1. THERMAL COMFORT

2. THERMAL COMFORT Perception of temperature influenced by: Season
Clothing
Humidity
Air Movement
Presence of heat given off by other bodies and equipment

3. THERMAL COMFORT Body temperature regulated through: Skin Clothing
Buildings

4. THERMAL COMFORT Normal Body Temperature: 98.6 degrees Fahrenheit
Few degree variation = distress

5. THERMAL COMFORT
Between 1920 and 1970, a period of cheap energy costs, people developed a preference for year round temperatures in the range of 72 – 78 degrees Fahrenheit
Preferred comfortable temperature for most people is 65 – 76 degrees Fahrenheit in the winter

6. THERMAL COMFORT Cold Sensitive Areas: Upper Lip Nose Chin Chest
Fingertips

7. THERMAL COMFORT
Thermal comfort is achieved when a stable, normal body temperature is achieved
The result of a balance between the body and its environment

8. MAINTAINING THERMAL EQUILIBRIUM
…when heat production equals heat loss

9. Building Heating and Cooling Systems:
THERMAL COMFORT
Building Heating and Cooling Systems:
Used to control how much heat the human body gives off
Does not heat/cool the body but adjust the thermal characteristics of the indoor space to reduce the rate at which our bodies lose heat

10. THERMAL COMFORT Gender Differences
Men feel warmer than women when first in a space, but later feel cooler than a woman would
Men take 1 – 2 hours to feel as warm/cool as a female in the same space

11. THERMAL COMFORT Age Differences
Elderly and college age students are similar in the responses to thermal preferences and responses

12. THERMAL COMFORT Comfort Conditions
Independent of the time of day or night
Individuals are consistent in their thermal preferences

13. THERMAL COMFORT
ASHRAE Standard : Thermal Environmental Conditions for Human Occupancy
Describes the combinations of indoor space conditions and personal factors that create comfort

14. THERMAL COMFORT
ASHRAE Standard : Thermal Environmental Conditions for Human Occupancy
Report indicates that our sense of being warm or cool enough is the result of interactions between:
Temperature
Thermal Radiation
Humidity
Air Speed
Personal Activity Level
Clothing

15. THERMAL COMFORT Thermal Sensations – feelings of being: Hot Warm Cool
Cold
Range of classifications in-between

16. THERMAL COMFORT
Indices/Indexes – Integrate environmental factors used to describe thermal comfort conditions
Dry-Bulb Temperatures
Wet-Bulb Temperatures
Operative Temperature

17. THERMAL COMFORT Dry-Bulb Temperatures
The ambient air temperature as measured by a standard thermometer
Wet-Bulb Temperatures
Estimate the effect of temperature, humidity, wind speed and radiation

18. THERMAL COMFORT Operative Temperature
Uniform temperature of an imaginary enclosure in which the occupant would exchange the same heat by radiation and convection as in the actual environment

19. Source: Bradshaw. The Building Environment. Wiley
THERMAL COMFORT
Effective Temperature Scale
Correlated to Physiological Reactions, Comfort and Health
Source: Bradshaw. The Building Environment. Wiley

20. Source: Bradshaw. The Building Environment. Wiley
THERMAL COMFORT
Guidelines for Room Air Temperatures
Source: Bradshaw. The Building Environment. Wiley

21. THERMAL COMFORT Principles of Heat Transfer
Heat always moves from the region of higher temperature to the region of lower temperature
Heat flows from an area of active molecular movement to an area of less movement

22. THERMAL COMFORT Principles of Heat Transfer
Tendency to decrease the temperature and amount of activity in the area with the higher temperature, and increase the temperature and activity in the area with the lowest temperature
When there is no difference = Thermal Equilibrium

23. THERMAL COMFORT Principles of Heat Transfer
Heat energy transferred by:
Radiation
Conduction
Convection
beyondpenguins.ehe.osu.edu

24. THERMAL COMFORT Principles of Heat Transfer
Heat energy transferred by:
Radiation
Conduction
Convection

25. THERMAL COMFORT Principles of Heat Transfer Radiation
Occurs when heat flows in electromagnetic waves from hotter surfaces through any medium to detached colder surfaces

26. THERMAL COMFORT Principles of Heat Transfer Radiation
Infrared electromagnetic waves emanate from an object and carry energy to all bodies within a direct line of sight of that object

27. THERMAL COMFORT Principles of Heat Transfer Radiation
Electromagnetic waves excite the molecules in the objects they hit, increasing the internal energy, and raising the temperature

28. THERMAL COMFORT Principles of Heat Transfer
Radiation: How building materials radiate heat
Reflectance
Absorptance
Emittance

29. THERMAL COMFORT Principles of Heat Transfer
Radiation: How building materials radiate heat
Reflectance
Absorptance
Emittance
Amount of incoming radiation that bounces off a material, leaving the temperature of the material unchanged
White paint

30. THERMAL COMFORT

31. THERMAL COMFORT Principles of Heat Transfer
Radiation: How building materials radiate heat
Reflectance
Absorptance
Emittance
Opposite of reflectance
Allows thermal energy to enter, raising the temperature
Stone

32. THERMAL COMFORT

33. THERMAL COMFORT Principles of Heat Transfer
Radiation: How building materials radiate heat
Reflectance
Absorptance
Emittance
Ability of a material to radiate absorbed heat outward
Black surfaces, stone

34. THERMAL COMFORT

35. THERMAL COMFORT Principles of Heat Transfer
Radiation: Mean Radiant Temperature
Air temperature alone does not adequately measure comfort in a space
Engineers use a calculation called the Mean Radiant Temperature (MRT)
Calculation takes into account heat emitted from surfaces etc

36. THERMAL COMFORT

37. THERMAL COMFORT Principles of Heat Transfer
Radiation: Operative Temperature
Physical measurement
Average of the air temperature of a space and the average of the various surface temperatures surrounding the space

38. THERMAL COMFORT Principles of Heat Transfer Radiation:
Mean Radiant Temperature and Operative Temperature are used by engineers to determine the amount of supplementary heating/cooling needed in a space

39. THERMAL COMFORT Principles of Heat Transfer Conduction
Flow of heat through a solid material
Represents a small fraction of heat loss from our bodies

40. THERMAL COMFORT Principles of Heat Transfer Convection
Transfer of heat by means of a moving stream of a fluid (liquid or gas) rather than another object
Air movement, water

41. THERMAL COMFORT Principles of Heat Transfer Evaporation
Process that results from the three types of heat transfer
Incorporates both sensible and latent heat

42. THERMAL COMFORT Principles of Heat Transfer Evaporation: Sensible Heat
Created by the motion of molecules
Latent Heat
Heat that is transferred when a material changes from a solid to a liquid, or liquid to a gas form

43. THERMAL COMFORT Principles of Heat Transfer Evaporation:
Evaporative Cooling
Occurs when moisture evaporates and the sensible heat of the liquid is converted into the latent heat in the vapor
Air movement increases heat loss caused by evaporation

44. THERMAL COMFORT
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45. THERMAL COMFORT Principles of Heat Transfer
Air Temperature and Air Motion
Natural convection of air over the body dissipates body heat without added air movement
When temperatures rise – air movement must be increased to maintain thermal comfort

46. THERMAL COMFORT Principles of Heat Transfer
Air Temperature and Relative Humidity (RH)
Ratio of the amount of water vapor actually present in the air to the maximum amount that air could hold at the same time

47. THERMAL COMFORT Ted Talk