The presentation shows the various measures to calculate the thermal comfort in buildings from ASHRAE to IMAC and also provides low energy methods to improve thermal comfort.

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Thermal Comfort
in Buildings
Green Building and
Energy
Management.
Presented by
Nataraja Sai
Charan.

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"That condition of mind
that expresses satisfaction
with the thermal environment"
It is maintained when the heat
generated by the human metabolism
is allowed to dissipate at a rate that
maintains thermal equilibrium in the
body. Any heat gain or loss beyond
this generates substantial discomfort.
What is
Thermal
Comfort?

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Building Energy
consumption by
type
 Air conditioning
accounts for 44% of a
building’s energy
consumption. This
showcases the
necessity for the
designers to opt for
energy efficient space
conditioning systems.

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SIX VARIABLES THAT
DRIVE OCCUPANT
THERMAL COMFORT
 The American Society
of Heating,
Refrigeration and Air-
Conditioning Engineers
(ASHRAE) identify six
variables that predict a
person’s thermal
comfort.
 These can be clubbed
under Environmental
Factors and Personal
Factors.

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PMV(Predictive Mean Vote)
 The ASHRAE 55 comfort standard uses a formula to translate
these six variables into a single output, called predictive mean
vote (PMV) which is a 7 point thermal scale( ranging from -3
cold 0 for Neutral to +3 hot) . A PMV of 0.5 indicates that at
those conditions 90% of people in the space will vote they are
comfortable.
 While using the six variables to determine the thermal comfort
zone, there is no range for individual parameters as such under
PMV. The value range of one of the parameter depends on rest
of the five parameters. The PMV is looked in relation to
Predicted Percent Dissatisfied (PPD) which gives the % of
people who are comfortable at the given temperature.

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PMV and
PPD

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ASHRAE
comfort chart
 The comfort zone shifts
from left to right based on
the clothing, wherein for
higher value for clothing
the zone shifts to the left.
 Even the zone of comfort
changes based on the
indoor movement of air, in
general for higher
movement of air the
comfort zone shifts to the
right.( it is 0.1m/s to 0.2m/s
for still air and if more than
05 m/s it is high indoor air
movement.)

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z Nominative
Appendix A-
Activity levels-
Metabolic Rates
for Typical Tasks.

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Formula used for determining the indoor
design temperature:
 T min @ I cl = ((l cl - 0.5) x T min @ 1 Clo + (1.0 – l cl) x T min
@ 0.5 Clo ) / 0.5
 T max @ I cl = ((l cl - 0.5) x T max @ 1 Clo + (1.0 – l cl) x T max
@ 0.5 Clo ) / 0.5

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IACM Indian Adaptive Comfort Model
 IACM classifies the
building ventilation into
three types based on their
HVAC system ranging
from naturally ventilated
to complete Air-
Conditioning.

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Contd.
 The standard classification is based on the ADAPTIVE thermal
comfort model which differentiates the thermal tolerance of
occupants accustomed to monotonic temperature (such as air –
conditioned places) and people habituated to variation in internal
temperatures (such as naturally ventilated structures).
 The indoor operative temperature values for different building
types (NV, MM & A/c) are pre-calculated for most Indian cities.
These are available in Appendix-1, GRIHA v-2015 manual

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Naturally Ventilated building

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Mixed Mode
Ventilated buildings
 The MM Ventilated
buildings takes into
consideration the
combination of natural
ventilation and the
availability of air-
conditioning when
necessary.

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AC buildings- Air Temperature Based
Approach
 Equation: Indoor Operative Temp. (˚C) = 0.078 * Mean
Monthly Outdoor DBT + 23.25
 Acceptability Range for Air Conditioned buildings is ± 1.5˚C

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Improving Thermal Comfort In
Residential Buildings
1. Proper orientation of Buildings, this reduce the impact of
unfavorable weather conditions like solar radiation, driving rain
and thunderstorm.
2. Proper Ventilation- proper positioning the windows and
opening them create air movement in the house. Walls and
vegetation should not be too close to the building in order to
avoid diversion of wind away from the openings, thereby
reducing air flow within the building. If possible, the rooms
should be cross ventilated.

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Contd.
3. Using Shading Devices- use of overhangs or horizontal projections
over windows. Double pane windows with tinted glass and glass
coated with reflective film should be used for windows instead of
steels, wood and zincs.
4. Creation of Microclimate- trees can be planted to create micro-
climate that is, small-scale climatic condition at a spot or area or site.
5. Preventing Infiltration – Infiltration can be prevented by sealing the
sites of air leaks. This can be achieved by caulking, weatherizing, good
workmanship, and replacing some aged parts of buildings. Etc.

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Thank you