CLIMATE :
IT CAN BE DEFINED AS AN INTEGRATION IN TIME OF PHYSICAL STATES OF THE ATMOSPHERE,ENVIRONMENT, CHARACTERISTIC OF A CERTAIN GEOGRAPHICAL LOCATION.
WEATHER:
WEATHER IS THE MOMENTARY STATE OF ATMOSPHERIC ENVIRONMENT A CERTAIN LOCATION.
CLIMATE COULD BE DEFINED AS THE INTEGRATION IN TIME OF WEATHER CONDITIONS.
ATMOSPHERE
THE MIXTURE OF GASES ENVELOPING THE SURFACE OF THE EARTH HELD BY GRAVITATIONAL FORCE AND FRICTION IS THE ATMOSPHERE.
TOPOSPHERE 8-13 KM
STATOSPHERE 200 KM
INOSPHERE 300 KM
EXOSTSPHERE 1300 KM
OZONE LAYER
GLOBAL FACTORS
SOLAR RADIATION
EARTHS-SUN RELATIONSHIP
EARTHS THERMAL BALANCE
WINDS
OCEAN AND OCEAN CURRENTS
TOPOGRAPHY
SOLAR RADIATION
THE EARTH RECEIVES ALMOST ALL ITS ENERGY FROM THE SUN IN THE FORM OF RADIATION THUS,THE SUN IS THE DOMINATING INFLUENCE ON CLIMATES.
THE SPECTRUM OF THE SOLAR RADIATION EXTENDS FROM 290 TO 2300NM.
EARTH-SUN RELATIONSHIP
SEASON:TILT OF AXIS OF EARTH IS CONSTANT THUS THE CYCLIC CHANGES IN ATMOSPHERE ARE CALLED AS SEASONS.
EARTHS THERMAL BALANCE
THE RADIATION RECEIVED BY THE EARTH OR ABSORBED BY THE EARTH EACH YEAR IS BALANCED BY CORRESPONDING HEAT LOSS.WITHOUT THIS COOLING THE THERMAL BALANCE WOULD NOT BE MAINTAINED.
THE EARTHS SURFACE LOOSES HEAT.
A)BY EVAPORATION.
B)BY LONG WAVE RADIATION TO THE OUTER SPACE.
C)RISING OF HOT AIR.
WINDS
THE AIR MOVEMENT ON THE SURFACE OF EARTH DUE TO DIFFERENCE IN PRESSURE WHICH IS CAUSED DUE TO CHANGE IN TEMPERATURE IS CALLED WINDS.
THE DIFFERENCE IN ATMOSPHERIC PRESSURE ARE INVERSELY PROPORTIONAL TO EACH OTHER.
THE ATMOSPHERIC MOVEMENT IS FROM HIGHER PRESSURE BELT TO LOWER PRESSURE.
TYPES OF WIND FLOWING OVER SURFACE OF EARTH ARE,
1.PLANETARY WINDS
2.MONSOON WINDS
3.CYCLONIC/ANTICYCLONIC WINDS
OCEAN CURRENTS
DEVELOPED DUE TO THE FOLLOWING REASONS:
UNDULATING SEA CORE/SEA BED
DIFFERENCE IN SALINITY OF WATER
UNEQUAL HEATING OF BODIES
SURFACE WINDS
TOPOGRAPHY
ON A LARGER SCALE INTERACTION OF TEMPERATURE PATTERNS ARE CREATED BY DIFFERENTIAL HEATING ON LAND,FOREST AND OCEAN.
THIS CAUSES CHANGE IN WEATHER.
VENTILATION
VENTILATION MAY BE DEFINED AS THE SYSTEM OF SUPPLYING OR REMOVING AIR BY NATURAL OR MECHANICAL MEANS TO OR FROM ANY ENCLOSED SPACE.
