NATURAL VENTILATION

SUBMMITTED BY :- KIRAN MAI DAS B.ARCH IX SEMESTERDCA , ANJORA, DURG

AIM-• TO STUDY THE APPLICATION OF NATURAL VENTILATION AND

TECHNIQUES USED TO MINIMIZE EXTERNAL ENERGY AND ENHANCE THE QUALITY OF BUILDING.

OBJECTIVE– • TO STUDY HOW TO OPTIMIZE NATURAL VENTILATION IN

BUILDINGS AND TO MINIMIZE MECHANICAL SYSTEMS FOR VENTILATION

• TO STUDY THE SPECIFIC APPROACH AND DESIGN OF NATURAL VENTILATION SYSTEMS WHICH VARIES AND BASED ON BUILDING TYPE AND LOCAL CLIMATE .

• TO STUDY THE DIFFERENT TYPES OF FUNCTIONS AND TECHNIQUES USED FOR NATURAL VENTILATION .

NATURAL VENTILATION TYPES

WIND

BUOYANCY

WIND BLOWS THROUGH INLET ON WINDWARD SIDEAND COMES OUT FROM LEEWARD SIDE FROM OPENINGS AND ROOF.AN EXPRESSION FOR THE VOLUME OF AIRFLOW INDUCED BY WIND IS:-QWIND = K X A X V, WHEREQWIND = VOLUME OF AIRFLOW (M³/H)A = AREA OF SMALLER OPENING (M²)V = OUTDOOR WIND SPEED (M/H)K = COEFFICIENT OF EFFECTIVENESS

WIND

BUOYANCY:-• BUOYANCY OCCURS WHEN DIFFERENCE IN

TEMPERATURE OF OUTDOOR AND INDOOR AIR

• IT CAN BE TEMPERATURE INDUCED :- EG. STACK VENTILATION

• OR IT CAN BE HUMIDITY INDUCED :- EG. COOL TOWER

TEMPERATURE DIFFERENCES BETWEEN WARM AIR INSIDE AND COOL AIR OUTSIDE CAN CAUSE THE AIR IN THE ROOM TO RISE AND EXIT AT THE CEILING OR RIDGE, AND ENTER VIA LOWER OPENINGS IN THE WALL.

TEMPERATURE DIFFERENCE :-

HUMIDITY INDUCED:-• THE COOL AIR IS HEAVY DUE TO ITS HUMDITY

CONTENT AND DROPS DOWN TO THE INDOOR AREA .

• IT CAN BE ACHIEVED PROPERLY WITH A COOL TOWER OR WIND CATCHER OR MALQAF AND BADGIR

• COOL TOWER VENTILATION IS ONLY EFFECTIVE WHERE OUTDOOR HUMIDITY IS VERY LOW

• NATURAL VENTILATION IS THE PROCESS OF SUPPLYING AND REMOVING AIR THROUGH A SPACE BY NATURAL MEANS IT CAN BE ACHIEVED WITH OPENABLE WINDOWS OR TRICKLE VENTS.

WHAT IS NATURAL VENTILATION ?

• NATURAL VENTILATION AND AIR MOVEMENT CAN BE SIMPLY ACHEVIED BY ‘STRUCTURAL CONTROLS’ AS IT DOES NOT DEPENDS ON ANY FORM OF EXTERNAL ENERGY SUPPLY OR MECHANICAL INSTALLATION.

SECTION SHOWING AIR FLOW

WHY NATURAL VENTILATION ?• NATURAL VENTLILATION STARTED FROM HISTORY

ACCORDING TO THE DIFFERENT CLIMATES

TYPICAL SECTION THROUGH SHAHAJAHANABAD HOUSE. TO FACILITATE THE MOMENT OF COOL AIR INTO THE HOUSE, PARAPETS ARE NOT BUIL TOWARDS THE COURTYARD

VARIOUS TECHNQUES USED IN OLD TIMES :-

DOUBLE APERTURES USED FOR ENSURING VENTILATIONIN SHAHJAHANABAD HOUSES

WINDOW FOR VIEW AND JALI VENTILATION USED ATAMBER FORT

COLUMN COURTYARD COOLING SYSTEM-DIWAN E-KHAS, RED FORT, DELHI

•

MULTI-DIRECTIONAL WINDCATCHER

WHY NATURAL VENTILATION• THEN PEOPLE STARTED

USING EXTERNAL ENERGY FOR THERMAL COMFORT.

• TIME PASSES AND IT GROWNED UP IN MORE SOPHISTICATED WAY.

WHY NATURAL VENTILATION• AND AGAIN DUE

TO ENERGY CRISES AND COMLEXITY OF INSTALLATION AND FOR THE NEW LINE OF EVOLUTION PEOPLE STARTED USING NATURAL VENTILATION

FLOW OF AIR IN KANCHANJANGA APARTMENT MUMBAI

DIFFERENT TECHNIQUES TO ACHIEVE NATURAL VENTILATION:-

• STACK EFFECT • WIND TOWER • COURTYARD EFFECT • SOLAR CHIMNEY

STACK EFFECT :-STACK EFFECT DEPENDS ON THERMAL FORCES AND DIFFERENCE IN TEMPERATURE .REASON OF STACK EFFECT :-• PRESSURE DIFFERENCE BETWEEN THE OUTSIDE AIR

