BUILDINGS AND ENVIRONMENT
TEMPERATURE AND HUMIDITY IN THE INDOOR ENVIRONMENT
Key words: Thermal-humidity microclimate, temperature, humidity, thermal comfort, airflow rate, dew point, thermoregulatory mechanisms
THERMAL-HUMIDITY MICROCLIMATE
Thermal-humidity microclimate is a component of the indoor environment formed by thermal and humidity flows. From the point of view of health and comfort, the thermal-humidity microclimate ranks among the most important component of the indoor building environments. Hygrothermal microclimate is an essential part of indoor air quality (IAQ) constantly influenced by the heat and humidity flows. Hygrothermal microclimate is defined by three fundamental factors - indoor air temperature [°C], indoor relative humidity [%] and air velocity [m/s]. Change one of the variables results in a change in the other two. The temperature and humidity within the building closely interact.
The basic values determining the quality of the thermal-humidity microclimate in buildings are: air temperature, final temperature of spherical thermometer, operating temperature, air flow rate, relative humidity, specific air humidity, and dew point temperature.
The air temperature [°C] also dry temperature is the temperature around the human body, measured by any temperature sensor unaffected by the radiation of the surrounding areas.
The final temperature of spherical thermometer (°C) is the temperature in the vicinity of the human body measured spherical thermometer that includes the effect of the simultaneous action of the air temperature, the temperature of the surrounding surfaces and air velocity.
The operative air temperature (°C) is the uniform temperature of the enclosed space within which one would share radiation and flow as warm as in the real environment. It is determined by the calculation.
The mean radiant temperature (°C) is the uniform ambient temperature, which is shared by the radiation as warm as in the real heterogeneous environment. It is measured by radiometers or calculated from the final temperature of spherical thermometer and air temperature. It serves as one of the input values for operating temperature calculation.
The temperature of the wet thermometer (°C), called psychrometric, is the temperature of the forced-ventilated wet temperature sensor used to determine the relative humidity of the air by a psychrometer.
Relative humidity [%] represents the degree of air saturation by water vapor. It is defined by the ratio of water vapor density in air and humid air saturated with water vapor at the same temperature and pressure.
Dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface
The air flow velocity [m / s] characterizes the movement of air in the space. It is determined by its size and direction of flow. Because the velocity of airflow varies greatly in the space, it is necessary to express its variation with the mean value per time unit.
The basic values determining the quality of the thermal-humidity microclimate in buildings are: air temperature, final temperature of spherical thermometer, operating temperature, air flow rate, relative humidity, specific air humidity, and dew point temperature.
The air temperature [°C] also dry temperature is the temperature around the human body, measured by any temperature sensor unaffected by the radiation of the surrounding areas.
The final temperature of spherical thermometer (°C) is the temperature in the vicinity of the human body measured spherical thermometer that includes the effect of the simultaneous action of the air temperature, the temperature of the surrounding surfaces and air velocity.
The operative air temperature (°C) is the uniform temperature of the enclosed space within which one would share radiation and flow as warm as in the real environment. It is determined by the calculation.
The mean radiant temperature (°C) is the uniform ambient temperature, which is shared by the radiation as warm as in the real heterogeneous environment. It is measured by radiometers or calculated from the final temperature of spherical thermometer and air temperature. It serves as one of the input values for operating temperature calculation.
The temperature of the wet thermometer (°C), called psychrometric, is the temperature of the forced-ventilated wet temperature sensor used to determine the relative humidity of the air by a psychrometer.
Relative humidity [%] represents the degree of air saturation by water vapor. It is defined by the ratio of water vapor density in air and humid air saturated with water vapor at the same temperature and pressure.
Dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface
The air flow velocity [m / s] characterizes the movement of air in the space. It is determined by its size and direction of flow. Because the velocity of airflow varies greatly in the space, it is necessary to express its variation with the mean value per time unit.
