FAIRCONDITIONING
STUDENT CERTIFICATE
WORKSHOP
Thermal Comfort & Indoor Air Quality
OVERVIEW
1.
2.
3.
4.
5.
What is Thermal Comfort?
Why worry about Thermal Comfort?
Human Thermal Comfort.
Factors affecting human thermal comfort
Indoor Air Quality
THERMAL COMFORT
WHAT IS THERMAL COMFORT?
“That condition of mind which expresses
satisfaction with the thermal environment and
is assessed by subjective evaluation.”
ASHRAE Standard 55-2010
Thermal Environmental Conditions for Human Occupancy
HUMIDITY
WHAT IS THERMAL COMFORT?
TEMPERATURE
THERMAL COMFORT IN BUILDINGS
•Primary intent of built spaces: protect occupants from weather phenomenon,
control internal environments (thermal comfort, indoor environmental quality)
towards facilitating domestic life or perform work.
•Factors affecting Thermal Comfort such as air temperature, RH, air flows, met
rates are function of climate, architectural design, building envelope, internal heat
gains, occupancy type etc.
•Thermal comfort can be achieved and enhanced through passive and active
methods; active cooling significantly more energy intensive from a life-cycle
perspective (i.e. despite the possibly higher embodied energy of passive cooled
buildings)
WHY UNDERSTAND THERMAL COMFORT?
• Achieves a healthy indoor environment
• Increases productivity
• Forms the basis of design for Architectural and / or Air-Conditioning
design
• Is subjective – depends on climate, age, gender, clothing and even
moods
• Understanding comfort ranges based on variables is critical to
achieve comfort through design
HUMAN THERMAL COMFORT
-- unhealthy
-- unhealthy
CONDITIONS
THE BODY’S RESPONSE
Thermal Comfort is experienced when one’s body expends negligible effort to maintain
internal body temperature at 37°C
Image Source: http://www.medguidance.com/thread/Body-Temperature-Regulation.html
HUMAN THERMAL COMFORT
• The human body employs a multitude of processes to maintain a constant
internal body temperature of 37°C. eg. the body shivers when cold and sweats
when hot
• comfort involves a heat balance (a thermal equilibrium) where: heat in ≈ heat
out
• ‘heat in’ is the consequence of metabolism, radiation, conduction, convection
• ‘heat out’ occurs via radiation, conduction, convection, evaporation
Image Source: http://www.medguidance.com/thread/Body-Temperature-Regulation.html
ARE YOU THERMALLY
COMFORTABLE IN THIS ROOM?
Factors affecting Human Thermal Comfort
1.
Air temperature
2.
Radiation
3.
Air motion
4.
Relative humidity
5.
Clothing
6.
Metabolic rate
Body will react to these
‘Environmental factors’
inside a building and try to
maintain the heat balance
in order to achieve thermal
comfort
Factors affecting Human Thermal Comfort
1.
Air temperature
2.
Radiation
3.
Air motion
4.
Relative humidity
5.
Clothing
6.
Metabolic rate
Need to be controlled
through design
Factors affecting Human Thermal Comfort
1.
Air temperature
2.
Radiation
3.
Air motion
4.
Relative humidity
5.
Clothing
6.
