simplified equations (e.g., to calculate the respiratory losses). The results generated using the Gagge model are estimates for healthy and fit standard participants. The model does not forecast a single subject's physiological response, and the recommendations in this tool are not intended to replace professional medical advice. As a result, the findings may not apply to everyone, including people who have sweating problems owing to age, anticholinergic drugs, or other pre-existing diseases that interfere with thermoregulation. More empirical evidence is needed to confirm the model's applicability in diverse environments and to more vulnerable populations, such as the elderly. More evidence is needed, in particular, to evaluate the Gagge model's applicability in hot and dry conditions, i.e., RH less than 20% and tdb more than 40 °C. Because hyperthermia isn't the primary cause of death during extreme weather, hot and dry surroundings can aggravate cardiovascular strain by increasing epidermal blood flow [1]. While the Gagge adjusts for this, further laboratory-based research is needed to demonstrate that using a fan does not worsen cardiovascular strain in healthy persons in the situations stated above.
[1] N. B. Morris, G. K. Chaseling, T. English, F. Gruss, M. F. B. Maideen, A. Capon, O. Jay, Electric fan use for cooling during hot weather: a biophysical modelling study, The Lancet Planetary Health 5 (2021) e368 e377. doi:10.1016/s2542-5196(21)00136-4.
[2] B. Yang, S. Schiavon, C. Sekhar, D. Cheong, K. W. Tham, W. W. Nazaroff, Cooling efficiency of a brushless direct current stand fan, Building and Environment 85 (2015) 196{204. doi:10.1016/j.buildenv.2014.11.032.
[3] O. Jay, R. Hoelzl, J. Weets, N. Morris, T. English, L. Nybo, J. Niu, R. de Dear, A. Capon, Fanning as an alternative to air conditioning { A sustainable solution for reducing indoor occupational heat stress, Energy and Buildings 193 (2019) 92{98. doi:10.1016/j.enbuild.2019.03.037.
[6] C. U. D. of Health, H. Services, Frequently asked questions (faq) about extreme heat | natural disasters and severe weather | cdc, https: //www.cdc.gov/disasters/extremeheat/faq.html, 2012. (Accessed on 11/05/2020).
[7] United States Environmental Protection Agency, Excessive Heat Events Guidebook, 2006
[8] N. M. Ravanelli, S. G. Hodder, G. Havenith, O. Jay, Heart Rate and Body Temperature Responses to Extreme Heat and Humidity With and Without Electric Fans, JAMA The Journal of the American Medical Association 313 (2015) 724{725. doi:10.1001/jama.2015.153.
[9] O. Jay, M. N. Cramer, N. M. Ravanelli, S. G. Hodder, Should electric fans be used during a heat wave?, Applied Ergonomics 46 (2015) 137{143. doi:10.1016/j.apergo.2014.07.013. arXiv:arXiv:1011.1669v3.
[10] D. Gagnon, S. A. Romero, M. N. Cramer, K. Kouda, P. Y. Poh, H. Ngo, O. Jay, C. G. Crandall, Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity, Medicine and Science in Sports and Exercise 49 (2017) 2333{2342. doi:10.1249/MSS.0000000000001348
[11] A. P. Gagge, A. P. Fobelets, L. G. Berglund, A standard predictive Index of human reponse to thermal enviroment, American Society of Heating, Refrigerating and Air-Conditioning Engineers (1986) 709{731.
If you want to change any additional inputs (e.g., external work, body position) or the above-mentioned assumptions. We highly encourage you to use the function use_fans_heatwaves() which is included in the Python package pythermalcomfort. Please find out more about how to use the aforementioned function .
[4] WHO, Heat and health, fact-sheets/detail/climate-change-heat-and-health, 2018. (Accessed on 10/23/2020).
[5] Ready, Extreme heat | ready.gov, , 2020. (Accessed on 11/05/2020).
