TROPICAL ARCHITECTURE
1.0 Climate
1.1. Climatic factors
1.2. Climatic elements
1.3. Microclimatic conditions
2.0 World Climates
2.1. Thermal Comforts
2.2. Microclimate
2.3. Tropical Climate
2.4. Tropical Design
2.5. Characteristics of Tropical Climate
3.0 Heat Transfer
3.1 Conduction
3.2 Convection
3.3 Radiation
3.4 Evaporation Condensation
4.0 Passive Cooling
4.1 Building Configuration
4.2 Building Orientation
4.3 Solar control devices (sun shading devices)
5.0 Wind and Natural Ventilation
5.1 Stack effect/ Chimney effect
5.2 Cross ventilation
2
TROPICAL ARCHITECTURE
1.0
Climate
•
•
Weather describes the variations which occur in the atmosphere on a
daily basis
Climate is a measure of the typical weather found at a place.
A diagram showing the earth’s climatic zones. <Philippines at the right side>
Equable climate - This means 'lack of extremes'
• Does not usually receive long periods of hot or cold weather, or long
periods of prolonged drought or rainfall
• Usually that of cool summers, steady rainfall and mild winters.
3
TROPICAL ARCHITECTURE
1.1 Climate of the Philippines
•
The Climate of the Philippines is tropical and maritime
o Relatively high temperature
o High humidity and
o Abundant rainfall
o Temperature, humidity, and rainfall are the most important
elements of the country's weather and climate.
Temperature
Philippines
• Mean annual temperature is 26.6o C.
• Coolest months - January (25.5oC)
• Warmest month – May (28.3oC)
• Latitude is an insignificant factor in the variation of temperature
• Altitude shows greater contrast in temperature.
o Baguio - altitude of 1,500 meters is 18.3oC.
o Comparable with those in the temperate climate\
o Known as the summer capital of the Philippines.
o There is essentially no difference in the mean annual
temperature of places in Luzon, Visayas or Mindanao measured
at or near sea level.
Humidity
Humidity - the moisture content of the atmosphere.
•
•
•
•
Philippines has a high relative humidity.
Average monthly relative humidty - 71 percent (March) and 85 percent
(September)
The combination of warm temperature and high relative and absolute
humidities give rise to high sensible temperature
March to May- Uncomfortable (temperature and humidity at maximum
levels.)
Rainfall
•
•
•
Most important climatic element in the Philippines.
Varies from one region to another, depending upon the direction of the
moisture-bearing winds and the location of the mountain systems
Mean annual rainfall of the Philippines varies from 965 to 4,064
millimeters annually.
o Baguio City, eastern Samar, and eastern Surigao receive the
greatest amount of rainfall
4
TROPICAL ARCHITECTURE
o the southern portion of Cotabato receives the least amount of rain.
(978 millimeters.)
Seasons
Using temperature and rainfall as bases, the climate of the country can be
divided into two major seasons
(1) The rainy season (June to November)
(2) The dry season (December to May)
a. Cool dry season (December to February)
b. Hot dry season (March to May)
Prevailing Wind in the Philippines :
Amihan (NE) – November to April
Habagat (SW) - May to October
Sky Conditions – Overcast Sky most of the time; a lot of reflected heat/ solar
gain
Precipitation – high during the year – average of 1000mm/yr
5
TROPICAL ARCHITECTURE
Climate Types
Based on the distribution of rainfall, four climate types are recognized, which are
described as follows:
Typhoons
• Have a great influence on the climate and weather conditions of the
Philippines
• A great portion of the rainfall, humidity and cloudiness are due to the
influence of typhoons
• Originate in the region of the Marianas and Caroline Islands of the Pacific
Ocean (same latitudinal location as Mindanao
• Northwesterly direction, sparing Mindanao from being directly hit by
majority of the typhoons that cross the country
o Southern Philippines - very desirable for agriculture and industrial
development.
6
TROPICAL ARCHITECTURE
1.2 Climatic factors
•
•
•
•
•
•
•
Distance From The Sea
Ocean Currents
Direction of Prevailing Winds
Relief
Proximity To The Equator
The El Nino Phenomenon
Recently, it has been accepted that human activity is also affecting climate
Distance From The Sea (Continentality)
• Coastal areas are cooler and wetter than inland areas
• Clouds form when warm air from inland areas meets cool air from the sea
• The centers of continents are subject to a large range of temperatures.
o In the summer, temperatures can be very hot and dry
 Moisture from the sea evaporates before it reaches the
centre of the continent.
Ocean Currents - Ocean currents can increase or reduce temperatures.
Direction of Prevailing Winds
•
Winds that blow from the sea often bring rain to the coast and dry weather
to inland areas
Relief
• Climate can be affected by mountains
• Mountains receive more rainfall than low lying areas because the
temperature on top of mountains is lower than the temperature at sea
level
7
TROPICAL ARCHITECTURE
•
o Snow on the top of mountains all year round
The higher the place is above sea level the colder it will be
o As altitude increases, air becomes thinner - less able to absorb
and retain heat.
Proximity To The Equator
The Earth's Position in Relation to the Sun
•
The equator receives the more sunlight than anywhere else on earth
o Due to its position in relation to the sun
o Equator is hotter because the sun has less area to heat
o Cooler at the north and south poles as the sun has more area to
heat up. It is cooler as the heat is spread over a wider area.
El Nino
• A wind and rainfall patterns
• Blamed for droughts and floods in countries around the Pacific Rim
• Refers to the irregular warming of surface water in the Pacific. The
warmer water pumps energy and moisture into the atmosphere, altering
global wind and rainfall patterns.
8
TROPICAL ARCHITECTURE
Human Influence
•
•
•
The factors above affect the climate naturally.
Trees were cut down to provide wood for fires
o Trees take in carbon dioxide and produce oxygen.
o A reduction in trees will therefore have increased the amount of
carbon dioxide in the atmosphere.
Industrial Revolution (end of 19th Century)
o Invention of the motor engine and the increased burning of fossil
fuels have increased the amount of carbon dioxide in the
atmosphere
o The number of trees being cut down has also increased
o The extra carbon dioxide produced cannot be changed into
oxygen.
Köppen climate classification system
The Köppen climate classification system - one of the most widely used
systems for classifying climate
•
•
•
•
Easy to understand
Data requirements are minimal
Empirical system
Largely based on annual and monthly means of temperature and
precipitation.
The Köppen system uses a letter coding scheme to classify climate. There are
three levels of letter coding except for the A-type climates. The five main groups
of climates are designated by capital letters, all but the dry climates being
thermally defined.
•
•
•
•
•
A - Tropical climates (sometimes identified as "equatorial" climates)
B - Dry climates (sometimes identified as "arid" climates)
C - Warm temperate climates
D - Subarctic climates (sometimes identified as "snow" or "boreal"
climates)
E - Polar climates
The second letter relates to the seasonality of precipitation
Third letter relates to an additional temperature qualifier.
• f - Moist with adequate precipitation in all months and no dry season. This
letter usually accompanies the A, C, and D climates.
9
TROPICAL ARCHITECTURE
•
•
•
m - Rainforest climate in spite of short, dry season in monsoon type cycle.
This letter only applies to A climates.
s - There is a dry season in the summer of the respective hemisphere
(high-sun season).
w - There is a dry season in the winter of the respective hemisphere (lowsun season).
To further denote variations in climate, a third letter was added to the code.
• a - Hot summers where the warmest month is over 22°C (72°F). These
can be found in C and D climates.
• b - Warm summer with the warmest month below 22°C (72°F). These can
also be found in C and D climates.
• c - Cool, short summers with less than four months over 10°C (50°F) in
the C and D climates.