Metabolic rate
These are
‘Personal factors’
Factors affecting Human Thermal Comfort
•Metabolic rate (met): energy generated from the human body
•Clothing insulation (clo):amount of thermal insulation worn (Clo = 1 - corresponds to the insulating
value of clothing needed to maintain a person in comfort sitting at rest in a room at 21 ℃ (70 ℉) with air
movement of 0.1 m/s and humidity less than 50% - typically a person wearing a business suit)
•Air temperature: temperature of the air surrounding the occupant
•Relative humidity: percentage of water vapour in the air relative to the maximum possible moisture it
can contain at a given temperature
•Air velocity: rate of air movement
•Mean Radiant Temperature (MRT) : weighted average temperatures of all surfaces surrounding an
occupant
W/m2
W1)
Btu/hr1)
Met
Reclining, Sleeping
46
83
282
0.8
Seated relaxed
58
104
356
1.0
Standing at rest
70
126
430
1.2
Sedentary activity (office, dwelling, school, laboratory)
70
126
430
1.2
Car driving
80
144
491
1.4
Standing, light activity (shopping, laboratory, light industry)
93
167
571
1.6
Teacher
95
171
583
1.6
Domestic work -shaving, washing and dressing
100
180
614
1.7
Walking on the level, 2 km/h
110
198
675
1.9
Standing, medium activity (shop assistant, domestic work)
116
209
712
2.0
Washing dishes standing
145
261
890
2.5
Domestic work - raking leaves on the lawn
170
306
1043
2.9
Domestic work - washing by hand and ironing (120-220 W)
170
306
1043
2.9
Iron and steel - ramming the mold with a pneumatic hammer
175
315
1075
3.0
Building industry -forming the mould
180
324
1105
3.1
Walking on the level, 5 km/h
200
360
1228
3.4
Volleyball, Bicycling (15 km/h)
232
418
1424
4.0
Building industry - loading a wheelbarrow with stones and mortar
275
495
1688
4.7
Golf, Softball
290
522
1780
5.0
Gymnastics
319
574
1959
5.5
Aerobic Dancing, Swimming
348
624
2137
6.0
Sports - Ice skating, 18 km/h, Bicycling (20 km/h)
360
648
2210
6.2
Handball/Hockey/Racquetball/Cross County Skiing/Soccer
464
835
2848
8.0
Sports - Running in 15 km/h
550
990
3377
9.5
ACTIVITY
met VALUES FOR
VARIOUS ACTIVITIES
Source: http://www.engineeringtoolbox.com/met-metabolic-rate-d_733.html
CLOTHING
clo VALUES
Cumulative clo values for
a outfit combinations are
derived by summing clo
values of components
The mean surface area of
the
human
body
is
approximately 1.7 m2
Trousers
Coveralls
Highly-insulating coveralls
Sweaters
Jacket
Coats and overjackets and
overtrousers
Skirts, dresses
Source: http://www.engineeringtoolbox.com/clo-clothingthermal-insulation-d_732.html
Clo
R Value = m2K/W
Light blouse with long sleeves
Light shirt with long sleeves
Normal with long sleeves
Flannel shirt with long sleeves
Long sleeves with turtleneck blouse
Shorts
Walking shorts
Light trousers
Normal trousers
Flannel trousers
Overalls
Daily wear, belted
Work
Multi-component with filling
Fiber-pelt
Sleeveless vest
Thin sweater
Long thin sleeves with turtleneck
Thick sweater
Long thick sleeves with turtleneck
Vest
Light summer jacket
Smock
Jacket
Overalls multi-component
Down jacket
Coat
Parka
Light skirt 15 cm. above knee
Light skirt 15 cm. below knee
Heavy skirt knee-length
Light dress sleeveless
0
0.15
0.20
0.25
0.30
0.34
0.06
0.11
0.20
0.25
0.28
0.28
0.49
0.50
1.03
1.13
0.12
0.20
0.26
0.35
0.37
0.13
0.25
0.30
0.35
0.52
0.55
0.60
0.70
0.01
0.18
0.25
0.25
0
0.023
0.031
0.039
0.047
0.053
0.009
0.017
0.031
0.039
0.043
0.043
0.076
0.078
0.160
0.175
0.019
0.031
0.040
0.054
0.057
0.020
0.039
0.047
0.054
0.081
0.085
0.093
0.109
0.016
0.028
0.039
0.039
Winter dress long sleeves
0.40
0.062
Nude
Shirts
INSULATION
Thermal Comfort Zone
Certain combinations of air temperature, relative humidity, air
motion, and MRT will result in what most people consider thermally
comfortable condition. This is defined as the ‘comfort zone’
Thermal comfort zone
ASHRAE Standard 55 defines two thermal comfort zones.
1.
ASHRAE Std 55 criteria
2.
Adaptive comfort criteria
Thermal Comfort Standards
Premise
Thermal Comfort depends on
Traditional Standard: ASHRAE Std. 55
Physiological Factors
Environment(temperature, thermal radiation,
humidity, airspeed)
+
Personal Factors (clothing and activity)
New Standard:ASHRAE Adaptive Standard
Slide 19 of 115
Physiological Factors
+
Behavioral Factors
+
Psychological Factors
Introduction to Passive Design
Thermal Comfort
Thermal Loads
Thermal Comfort
ASHRAE Std 55 comfort model
This is the visual
representation of
the thermal
comfort zone
ASHRAE Std 55 comfort model
The upper and
lower limits of
temperature and
relative humidity
is defined here for
thermal comfort
ASHRAE Std 55 comfort model
The definition of
winter and
summer thermal
comfort is slightly
different.
ASHRAE Std 55 comfort model
In the winter, it is
slightly lower
temperatures are
acceptable for
occupants since
the outdoor
temperatures are
very low.
ASHRAE Std 55 comfort model
Likewise in summer,
slightly higher
temperatures are
acceptable for
occupants since the
outdoor
temperatures are
very high.
