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8/8/2019 Investigation Indoor Air Quality and Thermal Comfort in Bangkok
1/13
AninvestigationofIndoorAirQualityand
ThermalComfortofaclassroominBangkok
(Aparticular
case
study)
(Asacourse
requirement
for
DPL
642
Indoor
Air
Quality
and
Thermal
Comfort)
by
bhargav
kaushik
&
tanith
vachiraprakanskul
SchoolofArchitecture&Design,KMUTT.
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Introduction
Thehistoryandtimehaveevidencedthatwhenmanacquiredapartofknowledge,
heusedit,hechangedhisactions,andfoundsomemoreknowledge.Thishasbeentheloop
ofevolutionofhumanbeings,atleasttotheextentofscientificdiscoveriesandinventions
thatgeneratedthemodernsocietyatpresent. Ifthefirstman ignoredfireandwheeland
its use, we would not have reached where we are at this moment. We must not let
ignoranceprevailuponourconscienceovercertain issuesthat isnotvisiblebutaffectsus
implacablybutquietly.
Today,ouronlyhope forcarryingourancestorsperseveranteffort tobecome the
best, lies inthehandsofeducationsystem.Thisgiganticsystem inturn isbasedonavery
fundamentalbuilding
block,
classrooms.
As
the
rate
of
academic
inflation
is
rising,
more
and
more studies aregoing on, in classrooms; with even more intensely than any ofour last
centuries have observed in as much larger scale as our current and future population.
Merely, 0.01 score in one GPA can completely change the life and the career, for which
fanaticallytonicsandperformanceenhancingmedicationsarecommercialisedwithvariety
ofsupportsystemworkingtoimproveonelearner.
Withthese,rushinganduptightsurrounding,one tendsto forgetwhat isstored in
nature,andloseslotmorethanwhat isgained.Aclearpictureofthisphenomenoncanbe
seenin
mechanization
of
our
living
conditions,
we
call
them
technologies.
Many
atimes,
our
beloved technologiesdonothelpas itseems tous; for instance, the lovelycoolorwarm
artificialweatherinsideanairtightcontainer.Yes,thatistheHVACsystemanditsminiature
model, the air conditioner. Air conditioners provide a preferred temperature with the
lowest humidity possible to us but fail to supply fresh air. Even if we have the new
generationHVAC system that introduces fresh air concept in their design for which they
chargequitesignificantlyforaplusbonusofnominalreductioninenergybillsthatwetake
homeveygracefully.Alas!Theseairconditionersalsocannothelpushavingtheheaven in
ourhomesthatwasgiftedbynature.Theyalsohavepollutantintheirductsystem.
Pollutionisawordthateveryoneinthisworldwouldbeafraidof,exceptionsarestill
therethough,becauseitsmagnitudeiscomparedthatofthehumanscale.
Comingbacktotheclassrooms,inthisreportitistriedtoexaminetheconditionsof
aclassroom intermsof IndoorAirQualityandThermalComfort,analysetheconditionsto
findouttherealcausesandsuggestthepossibleimprovementinordertoprovideabetter
airqualityandthermalcomfort.Firstthemethodologydescribedhowthetextweredone,
experiments conducted and measurements were recorded. Next the results are brought
into light fordetaileddiscussionwhich is followedbya syntheticdiscussionaboutall the
resultsbeforecomingdowntotheconclusion.
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Methodology:
The indoor air qualityand thermal comfort of a classroomwas observed in three
differentstates:1)AirConditioned,2)NaturalVentilationand3)AidedNaturalVentilation.
First,
air
conditioned
state
was
conducted
by
using
the
air
conditioner
and
one
exhaust
fan
nexttoitasthemeansofairchangeintheroom.Second,naturalventilationwasobserved
bymeansofthreewindowsof2.25m2eachandadooropenedonoppositeside.Thirdthe
naturalventilationwasaidedbykeepingplantsoutsidethewindows.Theobservationwas
done in a classroom of School of Architecture and Design (KMUTT) with a population of
approximately40students.Theusers(students)wereprovidedwithaquestionnairetogive
their feedback about the comfort level in the class room. There were three equipments
usedinthisexperiment.
1. GASMET
TheparticlesweremeasuredbyusingtheGASMET4030FTIR,alightweightFTIRgas
analyserthatcandetectVOC,TICandanaestheticgas.ThisEquipmentwasconnectedwith
alaptopthatrecordedthemeasuredvalues.
2. Testo445
ThetemperatureandwindspeedwithintheclassroomwassampledbytheTesto445in
5differentspots.Thewindspeedgunwaskeptataheightof1.2Mfromthefloorlevel.