• d - Very cold winters with the coldest month below -38°C (-36°F) in the
D climate only.
• h - Dry-hot with a mean annual temperature over 18°C (64°F) in B
climates only.
• k - Dry-cold with a mean annual temperature less than 18°C (64°F) in B
climates only
For the B-type (dry) climates the first two letters are combined, BW for desert and
BS for steppe
• The third letter is used to subdivide these on the basis of temperature
Additional Informations.
Typical Climatic Factors in Philippines
•
•
•
•
Sun = The Sun emits heat which causes the Philippine Climate to go high
in temperature or drop to 15 Degrees Celsius.
Equator = Philippine Geographical Location is just few longitudes away
from the equator
o Suffer direct sunlight and heat, which cause two seasons: Wet and
Dry Season.
Global Warming: Philippine Climate goes high or sometimes low
El Nino - affected by the abnormal heating of the Pacific which produces
stormy climate.
10
TROPICAL ARCHITECTURE
1.3 Climatic elements
Some facts about climate
The sun's rays hit the equator at a direct angle between 23 ° N and 23 ° S
latitude. Radiation that reaches the atmosphere here is at its most intense.
In all other cases, the rays arrive at an angle to the surface and are less intense.
The closer a place is to the poles, the smaller the angle and therefore the less
intense the radiation.
Our climate system is based on the location of these hot and cold air-mass
regions and the atmospheric circulation created by trade winds and westerlies.
Trade winds north of the equator blow from the northeast. South of the equator,
they blow from the southeast.
•
•
•
The trade winds of the two hemispheres meet near the equator, causing
the air to rise.
As the rising air cools, clouds and rain develop.
The resulting bands of cloudy and rainy weather near the equator create
tropical conditions.
Westerlies blow from the southwest on the Northern Hemisphere and from the
northwest in the Southern Hemisphere. Westerlies steer storms from west to east
across middle latitudes.
Both westerlies and trade winds blow away from the 30 ° latitude belt.
•
•
•
•
Over large areas centered at 30 ° latitude, surface winds are light.
Air slowly descends to replace the air that blows away.
Any moisture the air contains evaporates in the intense heat.
The tropical deserts, such as the Sahara of Africa and the Sonoran of
Mexico, exist under these regions.
Seasons
The Earth rotates about its axis, which is tilted at 23.5 degrees.
•
•
•
•
This tilt and the sun's radiation result in the Earth's seasons.
The sun emits rays that hit the earth's surface at different angles.
These rays transmit the highest level of energy when they strike the earth
at a right angle (90 °).
Temperatures in these areas tend to be the hottest places on earth.
11
TROPICAL ARCHITECTURE
•
Other locations, where the sun's rays hit at lesser angles, tend to be
cooler.
As the Earth rotates on it's tilted axis around the sun, different parts of the Earth
receive higher and lower levels of radiant energy. This creates the seasons.
Climatology - the study of the long-term state of the atmosphere, or climate.
• The long-term state of the atmosphere is a function of a variety of
interacting elements
o Solar radiation
o Air masses
o Pressure systems (and cyclone belts)
o Ocean Currents
o Topography
Solar radiation
• Probably the most important element of climate.
• Solar radiation heats the Earth's surface, which in turn determines the
temperature of the air above.
• The receipt of solar radiation drives evaporation, so long as there is water
available.
• Heating of the air determines its stability, which affects cloud development
and precipitation.
• Unequal heating of the Earth's surface creates pressure gradients that
result in wind.
Just about all the characteristics of climate can be traced back to the receipt of
solar radiation.
Air masses
• Subsumes the characteristics of temperature, humidity, and stability.
• Location relative to source regions of air masses in part determines the
variation of the day-to-day weather and long-term climate of a place.
o Stormy climate of the midlatitudes is a product of lying in the
boundary zone of greatly contrasting air masses called the polar
front.
Pressure systems
• Places dominated by low pressure tend to be moist
• Those dominated by high pressure are dry.
• The seasonality of precipitation is affected by the seasonal movement of
global and regional pressure systems
o Climates located at 10o to 15o of latitude
12
TROPICAL ARCHITECTURE
•
•
Wet period when dominated by the Intertropical
Convergence Zone
• Dry period when the Subtropical High moves into this region.
o Asia is impacted by the annual fluctuation of wind direction due to
the monsoon.
Pressure dominance also affects the receipt of solar radiation.
o Places dominated by high pressure tend to lack cloud cover and
hence receive significant amounts of sunshine, especially in the low
latitudes.
Ocean Currents
• Ocean currents greatly affect the temperature and precipitation of a
climate.
• Climates bordering cold currents tend to be drier
o Cold ocean water helps stabilize the air
o Inhibit cloud formation and precipitation.
o Air traveling over cold ocean currents loses energy to the water
 Moderate the temperature of nearby coastal locations.
• Air masses traveling over warm ocean currents promote instability and
precipitation
o Warm ocean water keeps air temperatures somewhat warmer than
locations just inland from the coast during the winter.
Topography
The orientation of mountains to the prevailing wind affects precipitation.
• Windward slopes, those facing into the wind
o Experience more precipitation due to orographic uplift of the air.
• Leeward sides of mountains are in the rain shadow
o Receive less precipitation.
• Air temperatures are affected by slope and orientation
o Slopes facing into the Sun will be warmer than those facing away
• Temperature also decreases as one moves toward higher elevations.
o Mountains have nearly the same affect as latitude does on climate.
o On tall mountains a zonation of climate occurs as you move
towards higher elevation.
13
TROPICAL ARCHITECTURE
1.4 Microclimatic Conditions
• Any climatic condition in a relatively small area,
• Within a few metres or less above and below the Earth’s surface and
within canopies of vegetation
• Usually applies to the surfaces of terrestrial and glaciated environments
• Also pertain to the surfaces of oceans and other bodies of water.
o The strongest gradients of temperature and humidity occur just
above and below the terrestrial surface.
o Complexities of microclimate are necessary for the existence of a
variety of life forms because
o strongly contrasting microclimates in close proximity provide a total
environment in which many species of flora and fauna can coexist
and interact.
Microclimatic conditions depend on the following factors
• Temperature
• Humidity
• Wind and turbulence
• Dew
• Frost
• Heat balance
• Evaporation
• Soil type – considerable
o Sandy soils and other coarse, loose, and dry soils are subject to
high maximum and low minimum surface temperatures.
o Soils of lighter colour reflect more and respond less to daily
heating.
o Ability of the soil to absorb and retain moisture, which depends on
the composition of the soil and its use.
• Vegetation - controls the flux of water vapour into the air through
transpiration.
o Can insulate the soil below
o Reduce temperature variability.
o Sites of exposed soil then exhibit the greatest temperature
variability.
Topography - affects the vertical path of air in a locale and, therefore, the relative
humidity and air circulation.
• Air ascending a mountain
o Decreases in pressure
o Releases moisture in the form of rain or snow.
• As the air proceeds down the leeward side of the mountain
o Compressed
14
TROPICAL ARCHITECTURE
•
o Heated
o Promotes drier, hotter conditions
An undulating landscape can also produce microclimatic variety through
the air motions produced by differences in density.
The microclimates of a region are defined by
 Moisture
 Temperature
 Winds of the atmosphere near the ground
 Vegetation
 Soil
 Latitude
 Elevation
 Season
 Weather is also influenced by microclimatic conditions.
o Wet ground promotes evaporation and increases atmospheric
humidity
o The drying of bare soil creates a surface crust that inhibits ground
moisture from diffusing upward, which promotes the persistence of
the dry atmosphere.
Microclimates control evaporation and transpiration from surfaces and influence
precipitation, and so are important to the hydrologic cycle —the processes
involved in the circulation of the Earth’s waters.
