This document discusses thermal comfort and factors that affect it. Thermal comfort is defined as a psychological state of satisfaction with one's thermal environment. It is affected by environmental factors like air temperature, humidity, air speed, and radiant heat as well as personal factors like activity level and clothing. Proper ventilation and control of temperature, humidity, and air speed are needed to maintain thermal comfort. The building envelope and mechanical systems work together to provide thermal comfort by minimizing heat transfer and maintaining a balance between heat production and heat loss in the body.

1. VENTILATION
QSB 1714
Prepared by: Lim T. S.

2. Thermal Comfort

3. Thermal Comfort
 Thermal comfort is defined in British
Standard BS EN ISO 7730 as:
 ‘that condition of mind which
expresses satisfaction with the
thermal environment.’
 So the term ‘thermal comfort’
describes a person’s
psychological state of mind and is
usually referred to in terms of
whether someone is feeling too
hot or too cold.

4. Thermal Comfort
 Thermal comfort is very difficult to define
because you need to take into account a
range of environmental and personal factors
when deciding what will make people feel
comfortable.
 Even people who are in the same room can feel
significant temperature differences due to their
metabolic rates, which makes it very hard to
find an optimal temperature for everyone in a
given location.
 The best that you can realistically hope to
achieve is a thermal environment that satisfies
the majority of people in the workplace, or put
more simply, ‘reasonable comfort’.

5.  Thermal comfort is a term used by the American
Society of Heating, Refrigerating and Air-
Conditioning Engineers, an international body. It
is defined as the state of mind in humans that
expresses satisfaction with the surrounding
environment (ANSI/ASHRAE Standard 55).
Maintaining this standard of thermal comfort for
occupants of buildings or other enclosures is
one of the important goals of HVAC (heating,
ventilation, and air conditioning) design
engineers.
Thermal Comfort

6.  Thermal comfort is affected by heat
conduction, convection, radiation, and
evaporative heat loss. Thermal comfort is
maintained when the heat generated by
human metabolism is allowed to dissipate,
thus maintaining thermal equilibrium with
the surroundings. It has been long
recognised that the sensation of feeling hot
or cold is not just dependent on air
temperature alone.
Thermal Comfort

7.  Thermal discomfort has been known to
lead to Sick Building Syndrome symptoms.
The combination of high temperature and
high relative humidity serves to reduce
thermal comfort and indoor air quality. The
occurrence of symptoms increased much
more with raised indoor temperatures in the
winter than in the summer due to the larger
difference created between indoor and
outdoor temperatures.
Importance of thermal comfort

8. Thermal Comfort
What affect thermal comfort?
 Personal factors (health, psychology, sociology
& situational factors)
 Activity levels
 Insulative clothing
 Air temperature
 Mean radiant temperature
 Air movement/velocity (see wind chill factor)
 Relative humidity (see also perspiration)

9.  Each person has a different metabolic rate,
and these rates can fluctuate when a person is
performing certain activities, or under certain
environmental conditions.
 Level of activity influences the level of heat
generated. In high activity the temperature rises
and the more heat you will give off.
 Typical heat output of an adult male

10.  The amount of clothing that we wear generally depends
on the season and affects our thermal comfort.
 Clothing is measured in a scale called clo value.
 During cold weather, layers of insulating clothing can
help keep a person warm. At the same time, if the
person is doing a large amount of physical activity, lots
of clothing layers can prevent heat loss and possibly
lead to overheating. Activity level is compared to being
seated quietly, such as in a classroom. This standard
amount of insulation required to keep a resting person
warm in a windless room at 70 °F (21.1 °C) is equal to one
clo.

11. Environmental Comfort Factors
The conditions that maintain the thermal balance
in a building are:
 Air temperature (dry bulb – deg C)
 Humidity of the air (%)
 Air speed (m per sec)
 Radiant conditions
These factors are controllable through design
– a passive system should control all four factors;
– an active (HVAC) system is expected to control the first three
(with “architecture” controlling the fourth)

12. When we adjust a thermostat,
we are setting a goal for a comfort air temperature.

13. …and the level of humidity at that temperature.
 Relative humidity creates the perception of an extremely
dry or extremely damp indoor environment.
 This can then play a part in the perceived temperature
and their thermal comfort. The recommended level of
indoor humidity is in the range of 30-60%.

14. and the temperature* of the wall, window,
ceiling, and floor surfaces in the room
* This condition is called the
“mean radiant temperature”

15. To feel good, a range of combinations
create a comfort field in which:
 The air is not too humid
 Air speeds remain within established limits
 The difference between radiant and air
temperature remains small
 The difference of the radiant temperature
in different directions (between your body
and adjacent surfaces) remains small.
 Room air temperature between head and
feet is small
 The air is clean

16. Optimal thermal comfort requires the heat loss of the
human body to be in BALANCE with its heat production.
This is similar to the relationship between an activity
(exercising, skiing…) and clothes - our second skin.

