TROPICAL DESIGN

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Minimize SUN

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Maximize WIND

TROPICAL DESIGN

TROPICAL DESIGN = passive cooling

PASSIVE COOLING: design with no mechanical equipment used to induce comfort conditions in building interior

PASSIVE COOLING = inducing air movements

INDUCING AIR MOVEMENTS: relevant for areas with temperature variations of 10° and with high humidity

INDUCING AIR MOVEMENTS: can improve thermal comfort up to building interiors 15 meters deep

Passive Systems for Various Climates

HOT-HUMID CLIMATE: maximize wind exposure maximize internal airflow minimize radiant heat gain

HOT-DRY CLIMATE: minimize radiant heat gain moderate wind resistance moderate internal airflow

COOL CLIMATE: maximize thermal retention maximize radiant heat gain minimize wind resistance

TEMPERATE CLIMATE: moderate thermal retention moderate radiant heat gain

slight wind exposure (for humidity control)

moderate internal airflow

AIR MOVEMENT ≡ wind

1. Air flows from a high-pressure to a low-pressure area.

2. INERTIA. Once set in motion, air tends to continue to flow in its initial direction until some intervening

force is met.

3. Air flows through the path of least resistance.

Principles of Air Movement

GLOBAL AIR MOVEMENT

1. Equator receives more radiation than do polar regions.

2. Heat from equator move towards polar regions.

3. Hot air moves upwards going to polar regions.

4. Cold air moves to equator close to earth’s surface.

General Conditions

GLOBAL AIR MOVEMENT

1. Rotation of earth deflects the air = Coriolis Force

2. Wind flows due to heat exchange.

• Air temperature changes faster than ground temperature

• Daily fluctuations of air temperature caused by physical conduction up to 3 meters above the

ground

• Marked differences of air temperature between night and day

Specific Conditions

GEOGRAPHICAL AIR MOVEMENT

1. Daytime Heating: land warms more rapidly than water

• SEA BREEZE – wind from the sea directed toward land

• Strongest in the afternoon when heating variance is greatest

2. Night Time Cooling: land cools faster than water

• LAND BREEZE – wind from land directed to sea

Land and Sea Breezes

Daytime Sea Breeze

Night Time Land Breeze

WARM

COOL

COOL

WARM

MONSOONS IN THE PHILIPPINES

1. Northeast Monsoon = AMIHAN = the winter monsoon• Appears in October • Attains maximum strength in January• Gradually weakens in March • Disappears in April

2. Southwest Monsoon = HABAGAT = the summer monsoon

• Appears early May • Maximum flows during August • Disappears gradually in October • Persists from November to December

Monsoon: large-scale seasonal currents

AIR MOVEMENT IN BUILDINGS

1. Windward side = positive pressure Leeward side = negative pressure

2. Air enters through openings located in the positive pressure zone Air exits through openings located at the negative pressure zone

3. Air enters through lower level openings Air exits at higher level openings

4. Window width ÷ wall width = 50% to increase indoor air speed

5. Window heights = 1.10 meters for effective indoor air movement

6. Wind deflectors, horizontal and vertical, to redirect air flow

7. Prevent wind shadows by placing openings

EFFECT OF LANDSCAPE ELEMENTS

1. Hedges/shrubs should not be more than 3 meters from building

2. Tree foliage above openings promote air motion into openings

3. Combine tree, hedge and building to achieve air flow control

4. Lateral air channels to direct air flow

5. Arrange trees to determine wind shadow

6. Make use of earth mounds to achieve better air movement

SOLAR GEOMETRY

1. Rays of the sun vary with time and place (latitude)

2. Celestial Sphere: earth is static; sun moves from east to west

3. The sun moves across the sky at a rate of 15.04° per hour

4. The earth’s polar axis is inclined at 23°47’ from the vertical

5. June 21 is considered the longest day = summer solstice

6. December 21 is the shortest day = winter solstice

7. March 21 and September 21 = equinoxes

SUN PATH

1. Solar Altitude Angle = the angle with height above the horizon. Ranges from 0° when on horizon to 90° when directly above

(noon)

2. Solar Azimuth Angle = the sun’s position as projected on a horizontal plane.

3. The two solar angles change with Latitude (location on Earth)

4. Metro Manila is located at 14.5° N Latitude

5. Two Methods for Calculating Solar Angles • Using graphs • By mathematical calculation

6. Solar Chart = Sun Path Diagrams

7. Different Solar Charts for Different Latitudes

10°

20°

30°

40°

50°

60°

70°

80°

12 1110

98

76

12

34

56

20°30°

40°

50°

60°70°

90°80°

100°110°

120°130°

140°150°