15
TROPICAL ARCHITECTURE
2.0 World Climates
Climate – the characteristic condition of the atmosphere near the earth's surface
at a certain place on earth.
• Long-term weather of that area (at least 30 years).
• Includes the region's general pattern of weather conditions, seasons and
weather extremes like hurricanes, droughts, or rainy periods.
• Factors determining an area's climate
o Air temperature
o Precipitation.
World biomes are controlled by climate. The climate of a region will determine
what plants will grow there, and what animals will inhabit it.
Components of a BIODOME
• Climate
• Plants
• Animals
2.1 Thermal Comfort
Thermal comfort - the sensation of physical well being in relation to body heat
loss to the surroundings
•
•
Internal body temperature is comfortable at 36.5°-37°C.
There is continuous exchange of heat between the human body and its
surroundings.
4 physical ways
The heat exchange between the body and its surroundings takes place in four
physical ways:
•
Conduction - the transmission of heat from materials in contact with the
skin.
o It is not advisable to wear wool and heavy clothing in hot weather.
o Select the proper materials, coverings, and finishes in warm
climate.
•
Convection - the exchange of body heat with ambient air, depending on
the difference in temperature between the body and the air and also air
movement
o Ambient temperature is comfortable at 26°C.
o Window openings allow air exchange; recommended to be not less
than one-tenth of floor area, and one-third of wall area.
16
TROPICAL ARCHITECTURE
o Operable windows are preferable to fixed glass windows.
o Buildings and homes are comfortable when planned and designed
according to topography and wind direction.
o Stack effect - the tendency of warm air to rise and go out through
the opening in the higher level. The hot air will be replaced by cool
air entering through the lower openings.
o Natural night ventilation should be allowed indoors to reduce air
temperature during hot weather.
•
Long-wave radiation - heat transfer between the human body and the
surrounding internal surfaces like the walls, ceiling, and floors.
o Heat from the ceiling is reported to affect us more than heat from
walls.
o Ceiling height and thermal property of ceiling and wall materials are
therefore important considerations in designing homes and
buildings.
o Poorly insulated buildings have hot internal surfaces.
o Light-colored paint on external walls is recommended in hot climate
because it will reflect solar radiation.
o Green roofs, climbing plants, and koi ponds reduce temperature of
roofs and walls and internal surfaces.
o Sunshades and shutters reduce sunlight penetration.
•
Evaporation - occurs when the temperature of surrounding air and
surfaces is above 25°C.
o The body loses heat through evaporation or perspiration depending
on clothing worn, temperature, relative humidity, and air movement.
o Humans normally lose one liter of water per day due to perspiration
and respiration, and it takes heat from the body and its
surroundings to evaporate it.
o Relative humidity (the amount of moisture in the air as percentage
of the maximum moisture the air can contain at a certain
temperature and pressure)
 Affects heat loss by evaporation.
 If the surrounding air has higher temperature than the skin,
the cooling effect of evaporation is not possible even if
relative humidity is below 100 percent.
 Air speed does not decrease the temperature but causes a
cooling sensation through heat loss by convection and
increased evaporation.
2.2 Microcllimate
17
TROPICAL ARCHITECTURE
Microclimate - local atmospheric zone where the climate differs from the
surrounding area
•
•
•
May refer to areas as small as a few square feet (for example a garden
bed) or as large as many square miles (for example a valley).
Examples
o Near bodies of water which may cool the local atmosphere
o In heavily urban areas where brick, concrete, and asphalt
absorb the sun's energy, heat up, and reradiate that heat to the
ambient air: the resulting urban heat island is a kind of
microclimate.
o Slope or aspect of an area.
• South-facing slopes in the Northern Hemisphere and
north-facing slopes in the Southern Hemisphere are
exposed to more direct sunlight than opposite slopes and
are therefore warmer for longer.
o The area in a developed industrial park may vary greatly from a
wooded park nearby
• Natural flora in parks absorb light and heat in leaves
• Building roof or parking lot just radiates back into the air
• Widespread use of solar collection can mitigate
overheating of urban environments by absorbing sunlight
and putting it to work instead of heating the foreign
surface objects.
o Cities often raise the average temperature by zoning, and a
sheltered position can reduce the severity of winter.
• Roof gardening exposes plants to more extreme
temperatures in both summer and winter.
• Tall buildings create their own microclimate, both by
overshadowing large areas and by channeling strong
winds to ground level.
• Wind effects around tall buildings are assessed as part of
a microclimate study.
Also refer to purpose made environments, such as those in a room or
other enclosure.
o Commonly created and carefully maintained in museum display
and storage environments.
• Passive methods, such as silica gel, or with active
microclimate control devices.
2.3 Tropical Climate
A tropical climate is a climate of the tropics.
18
TROPICAL ARCHITECTURE
•
Köppen climate classification
o Non-arid climate in which all twelve months have mean
temperatures above 18 °C (64 °F).
o With season, tropical temperature remains relatively constant
throughout the year and seasonal variations are dominated by
precipitation
Tropical Designs Considerations
1. Naturally comfortable houses are low energy houses
2. Ceiling fans provide low energy cooling if you only use them whilst
rooms are occupied
3. Light colored roofs (or zinc alum) reflect the heat
4. Use orientation and shading to eliminate direct sun on walls
5. Minimize east and west wall areas and avoid windows on east and
western walls to prevent low morning and afternoon sun heating up the
house
6. Correctly sized eaves can provide permanent shade to north and south
windows and walls (northern verandas make sense
7. Plant tall trees on the east and west sides of the house to shade walls
19
TROPICAL ARCHITECTURE
8. Tall trees on north and south shade roof (minimized mid-height foliage
to let breeze through for naturally ventilated houses). Consider leaving
half roof un-shaded if solar panels are to be used
Design for Natural Ventilation
Use the breeze for cross ventilation through openings in opposite walls and internal
partitions
Maximize the area of windows (e.g. louvres) that can be opened
Orientate house to catch the breeze (whilst still minimizing sun on east and west
walls)
A long narrow floor plan catches the breeze best.
Trees and shrubs act to cool the air passing through the house.
Don't use exposed concrete on ground immediately outside the house as it heats the
air.
Roof space ventilation draws the heat out.
Dirty fly-screens block more breeze. Consider using operable/removable fly-screen
shutters
Minimum Insulation Standard
1. Light coloured well ventilated roofs: foil/sisalation
2. Other roofs: R1.5 batts and foil/sisalation
3. Full shading of wall is much more important than wall R-value. Unshaded,
masonry walls store heat and release it well into the night.
4. Shelter windows with louvres, canopies, shutters or fixed overhangs - then
you can enjoy the cooling effect of rain.
Design for Air-Condition
20
TROPICAL ARCHITECTURE
NOTE:
House designs depending on full air-conditioning for comfort are not very suitable
for our tropical climate nor environmentally sensitive.
1. Energy costs will be high when air-conditioning is running and comfort
levels will be low when air conditioning is switched off. Occupants can
have difficulty acclimatizing to outside temperatures
2. The better your house seals and is insulated, and the less glass area, the
less energy air-conditioning will use.
3. Keep the heat and moisture out and the cool in!
4. Shade walls and choose the highest wall R-value (lowest U-value)
possible.
Windows
1. Medium sized with the greatest possible operable area per window, and
placed for cross ventilation, so you don't have to air-condition all the time
2. Heavy snug fitting curtains and pelmets prevent cooling energy loss from
radiation and air flow against glass
3. A square floor plan minimizes external wall area and therefore reduces
cooling energy loss through walls.
4. Exposed heavy construction materials (e.g. concrete and bricks) inside
insulation barrier store cooling energy.
