Calculating Thermal Comfort

What is Thermal Comfort?

Thermal Comfort, as the name suggests relates to the comfort of an individual within their environment.

It is the condition of mind that expresses satisfaction with the thermal comfort of the environment and is assessed by subjective evaluation (ANSI/ASHRAE Standard 55) .

When the mind is satisfied, both physical and mental productivity can reach their most optimal point.

The thermal comfort equation was established by P.O Fanger in the 1970s, penned as “Fanger’s Comfort Equation”.

Using Fanger’s equation we can identify a figure know as Predicted Mean Vote (PMV), the Predicted Mean Vote allows us to predict the Percentage of People Dissatisfied (PPD), a surprisingly accurate statistic.

This gives us a strong indication of how the occupants of an area will judge the climate of their environment.

This PMV model has become the internationally accepted model for describing the predicted mean thermal comfort of occupants in indoor environments.

How it works .

To calculate thermal comfort, six primary factors must be accounted for. These factors can be grouped into 2 categories – personal & environmental.

Personal Factors (characteristics of the occupants)

– Metabolic rate

– Clothing insulation.

Environmental Factors (conditions of the thermal environment):

– Air temperature

– Mean radiant temperature

– Air speed

– Humidity

When in a cold environment, human bodies lose heat and personal factors must be adapted to maintain a comfortable temperature i.e. metabolic rate will naturally increase, and an individual can increase their clothing insulation by adding layers.

In hot environments, the opposite is true. Human bodies need to take measures to reduce their temperature, by dispersing their produced heat into the environment, which becomes more difficult the warmer the environment is.

Both of these scenarios will cause people to feel uncomfortable, with comfort levels becoming worse as the temperature continues to rise or fall with most individuals typically feeling most comfortable in an environment of between 20°C and 22°C (68°F and 71.6°F).

In the UK, the Approved Code of Practice set out in the Workplace (Health, Safety, and Welfare) Regulations 1992 suggest a workplace’s minimum temperature should be 16°C, or 13°C where the work involves rigorous effort. There is no suggested maximum temperature due to some workplaces involving work in heat environments e.g. foundries.

Despite this, there are no legal limits to working temperatures, provided appropriate controls are present.

Why is thermal comfort important?
Simply put, workers who are satisfied with their thermal comfort are more productive.

There is a close correlation between thermal comfort and the levels of productivity in offices, and in many cases, if the temperature issues are not addressed within a reasonable time scale, this will naturally lead to higher staff turnover.

So not only are some poorly controlled buildings causing their employers to see greatly reduced productivity, but they could also be a major contributing factor to the turnover of staff and the associated lost time and costs that come with having to recruit replacement staff that inevitably repeat the process.

Headaches which could have been easily avoided by using a thermal comfort calculator to identify these issues earlier.

Try it yourself

Due to the “uncomfortable” weather, we’re experiencing right now across Europe we’ve decided that now is the perfect time to test out the accuracy of Fanger’s Thermal Comfort equation by opening up a simplistic version of our thermal comfort calculator for anyone to try out.

We obviously don’t have any temperature or humidity sensors in your office, but if you have a rough idea of the temperature or are just curious to see it in action, give our thermal comfort calculator a try here, and let us know if the result matches your comfort level.

About our Allander Analytics Comfort Calculator

The Allander Analytics Comfort Calculator can dynamically calculate the PMV and PPD from the values entered by its user.

As mentioned earlier when discussing the PMV model, our comfort calculator and Building Book application use Fanger’s PMV model. The calculator displays the PMV and PPD values for the data entered as well as a colour-coded gauge which provides a graphical representation of the PMV. The calculator is dynamic and will automatically update when any one of the parameters is changed, if necessary.

To start with, our calculator will first ask you to vote on your on how you currently feel in your current environment. The options are Satisfied, Too Hot or Too Cold. You can only submit one response per day.

You’ll then be able to use our calculator to input some information about your current environment to view the predicted PPM & PPD. Does it match your response?

We hope that you find the comfort calculator useful and that the results match how you voted. If you want to find out more about thermal comfort and the models associated with click here and for more information about the comfort calculator visit Allander Analytics

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