3. ThermoGun
TheRaytekLaserTempGunMX2foundthemeanradianttemperatureofthesurfaces in
theclassroom
interior.
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Results:
The resultsare focusedona fewgaseousparticles;Vapour (H2O),CarbonDioxide
(CO2);howevertherewereotherharmfulparticlesmeasurebutnottothedangerouslevel.
The
graphs
below
shows
the
levels
of
carbon
dioxide
(H20)
and
water
vapour
(H20)
during
theobservationinthethreestatesrespectively,
During the observation the
level of carbon dioxide went
dramatically high within an hour
because there was no ventilation
other than the air conditioner and
exhaust fan, therefore thedoorwas
left open for 30mins at 10:58 am.
The line goes up again when there
was no ventilation. This shows how
quickly carbon dioxide can reach a
harmful level with only air
conditionerasameanofairchange.Figure1:CarbonDioxidelevelwithAirconditioning
The followingday the roomwas measuredwith naturalventilation insteadof air
conditioning,theCO2levelinthegraphbelowshowthatitremainsconsiderablywellunder
thedangermarkof2000ppm.However,theairconditionerwasturnedonforpsychological
satisfactionof
some
students
and
teacher
for
which
the
CO2
level
went
up
slightly.
Figure2:
Carbon
Dioxide
level
with
Natural
Ventilation
On the third day, natural ventilation was observed with 67 plants placed on the
balcony from where the wind comes in. At first the class was conducted with air
conditioningturnedonandhencethelevelofCO2was
initially higher, which later came down with natural
ventilationapplied.
In this graph on the right it is very clear that
naturalventilationcanworkmuchbetter if it isaided
withplantmaterialsandmechanicalelementslikefan.
Althoughthedurationofthethreeobservationsvaried
we could have the same time frame to see theFigure3:CarbonDioxidelevelwithAided
NaturalVentilation
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comparisonofthethreestates.
0
500
1000
1500
2000
2500
3000
11:17:37
11:22:37
11:27:37
11:32:37
11:37:37
PPM
Levels
TimeIntervals
Comparison
Day1
Day2
Day3
The graph on the right shows the
comparisonofCarbonDioxide (CO2) levels in
threedifferentVentilationstates:Day1=Air
Conditioned;Day2=NaturalVentilationand
Day3=AidedNaturalVentilation.Thelevelof
theCarbonDioxidegoesupto24timeswhile
the Airconditioner is provided as the only
mean of ventilation, actually it does not
ventilatejustcirculate the sameairwith the
temperature and humidity reduction. It is
harmfulforstudentstohavealevelofCarbon
Dioxide
over
than
2400
ppm
(Joan
M.
Daisey)
in the air they breathe, because it causes
concentration loss, which is a major reason
forthemtofellasleepintheclassroomwhile
thelectureisstillon.
Figure4:ComparisionofCarbonDioxidelevelswiththe
sametimeframeonthreedays(states)
The next particle to consider was the water vapour, contributing to the relative
humidity. Bangkok falls within the hot and humid climatic zone. The average relative
humidity remains within the range of 70% 78% in outdoor areas. According to
psychometric chart 35% 70% of relative humidity is bearable without any physical
discomfort;howeverthepreferencechangesfrompersontopersondependingupontheir
clothing,metabolism,andpsychologicaladaptation.Thedataobtainedfromtheequipment
showsthewatervapourpresentintheclassroominpercentage.
The first day of these experiments, the air
conditioner was operating until 11:20 am;
then it was shut down and windows were
opened forhalfanhour11:50ambecause
of thealarming level in theCarbonDioxide
presentin
the
room.
The
maximum
level
of
1.8%down to0.98%asminimum levelof
watervapourfoundintheairintheroom.
The second day first
half was on natural
ventilation mode until
11:30 am, the
maximum of 2.6% and
minimumof
1.47%
for
thewatervapour.
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The third day, with the aided natural
ventilationmode,beginningfrom11:10amthegraph
startsgoingupandreachesalevelof2.7%.
The relative humidity relates to the water
vapour inaway thatamountofwatervapour in the
airmeasured to theratioofamountof itssaturation
level,i.e.;
asasimplifiedequation.
Thepercentageamountofwatervapourpresentintheindoorroomairinclassroom
variesfrom
2.23%
to
2.68%
during
natural
ventilation
and
for
air
conditioned
state
it
lies
between 0.99% and 1.74% leaving the transitional values due to the change of states.