Combined Air-Conditioning and Naturally Ventilated Houses
1. Many houses in tropical regions have some air conditioned spaces and
some naturally ventilated spaces or the same spaces are naturally
ventilated and air-conditioned at different times
21
TROPICAL ARCHITECTURE
2. Design of each area should follow principles for natural ventilation or airconditioning as relevant.
3. Walls separating naturally ventilated and cooled spaces should be
insulated and have doors to limit loss of cooled air.
2.4 Characteristics of Tropical Climate
•
•
•
Much of the equatorial belt within the tropical climate zone experiences
hot and humid weather.
There is abundant rainfall due to the active vertical uplift or convection of
air that takes place there,
o Thunderstorms
o Considerable sunshine
o Provides ideal growing conditions for luxuriant vegetation.
o Principal regions
 Amazon Basin in Brazil
 Congo Basin in West Africa and Indonesia
Substantial sun’s heat is used up in evaporation and rain formation
o temperatures in the tropics rarely exceed 35°C
o a daytime maximum of 32°C is more common
o At night the abundant cloud cover restricts heat loss
o Minimum temperatures - 22°C
o Temperature - little variation throughout the year
o The seasons are distinguished not as warm and cold periods but by
variation of rainfall and cloudiness
 Greatest rainfall occurs when the Sun at midday is overhead
(March and September)
 Two wet and two dry seasons.
o Further away from the equator, the two rainy seasons merge into
one, and the climate becomes more of a Monsoonal
 One wet season
 one dry season
 Northern Hemisphere, the wet season occurs from May to
July
 Southern Hemisphere from November to February.
Tropical rainforest climate (Af):
•
All twelve months have average precipitation of at least 60 mm (2.4 in).
•
These climates usually occur within 5–10° latitude of the equator.
22
TROPICAL ARCHITECTURE
•
In some eastern-coast areas, they may extend to as much as 25° away
from the equator.
•
This climate is dominated by the Doldrums Low Pressure System all year
round, and therefore has no natural seasons.
•
Examples
o Kuala Lumpur, Malaysia
o Belém, Brazil
o Hilo, Hawaii, United States
o Georgetown, Guyana
o Amazon Basin, Brazil
o Congo Basin, Congo
Tropical monsoon climate (Am):
•
Most common in southern Asia and West Africa,
•
Results from the monsoon winds which change direction according to the
seasons.
•
This climate has a driest month (which nearly always occurs at or soon
after the "winter" solstice for that side of the equator) with rainfall less than
60 mm, but more than (100 − [total annual precipitation {mm}/25]).
Examples
•
Conakry, Guinea
•
Chittagong, Bangladesh
•
Miami, Florida, United States
•
Cairns, Australia
Tropical wet and dry or savanna climate (Aw):
•
These climates have a pronounced dry season,
•
Driest month having precipitation less than 60 mm and also less than (100
− [total annual precipitation {mm}/25]).
Examples:
23
TROPICAL ARCHITECTURE
•
Mumbai, Maharashtra, India
•
Jakarta, Indonesia
•
Rio de Janeiro, Rio de Janeiro, Brazil
•
Veracruz, Veracruz, Mexico
•
Port-au-Prince, Haiti
•
Dar es Salaam, Tanzania
•
Lagos, Lagos State, Nigeria
•
Darwin, Northern Territory, Australia
•
Honolulu, Hawaii, United States
Problems in Areas with Tropical Climate
Bionetwork
In Tropical Asia, momentous elevational lifts on the ecosystems on the
mountains show change in distribution and behavior of the rainforest.
• In Thailand, for instance, the area of tropical forests could increase
from 45% to 80% of the total forest cover
• In Sri Lanka, a substantial change in dry forest and decrease in wet
forest might occur.
• With predictable increases in evapotranspiration and rainfall
changeability, likely a negative impact on the viability of freshwater
wetlands will occur, resulting in contraction and desiccation.
• Sea level and temperature rises are the most likely major climate
change-related stresses on ecosystems.
• Coral reefs might be capable of surviving this intensification, but
suffer bleaching from high temperatures.
• Landward migration of mangroves and tidal wetlands is likely to be
inhibited by human infrastructure and human activities.
Coastal lands
Coastal lands, in particular, are very vulnerable to major climate changes
especially on seas.
• Particularly, heavily settled and intensified used low-level coastal
plains, deltas, and islands are particularly susceptible to coastal
erosion and land loss, sea flooding and barrage, especially
vulnerable to
o Coastal erosion
o Land loss
o Inundation
24
TROPICAL ARCHITECTURE
Sea flooding, upstream movement of the saline/freshwater
front and seawater incursion into freshwater lenses.
Mainly at risk are large delta regions of Bangladesh, Myanmar, Viet
Nam and Thailand, and the low-lying areas of Indonesia the
Philippines and Malaysia.
Socio-economic effects may be noticeable to major cities and ports,
tourist resorts, artisinal and commercial fishing and coastal
agriculture, and infra-structure development.
Global studies have expected the dislodgment of several millions of
people from the region's coastal zone, probably a 1 metre rise in
sea level.
o
•
•
•
Hydrology
In Tropical Asia, the Himalayas are crucial to the provision of water of the
continental monsoon.
Augmented temperatures and seasonal variability could cause a backdrop of
glaciers and increasing danger from glacial lake outburst floods.
Then, a diminution of average flow of snow-fed rivers, mixed with an increase in
peak flows and sediment yield, could have major effects on hydropower
generation, urban water supply and agriculture.
Supply of hydropower generation from snow-fed rivers can occur in the short
term, though not in the long term—run off snow-fed rivers might change as well.
As stated before, an increased amount economic, agriculture, and industrial
resources, can affect climate, but it can put an extra stress on water.
Lower level basins are expected to be most affected. Hydrological changes on
island and drainage basins will be relatively low to Tropical Asia, despite those
relate to sea rise.
Food ration
The sensitivity of major cereal and tree crops, changes in temperature, moisture
and CO2 concentration of the magnitudes estimated for the region has been done
in many studies.
One instance is the influences on rice fields, wheat yield and sorghum yield imply
that any increase in production associated with CO2 fertilization will most likely be
offset by reductions in yield from temperature or moisture changes.
25
TROPICAL ARCHITECTURE
Even though climate impression may result huge changes in crop yields, storage,
and distribution., the continuing effect of the region-wide changes is tentative
because of varietal disparity; local disparity in emergent season, crop
management, etc.( the lack of inclusion of possible diseases, pests, and
microorganisms in crop model simulations); and the vulnerability of agricultural
(especially low-income rural population) areas to periodic environmental hazards,
such as floods, droughts and cyclones.
Human health
The occurrence and level of some vector-borne diseases are anticipated to rise
with global warming.
• Malaria
• Schistosomiasis and
• Dengue
These are significant causes of humanity and morbidity in Tropical Asia, are very
sensitive to climate and are likely to spread into new regions on the margins of
currently widespread areas as a result of climate change.
Lately affected populations initially would go through higher fatality rates.
According to one study, specifically focused on climate influences on infectious
disease in present vulnerable regions, a growth in epidemic potential of
• 12-27 per cent for malaria and
• 31 to 47 per cent for dengue and
• A decrease of schistosomiasis of 11-17 per cent .
Waterborne and water related infectious diseases, already accounting for the
majority of epidemic emergencies in the area, are also expected to increase
when higher temperatures and higher humidity are placed over on existing
conditions and estimated upsurge in population, urbanization, deduction of water
quality and other trends.
26
TROPICAL ARCHITECTURE
Heat Transfer
•
•
•
•
Heat conduction
Convection
Thermal radiation
Phase-change transfer
Conduction - also called diffusion, is the direct microscopic exchange of kinetic
energy of particles through the boundary between two systems.