ASHRAE Std 55 comfort model
This comfort band of
about 21C to 27C is to
be maintained inside
the building throughout
the year
ASHRAE Std 55 comfort model
Which means that the
interiors have to be
climate controlled.
This is exactly what air
conditioning systems do.
ASHRAE Std 55 comfort model
But there are many times
in a year when the
outdoor conditions are
favourable.
Which means, that the
outdoor conditions are
comfortable.
ASHRAE Std 55 comfort model
During that time, we
should not be
mechanically conditioning
the interiors, but instead
opening out the building
to the natural
environment.
ASHRAE Std 55 comfort model
But that does not happen
in buildings, especially in
commercial buildings
which are largely centrally
air conditioned.
In the residential sector,
this is not the case where
occupants take control of
their thermal comfort
ASHRAE Std 55 comfort model
The question is – do we
need to stick to this tight
temperature conditions
throughout the year ?
Or can we vary the
internal conditions as per
the outside conditions ?
Introduction to Passive Design
Thermal Comfort
Thermal Loads
Thermal Comfort
Adaptive Comfort Model
• Occupants are
acceptable of slightly
higher temperatures
inside the building
when the outside
temperatures increase
• Hence the shape of
this model looks like
an ascending line
IMAC - India Model for Adaptive (Thermal) Comfort
Current buildings in India follow the stringent ISO-2005 and ASHRAE-55 criteria leading to
sealed air-conditioned buildings
• IMAC proposes new, India-specific comfort guidelines
•
Some Study Outcomes:
Indian occupants are more tolerant of warmer temperatures than what is predicted for
ASHRAE Standard
Occupants in AC buildings find temperatures 22-27°C acceptable compared to current
stringent 22.5±1°C
Occupants in naturally ventilated buildings find temperatures between 18.1-30.9°C acceptable
Using this criteria will lead to lower energy consumption and higher occupant comfort
Source: An Introduction to India Model for Adaptive(Thermal) Comfort , CEPT University
BIKANER – HOT & DRY
MUMBAI – WARM & HUMID
NEW DELHI – COMPOSITE
BANGALORE – MODERATE
Applying thermal comfort model
1.
It is important to understand which comfort model is to be used
2.
You could choose to apply different comfort models in sections of
the building.
3.
Thus, this criteria can also inform the programmatic zoning of
spaces
Applying thermal comfort model
1.
For eg, you could apply the adaptive comfort model to the naturally
ventilated public spaces and you could use the ASHRAE Std 55
model for the laboratory spaces which needs to be climate
controlled.
2.
This method can go a long way in ensuring thoughtful cooling and
energy efficiency
MEASUREMENT OF THERMAL COMFORT
• Pre-construction – Building simulations to predict thermal
comfort
• Post Occupancy – PMV Index, PPD, measurements of
thermal comfort parameters
MEASUREMENT OF THERMAL COMFORT - PMV
http://sustainabilityworkshop.autodesk.com/buildings/human-thermal-comfort
MEASUREMENT OF THERMAL COMFORT - PMV Index
The PMV index predicts the mean response of a large group of people according
to the ASHRAE thermal sensation scale.
PMV = (0.303
-0.036M
e
+ 0.028) L
PMV = Predicted Mean Vote Index
M = metabolic rate
L = thermal load defined as the difference between the internal heat production and the heat loss to the
environment , for a person at comfort skin temperature and experiencing evaporative heat loss by
sweating at the actual activity level
Source: http://www.engineeringtoolbox.com/predicted-mean-vote-index-PMV-d_1631.html
MEASUREMENT OF THERMAL COMFORT - PPD
Source: http://ceae.colorado.edu/~brandem/aren3050/docs/ThermalComfort.pdf
Thermal Comfort Tool
http://comfort.cbe.berkeley.edu
Exercise: Comfort Zone on a Psychrometric chart
Plot the following on the City-Specific Psychrometric Chart
1)DB=20C,
2)DB
RH=20%
=20C, RH=80%
3)DB=23C,
RH=20%
4)DB=23C,
RH=60%
5)DB=23C,
RH=80%
6)DB=26C,
RH=20%
7)DB=26C,
RH=50%
Join the dots
Observe the approximate % of ‘dots’ inside the comfort zone
I think this should start giving you many ideas right
away..
What kind of design
strategies are
applicable in this region
so as to move the
conditions within the
comfort zone ??
