INTRODUCTION -  Natural Ventilation is not new.

-  Only 150 years ago mechanical ventilation has been introduced/used.

-  Prior to that period, all enclosure occupied by humans were naturally ventilated.

EARLY DESIGN OF NATURAL VENTILATION

-  Early designs of natural ventilation were evolved from experience (long-term experiments at full scale).

What are the challenges of ‘Natural Ventilation’ in modern buildings?

-  Modern buildings are more demanding

-  Standards for health and comfort have to be met

-  Satisfying requirements for low energy consumption and sustainability

TRADITIONAL APPROACHES

Wind-Driven Cross Ventilation

Stack Effect

Wind-Driven Cross Ventilation

Hot Air

Hot Air

Hot Air

Fresh Air

Fresh Air

Fresh Air

PASSIVE DESIGN STRATEGIES IN TMH

1. Allowing adequate ventilation for cooling and reduction of humidity.

2. Using of low thermal capacity building materials so that little heat is transmitted into the building.

3. Controlling direct solar radiation

4. Controlling glare from the open skies and surroundings

5. Protecting against heavy rain

6. Assuring adequate natural vegetation in the surroundings to provide a cooler microclimate

Traditional Malay House strategies to attain optimal climatic control which include;

What are government buildings that using natural ventilation?

-  Schools (Classroom,s workshops, canteen, etc)

-  Mosque, surau

-  Quarters etc.

Natural Ventilation

Low Thermal Material

Control Solar Radiation

Control Solar Glare

Protect Against Heavy Rain

ADVANTAGES & DISADVANTAGES OF NATURAL VENTILATION

Advantages -  Suitable for many types of buildings -  Contributes to a sustainable building

environment -  Reduces capital and operating costs -  No electricity; reduces energy -  Less maintenance -  Occupants have control over their

environment -  Does not require space for plant

rooms or ducts -  No fan or system noise

Disadvantages -  Limited to provide cooling in hot and

humid climates. -  May need to combine with some

sustainable cooling system to achieve comfort.

-  Errors in the design of Natural Ventilation may be difficult to correct

-  Air flow rates and the pattern of air flow are not constant

-  Deep plan and multi-roomed buildings may not be possible

-  Unsuited to noisy and polluted locations -  Some designs may present a security risk

NATURAL VENTILATION DRIVING FORCES

The air motion in a room is generated by sources of

1.  Momentum (wind velocity)

2.   Buoyancy (temperature difference)

MOMENTUM -  The air flows through the openings -  Vary according to some factors;

wind speed, wind direction, opening size etc.

Greater pressure difference = Higher airflow

Larger opening size = Higher airflow

NATURAL VENTILATION DRIVING FORCES (CONT.)

BUOYANCY -  Heat transfer at solid surfaces is

the major source of buoyancy -  Warm air is less dense than cool

air (more buoyant); works when indoor air is warmer than outdoor air.

-  Variations of the internal temperature can effect the flow rates

Cool Air ++++

(More Dense)

Hot Air - - - -

(Less Dense)

MALAYSIA’S WIND SPEED DATA

Wind Speed

-  Average wind speed is low (<0.5m/s) from 8pm to 8am.

-  Starts increasing from 8am and has average peak of 3.5m/s at 3pm.

-  Light & Gentle Winds (1.6m/s to 5.4m/s) usually can be felt from 9am to 6pm.

-  The wind speed is not constant. It is possible to have high wind speed and zero wind speed at any time of the day.

Source: BSEEP

MALAYSIA’S WIND SPEED DATA (CONT.) Wind Direction

-  47% of the total cool wind is from North & North West (29% - North and 18% - North-West).

-  In NV, capturing wind from North and North-West should be the primary objective.

-  Ideally, the occupants should have control over the NV

Design Issues -  When the dry bulb low, the wind

speed is also low and the chances of bringing the hot air into the building is high.

-  Therefore, the NV designs need to consider how to reduce the hot air temperature while entering the building.

-  Adjustable louvers with temperature sensors may also be used to divert the hot wind and to allow the cool wind.

TYPES OF NATURAL VENTILATION APPROACHES

1. Wind-Driven Cross Ventilation 2.  Single-Sided Natural Ventilation 3.  Stack Effect 4.  Atrium Ventilation 5.  Wind Tower or Wind Catcher

1. WIND-DRIVEN CROSS VENTILATION

Airflow

Effectiveness Factor

Wind Velocity

Area of Opening

WIND-DRIVEN CROSS VENTILATION (CONT.)

Rule of Thumb : Width (W < 5H) Height

WIND-DRIVEN CROSS VENTILATION (CONT.)