IN ORDER TO PRODUCE AND TO MAINTAIN EITHER HEALTHFUL,COMFORTABLE,OR THE NECESSARY AIR CONDITIONS WITHIN A STRUCTURE IT MAY BE NECESSARY TO INTRODUCE INTO AND REMOVE FROM THE SPACES OF THE BUILDING A DEFINITE AMOUNT OF AIR IN DEFINITE TIME.
NEED FOR VENTILATION
TO REMOVE HEAT AND MOISTURE GIVEN OFF BY THE OCCUPANTS.
TO PREVENT UNDUE CONCENTRATION OF BODY ODOURS,FUMES,VAPOURS,DUST,ETC.
TO PREVENT AN UNDUE CONCENTRATION OF BACTERIA-CARRYING PARTICLES.
TO PREVENT OXYGEN DEPLETION AS THE RESULT OF THE COMBUSTION OF FUELS AND OTHER MATERIALS.
TO PREVENT FLAMMABLE CONCENTRATION OF GAS,VAPOURS OR DUST.
TO PREVENT SMOKE AND FOG PRODUCTION.
TO CREATE AIR MOVEMENT AND THUS PREVENT EXCESSIVE HEAT FROM ALL SOURCES.
NATURAL VENTILATION
NATURAL VENTILATION DEPENDS ON AIR MOVEMENT INDUCED BY WIND AND TEMPERATURE DIFFERENCE.
SINCE THE RATE OF FLOW OF AIR THROUGH AN OPENING DEPENDS ON WIND VELOCITY,THE ADJUSTMENTS OF THE AREA OF THE OPENINGS TO MAINTAIN THE CONSTANCY OF AIR CHANGE BECOMES NECESSARY.
THE MAXIMUM AREA OF WINDOW OPENINGS SHOULD BE ONE-FIFTH OF THE FLOOR AREA.AS A MINIMUM IT SHOULD NOT BE LESS THAN ONE-TENTH OF THE FLOOR AREA.
WINDS-NATURAL VENTILATION
USE THE WIND FOR COOLING.
PRESERVE EACH BUILDINGS ACCESS TO COOLING BREEZES DURING OVERHEATED PERIOD.
ORIENT BUILDINGS TOWARDS COOLING BREEZES.
PROVIDE OPENINGS FOR VENTILATION THAT CAN BE SEPARATE THE HOUSE USED FOR VIEWS,SUNLIGHT,DAYLIGHT.
ADDITIONALLY,DURING PERIODS OF CALM,MICROCLIMATIC THERMAL WINDS CAUSED BY VALLEY EFFECTS,CITY EFFECTS OR WATER BODIES MAY OCCUR.
TYPES OF VENTILATION
OPEN OR MIXED VENTILATION SCHEME FOR YOUR BUILDING.
CLOSED SCHEME FOR THE OVERHEATED MONTHS,A MIXED SCHEME IS OFTEN APPROPRIATE FOR COOLER MONTHS.
MIXED SCHEME IS FOR AN INTERNALLY DOMINATED LOAD BUILDING.
OPEN BUILDINGS
NATURAL VENTILATION AND DEPEND ON THERMALLY OR WIND INDUCED INTERNAL AIR FLOW FOR COOLING.THIS COOLING STRATEGY WORKS ONLY IF THE INSIDE AIR TEMPERATURE IS HIGHER THAN THE OUTSIDE TEMPERATURE.
NATURAL VENTILATION CAN BE USED EVEN IN THE HOTTEST MONTH.
IN DRIER CLIMATES,COOLING CAN BE ACCOMPLISHED NEAR THE UPPER LIMIT OF THE COMFORT ZONE BY MOVING AIR AS WARM AS 87 DEGREE F.
THIS TEMPERATURE HAS TO BE SIGNIFICANTLY LOWER IN MORE HUMID CLIMATE.
CLOSED BUILDINGS
CLOSED BUILDINGS USE HIGH MASS WITHOUT SIMULTANEOUS VENTILATION.
THESE BUILDINGS MAY ALSO USE EVAPORATIVE COOLING ,DESICCANT COOLING,EARTHTUBE COOLING,ROOF PONDS,AND MECHANICAL REFRIGERATION.