Introduction to Passive Design
Patna
Thermal Loads
12% comfort hours
Thermal Comfort
2% comfort hours
Nagpur
①
Jaipur
psychrometric
14% comfort hours
Thermal Comfort
Chennai
15% comfort hours
MEASURING INSTRUMENTS
WETBULB AND DRY BULB
TEMPERATURE THERMOMETER
DATA LOGGER – MEASURES
EITHER SINGLE PARAMETERS
OR MULTIPLE PARAMETRS
AT SET FREQUENCIES AND
MAINTAINES A
COMPUTERIZED LOGS OF
DATA RECORDED
VELOCITY METERS – MEASURES AIR
VELOCITY AND SOME METERS ARE
CAPACITATED TO MEASURE
HUMIDITY AND TEMPERATURE.
SUMMARY: Thermal Comfort
• Thermal comfort is an important and basic design intent. It is the ‘end’
goal, while ‘Air Conditioning’ is a ‘means’
• Understanding values of thermal comfort parameters for a specific site in
a particular climatic region avoids overdesign of mechanical systems.
• Approaching building design through the lens of ‘thermal comfort’ rather
than the lens of ‘Air Conditioning’ is the essence of ‘thoughtful cooling’;
reduces operational energy, environmental impacts and also life-cycle
costs
INDOOR AIR QUALITY
WHAT IS INDOOR AIR QULAITY (IAQ)?
Acceptable indoor air quality is defined as (as per ASHRAE 62.1):
“The air in which there are no known contaminants at
harmful concentrations as determined by cognizant
authorities and with which a substantial majority (80% or
more) of the people exposed do not express
dissatisfaction”
What is IAQ?
• IAQ is an intrinsic part of ‘Indoor Environmental
Quality’ (IEQ)
• IEQ refers to the following aspects of indoor
environment such as  Lighting – Lux levels, Intensity, Glare etc
 General Aesthetics – Interior architectural design,
furniture layout, zoning of spaces.
 Thermal Comfort – Temperature, Humidity, Wind
Velocity, Clothing, Metabolism..etc
 Acoustics – Noise levels, Reverberations,
sound insulation etc.
 Indoor Air Quality (IAQ)
IAQ ISSUES
• Reduced Oxygen levels
• Air pollution from indoor and/ or outdoor pollutant sources
• Discomfort due to over or under-draught of air
• Dust generation
• Strong odors, VOC’s and irritants
CAUSES OF IAQ ISSUES
• Inadequate Ventilation (mechanical and natural ventilation)
• Inadequate or no fresh air intakes; can be avoided through use of passive cooling
techniques versus conventional HVAC systems
• Materials for building construction and interiors: high VOC paints, adhesives
sealants, formaldehyde-based wood products
• Absence of exhaust mechanisms to vent pollutants, odour and air borne irritants
from indoor spaces eg. strong odours/fumes from kitchen, printer rooms, photocopy
rooms, battery rooms, storage areas, smoking rooms, laundry rooms etc.
• Ineffective mechanisms to shield indoor spaces from external dust
CONSEQUENCES
• IAQ issues are often neglected since negative impacts are often intangible or
precipitate adverse impacts over protracted time periods
• Adverse impacts on health, well being and productivity of occupants are
significant yet silent (not causally linked by occupants to intrinsic building
features)
• Buildings with poor IAQ often exhibit symptoms of SICK BUILDING
SYMDROME; a design-related phenomenon that plagues a broad spectrum
of commercial buildings globally and detrimentally affects well being of
occupants
CONTROL STRATEGIES FOR REDUCING AIR CONTAMINATION
Adequate
Ventilation
Pollutant
source control
Removal of
Pollutants
Treatment of
Pollutants
• Ventilation helps in the dilution of pollutants
• It further improves the air by providing more O2
• May also bring cooling comfort by reducing the temperature of air.
• Do not use products which emit pollutants. Ex: Use Low VOC paints and
Wood no Urea formaldehyde content.
• Identify potential pollutant sources and design spaces systems
accordingly.
• Removing pollutants by physical or chemical means.
• Treating of contaminants by physical, chemical or biological means to
produce harmless products; example – Ozone generators, indoor plants
etc
MEASUREMENT AND MONITORING OF IAQ
• Indoor air quality test to be performed before occupancy of
a building.
• The major types of contaminates and others that need to be
checked (in terms of ppm-parts per million) and monitored
are as follows:
POLLUTANT DECTECTOR IN
PARTS PER BILLION
a. Formaldehydes
b. Particulate matters (PM 10),
c. Total volatile organic compounds,
d. Carbon monoxide,
e. Phenyl cyclohexene (found in carpet fabrics)