17. And our home….
…which we might think of as our third “skin”.

18. What are the qualities that assure we are
comfortable in our homes?

19. The ability to provide thermal comfort is one of the
most important functions of a building.
not too hot, not too cold

20. Comfort in building
 Good building is not only about avoiding
problems, it should also be about creating
positively pleasurable and healthy living places.
 Comfort in building is about the physical
environment in its totality.

21. Comfort in building
 Human beings operate and feel better when they
are at temperatures which are comfortable. It is now
well understood that in the workplace, accidents
increase as temperatures go outside the zone of 16
to 24°C. However temperature is also strongly linked
to humidity levels as regards comfort.
 In the section on health, controlling humidity and
temperature was seen as a method of controlling
pollutants . Interestingly the levels of humidity and
temperature which are most healthy are also the
most comfortable. There is no conflict between
health and comfort.

22. Maintaining this comfort field is the
domain of these two important
building systems:
 BUILDING ENVELOPE
Which includes the walls, floors, and roof or ceilings that
enclose the building, and any penetrations of that
enclosure for doors, windows, chimneys, vents, etc. plus
the accumulated air leakage created by gaps in the
structure
 MECHANICAL SYSTEMS
That provide supplemental heating, sometimes cooling,
and any controlled ventilation.

23. Shortcomings in the building envelope often require
us to tolerate conditions outside the comfort field.
Buildings that are leaky,
drafty, and minimally
insulated, with average
windows, variation in
temperature between
ceiling and floor, and
cold surrounding
surfaces are likely to be
experienced as
uncomfortable
…this is typical of MOST
buildings!

24. We seek control over these conditions thru the use
of mechanical systems like boilers and furnaces.

25. To overcome our discomfort
we may rely (at a cost) on
additional fans, heaters,
humidifiers, etc. to establish a
local comfort zone.
…or just wear more clothes

26. Comfort design in building
What would you consider in design to maintain
temperature in buildings?
 The resistance of a material to the passage of
heat and the thermal conductivity of the
material in passing the heat along are the
basics of understanding of maintaining a steady
temperature and a comfortable thermal indoor
environment.
 In order to maintain a comfortable room
temperature the building must be provided with
as much heat as is lost through ventilation.

27. Comfort design in building
 Comfortable temperature for humans is provided by
balancing the heat lost through conduction and
ventilation through the fabric with similar heat.
 Optimum temperature will depend on material used
, type of construction, orientation of the building and
degree of exposure to the rain and wind.
 What will the loss of heat in buildings depend on?
 Materials used
 Type of construction
 Orientation of the building in relation to the sun
 Degree of exposure to rain and wind

28. These are the building design strategies and effects that we rely
on to create the conditions that assure thermal comfort.

29. Indoor Air Quality

30. Causes of Indoor Air Quality Problem
 Temperature and/or Humidity
 Too much glare
 Inadequate fresh air
 Lead to carbon dioxide (CO2) buildup
 Normal outdoor CO2 Level is 350 ppm
 Indoor CO2 level can be 600-800 ppm
 > 1000ppm CO2 levels –Tired/sleepness
 Cal/OSHA permissible exposure limit for
CO2 is 5000 ppm.

31. Sources of Indoor Pollutants
Base on Specific Building
 Combustion activity
 Furniture
 Chemical
 Building materials
 Food
 Water
 Smoking activity
 Outdoor air pollution

32. Control of indoor pollutant methods include:
1. remove source of pollution
2. provide local extract at pollution sources
3. provide sufficient general ventilation to
dilute and remove the pollution
4. purify internal air

33. Introduction of Chemicals &
Contaminants into the Building
 Old food – Forgotten lunches/snacks
 Building Remodeling – Adhesives, Paints
 Select Low volatile/low toxicity products
 Schedule work on weekends/after hours
 Allow remodeled area to off-gas prior
to re-occupation
 Temporarily relocate employees

34. Introduction of Chemicals &
Contaminants into the Building
 Building air inlet – Auto exhaust
 Cleaners
 UCOP Uses green seal cleaning supplies
 Non-Toxic
 Not a skin sensitizer
 Does not contain substance which
contribute to poor indoor air quality
 If using a cleaner – be aware of how
your actions may impact your co-
workers

35. Introduction of Chemicals &
Contaminants into the Building
 Printer/Copying Machines
 Can generate particulate and
ozone
 Ozone –eye & respiratory irriation
 Do not place in room with poor
ventilation
 Do not point printer exhaust at
individuals

36. PASSIVE STACK VENTILATION
(PSV)

37. Passive Stack Ventilation (PSV)
 Combines with trickle ventilation through window
frames.

38. The simple vertical (or as near vertical as possible)
ducts from kitchen and bathroom to ridge vents or a
roof terminal.

