investigation indoor air quality and thermal comfort in bangkok

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.

0


2/13

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.

1


3/13

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.

2


4/13

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

3


5/13

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.

4


6/13

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/


7/13

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.

6


8/13

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.

7


9/13

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.

8


10/13

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.

9


11/13

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).

10


12/13

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.

11


13/13

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.

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