•
•
•
The transfer of energy between objects that are in physical contact
When an object is at a different temperature from another body or its
surroundings, heat flows so that the body and the surroundings reach the
same temperature at thermal equilibrium
Spontaneous heat transfer always occurs from a region of high
temperature to another region of lower temperature, (Second law of
Thermodynamics)
Transfer by thermal radiation is the transfer of energy by transmission of
electromagnetic radiation described by black body theory.
Convection
The transfer of energy between an object and its environment, due to fluid motion
Radiation
The transfer of energy to or from a body by means of the emission or absorption
of electromagnetic radiation
Mass transfer
The transfer of energy from one location to another as a side effect of physically
moving an object containing that energy
Condensation - change from a vapor to a condensed state (solid or liquid).
Evaporation - change of a liquid to a gas
27
TROPICAL ARCHITECTURE
3.1Conduction
On a microscopic scale
• Heat conduction occurs as hot, rapidly moving or vibrating atoms and
molecules interact with neighboring atoms and molecules, transferring
some of their energy (heat) to these neighboring particles
• Heat is transferred by conduction when adjacent atoms vibrate against
one another, or as electrons move from one atom to another
• Most significant means of heat transfer within a solid or between solid
objects in thermal contact
o Fluids—especially gases—are less conductive
Thermal contact conductance - is the study of heat conduction between solid
bodies in contact.
Steady state conduction - a form of conduction that happens when the
temperature difference driving the conduction is constant
• After an equilibration time, the spatial distribution of temperatures in the
conducting object does not change any further
• The amount of heat entering a section is equal to amount of heat coming
out.
Transient conduction - occurs when the temperature within an object changes
as a function of time.
• Analysis of transient systems is more complex and often calls for the
application of approximation theories or numerical analysis by computer.
3.2 Convection
Convective heat transfer, or convection - the transfer of heat from one place
to another by the movement of fluids
Fluid - means any substance that deforms under shear stress
• Liquids
• Gases
• Plasmas
• Some plastic solids
Bulk motion of the fluid enhances the heat transfer between the solid surface and
the fluid.
•
•
Dominant form of heat transfer in liquids and gases
Combined effects of conduction and fluid flow
28
TROPICAL ARCHITECTURE
Free, or natural convection - occurs when the fluid motion is caused by
buoyancy forces that result from density variations due to variations of
temperature in the fluid
Forced convection - fluid is forced to flow over the surface by external means
• Fans
• Stirrers
• Pumps
— creating an artificially induced convection current
Convection in Newton's law of cooling - "The rate of heat loss of a body is
proportional to the difference in temperatures between the body and its
surroundings."
3.3Radiation
A red-hot iron object, transferring heat to the surrounding environment primarily
through thermal radiation.
Thermal radiation - energy emitted by matter as electromagnetic waves due to
the pool of thermal energy that all matter possesses that has a temperature
above absolute zero
• Propagates without the presence of matter through the vacuum of space
• Direct result of the random movements of atoms and molecules in matter
o Atoms and molecules are composed of charged particles (protons
and electrons)
o Their movement results in the emission of electromagnetic
radiation, which carries energy away from the surface.
• Unlike conductive and convective forms of heat transfer, thermal radiation
can be concentrated in a small spot by using reflecting mirrors
o Exploited in concentrating solar power generation
 Sunlight reflected from mirrors heats the PS10 solar power
tower and during the day it can heat water to 285 °C (545 °F)
29
TROPICAL ARCHITECTURE
3.4 Mass Transfer
In mass transfer – energy (including thermal energy) is moved by the physical
transfer of a hot or cold object from one place to another
• Can be as simple as placing hot water in a bottle
• Heating a bed
• Movement of an iceberg in changing ocean currents
• A practical example is thermal hydraulics
3.5 Evaporation and Condensation
Evaporation – a type of vaporization of a liquid that occurs only on the surface of
a liquid
Other type of vaporization
• Boiling - occurs on the entire mass of the liquid.
Evaporation is also part of the water cycle
.
• The molecules in a glass of water do not have enough heat energy to
escape from the liquid
• With sufficient heat, the liquid would turn into vapor quickly (boiling point)
• When the molecules collide, they transfer energy to each other in varying
degrees, based on how they collide
• Sometimes the transfer is so one-sided for a molecule near the surface
that it ends up with enough energy to escape.
Not all liquids evaporate visibly at a given temperature in a given gas (e.g.,
cooking oil at room temperature)
• They have molecules that do not tend to transfer energy to each other in a
pattern sufficient to frequently give a molecule the heat energy necessary
to turn into vapor
• However, these liquids are evaporating. It is just that the process is much
slower and thus significantly less visible.
Evaporation is an essential part of the water cycle
• Solar energy drives evaporation of water from oceans, lakes, moisture in
the soil, and other sources of water
• In hydrology, evaporation and transpiration (which involves evaporation
within plant stomata) are collectively termed evapotranspiration
• Evaporation - caused when water is exposed to air and the liquid
molecules turn into water vapor, which rises up and forms clouds
30
TROPICAL ARCHITECTURE
•
Condensation occurs when a vapor is cooled and changes its phase to a
liquid
o Condensation heat transfer – during condensation, the latent heat
of vaporization must be released
o The amount of the heat is the same as that absorbed during
vaporization at the same fluid pressure
Types of condensation
•
•
•
Homogeneous condensation - as during a formation of fog.
Condensation in direct contact with sub-cooled liquid.
Condensation on direct contact with a cooling wall of a heat exchanger - most
commonly used in industry
Filmwise condensation is when a liquid film is formed on the sub-cooled surface,
and usually occurs when the liquid wets the surface
Dropwise condensation is when liquid drops are formed on the sub-cooled
surface, and usually occurs when the liquid does not wet the surface.
• Difficult to sustain reliably
• Industrial equipment is normally designed to operate in filmwise condensation
mode
3.0
Passive Cooling
“Passive” - implies that energy-consuming mechanical components like pumps
and fans are NOT used.
Passive cooling building design attempts to integrate principles of physics into
the building exterior envelope to:
•
•
Slow down heat transfer into a building.
o Involves an understanding of the mechanisms of heat transfer
 Heat conduction
 Convective heat transfer
 Thermal radiation (primarily from the sun)
Remove unwanted heat from a building
In mild climates with cool dry nights this can be done with ventilating.
In hot humid climates with uncomfortable warm / humid nights, ventilation is
counterproductive, and some type of solar air conditioning may be cost effective.
31
TROPICAL ARCHITECTURE
Shading
•
•
•
•
•
Shading a building from solar radiation can be achieved in many ways.
Buildings can be orientated to take advantage of winter sun (longer in the
East / West dimension)
Location-specific wide eaves or overhangs above the Equator-side vertical
windows
o South side in the Northern hemisphere
o North side in the Southern hemisphere
Passive solar buildings should not allow direct sunlight through use large
glass areas directly into the living space in the summer
A greenhouse / solarium is usually integrated into the equator side of the
building
o Captures low winter sun
o Blocks direct sunlight in the summer, when the sun's altitude is 47
degrees higher
o The outer glass of the solarium, plus interior glass between the
solarium and the interior living quarters acts like a Thermal Buffer
Zone - Two smaller temperature differentials produce much lower
heat transfer than one large temperature differential
The quality of window-and-door fenestration can have a significant impact on
heat transfer rate (and therefore on heating and cooling requirement)
• A solid wood door with no windows conducts heat about twelve times
faster than a foam-filled door
• Older fenestration, and lower-quality doors and windows can leak a lot of
outside air infiltration, conduct and radiate a lot of undesirable heat
transfer through the exterior envelope of a building
• Roof-angled glass is not a great option in any building in any climate
o In the summer, it creates a solar furnace, with the sun nearly
perpendicular to it
o On cold winter days, the low angle of the sun mostly reflects off of
roof-angled glass
o Warm air rises by natural convection, touches the roof angled
glass, and then conducts and radiates heat outside
• Vertical equator-facing glass is far superior for solar gain, blocking
summer heat, and day-lighting throughout a well-designed passive solar
building
Awnings, shade screen, trellises or climbing plants can be fitted to existing
buildings for a similar effect.