Advantages

-  Cross flow will provide more liable ventilation than single-sided ventilation

-  Minimum resistance to air flow and provides good ventilation to a space

Disadvantages

-  Cross flow of ‘used’ air into other occupied spaces should be avoided

-  Interior design layout can be more complex to avoid ineffectiveness of air flow

-  No deep planning. Depth must equivalent or less than 5 x ceiling height

2. SINGLE-SIDED NATURAL VENTILATION

By Wind

By Stack Effect

2. SINGLE-SIDED NATURAL VENTILATION (CONT.)

SINGLE-SIDED NATURAL VENTILATION (CONT.)

Rule of Thumb (by Wind) = Width (W < 2H) Height

Rule of Thumb (by Stack Effect) = Width (W < 2.5H) Height

SINGLE-SIDED NATURAL VENTILATION (CONT.)

Advantages

-  Popular because openings are located on one face only

Disadvantages

-  No defined exit route for air

-  Net driving forces may be small resulting in poor ventilation

-  Depth of penetration of air restricted to 2.5 x ceiling height

Single-sided natural ventilation should be avoided!

3. STACK EFFECT

STACK EFFECT (CONT.)

STACK EFFECT (CONT.)

Advantages -  Can relieve the problem of single-sided ventilation by providing stacks in

the building -  Can be used in conjunction with wind induced ventilation by locating the

roof termination in the negative pressure region.

Disadvantages -  Each room should be individually ducted since shared ducts may result in

cross contamination between zones -  Potential for reverse flow if the column of air in the stack becomes cold -  Requires a temperature differential between inside and outside

4. ATRIUM VENTILATION

Source: BSEEP

What is the difference between ‘Stack Effect Ventilation’ & ‘Atrium Ventilation’?

5. WIND TOWER OR WIND CATCHER

-  Wind intake at 360 degree around tower

-  Vertical air shafts bring cool air into the building

-  Minimum height from the highest vented floor is 7 meters.

-  May associated with water elements to lower down the air temperature

GUIDELINES FOR SUCCESSFUL NATURAL VENTILATION

1.  Wind Orientation & Direction 2.   Window Locations 3.   Fin Walls 4.   Windows Types 5.   Vertical Disposition of Windows 6.   Inlet & Outlet Sizes and Locations 7.  Roof Vents 8.   Fans 9.   Internal Planning Guidelines

1. WIND ORIENTATION & DIRECTION

•  Wind exerts a maximum pressure when perpendicular to a surface

•  This reducing by 50% when the wind hits the face of building at an angle of 45 degrees.

•  Indoor ventilation is effective with oblique paths because they create greater turbulence indoors.

•  wind direction varies throughout the year.

2. WINDOW LOCATIONS

•  Cross ventilation is a very effective because of the movement of air from positive pressure to negative pressure located on opposite ends of a building enclosure.

•  Ventilation from windows on one side of a building can range from fair to poor depending on the location of the windows.

•  It improves where there is an asymmetric placing of windows in a building enclosure.

3. FIN WALLS

•  Fin walls can increase the ventilation through windows on the same side of a building by changing pressure distribution.

4. WINDOW TYPES

•  The type and design of windows have great bearing on the quantity and direction of air flow.

•  Although double hung and casement windows do not change the direction of any airstream, they block minimum of 50% of any airflow.

•  Casement windows however whilst allowing greater air ingress can deflect airstreams in a similar way to fin walls.

5. VERTICAL DISPOSITION OF WINDOWS

•  For comfortable ventilation, windows should be low at the level of persons in any room placing a window cell in the region of 600-1000mm above floor level.

•  Additional high windows should be considered in some climatic circumstances to exhaust hot air reaching the ceiling.

•  in warm climates: align window openings to user height - eg desks, seats, tables.

•  high level openings allow night cooling of thermal mass

6. INLET & OUTLET SIZES AND LOCATIONS

•  Inlet and outlet sizes should be simiar to each other as the amount of admitted air is a function of intake size.

•  Inlet opening not only determines velocity but also internal airflow patterns in the room.

•  the location of the outlet has little effect on velocity and air pattern.

7. ROOF VENTS

•  Passive roof ventilators are typically used to reduce high level temperature and do facilitate stack ventilation.

•  The size and type of ventilators can have a radical effect on the amount of air extracted.

•  Compared to a simple vent, a wind driven turbine will increase air movement by 130% whilst a deflector can increase movement in excess of 220%.

8. FANS

In many climates, wind is not sufficiently present when required, and this is then usually augmented with fans - to form a hybrid system. The key uses for fans are:

• As part of a heat avoidance strategy

• To bring in outdoor air to cool people or cool a building at night as part of a night purging strategy.

