Lecture 7 passive ventilation system

Part of Climatic Design Course

1. Prepared by
Dr. Nedhal Al-Tamimi
Arch. Eng. Dept.,
Faculty of Engineering
Najran University, KSA
[email protected]
Passive ventilation system
Lecture
No. 7
Climatic Design AE 353-2

2. Scope of Presentation
1.Introduction to Ventilation Systems
2.Natural Ventilation
3.The benefits of natural ventilation
4.Types of Natural Ventilation
5.Functional requirements of a Ventilation system
6.General considerations and rules
7.Land Scape Elements for cooling

3. Bioclimatic chart
EXAMPLE:
Determinetheviable
passivestrategiesfor
DodgeCity,

4. Bioclimatic chart
EXAMPLE:
Determinetheviable
passivestrategiesfor
NajranCity,

5. EXAMPLE:
Determinetheviable
passivestrategiesfor
NajranCity,
https://drajmarsh.bitbucket.io/psychro-chart2d.html
Bioclimatic chart

6. Ventilation Systems
Natural
VentilationMechanical
Ventilation
VentilationSystemsis:
Theprocessofremovingorsupplyingairbynaturalor
mechanicalmeanstoandfromaspace.
Therearetwotypesofventilations:

7. Natural Ventilation
▪NaturalVentilationis:theprocessofsupplyingandremoving
airthroughanindoorspacebynaturalmeans
▪Itfacilitateoutsideairtoinsideofabuildingthrough
windows,doors,ventilationorotheropenings.
▪Openingsshouldnotbelessthan1/20
th
or(5%)ofthefloor
area.
▪Itreferstotheflowofexternalairtoanindoorspaceasa
resultofpressureortemperaturedifferences

8. Natural Ventilation

9. The benefits of natural ventilation
The benefits of natural ventilation include:-
1.Improved Indoor air quality (IAQ) (level of Oxygen,
Carbon Dioxide)
2.Energy savings by lowering the heat level
3.Reduction of greenhouse gas emissions
4.Control the moisture level
5.Remove dust and odors
6.Reduction in occupant illness
7.Increased worker productivity

10. Types of Passive ventilation system
Therateofventilationbynaturalmeansdependson:
Wind effect
Stack effect

11. Wind effect
▪Ventilationiseffectedbythe
directionandvelocityofoutside
wind.Inadditiontothesizeand
positionoftheopenings.
▪Wind creates pressure
differencesandwhenitblows
againstabuilding,apositive
pressureiscreatedonthe
windwardsideandnegative
pressureonleewardside.

12. Wind effect

13. Windeffect
Single opening ventilation
▪Roomswithwindowsononeside
only.Coldairwillstreamin,and
warmairwillstreamoutagain
throughthesamewindow.
▪Thiskindofventilationisnormal
andgenerallypractised,butitis
onlyusefuluptoacertainroom
depth.

14. Double opening ventilation
▪Anadvancementofthesingle
sidedprincipleprovidesadouble
opening,whichisconsiderably
moreefficient.
Windeffect

15. Crossventilation
▪Inthecaseofcross-
ventilation,(windowsopen
onbothsidesofthe
room/building)
▪Thepressuredifferenceis
usedbetweenthesideof
thebuildingfacingthewind
andthesideawayfromthe
wind.
Windeffect

16. Crossventilation
▪Thepositivepressureonthewindward
and/oravacuumeffectontheleeward
sideofthebuilding,causesair
movementthroughthebuildingfromthe
windwardtotheleewardside.
▪Inordertoobtaintheoptimalairflowwith
minimaldraught,thewindowsonthe
windwardsideareopenedlessthanon
theleeside.
Windeffect

17. Stackeffect
Stackventilation
▪Dependsuponverylowopeningsto
admitoutdoorairandveryhigh
openingstoexhaustair;itisdriven
bytheprinciplethathotairrises.
▪Stackventilationisgenerallyweaker
thancross‐ventilation—exceptwhen
thereisnowindatall.