West-facing rooms – prone to overheating because the low afternoon sun
penetrates deeper into rooms during the hottest part of the day
• Methods of shading
32
TROPICAL ARCHITECTURE
•
o Deciduous planting
o Vertical shutters or blinds
Should be minimized or eliminated in passive solar design
Solar heat also enters a building through its walls and roof
• In temperate climates, a poorly insulated building can
o Overheat in summer
o Will require more heating in winter
One sign of poor thermal design is an attic that gets hotter than the peak outside
summer air temperature.
• This can be significantly reduced or eliminated with a cool roof or a green
roof
o Can reduce the roof surface temperature by 70 degrees F (21
degrees C) in the summer
o Below the roof there should be a radiant barrier and an air gap
• Blocks 97% of downward radiation from the sun
Radiation is one of the most significant in most climates
• Least easy to model
o There is a linear relationship between temperature differential and
conductive / convective heat transfer rate
o But, radiation is an exponential relationship, which is much more
significant when the temperature differential is large (summer or
winter).
The rate of heat transfer
• Related to heating-and-cooling requirement
• Determined in part by the surface area of the building
• Decorative corners can double or triple the exterior envelope surface area
• Also create more opportunities for air infiltration leaks
.
In mild arid climates with comfortable cool dry nights, two types of natural
ventilation can be achieved through careful design
• Cross ventilation
• Passive-stack ventilation.
Cross ventilation requires openings on two sides of a room
Passive-stack ventilation uses a vertical space, like a tower, that creates a
vacuum as air rises by natural convection
• An inlet for cool air at the bottom of this space creates an upward-moving
air current
33
TROPICAL ARCHITECTURE
Allergens such as pollen can be an issue when windows are used for fresh air
ventilation.
Anything that creates an air pressure difference (like an externally vented clothes
dryer, fireplace, kitchen and bathroom vents) will draw unfiltered outside air in
through every small air leak in a building
In hot humid climates with uncomfortable nights, fresh air ventilation can be
controlled, filtered, dehumidified, and cooled (possibly using an air exchanger).
In a climate that is cool at night and too warm in the day, thermal mass can be
strategically placed and insulated to slow the heating of the building when the
sun is hot.
Passive Cooling Techniques
1. BUILDING CONFIGURATION, SITE LAYOUT and SITE PLANNING
Example : A building can be protected from direct sunlight by placing it on a
location within the site that utilizes existing features such as trees, terrain etc.
2. BUILDING ORIENTATION
Example : In tropical countries such as the Philippines, it is best to place service
areas in the west and east facing sides of the building because these sides are
exposed to direct sunlight.
3. FACADE DESIGN
Use of Double-layered façade
Use Low-emissivity glass (Low-E glass)
Use of Insulation
4. CROSS VENTILATION
The circulation of fresh air through open windows, doors or other openings on
opposite sides of a room
STACK EFFECT / CHIMNEY EFFECT
The tendency of air or gas in a shaft or other vertical space to rise when heated,
creating a draft that draws in cooler air or gas from below
5. SUNSHADING DEVICES
VERTICAL TYPES
Vertical Sun Shades are generally used on the East-Facing and West- Facing
Sides
of a building
EGGCRATE TYPES
Combination of Horizontal and Vertical Shades
34
TROPICAL ARCHITECTURE
Passive cooling techniques (solar chimneys, thermal mass, ventilation, roof
ponds, etc…).
And, efficient active cooling techniques
Passive Cooling:
•
Passive Cooling Guides and Tools
•
Shading
•
Reflective Roofs (and Walls)
•
Cooling Towers & Solar Chimneys
•
Earth Tubes
•
Reflectors
•
Tips
Active Cooling:
•
Efficient Active Cooling - Ventilation
•
Efficient Active Cooling – Evaporative
•
Efficient Active Cooling - More ways
35
TROPICAL ARCHITECTURE
A home that illustrates how a number of simple cooling techniques that were
combined in this house to avoid the need for air conditioning
A good overview of passive cooling strategies.
WIND ANALYSIS
36
TROPICAL ARCHITECTURE
Wind direction: Desirable and undesirable winds in each of the climatic zones
depend largely on local conditions.
Any breeze in the lower latitude (tropical and arid climates) is beneficial for most
of the year.
Cross ventilation: Cross ventilation is far more important in the tropics than in
temperate zones.
The theoretical strategy for blocking or inducing wind flow into a building is based
on local prevailing wind conditions. Generally, for the tropical zones as much
ventilation as possible is desired.
Influences on Built Form
1. Zoning for transitional spaces -the traditional spaces used for lobbies, stairs,
utility spaces, circulation, balconies and any other areas where movement take
place.
These areas do not require total climatic control and natural ventilation is
sufficient.
For the tropical and arid zones, the transitional spaces are located on the north
and south sides of the building where the sun's penetration is not as great.
An atrium can also be used a transitional space.
2. Use of atrium
In the tropical zone the atrium should be located so as to provide ventilation
within the built form. In the arid zone the atrium should be located at the centre of
the building for cooling and shading purposes.
Influences on Built Form
1. Form: Optimum building form for each climatic zone.
• Research has shown that the preferred length of the sides of the building,
where the sides are of length x:y, are: tropical zone - 1:3
•
Analysis of these ratios shows that an elongated form to minimize east
and west exposure is needed at the lower latitudes.
2. Orientation: Orientation as well as directional emphasis changes with latitude
in response to solar angle.
• Building's main orientation for tropical countries would have a directional
emphasis on an axis 5deg north of east
37
TROPICAL ARCHITECTURE
3. Vertical cores and structure
• The arrangement of primary mass can be used as a factor in climatic
design as its position can help to shade or retain heat within the building
form.
• For the tropical zone, the cores are located on the east and west sides of
the building form, so as to help shade the building from the low angles of
the sun during the major part of the day.
4.1Building Configuration
Factors that affect building’s energy use and its sustainability.
• Building's shape
• Solar orientation
• Interior layout
• Size
In cold climates building form should be
• Compact to reduce heat loss caused by winter winds
• Elongated on the east west axis to maximize solar gain.
• The length of the roof overhangs for summer shading is a critical factor.
o The correct length varies with distance and latitude.
In a humid hot climate
• Heat gain through windows should be minimized
• Ventilation and shading maximized.
• Air movement should be maximized with cross ventilation.
• Increasing the surface area by making the building taller or longer
increases the area of heat transfer.
o This is inefficient in winter
o Desirable in hot weather.
38
TROPICAL ARCHITECTURE
Shape and surroundings of any building
•
•
May cause heat gain when cooling is required and heat loss when heat
gain is required.
For any given enclosed building volume, there are numerous ways in
which actual dimensions of height, length and breadth can vary resulting
in different total surface areas.
o Two buildings, both having the same volume and built of the same
materials, may have quiet different surface areas and hence
different rate of heat loss and heat gain.
o The way the volume and surfaces of the building are oriented also
severely affect the heat gain or loss from a building.
4.2 Building Orientation
Orientation of the building generally used to refer to solar orientation
• The placement of building with respect to solar access.