MIXED BUILDINGS
MIXED BUILDINGS CAN BE CLOSED DURING VERY HOT HOURS,THEN OPENED FOR NIGHT VENTILATION TO REMOVE STORED HEAT.
THE SIGNIFICANT DIFFERENCE BETWEEN OPEN AND MIXED STRATEGIES IS THAT OPEN VENTILATION REMOVES HEAT AS IT IS GENERATED WHILE THE MIXED STRATEGIES REMOVES THE ENTIRE DAYS HEAT DURING A SHORT VENTILATION PERIOD.
PASSIVE VENTILATION
TWO BASIC WAYS----
CROSS VENTILATION-
DEPENDS ON THE FORCE OF THE WIND TO EXPEL HOT AIR FROM THE LEEWARD SIDE OF THE BUILDING TO BE REPLACED BY COOLER AIR FORCED IN THE WINDWARD SIDE.
STACK VENTILATION-
DEPENDS ON HOT AIR RISING TO EXPEL HOT AIR FROM OPENINGS HIGH IN A BUILDING.THIS HOT AIR IS THEN REPLACED BY COOLER AIR DRAWN IN THROUGH MUCH LOWER OPENINGS IN THE BUILDING ENVELOPE.THIS IS PARTICULARLY USEFUL IF YOU HAVE CALM WIND CONDITIONS DURING OVERHEATED MONTHS.IT CAN ALSO BE EFFECTIVE WITH EARTHTUBE COOLING.
VENTILATION AIR FLOW
1.FOR OPEN AND MIXED BUILDINGS-
SHOW THE AIR FLOW VENTILATION PATH.
ON SITE PLAN,FLOOR PLANS AND SECTIONS DRAW FLOW OF VENTILATION AIR AROUND AND THROUGH THE BUILDING FOR MONTHS IT NEEDS TO BE COOL.
WIND FLOWS FROM +VE PRESSURE TO –VE PRESSURE AREAS
HOT AIR RISES ,COOL AIR FALLS.
2.FOR CLOSED AND MIXED BUILDINGS-
SHOW THE RADIATION/AIRFLOW PATHS-
ON FLOOR PLANS AND SECTIONS INDICATE THE LOCATIONS OF THERMAL MASS.IN ORDER TO MASS COOLING STRATEGIES THE MASS MUST HAVE A LARGE AMOUNT OF SURFACE AREA AS COMPARED TO ITS VOLUME.
IF THE MASS WILL BE COOLED PRIMARILY BY RADIATION,DRAW THE PATH OF RADIANT TRANSFER FROM THERMAL MASS TO HEAT SINK AND SPECIFY THE TYPE OF HEAT SINK (NIGHT SKY,WATER BODY)
IF BUILDING RELIES ON NIGHT VENTILATION,WHERE THE MASS IS COOLED BY CONDUCTION/CONVECTION,DRAW THE PATH OF AIR CURRENTS OVER THE SURFACE OF MASS.
WINDCATCHERS AND TURBOVENTILATORS
WINDCATCHERS/WIND SCOOPS ARE USED TO TAKE COOL AIR INSIDE THE STRUCTURE.THESE ARE TALL STRUCTURE LIKE CHIMNEY FROM WHICH THE HOT AIR IS REMOVED.
TURBOVENTILATORS ARE ALSO USED WHICH ARE FIXED IN ROOF BECAUSE OF THE HOT AIR THESE TURBO-VENTILATORS ROTATES AND COOL AIR FIND ITS PATH THROUGH.
MANYTIMES CAVITY IS CREATED IN THE WALL WHERE COOL AIR IS ABSORBED AND WHILE PASSING ONTO THE HOT WALL IT ABSORBS THE HEAT AND ESCAPES AT THE ROOF LEVEL.
VENTILATORS PROVIDED AT ROOF LEVEL ALSO HELPS FOR NATURAL VENTILATION.
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