Thermal well-being urban planning

Introduction

Thermal comfort, hygrothermal comfort, or more properly hygrothermal comfort, can be defined as the absence of thermal discomfort. In physiology it is said that there is hygrothermal comfort when the body's thermoregulatory mechanisms do not have to intervene for sedentary activity and with light clothing. This situation can be recorded by indices that should not be exceeded so that the thermoregulatory systems (metabolism, sweating and others) do not come into operation.

Physiology, environment and comfort

The human body is prepared to react to climate changes, but these reactions cause it to consume metabolic energy. The feeling of comfort arises from staying in a microclimate that avoids the body's reaction, saving energy costs, which is called "natural thermoregulation" (as opposed to shelter, which is a phenomenon of artificial thermoregulation).

Normal body temperature is 36.5°C. In diseases it can rise to 41 °C or 42 °C (hyperthermia) where it becomes dangerous. The human body is very sensitive to increases in indoor temperature and just 5 or 6 degrees more can cause very significant damage and even death. Low temperatures are even less tolerated and at 35 °C (hypothermia) you begin to feel drowsy until you fall into deep lethargy.

Sitting in a room with light clothing and doing light activity, the sensation of thermal satisfaction is reached between 21 °C and 25 °C. Relative humidity -RH-, which is usually blamed as the cause of discomfort, is less significant since the body's tolerance is great, allowing limits between 20% and 75%.

The body is very sensitive to changes in radiation. If the temperature is below 18 °C but there is good sun, you immediately feel that the sensation of hygrothermal comfort increases. This principle is used by radiant slab or radiant floor heating and by the radiator system. But just as it is pleasant for the sun to shine through a window in winter, it becomes unpleasant in the summer.

To understand what conditions well-being and its relationship with architecture, it must be assumed that the human body produces heat and exchanges it with the environment that surrounds it.

Chemical transformations occur within the human organism that maintain life by producing heat, through homeostasis. Thus there is a thermodynamics of living organisms. This permanent flow of energy is assessed by the metabolic rate and varies according to the person's activity level, age, sex and psychological state.

Thermal well-being urban planning

Introduction

Physiology, environment and comfort

To understand what conditions well-being and its relationship with architecture, it must be assumed that the human body produces heat and exchanges it with the environment that surrounds it.

Buildings and hygrothermal comfort

Thus, an organism must be maintained at a constant temperature, to avoid cooling or heating, with

This purpose has residual heat evacuation mechanisms that are normal heat exchange mechanisms.

They are the following:

• - Convection: It is the transmission of heat from the skin to the ambient fluid or vice versa. The heat flow is proportional to a convection coefficient and the temperature difference between the air and the skin; The speed of the air (wind) accelerates convection (if it is done by a fan, it is called forced or assisted).

• - Conduction: It is the transmission of heat between the surface of the body and the contact elements. This heat flow depends on the thermal conductivity coefficient of these elements.

• - Radiation: It is the transmission of heat through the environment, mainly by infrared radiation. This heat flow is proportional to the universal radiation constant, the absorption power of the skin (which is very high) and the temperature difference between the skin and the radiating walls.

• - Evaporation: It is the unidirectional transmission of heat from the body to the ambient air through cutaneous and respiratory evaporation. This heat loss from the body depends on the amount of sweat (water) evaporated and evaporation depends on the speed of the ambient air, its temperature and the partial pressure of water vapor.

While the first three forms of transmission refer to sensible heat, evaporation refers to latent heat.

In order for the internal temperature of the human body to remain constant, the thermal balance that includes heat contributions and losses by convection, conduction, radiation and evaporation must remain constant.

The feeling of hygrothermal comfort does not depend solely on the air temperature.

Hygrothermal comfort depends on:.

• - the radiation (or lack thereof) of the surrounding materials and mainly of the walls of the building envelope, that is, also its temperature and heat capacity;.

• - the ambient temperature of the air;.

• - the air speed (prevent or cause forced ventilation#Forced_ventilation "Ventilation (architecture)"), air flow...);

• - the partial pressure of water vapor or vapor tension of the ambient air.

As seen, hygrothermal comfort is not defined only by a fixed temperature and relative humidity. The fact that an indoor environment has an air conditioning system, with the thermostat set at 23 °C and 50% relative humidity, does not mean that hygrothermal comfort is required because it also depends on other parameters, such as the metabolic rate and the clothing (coat) index.

Thus, since the beginning of the century, various authors have been developing comfort models, either to respond with thermomechanical means or through natural means. In the first case, the comfort nomograms of the United States Association of Engineers were developed to advance alongside the air conditioning systems created by Carrier and in the second to maintain comfort with the design of the building and its envelope through passive design techniques.

The models most accepted by the community of bioclimatic architects and engineers are those developed by the Olgyay brothers and Baruch Givoni.

Buildings and hygrothermal comfort

Thus, an organism must be maintained at a constant temperature, to avoid cooling or heating, with

This purpose has residual heat evacuation mechanisms that are normal heat exchange mechanisms.

They are the following:

• - Conduction: It is the transmission of heat between the surface of the body and the contact elements. This heat flow depends on the thermal conductivity coefficient of these elements.

While the first three forms of transmission refer to sensible heat, evaporation refers to latent heat.

The feeling of hygrothermal comfort does not depend solely on the air temperature.

Hygrothermal comfort depends on:.

• - the radiation (or lack thereof) of the surrounding materials and mainly of the walls of the building envelope, that is, also its temperature and heat capacity;.

• - the ambient temperature of the air;.

• - the air speed (prevent or cause forced ventilation#Forced_ventilation "Ventilation (architecture)"), air flow...);

• - the partial pressure of water vapor or vapor tension of the ambient air.

The models most accepted by the community of bioclimatic architects and engineers are those developed by the Olgyay brothers and Baruch Givoni.

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Thermal well-being urban planning

Introduction

Physiology, environment and comfort

Thermal well-being urban planning

Introduction

Physiology, environment and comfort

Buildings and hygrothermal comfort

Buildings and hygrothermal comfort