According to Meteorologist Jeff Haby; (htt4) water vapor varies by volume in the
atmosphere froma trace toabout4%.Therefore,onaverage,onlyabout2 to3%of the
molecules in the airarewatervapormolecules. Theamountofwater vapor in theair is
smallinextremelyaridareasandinlocationwherethetemperaturesareverylow(i.e.polar
regions,verycoldweather).Thevolumeofwatervaporisabout4%inverywarmandhumid
tropicalair.Therefore,itcanbeconsideredthatthewatervaporlevelintheclassroomwas
withinthelimitofnormalcyinthecontextofthehotandhumidclimateofThailand.
However it isquite clear that air conditioning of the classroomkept the humidity
levelalmosttwotimeslowthanitwasduringthenaturalventilation.Inpsychometricchart,
the comfort level is given as below by a Thai forum member named ...,
inhttp://www.tfma.or.th/webboard.(www3)
This chart shows that the
human comfort level is confined
between25Cand31Cintemperature
and35%
to
80%
in
relative
humidity.
However, there are six factor acting
upon thehumancomfort level:1)Dry
Bulb Temperature, 2) Relative
Humidity, 3) Air Movement and 4)
Mean Radiant Temperature being the
environmentalfactors,additionallythe
psychological factors are a) Metabolic
Rate and b) Clothing Level. These factors and their influence on human comfort will be
discussedin
the
discussion.
It
is
necessary
to
mention
that
the
last
factor
can
be
very
useful
forcombatinghumidity in indooraswellasoutdoorenvironments.Thenextdata should
reflectthefourthfactor:MeanRadiantTemperatureofthesurfacesintheclassroom.
5
http://www.theweatherprediction.com/habyhints/281/http://www.tfma.or.th/webboardhttp://www.tfma.or.th/webboardhttp://www.theweatherprediction.com/habyhints/281/8/8/2019 Investigation Indoor Air Quality and Thermal Comfort in Bangkok
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Therewereintotaltwelveitemswithlargesurfaceareasintheclassroom,theother
twoitemswithnoticeablesurfaceareasarenottakentotheconsideration:1)Furnitureand
2)WindowBlinds.The tablesbelowshow themeanradianttemperaturevalues taken for
eachsurface.
Thefirst
day
the
air
conditioner
was
operated
at
23C
for
the
whole
period,
however
itwas turnedoffduring thebreak time for5minutesor so.Therefore themean radiant
temperature on that day was comparatively lower than the later two dates. Only one
particularmaterialthathashighestmeanradianttemperaturevalueonthatdayistheglass
used in the windows. The mean radiant temperature value of a material is directly
proportionate to the temperature of its surroundings, which means that if the materials
withhigherMRTvalueisusedthenitmightbeinfluentialintemperatureriseintheroom.
The next factor to look at is the air
movement,or
wind
speed
(indoor).
The
tables
on
leftshowthewindspeedasmeasuredat5pointsas
shownagaininthepicturebelow:
The above tables indicates that the difference between the air movement in five
different points in the classroom shown in the picture of the right. On day 1 (with air
conditioning) thewindspeedvalueatpoints1and3 ismore than thatofpoints2and4
havingpoint5atthetopwithmaximumwindspeed,howeverthedifferenceisonly0.2m/s
onaaverage.Whilewithnaturalventilationthewindspeedincreasesupto3.3m/stowards
thewindowsidepoints,but thepoint3has the leastairmovementwith0.81m/sat the
maximum.
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Apart from the measurements of the classroom and its conditions, the human
satisfaction level was also brought under observation, since it is a ready reference to
discuss.Therewerequestionnairesgivenouttotheobservedstudentsaskingfivequestions.
Thefollowingistheformatofthatquestionnaire.
Questionnaire (Please tick mark the option(s) as your response,you can choose more than one)
1. How do you physically feel while being in this classroom? Alert, Healthy, Sleepy, Allergic, Hungry, Other: _______________
2. How do you mentally feel while being in this classroom? Fresh, Active, Normal, Bored, Anxious, Other: ________________
3. How do you rate the temperature of the room for you? Too Cold, Cold, Normal, Warm, Hot, Very Hot
4. Where would you like to sit in this classroom? (Towards.) Door Side Wall, Window Side Wall, Back Side Wall, Front Side Wall, Center
5. Please you tell us about the illness/sickness or diseases that you suffer often._____________________________________________________________________________________
Thank you for your participation
However the
students were not
exactly equal in
numbers because
there were some
absents and some
students
did
not
return the
questionnaires. The
followinggraphsare
the students
response to the
questionnaire.
The most of
the
students
feel
sleepy and hungry
while being asked
the first question.