18. Stackeffect
▪Airmovementiscreatedbycool
airbeingdrawntospacelow
downtoreplacewarmerair
▪Toobtaincooling,incomingair
mustbecoolerthaninternal
temperature
▪Alsoknownaschimneyeffect

19. Windcatcher
▪Thefunctionofthistoweristocatch
coolerbreezethatprevailatahigher
levelabovethegroundandtodirect
itintotheinteriorofthebuildings.
▪Awatermanagementsystemused
toprovideareliablesupplyofwater
tohumansettlementsorfor
irrigationinhot,aridandsemi-arid
climates

20. Examplesofwindcatcher

21. Functional requirements of a Ventilation system
▪Numberofairchangesdependupontypeofbuildingsandits
occupancy.
▪Airchangesperhour(ACH)isthevolumeofoutsideair
allowedinaroominonehourcomparedwiththevolumeof
theroom.
Forexample:Inresidentialbuildings
▪Livingroomsandbedrooms:3airchangesperhour
▪Kitchen:6airchanges/h
▪BathroomsandW.C:6airchanges/h
▪Hallsandpassages:1airchange/h

22. Generalconsiderationsandrulesfornaturalventilation
▪Inletopeningsinthebuildingshouldbewelldistributed
andshouldbelocatedinthewindwardsideatlowlevel.
▪Theoutletopeningsshouldbelocatedontheleeward
sideneartheceilinginthesidewallsandinroofs.
▪Inletandoutletopeningsshouldpreferablytobeof
equalsizeforgreatestairflow,butwhenoutletisinthe
formofaroofopeningtheinletshouldbelargerinsize.
Wherethewinddirectionisvariable,provideopeningsin
allwalls

23. Generalconsiderationsandrulesfornaturalventilation
▪Inletopeningsshouldnotbeobstructedby
obstructionsinthepathofflow(adjoiningbuildings,
trees,signboards,partitions,etc.)
▪Increasedheightoftheroomgivesbetterventilation
duetostackeffect
▪Thelongnarrowroomshouldbeventilatedby
providingsuitableopeningsinshortsides

24. Generalconsiderationsandrulesfornaturalventilation
▪Provideventilatorsasclosetotheceilingsas
possible
▪Forcrossventilation,thepositionofoutletsshouldbe
justoppositetoinlets
▪Iftheroomistobeusedforburninggasorfuel,
enoughquantityofairshouldbesuppliedbynatural
ventilationformeetingthedemandsofburningas
wellasventilationoftheroom.

25. MECHANICAL NATURAL
Use fan Not use any fan
Need to be install Ready fix to building
Allow warmer air escapefaster Depend on weather
High cost More economic
High maintenance Nomaintenance
Create air all time Same in temperature
Noise Silent
High electricitybill No electricity bill
Generalconsiderationsandrulesfornaturalventilation

26. Land Scape Elements for cooling (Surface)

27. Land Scape Elements for cooling (Surface)
▪Inthesummer,treesblock70-90%ofthesun’sradiation
onaclearsummerday.Whenproperlyplaced,treescan
reduceairconditioningdemandsby10-30%.
▪Indesertclimate,wheretemperaturestypicallycoolinthe
evening,shadingahomemayadequatelymoderate
temperatureswithouttheexpenseofairconditioning.

28. Land Scape Elements for cooling (Surface)

29. Shade streets are 10 to 40 degrees cooler and have higher market values.
▪Anotherimportantcoolingtechniqueistoshade
pavementandotherheat-storingmaterialslikethepatio
anddriveway.
▪Also,minimizingpavedsurfaceshelpskeeptheliving
areacool.
Land Scape Elements for cooling (Surface)

30. Land Scape Elements for cooling (Surface)
Vegetationcanbe
usedtoshadethe
buildingandcreatea
coolmicroclimate
aroundthebuilding.

31. Land Scape Elements for cooling (Surface)
Landscapeand
shadingdevices
canbeusedin
combinationto
provideanarea
ofcoolingaround
thebuilding.

32. Natural Lighting
Next Lecture
8
1.Principles of Natural Lighting
2.Variables Effect Illumination Level
3.Innovative Daylighting
Technologies
4.Controlling Daylight
5.Daylighting Design Guides

33. Climatic Design Thank You
Dr. NedhalAl-Tamimi
AE 353-2