1. Thermal wellness

and radiant systems

With the evolution of materials, construction techniques and

people's needs, the ultimate goal of building construction is in-

creasingly to provide a place to live or work that is also comfort-

able. The concepts of environmental well-being and comfort are

thus increasingly important and become the goals to achieve in

terms of acoustic, lighting and thermal comfort and air quality.

In this part we provide a general, easy-to-read overview of how

to measure and achieve well-being. Obviously, this is a simplifi-

cation because the conclusions discussed here are the final re-

sult of very complex considerations ranging from applied phys-

ics to the current standards.

Thermo-hygrometric well-being

It is difficult to define the quality of life in a space because well-

being is a subjective perception. Commonly, environmental

well-being is defined as a condition in which people are neither

too cold nor too warm and, thus, in a neutral state.

What we perceive is based on the thermal equilibrium of the hu-

man body and, in fact, feeling of cold or warm is nothing more

than the expression of the condition in which we find ourselves.

Our body is in a neutral condition, and therefore comfortable,

when the energy we produce, depending on the type of physical

activity we are doing, called metabolic activity, is equal to the

energy that we release to the environment. If, for example, we

are sitting in an office, our bodies have an, albeit low, metabolic

activity, but at the same time we are releasing mechanical and

thermal energy into the environment through respiration, con-

vection, conduction, irradiation and evaporation from the skin. If

the sum of these energy losses, which are affected by many fac-

tors as we shall see below, is equal to our energy metabolism,

we are in condition of comfort.

The factors that affect well-being

The energy exchanges that occur between our bodies and the

environment, and which, as seen above, affect comfort, are

therefore basically of two types: environmental and physical.

The parameters related to people are:

- metabolism, which, as mentioned, depends on the person's

type of physical activity, measured in METs (metabolic equiva-

lents);

- the type of clothing, which for obvious reasons will vary de-

pending on intended use of the space, the person's role, the

type of activity performed (for example, an office manager will

surely dress differently than a receptionist) measured in CLOs

(clothing units).

The environmental parameters are:

- relative humidity of the environment measured as a %;

- air speed in m/s;

- air temperature in °C;

- mean radiant temperature in °C.

The mean radiant temperature is given by the temperatures of

the surfaces that surround the person, corrected with view fac-

tors. In fact, the influence of the temperature of a surface on

an occupant varies depending on the position of the surface in

relation to the person. For example, in Figure 1, the temperature

of a surface placed along the X axis (such as a window or wall),

and thus in front of the person, will have a greater weight in the

calculation of the mean radiant temperature than the tempera-

ture of a surface placed along the Z axis (for example, ceiling or

floor). The influence of the temperature of the various surfaces

also varies in relation to the occupant's position, sitting, stand-

ing or lying.

From the mean radiant temperature and the air temperature, we

derive the operating temperature, which is taken into account

in the analysis of environmental comfort defined in the UNI EN

7730 standard where, based on this temperature and other fac-

tors, it is possible to establish the degree of comfort that can

be achieved. It seems clear that the operating temperature is

particularly influenced by radiant systems. As we will see later,

if positioned correctly radiant systems achieve excellent results

without the risk of increasing or decreasing the air temperature

too much and thus avoiding high vertical temperature differ-

ences (see below).

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Ceiling and wall radiant system – Product guide

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