AND THE AIR INSIDE THE BUILDING CAUSED BY DIFFERENCE IN TEMPERATURE

Outdoor air

Outdoor air

Section

• STACK EFFECT WORK WELL – WINTER• HIGHER THE SHAFT AND CROSS SECTION AREA GREATER THE STACK EFFECT • ‘MOTIVE FORCE’ – STACK PRESSURE• STACK PRESSURE CAN BE CALCULATED FROM:-• PS =

STACK PRESSURE IN N/M2

HEIGHT OF THE STACK IN M

TEMPERATURE DIFFERENCE IN DEG C

STACK VENTILATION SECTIONS :-

TALL ROOMS TALL ROOMS AT EDGE

STAIRS AS STACKTALL ROOMS WITHIN

WIND TOWER

• AIR ENTERS IN WIND TOWER THROUGH OPENINGS- COOLED DOWN- BECOMES HEAVIER AND SINKS DOWN ( PRESENCE OF AIR MOVEMENT)

• AFTER WHOLE DAY AIR EXCHANGE – TOWER BECOMES WARM IN THE EVENING .

• TOWER WALLS ABSORBS HEAT DURING DAYTIME AND RELASES AT NIGHT WARMING COOL NIGHT AIR AT NIGHT.

WIND TOWER

A TYPICAL WIND TOWER SECTION

EVAPORATIVE COOLING

DIFFERENT TYPES OF WIND TOWERS :-

WATER SUPPLY

MULTI DIRECTIONAL WIND CATCHER

EVAPORATIVE COOLING

EVAPORATIVE COOLING METHOD

WIND TOWER AND EVAPORATIVE TECHNIQUE USED IN INDIA :-

A VIEW OF THE WIND TOWER USED IN A HOSTEL BUILDING (JODHPUR)

VENTS CONNECTING WIND TOWER

WIND TOWER AND EVAPORATIVE TECHNIQUE USED IN INDIA :-

EVAPORATIVE COOLING SYSTEM IN TORRENT RESEARCH CENTRE, (AHMEDABAD)

SECTION OF THE BUILDING

PLAN OF THE BUILDING

COURTYARD EFFECT:-DUE TO INCIDENT SOLAR RADIATION IN A COURTYARD, AIR GETS WARMER AND RISES , COOL AIR FROM GROUND LEVEL FLOWS THROUGH THE LOWER OPENINGS

RADIATION TO SKY

LANDSCAPE OR WATER BODY

SECTION SHOWING COURTYARD EFFECT

HOW COURTYARD COURTYARD EFFECT WORK:-

IN SUCH PLACES NIGHT VENTILATION IS NOT VERY EFFECTIVE FOR COOLING AND NIGHT SKY RADIATION IS THE ONLY ANSWER.

TO FACILITATE THE MOMENT OF COOL AIR INTO THE HOUSE,PARAPETS ARE NOT BUILT TOWARDS LIVING AREA

PARAPET TOWARDS ROAD SIDE TO AVOID OUTSIDE HEAT

SECTION OF SAHAJANABAD DELHI

COURTYARD IN MODERN BUILDING :-

AMERICAN INSTITUTE OF INDIAN STUDIES (GURGAON):-

VIEW

SUNKEN COURTYARD INSIDE THE BUILDING WITH WATER BODY AND LANDSCAPE

PLAN

NATURAL VENTILATION EXTERNAL FEATURES:-

• ORIENTATION OF BUILDINGS• POSITION OF OPENINGS• CROSS VENTILATION• SIZE OF OPENINGS• OPENING TYPES

MASSING AND ORIENTATION OF BUILDING:-• AS A GENERAL RULE, THIN TALL BUILDINGS WILL

ENCOURAGE NATURAL VENTILATION AND UTILIZE PREVAILING WINDS, CROSS VENTILATION, AND STACK EFFECT.

• TALL BUILDINGS ALSO INCREASE THE EFFECTIVENESS OF NATURAL VENTILATION, BECAUSE WIND SPEEDS ARE FASTER AT GREATER HEIGHTS

Tall buildings improve natural ventilation, and in lower latitudes reduce sun exposure.

OREINTATION :-ORIENTING THE BUILDING SO THAT THE SHORTER AXIS ALIGN WITH THE PREVAILING WIND

WHILE ORIENTING IT PERPENDICULAR TO PREVAILING WINDS WILL PROVIDE THE LEAST PASSIVE VENTILATION.

OPENING SIZE:-

Pairing a large outlet with a small inlet increases incoming wind speed.

SMALL INLETLARGE

OUTLET

OPENING TYPE:-

OPENING CAN BE ANY TYPE ACCORDING TO THE BUILDING TYPE AND CLIMATIC CONDITION

CROSS VENTILATION:-

WINDOWS OR VENTS PLACED ON OPPOSITE SIDES OF THE BUILDING GIVE NATURAL BREEZES A PATHWAY THROUGH THE STRUCTURE.

SCOPE –

• TO MINIMIZE THE EXTERNAL ENERGY OR MECHANICAL SYSTEM.

• IMPLEMENTATION OF NATURAL VENTILATION SYSTEM- NATURAL DAYLIGHTING CAN BE PROVIDED.

• THERMAL COMFORT CAN BE ACQUIRED WITH LESS ECONOMICAL BUDGET

LIMITATION -

CALCULATION OF WIND THROUGH DIFFERENT TOOLS