Thermal comfort is a condition in which the psychological, physiological, and behavioral patterns a person feels comfortable to do the activity with a certain temperature in a lingkungan.Secara theory, humans have the ability to adapt to thermal changes which are divided into three categories, namely adaptation patterns of behavior, adaptation physiological and psychological adaptation.
Adaptation of human behavior patterns eg reflex will flutter when his face was in the room was hot and stuffy. Adaptation is a physiological, when the hand immersed in ice water for five minutes and then put into the water at room temperature, then the hand will feel the warm water and vice versa. Psychological adaptation is to change perceptions about a comfortable temperature level based on expectations and past experiences.
The increase in temperature in a room caused by some source of heat. The first heat source is a natural heat source, such as solar and geothermal. The second heat source is biological heat source, such as humans and animals. Last heat source is a heat source electrical mechanics, such as the engine, lights, and other equipment.
Perpindahaan heat from a heat source to a room is with the way heat radiation, convection, and conduction heat. Heat radiation is heat transfer that occurs through the medium of light. Convection heat is the heat transfer medium that propagates through liquids and gases. Heat conduction is the heat transfer medium that propagate through solid objects.
Factors that affect a person’s thermal comfort is the metabolic rate, the rate of ventilation clothing worn, the room temperature, room air humidity and air velocity at the surface of the skin.
Organizations often perform thermal comfort research, namely ASHRAE / ANSI. Standardization of thermal comfort that is generally used is the ANSI / ASHRAE Standard 55-2010. In addition, the standardization of thermal comfort from other organizations is the EN 15 251 and ISO 7730. Standardization thermal comfort in Indonesia with a number issued by SNI 03-6572-2001.
There are two approaches to research methods to determine the parameters of thermal comfort, ie with the methods of modeling static and adaptive modeling method. What is the method of modeling of static and adaptive modeling method? Let’s continue with the explanation below.
Thermal comfort Static Model
Thermal comfort is a static model search modeling method parameter thermal comfort developed with the assumption that the thermal conditions in a room is fixed. Thermal comfort is a static model does not care about the conditions and climate change outside of the building as well as differences in ability and behavior adaptation to the thermal environment. This study is based on the principle that the ideal temperature in a room should not be changed despite the state of climate change during the four seasons. In this case, the man regarded as passive objects which can not interact and adapt to thermal environments.
Thermal comfort static model is developed by collecting data on the reaction of respondents in a room with artificial climate static. There are two static modeling of thermal comfort, the PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied).
Both modeling was developed by PO Fanger by creating a statistical mathematical equation based on psychological studies of thermal comfort on the skin surface. Respondents were given a question with a scale of -3 to describe the sensation of cold at all up to +3 to describe the sensation of extreme heat and the value 0 to value neutral or comfortable. The values are then processed by a mathematical equation developed Fanger used to obtain roots of the predictive value of the average thermal comfort parameters of a group of respondents.
Six parameters are temperature, indoor thermal comfort, the average room temperature, relative humidity, air velocity, metabolic rate, and the type of clothing. PMV value recommendations are included in the thermal comfort zone is -0.5 <PMV <+0.5 with six boundaries above parameters.
Research to obtain thermal comfort parameter values of a diverse group of respondents is an important step to get comfortable thermal conditions. However, the method PMV does not provide a picture of the level of satisfaction of respondents to a static thermal conditions. Based on that idea, Fanger then developed a mathematical equation that can give you a satisfaction level of the respondents were given the term Predicted Percentage Dissatisfied (PPD).
Adaptive Thermal Comfort Model
Adaptive thermal comfort models based on the principle that the thermal conditions outside the building affect the thermal conditions in buildings and humans have the ability to interact and adapt to a variety of thermal conditions. Adaptive thermal comfort models are based on expectations of a person against thermal environmental conditions based on memories of the past, patterns of behavior, thermal conditions in the neighborhood. Behavior to adapt and interact with the thermal environment, such as opening closed the window, turn on cooling or heating, wear thick or thin, and so forth.
The results of this study have been used as a reference in the standardization of ASHRAE 55-2004 as modeling adaptive thermal comfort. The graph illustrates the adaptive zone occupant satisfaction of 80% and 90% of the temperature of a room than the outdoor temperature.
Standardization ASHRAE-55, 2010 using the outside temperature value of the building as input a question to the respondents and the satisfaction level of thermal comfort gained by finding the arithmetic average value of the average value of outdoor temperature for less than thirty days. Another way is to calculate the temperature value occupant satisfaction levels using different weighting coefficients, referring to the temperature input is outside of the building. These adaptive models should be applied to a building with natural ventilation can be controlled. However, without mechanical cooling systems, occupant activity with meth 1-1.3 metabolic rate and temperature outside the building ranging from 10 ° C (50 ° F) up to 33.5 ° C (92.3 ° F).
A number of researchers have conducted field research in a variety of countries around the world where they inquire about the thermal comfort of the building occupants expected ideal, while measurement of thermal environmental parameters. The results of the analysis of a database of 160 studies concluded that the occupants of the building with natural air circulation system is more accepting and sometimes like the difference thermal conditions greater than the occupants of the building with mechanical ventilation and cooling systems.
Research conducted by de Dear and Brager concluded that the inhabitants who used to live in a building with natural air circulation is much more tolerant of temperature changes are great. This was caused by self-adjustment capability psikolgi, physiology and behavior patterns. Standardization ASHRAE 55-2010 mention there were some adjustments made by occupants with respect to changes in room temperature, for example, wear clothing that is hotter or cooler, open windows to increase air flow, lowers the metabolic rate by reducing the level of activity of the body, or to change the psychological expectations.
Adaptive thermal comfort models also standardized, such as the standardization of the European Union EN 15 251 and International Standard ISO 7730. However, assuming the behavior of occupants and loss method is slightly different mathematical equations with ASHRAE 55-2004. The differences are more fundamental is the ASHRAE standard only applies to buildings without mechanical refrigeration system, while EN15251 can apply to the natural circulation of the building is equipped with a mechanical cooling system.
Future of Thermal Comfort in Indonesia
Before designing a building, we recommend the Architect to consider aspects of thermal comfort as part of the building design objectives. Designers can use static thermal comfort models, such as PMV or PPD on a building that is fully controlled room temperature water system condition. Whereas, for the design of office buildings that temperatures depend on natural air circulation, can use standardization adaptive thermal comfort models. As of this writing, there is no agreement on standardization which is more appropriate to be applied to the building is controlled by the air condition partly indoors or in a certain tempo.
Unfortunately, Indonesia does not have the thermal comfort of standardization are developed in accordance with the climate, the character of the community, and the traditional architectural Indonesia. Standardization of thermal comfort in Indonesia is currently at the thermal comfort issued by SNI. The thermal comfort parameter values obtained from adopting the value of international standardization taken not exhaustive and thus loses its substance.
Future challenges architects, designers, and consultants HVAC in Indonesia is making more standardization in accordance with the conditions of the Indonesian state. Ideally, Indonesia should have a standardized set of thermal comfort through field research that has been adapted to the climate conditions based on meteorological and geophysical data Indonesia, thermal measurement field, patterns of behavior, expectations, psychological, physiological responses, and traditional architectural Indonesia.
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