Mentally they dont
feelanyabnormality
except in the first
occasion of air
conditioned state,
19students
felt
bored.
Another
important
feedback
was
that
few
of
them
felt
affected
by
allergies. In terms of thermal comfort the majority expressed natural ventilation to be
normal,whiletherewereremarksaboutthecoldnessinairconditioningstateasinbelow.
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As plotted in the radial graphs on right side above, students sitting preferences
changeinthesethreedifferentstateswhichcanbedrawnasshowninthediagramsbelow.
Therewas
alist
derived
from
the
last
question
that
might
be
helpful
to
understand
whatsicknessthestudentshave.Thatlistincludes:BreathingProblem,Headache,General
Cold,Sinus,Migraine,Boredomordepression,Allergy,Stomachacheetc.
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Discussion:
ThefirstfindingmentionedasapartoftheresultsistheCO2levelintheclassroom,
during air conditioning state the level of CO2 goes up high to 4121ppm, well above the
ASHRAE
standards
level
of
1000ppm
in
air
conditioned
space
(www4).
The
CO2
level
is
harmful, at least to the classroom environment where student need to concentrate;
becauseat2000ppmCO2presencehinderstheirabilitytoconcentrate.Thislinkwecansee
between the CO2 graphs and responses to the questionnaire. The natural ventilation
however kept the CO2 level much lower at a level below 500ppm. There were similar
experiments done at five different schools inHongKong byS. C. Leeet. al suggested an
increaseofCO2levelinclassroomsfortheuseofairconditionersandconcludedtheeither
tohavenaturalventilationorreducetheoccupantstoASHRAEstandardsbeing1personin
2M2(S.C.Lee,41(2000)).Forthecasediscussedabove,therearetwooptionsleftinorder
toprovide
adequate
air
quality
as
per
ASHRAE
standards;
either
to
incorporate
natural
ventilationortolimitthenumberstudentsto30foroneclasssessionastheclassroomarea
is72M2.
The second word of the climate category of Thailand bothers users quite
substantiallythatdrivesthemtohaveairconditioningwithanaddedadvantageoflowering
down the temperature,asmean togetridofwhathasbeenassigned to thembynature.
However looking at the past life style of the local people a more sustainable way of
combatingtheclimaticdiscomfortcanbeconceive.Theuseoffanhasbeeneliminatedby
air conditioningandold style cottonfiberbased dressinghasbeen looked downupon in
everywhere in this region except residences. These two elements helped to reduce the
discomfortfromahot&humidclimate.Onotherhand,humidityorwatervapororH2Ois
notasbiggeranenemyasCO2,henceASHRAEhasthehumiditystandardsbetween30%
60% relative humidity. Fischer mentions that in hot and humid climate schools often
inefficient in providing adequate air quality using HVAC system and categorically they
mentionedthatthereshouldbenaturalventilationatalevelof15cfm/student(FischerJohn
C.).Moreoverfromthepreviousdiscussioninresultsitisclearthatthewatervaporlevelin
theroomremainswithinalimitofnormalcyasmentionedbyJeffHaby.
Thenext
factor
looked
into
was
the
mean
radiant
temperature
of
the
surfaces
in
the
room.TheMRTof theall thesurface isataconsiderably low level in theairconditioned
state,withanexceptionoftheglasspanelsonwindows.Itcertainlyindicatesthatwindows
arethemainsourceofheatgain intheclassroom.Actuallywindowsarenotrequired ifa
space is regulated by HVAC and artificial lighting, which contradicts the position of the
windowsintheclassroomastheyaretoprovidenaturalventilationandnaturallightinginto
theclassroomspace.Therealproblemisthatthereismuchglarefromthesurroundingthat
disables visibility on the projector screen or whiteboard and the wind in location
(Bangkhunthian)isstrongatanaverageof5m/s.
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Speakingofwindatthelocation(Bangkhunthian),theairmovementinsidetheclass
roomalsoshoweddifferences.Duringtheairconditioningstate,themaximumwindspeed
wasbetween0.26m/sand0.86m/s,astheblowerhitscenter(point5)themost,nextthe
doorsidewall(points1,3)andtheleasttothewindowsidewall(points2,4).While inthe
naturalventilation
the
maximum
wind
speed
was
between
0.63
m/s
and
3.69
m/s,
indicatingtheincreaseinairchange.ASHRAEdeterminedthestandardminimumairchange
forofficebuildingsinoccupancytobe5cfmwhichconvertstowindspeedof0.29m/swith
naturalventilation(InterpretationsforStandard62.12004,2004).Theoverallairmovement
issatisfactoryduringthenaturalventilationstatewiththeexceptionatpoint3.Thislowair
movementoccurredbecausetherewasnotexitforairintakefromwindowslikeinpoint1
withthedoorastheonlyairexitforthewholeclassroom.Thisphenomenoncanbeseenin
the followingpictures from left to right representing day1 (HVAC),day2 (NV) andday 3
(ANV)respectively.