THERMAL COMFORT
Thermal comfort can be defined as the state of the environment, which in humans causes welfare and meets his feelings. Man does not feel cold nor too warm. Thermal comfort is a state of balance between the person and indoor environment without the overburdening thermoregulatory system.
REGULATION OF THERMAL COMFORT
Both flows can be regulated in a variety of ways, such as changing activities or clothing. Differences between heat produced and heat removed from the body's environment compensate for thermoregulation mechanisms. Thermoregulatory processes are related to age, general health status, nutrition status, motion regime and are directly affected by the thermal and humidity status of the environment.
Thermal comfort is a subjective feeling. The higher indoor temperature is, the lower the performance of occupants is. Performance decreases approximately 25% when the indoor air temperature is 27 °C. Only half of performance is assumed at an indoor air temperature of 30 °C.
The optimal indoor air temperature should be maintained within the range of 19 - 24 °C if there is no difference between room temperature and room temperature than 2 °C at an air flow rate of approximately 0.2 m/s. It is necessary to ventilate shortly by the maximum cross section of the ventilation opening in winter.
In the summer, the negative impact of high temperatures on the human organism must be reduced. The recommended maximum indoor air temperature for the summer season is 26 - 27 ° C.
Thermal comfort is a subjective feeling. The higher indoor temperature is, the lower the performance of occupants is. Performance decreases approximately 25% when the indoor air temperature is 27 °C. Only half of performance is assumed at an indoor air temperature of 30 °C.
The optimal indoor air temperature should be maintained within the range of 19 - 24 °C if there is no difference between room temperature and room temperature than 2 °C at an air flow rate of approximately 0.2 m/s. It is necessary to ventilate shortly by the maximum cross section of the ventilation opening in winter.
In the summer, the negative impact of high temperatures on the human organism must be reduced. The recommended maximum indoor air temperature for the summer season is 26 - 27 ° C.
HUMIDITY AND HEAT COMFORT
Apartments with central heating is necessary to humidify in the winter. During this period, the relative air humidity drops to 20% or less čdue to heating, and thus intensive drying of the mucous membranes of the upper respiratory tract decreases their protective function and increases the possibility of penetration of harmful substances into the lower respiratory tract.
In the summer, high relative humidity associated with high temperature can adversely affect the body's thermal balance by limiting respiration and hence loss of heat. There are many sources of moisture in residential buildings.
The optimum moisture of the internal environment fluctuates from 30 to 50%. The humidity in the range from 30 to 70% is still considered as a comfortable indoor environment. The humidity level of indoor air is affected by the operation of the household and the rate of ventilation. Humidity of in the indoor environment should not exceed 70% during the summer. In winter, the indoor relative humidity should not fall below 30%.
Higher humidity can lead to degradation of materials and structures, and the formation and growth of many kinds of microorganisms and mold formation. Low humidity can damage the mucous membranes (drying, loss of defenses, etc.)
Optimal heat-humidity microclimate occurs when there is a thermal balance of the human body without sweating with optimum heat flow from the body to the environment and optimum skin temperature, optimal uniformity of body heat load in space and time, optimum convection, radiation and vapor flow from the body to the environment.
In the summer, high relative humidity associated with high temperature can adversely affect the body's thermal balance by limiting respiration and hence loss of heat. There are many sources of moisture in residential buildings.
The optimum moisture of the internal environment fluctuates from 30 to 50%. The humidity in the range from 30 to 70% is still considered as a comfortable indoor environment. The humidity level of indoor air is affected by the operation of the household and the rate of ventilation. Humidity of in the indoor environment should not exceed 70% during the summer. In winter, the indoor relative humidity should not fall below 30%.
Higher humidity can lead to degradation of materials and structures, and the formation and growth of many kinds of microorganisms and mold formation. Low humidity can damage the mucous membranes (drying, loss of defenses, etc.)
Optimal heat-humidity microclimate occurs when there is a thermal balance of the human body without sweating with optimum heat flow from the body to the environment and optimum skin temperature, optimal uniformity of body heat load in space and time, optimum convection, radiation and vapor flow from the body to the environment.