• Although any building will have different orientations for its different sides,
the orientation can refer to a particular room, or to the most important
facade of the building.
• The building orientation can have an impact on heating, lighting and
cooling costs.
o By maximizing southern exposure, for example, one can take
optimal advantage of the sun for daylight and passive solar heating
o This will result in lower cooling costs by minimizing western
exposures, where it's most difficult to provide shade from the sun.
39
TROPICAL ARCHITECTURE
40
TROPICAL ARCHITECTURE
Solar orientation is different to magnetic orientation
It is very important that you remember to orientate your house with respect to the
Sun and not to magnetic North (or South), see the diagram below.
Apparent magnetic North can be very different to where Solar North is (up to 20
degrees), this can make all the difference between a passive solar design being
viable or not
Living Area placement
Also of importance is that the rooms most used must be on the side of the house
orientated towards the sun, i.e. the kitchen, lounge, etc. Also put the least used
rooms on the side of the house in shade, i.e. garage, laundry; these will also act
as additional thermal mass, if properly insulated.
UNITS / TERMS:
The five elements of passive solar design include
Aperture Collector – (typically glass) the aperture collector is the area through
which sunlight enters the home or building.
41
TROPICAL ARCHITECTURE
Absorber - the absorber is typically a hard, darkened surface on the storage
element that sits in the path of sunlight and absorbs its heat.
Thermal Mass - the material(s) that retain the heat absorbed by the absorber
• Thermal mass can be composed of water, concrete, stones, bricks, tile or
other materials with high specific heat capacity.
Distribution - the means by which the solar heat is transferred from the storage
material(s) to areas of the home or building.
Control - elements that control the under- and overheating of a space, such as
overhangs, differential thermostats, and operable vents
A true passive solar building includes proper orientation, collection, and
distribution capability.
BACKGROUND FACTS:
Building orientation can maximize
• Opportunities for passive solar heating when needed,
• Avoidance of Solar heat gain during cooling time,
• Natural ventilation, and
• Daylighting throughout the year.
o Southern exposure is the key physical orientation feature for
passive solar energy in the northern hemisphere
o Winter in the northern hemisphere, the sun comes up in the
southeast and sets in the southwest.
o Summer in the northern hemisphere, the sun comes up in the
northeast and sets in the northwest.
o In the middle of the day in the summer, the sun is high in the sky
overhead.
o In the middle of the day in the winter, the sun is low in the southern
sky.
The basic considerations for optimizing the solar heating potential of a sunspace
include the directional orientation and the angle of the glazing (glass or
windows).
• In general, a south-facing orientation within 30o east or west of true south
will provide around 90% of the maximum static solar collection potential.
• The optimum directional orientation depends on site specific factors and
on local landscape features such as trees, hills, or other buildings that
may shade the sunspace during certain times of the day.
42
TROPICAL ARCHITECTURE
Rectangular buildings should be oriented with the long axis running east-west, so
the east and west walls receive less direct sun in the summer.
In the winter, passive solar heat gain occurs on the south side of the building.
Energy conservation strategies relating to building orientation:
•
Maximizing north and south façade exposure for daylight harvesting to
reduce lighting electrical loads
•
Using southern exposure for solar heat gain to reduce heating loads in
the heating season
•
Using shading strategies to reduce cooling loads caused by solar gain on
south façades
•
Turning long façades toward the direction of prevailing breezes to
enhance the cooling effect of natural ventilation
•
Turning long façades in the direction parallel to slopes to take advantage
of cool updrafts to enhance natural ventilation
•
Shielding windows and openings from the direction of harsh winter winds
and storms to reduce heating loads
•
Orienting the most populated building spaces toward north and south
exposures to maximize daylighting and natural ventilation benefit
•
Determining building occupant usage patterns for public, commercial,
institutional, or residential buildings, and how occupants will be affected by
the building orientation, by time of day, on different exposures
Application: Designing for Building Orientation:
The designer must consider and prioritize all factors and site conditions affecting
building orientation.
• Orientation factors depending on functional requirements:
o Designing for cooling load or heating load.
o To take advantage of north–south day lighting; the building may be
oriented along an east–west axis.
o But this may be counter to street lines and other site
considerations.
43
TROPICAL ARCHITECTURE
o Orientation of the building entrance may have to respect street
access, activity zones, and local urban design guidelines.
•
For most regions, optimum façade orientation is typically south.
o South-facing glass is relatively easy to shade with an overhang
during the summer to minimize solar heat gain.
o Light shelves also can work well with the higher sun in the southern
exposure
o North-facing glass receives good daylight but relatively little direct
isolation, so heat gain is less of a concern.
•
East and west window orientations and horizontal orientation (skylights) all
result in more undesired heat gain in the summer than winter
o East and west sun glare is also more difficult to control for occupant
comfort because of low sun angles in early morning and late
afternoon
•
Wind will affect tall buildings more than low structures.
o Design for wind direction—admitting favorable breezes and
shielding from storms and cold weather winds.
o Wind information is often available from airports, libraries, and/or
county agricultural extension offices.
o In cold climates, locate pedestrian paths and parking lots on south
and east sides of buildings to enable snow melting,
o In southern climates locate these on the less sunny east or north
sides of the building
•
In temperate and northern climates
o Locate deciduous trees for south-side shading in the cooling
season;
o In the heating season, the dropped leaves will permit desired solar
gain.
•
In urban settings, orientation may be strongly determined by
o Local regulation
o View easements
o Urban design regulations
•
Be aware of unique local and site-specific conditions
o Lake or coastal exposures
o Effect of mountainous conditions
o Special scenic easements.
•
To minimize heat losses and gains through the surface of a building
44
TROPICAL ARCHITECTURE
o A compact shape is desirable
 This characteristic is mathematically described as the
“surface-to-volume” ratio of the building.
 The most compact orthogonal building would be a cube.
 This configuration, however, may place a large portion of the
floor area far from perimeter day lighting
 Contrary to the cube, a building massing that optimizes day
lighting and ventilation would be elongated along its east–
west axis
• More of the building area is closer to the perimeter.
• Although this may appear to compromise the thermal
performance of the building
• The electrical load and cooling load savings achieved
by a well-designed day lighting system will be more
than compensate for the increased surface losses.
4.3 Sun Control and Shading Devices
There are many different reasons to want to control the amount of sunlight that is
admitted into a building.
• In warm, sunny climates excess solar gain may result in high cooling
energy consumption
• In cold and temperate climates winter sun entering south-facing windows
can positively contribute to passive solar heating
• In nearly all climates controlling and diffusing natural illumination will
improve day lighting.
• Well-designed sun control and shading devices can dramatically reduce
building peak heat gain and cooling requirements
• Improve the natural lighting quality of building interiors.
• Depending on the amount and location of fenestration, reductions in
annual cooling energy consumption of 5% to 15% have been reported.
• Sun control and shading devices can also improve user visual comfort by
controlling glare and reducing contrast ratios.
• Increased satisfaction and productivity.
• Opportunity of differentiating one building facade from another.
• Can provide interest and human scale to an otherwise undistinguished
design.
• An important aspect of many energy-efficient building design strategies
o Buildings that employ passive solar heating or daylighting often
depend on well-designed sun control and shading devices.
•
•
During cooling seasons, external window shading is an excellent way to
prevent unwanted solar heat gain from entering a conditioned space.
Shading can be provided by
45
TROPICAL ARCHITECTURE
•
•
•
o Natural landscaping
o Building elements such as
 Awnings
 Overhangs
 Trellises.
Some shading devices can also function as reflectors, called light
shelves, which bounce natural light for day lighting deep into building
interiors.
