Measuring well-being

Even though well-being is subjective, there are methods for es-

tablishing if we are comfortable or not based on several pa-

rameters.

The UNI EN 7730 standard describes the method for measuring

comfort and the first value to be defined is PMV, the Predicted

Mean Vote that the people in a space would give to the feeling

of warmth they are experiencing. In fact, PMV is based on the

thermal energy balance we spoke of above and ranges from a

value of -3 to +3 based on how the person feels.

PMV is thus linked to another parameter: PPD, the Predicted

Percentage Dissatisfied, or the percentage of people who will be

dissatisfied with the thermal condition in which they find them-

selves. For example, a PMV of 0.5 corresponds to a percentage

of dissatisfied of 10%.

The same standard establishes the comfort classes, A, B and C.

For these classes, benchmarks are indicated and even the limit

values of discomfort to maintain (see next point). In any case, it

is advisable to maintain PPD values below 10%

PMV index

+3

Hot

+2

Warm

+1

Fairly warm

0

Neither warm nor cold

-1

Fairly cold

-2

Cold

-3

Very cold

Indication of the percentage of dissatisfied

Category

A

B

C

Comfort classes

Thermal state of the body as a whole

<6

-0.2 < PMV < +0.2

<10

-0.5 < PMV < +0.5

<15

-0.7 < PMV < +0.7

Local discomfort

PPD

%

PMV

DR

%

vertical

difference

of air

temperature

PD

%

caused by hot

or cold floor

radiant

asymmetry

Radiant

<10

<20

<30

<3

<10

<5

<5

<10

<5

<10

<15

<10

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Ceiling and wall radiant system – Product guide

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