• To circulate indoor air at times where indoor air is cooler than outdoor air.

9. INTERNAL PLANNING GUIDELINES

•  Open plan forms are preferable to cellular accommodation as it does not impede any passage of air.

•  where partitions are inevitable - for example bedrooms.

•  Cross ventilation is often possible through open doors and internal vents.

•  Passive ventilation is very difficult to undertake with a central or ‘double loaded’ corridor.

•  this can be alleviated with single corridor models or in single storey buildings, the use of clerestorey venting above corridors.

•  For cross ventilation to be effective a maximum cross section of 5 x ceiling height is reccommended.

CASE STUDY 1 : MENARA UMNO, PENANG - Year of Completion : 1998

- Height : 94 meters (21 Stories)

- Building Function : Office

- Plan Depth : 14 meters (from core)

- Location of Plant Floors : Semi-Decentralized / Every Floor

Ventilation Overview :

- Ventilation Type : Mixed-Mode (Complementary-Alternative)

- Natural Ventilation Strategies : Wind-Driven Cross-Ventilation

- Design Strategies : “Wing Walls” which capture a wider range of wind directions

- Percentage of Annual Energy Savings for Heating and Cooling : 25% compared to a fully air-conditioned office building in Malaysia

- Typical Annual Energy Consumption (Heating/Cooling) : 180 kWh/m2

Location : Penang, Malaysia Geographic Position : Latitude 50 18’N, Longitude

1000 16’E Climate Classification : Tropical Prevailing Wind Direction : South-southwest

Average Wind Speed : 2.6 m/s (meters per second) Mean Annual Temperature : 28 oC Day/Night Temperature Difference : 8 oC

CASE STUDY 1 : MENARA UMNO, PENANG -  Wind “Wing Walls” (highlighted in green) -

to collect a wide range of wind directions on the South, South-West & North-East Facades.

-  Adjustable Windows adjacent to the ‘wing walls’ and balconies allow cross-ventilation at each floor.

CASE STUDY 2 : UM EXAM HALL, KL

Inspired by Traditional Melanau Tall House, 2 natural ventilation features : -  Breathing Wall -  Window Nostril (Top Hung Window)

Breathing Wall

-  Showcases a ‘breathing wall’, which is to significantly improve natural ventilation

-  All spaces excepts the halls and lobbies are naturally ventilated via ‘breathing walls’

CASE STUDY 2 : UM EXAM HALL, KL (CONT.)

Window Nostril (Top Hung Window)

-  Top hung window to allow cross winds to continually ventilate the interior space

-  The window acts as a ‘nostril’, breathing in air from the outside

-  Allows air while keeping the rain out (with the adjustable lever arm)

-  Provide users the flexibility to alter the interior comfort levels

COMPARATIVE STUDY ON NATURAL VENTILATION BETWEEN TRADITIONAL HOUSES AND LOW-COST HOUSING IN MALAYSIA

COMPARISON OF WINDOW OPENINGS

20.3% (Opening Area for Rumah Ibu) 16.7% (Opening

Area for Rumah Ibu)

9.8 % (Opening Area for Living/Dining)

COMPARISON OF INTERNAL & EXTERNAL AIRFLOW

Air Flow In

Air Flow Out

Max: 3.3m/s

Max: 7.9m/s

Max: 0.19m/s

Max: 0.34m/s

Max: 0.96m/s Max: 2.3m/s

Max: 0.32m/s Max: 0.41m/s

DEVELOPMENT OF THEORETICAL MODEL OF LOW-COST HOUSING UNIT

THEORETICAL MODEL CONCEPT

COMPARISON OF PRIVACY VALUE

COMPARISON OF WINDOWS PLACEMENT

THEORETICAL MODEL’S OPENING CONCEPT

COMPARISON OF AIR MOVEMENT

COMPARISON OF AIR MOVEMENT

Max Air Flow In: 3.1m/s & 5.3m/s Max Air Flow Out:

0.75m/s & 1.27m/s

Max Air Flow In: 0.19m/s & 0.34m/s

Max Air Flow Out: 0.32m/s & 0.41m/s

VS

NATURAL VENTILATION DESIGN PARAMETERS

PROJECT 1

PROJECT 1

Q & A

Some issues arising related to natural ventilation:

1.  Sound and Air Pollution?

2.  Safety Factor?

3.  The Effectiveness of NV in Hot-Humid Climate?

4.  Between thermal comfort and cost savings, which is more important?

Thank You for Listening.