Therefore, proper natural ventilation is not achieved equally in the classroom.
Accordingtotheprinciplesoffluiddynamics,thereshouldbeatleastonemoreexitinorder
tohavecompletechangeofthe indoorair.Sincethedoor isoftenclosedfortherequired
quietnessin
the
room
the
only
way
out
for
the
air
in
gets
interrupted
resulting
no
air
change
ornominal.Thereforeitisveryimportanttohaveanalternativeairexitfortheairchangeto
occur. With the consideration that CO2 is a heavier gas than air; an alternative air exit
shouldbeplacedtosweepoutthelowerportionoftheairvolumeintheclassroom.
Thehuman satisfactionwascoveredby thequestionnaireandcouldbesensedby
the response to it. Most of the students observed felt sleepy in classroom, presumably
becausetheyhadnothadenoughsleepthenightbefore,butwiththeresults itcannotbe
ruledout thatpresenceofCO2hadaneffectontheirconcentrationresultingdizzinessor
sleepiness.Withtheresponsetothequestions2&3studentshaveexpressedtheirconsent
to the natural ventilation, however there were little discomfort towards air conditioning
state.Actuallywhenapersonstaysinacolderstatethanthenormalbodytemperaturethat
heorshe tends to loseenergyoutbyconvectionandradiationas thebodyheatremains
constantat36.0Cto37.6C.
Deprivationofnaturalventilationcanbeexaggerated tobeaconcentrationcamp;
howeverthemaingoalofthispaperistoprojecttherealimportanceofnaturalventilation.
Thelackofnaturalventilationmightresultintophysicalsymptomslike:headache,migraine,
sinusandcoldassymptomsinourrespiratorysystem,andboredomasitsbyproduct;while
increaseinhungerandindigestionasaneffectonourdigestivesystem.Inaresearchonthe
relations between health symptoms and ventilation by Daisey et al. confirmed that poor
ventilationcanresultinlongtermrespiratoryproblems(JoanM.Daisey).
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Summarizingall theprevious text, it is found that theairconditioningstate in the
classroom of The School of Architecture and Design, KMUTT is not completely up to the
standardsfollowedbyASHRAEintermsofindoorairqualityandthermalcomfort.However,
asatisfactorylevelofairqualitycanbeachievedifthenaturalventilationisincorporated.It
willnot
only
provide
abetter
air
to
breath
during
the
intensive
study
time
of
class
period
but also reduce the energy expenses down dramatically. In order have the satisfactory
consentoftheusergroupofsuchspaces,thenaturalventilationmuchbeaidedwithgreen
vegetationorplantsandsomeenergyefficientmechanicaldevices.Asimilarresearchhad
been done in California, USA that shows how indoor air quality can be improved with
simultaneousenergysavings(MGApte&SMLiff,2003).Thereforeitishighlyrecommended
to installordeviceanewor renovativedesign toprovidenaturalventilation theusersof
suchspace.Themostencouragingfactaboutthesitelocationisthatithasanaveragewind
speedof5m/sandno industrialsettings inat leastakilometerradius.Theonlydifficulty
mightcome
on
humidity
as
it
is
surrounded
by
fisheries,
never
the
less
H2O
is
essential
for
lifebutCO2isdetrimental.
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12
Bibliography(n.d.).Retrievedfromhttp://www.theweatherprediction.com/habyhints/40/
(n.d.).Retrievedfromwww.tfma.or.th/webboard/index.php?topic=13.0
(n.d.).Retrieved
from
www.ashrae.org
FischerJohnC.,B.C.(n.d.).HumidityControlinSchoolFacilities.
InterpretationsforStandard62.12004.(2004,January).RetrievedfromASHRAE:
http://www.ashrae.org/technology/page/127
JoanM.Daisey,W.J.(n.d.).IndoorAirQuality,VentilationandHealthSymptomsinSchools:an
AnalysisofExistingingInformation.IndoorAir,3&9.
MGApte,D.D.,&SMLiff,L.R.(2003).SimultaneousEnergySavingsandIEQImprovementsin
RelocatableClassrooms.
ASHRAE
IAQ
Applications
.
S.C.Lee,M.C.(41(2000)).IndoorandoutdoorairqualityinvestigationatschoolsinHongKong.
Chemosphere,109113.