39. Passive Stack Ventilation (PSV)

42.  One option to provide
domestic ventilation is the use
of a passive stack (PSV) system.
 This uses a combination of the
air flowing over the roof and the
natural buoyancy of warm
moist air to lift the moist, stale air
from the kitchen, bathroom, etc
up ducting to the roof ridge
level where it escapes into the
atmosphere.

43. Fresh air is drawn into the
building through the trickle
vents in the windows and
doors etc.
Without the need for any
electric fans or control, PSV
system are energy
efficient. The amount of
ventilation achieved
depends largely on the
amount of movement of
the external air and the
external air temperature.

44. Factors Affecting Ventilation &
Wind Forces Include:
 Average wind speed
 Prevailing wind direction
 Seasonal and daily variation in wind speed and direction
 Local obstructing objects, such as nearby buildings and
trees
 Position and characteristic of openings through which air
flows; and
 Distribution of surface pressure coefficients for the wind.
 Natural ventilation systems are often designed for wind
speeds of half the average seasonal velocity because
from climatic analysis there are very few places where
wind speed falls below half the average velocity for many
hours in a year.

45. Guidelines for natural ventilation
 A natural ventilation system should be
effective regardless of wind direction and
there must be adequate ventilation even
when the wind does not blow from the
prevailing direction;
 Inlet and outlet openings should not be
obstructed by nearby objects;
 windows should be located in opposing
pressure zone since this usually will increase
ventilation rate;
 A certain vertical distance should be kept
between openings for temperature to
produce stack effect;
 Openings at the same level and near to
the ceiling should be avoided since much
of the air flow may bypass the occupied
zone;
 Architectural elements like wingwalls,
parapets and overhangs may be used to
promote air flow into the building;

46. Guidelines for natural ventilation
 Topography, landscaping, and surrounding buildings
should be used to redirect airflow and give
maximum exposure to breeze;
 In hot, humid climates, air velocities should be
maximized in the occupied zones for bodily cooling;
 To admit wind air flow, the long facade of the
building and the door and window opening should
be oriented with respect to the prevailing wind
direction;
 If possible, window openings should be accessible to
and operable by occupants;
 Vertical shafts and open staircases may be used to
increase and generate stack effects;
 Opening in the vicinity of the neutral pressure level
may be reduced since they are less effective for the
thermally induced ventilation;

47. Effects of natural ventilation of thermal comfort
 Many buildings use a HVAC (Heating Ventilation Air
Conditioning) unit to control their thermal environment.
Recently, with the current energy and financial
situation, new methods for indoor temperature control
are being used. One of these is natural ventilation.

48. Effects of natural ventilation of thermal comfort
 This process can make the controlled indoor air
temperature more susceptible to the outdoor weather,
and during the seasonal months the temperatures
inside can become too extreme. During the summer
months, the temperature inside can rise too high and
cause the need for open windows and fans to be used.
In contrast, the winter months could call for more
insulation and layered clothing to deal with the less
than ideal temperatures.

49. Barriers to the Application of
Natural Ventilation
 Barriers during building operations
 Safety concerns
 Noise from outdoor
 Dust and air pollution
 Solar shading covering the openings
 Draught prevention
 Knowledge of the users about how to take
the best advantage of natural ventilation

50. Barriers to the Application of
Natural Ventilation
 Barriers during building design
 Building and fire regulations
 Need for acoustic protection
 Difficult to predict pattern of use
 Devices for shading, privacy and daylighting may hamper
the free flow of air
 Problem with automatic controls in openings
 Lack of suitable, reliable design tools
 Other barriers
 Impact on architectural and envelope design
 Fluctuation of the indoor conditions
 Design a naturally ventilated building requires more work but
could reduce mechanical system (design fee on a fixed
percentage of system’s cost)
 Increase risk for designers
 Lack of suitable standards

51. Indoor Air Quality Council-USA
The IAQ Council offers certifications in five disciplines
related to indoor air quality:
 Microbial Consulting and Investigation
 Council-certified Microbial Consultant (CMC)
 Council-certified Microbial Investigator (CMI)
 Microbial Remediation
 Council-certified Microbial Remediation Supervisor
(CMRS)
 Council-certified Microbial Remediator (CMR)
 Indoor Air Quality Administration
 Council-certified Indoor Air Quality Manager (CIAQM)
 Council-certified Microbial Claims Adjuster (CMCA)

52. Indoor Air Quality Council-USA
Indoor Environmental Consulting and
Investigation
 Council-certified Indoor Environmental
Consultant (CIEC)
 Council-certified Indoor Environmentalist (CIE)
Residential Mold Inspection
 Council-certified Residential Mold Inspector
(CRMI)

53. Malaysian Approach
Green Building Index (GBI)
 The Green Building Index (GBI) is Malaysia’s
industry recognized green rating tool for buildings
to promote sustainability in the built environments
and raise awareness among Developers,
Architects, Engineers, Planners, Designers,
Contractors and the Public about environmental
issues and our responsibility to the future
generations.

54. THANK YOU