The design of effective shading devices will depend on the solar
orientation of a particular building façade
o Simple fixed overhangs are very effective at shading south-facing
windows in the summer when sun angles are high
o The same horizontal device is ineffective at blocking low afternoon
sun from entering west-facing windows during peak heat gain
periods in the summer.
Exterior shading devices are particularly effective in conjunction with clear
glass facades.
o High-performance glazing are now available that have very low
shading coefficients (SC).
o When specified, these new glass products reduce the need for
exterior shading devices.
Thus, solar control and shading can be provided by a wide range of building
components including:
• Landscape features such as mature trees or hedge rows
• Exterior elements such as overhangs or vertical fins
• Horizontal reflecting surfaces called light shelves
• Low shading coefficient (SC) glass
• Interior glare control devices such as Venetian blinds or adjustable louvers
•
Fixed exterior shading devices such as overhangs are generally most
practical for small commercial buildings
•
The optimal length of an overhang depends on the size of the window and
the relative importance of heating and cooling in the building
•
In the summer, peak sun angles occur at the solstice on June 21, but peak
temperature and humidity are more likely to occur in August.
•
Remember that an overhang sized to fully shade a south-facing window in
August will also shade the window in April when some solar heat may be
desirable
46
TROPICAL ARCHITECTURE
•
To properly design shading devices it is necessary to understand the
position of the sun in the sky during the cooling season
o The position of the sun is expressed in terms of altitude and
azimuth angles.
•
The altitude angle is the angle of the sun above the horizon, achieving its
maximum on a given day at solar noon.
•
The azimuth angle, also known as the bearing angle, is the angle of the
sun's projection onto the ground plane relative to south
•
Shading devices can have a dramatic impact on building appearance
o This impact can be for the better or for the worse.
o The earlier in the design process that shading devices are
considered they more likely they are to be attractive and well
integrated in the overall architecture of a project.
Designing Shading Systems
Given the wide variety of buildings and the range of climates in which they can
be found, it is difficult to make sweeping generalizations about the design of
shading devices.
However, the following design recommendations generally hold true:
1. Use fixed overhangs on south-facing glass to control direct beam solar
radiation. Indirect (diffuse) radiation should be controlled by other measures,
such as low-e glazing.
2. To the greatest extent possible, limit the amount of east and west glass since
it is harder to shade than south glass. Consider the use of landscaping to
shade east and west exposures.
3. Do not worry about shading north-facing glass in the continental United
States latitudes since it receives very little direct solar gain. In the tropics,
disregard this rule-of-thumb since the north side of a building will receive
more direct solar gain. Also, in the tropics consider shading the roof even if
47
TROPICAL ARCHITECTURE
there are no skylights since the roof is a major source of transmitted solar
gain into the building.
4. Remember that shading effects daylighting; consider both simultaneously. For
example, a light shelf bounces natural light deeply into a room through high
windows while shading lower windows.
5. Do not expect interior shading devices such as Venetian blinds or vertical
louvers to reduce cooling loads since the solar gain has already been
admitted into the work space. However, these interior devices do offer glare
control and can contribute to visual acuity and visual comfort in the work
place.
6. Study sun angles. An understanding of sun angles is critical to various
aspects of design including determining basic building orientation, selecting
shading devices, and placing Building Integrated Photovoltaic (BIPV) panels
or solar collectors.
7. Carefully consider the durability of shading devices. Over time, operable
shading devices can require a considerable amount of maintenance and
repair.
8. When relying on landscape elements for shading, be sure to consider the cost
of landscape maintenance and upkeep on life-cycle cost.
9. Shading strategies that work well at one latitude, may be completely
inappropriate for other sites at different latitudes. Be careful when applying
shading ideas from one project to another.
Materials and Methods of Construction
In recent years, there has been a dramatic increase in the variety of shading
devices and glazing available for use in buildings.
• A wide range of adjustable shading products is commercially available
o Canvas awnings
o Solar screens
o Roll-down blinds
o Shutters
o Vertical louvers.
48
TROPICAL ARCHITECTURE
•
While they often perform well, their practicality is limited by the need for
manual or mechanical manipulation.
o Durability and maintenance issues are also a concern.
Require A&E professionals to fully specify all glass
•
They should be prepared to specify
o Glass U-value
o SC
o Tvis
o Net window U-value
Shading coefficient (SC) of a glazing indicates the amount of solar heat gain
that is admitted into a building relative to a single-glazed reference glass.
o A lower shading coefficient means less solar heat gain.
The visible transmittance (Tvis) of a glazing material indicates the percentage
of the light available in the visible portion of the spectrum admitted into a building.
When designing shading devices, carefully evaluate all operations and
maintenance (O&M) and safety implications.
• In some locations, hazards such as nesting birds or earthquakes may
reduce the viability of incorporating exterior shading devices in the design.
• The need to maintain and clean shading devices, particularly operable
ones, must be factored into any life-cycle cost analysis of their use.
49
TROPICAL ARCHITECTURE
4.0 Wind and Natural Ventilation
Natural ventilation is the process of supplying and removing air through an
indoor space by natural means.
There are two types of natural ventilation occurring in buildings
• Wind driven ventilation
• Stack ventilation.
o The pressures generated by buoyancy, also known as 'the stack
effect', are quite low (typical values: 0.3 Pa to 3 Pa)
o Wind pressures are usually far greater (~1 Pa to 35 Pa).
o The majority of buildings employing natural ventilation rely primarily
on wind driven ventilation, but stack ventilation has several
benefits.
o The most efficient design for a natural ventilation building should
implement both types of ventilation.
The static pressure of air is the pressure in a free-flowing air stream and is
depicted by isobars in weather maps.
• Differences in static pressure arise from global and microclimate thermal
phenomena and create the air flow we call wind.
• Dynamic pressure is the pressure exerted when the wind comes into
contact with an object such as a hill or a building and it is related to the air
density and the square of the wind speed.
• The impact of wind on a building affects the ventilation and infiltration
rates through it and the associated heat losses or heat gains.
• Wind speed increases with height and is lower towards the ground due to
frictional drag.
The impact of wind on the building form creates areas of
• Positive pressure on the windward side of a building and
• Negative pressure on the leeward and sides of the building.
•
Thus building shape is crucial in creating the wind pressures that will drive
air flow through its apertures.
o In practical terms wind pressure will vary considerably creating
complex air flows and turbulence by its interaction with elements of
the natural environment (trees, hills) and urban context (buildings,
structures)
o Vernacular and traditional buildings in different climatic regions rely
heavily on natural ventilation for maintaining human comfort
conditions in the enclosed spaces
50
TROPICAL ARCHITECTURE
Design
Typical building design relies on rules of thumb for harnessing the power of wind
for the purpose of natural ventilation.
Design guidelines are offered in building regulations and other related literature
and include a variety of recommendations on many specific areas such as:
• Building location and orientation
• Building form and dimensions
• Window typologies and operation
• Other aperture types (doors, chimneys)
• Construction methods and detailing (infiltration)
• External elements (walls, screens)
• Urban planning conditions
Wind driven ventilation has several significant benefits:
• Greater magnitude and effectiveness
• Readily available (natural occurring force)
• Relatively economic implementation
• User friendly (when provisions for control are provided to occupants)
Some of the important limitations of wind driven ventilation:
• Unpredictability and difficulties in harnessing due to speed and direction
variations
• The quality of air it introduces in buildings may be polluted for example
due to proximity to an urban or industrial area
• May create strong draughts, discomfort.
Wind driven ventilation
Wind driven ventilation or roof mounted ventilation design in buildings provides
ventilation to occupants using the least amount of resources.
• Mechanical ventilation drawbacks include the use of equipment that is
high in embodied energy and the consumption of energy during operation.
• Wind driven ventilation takes advantage of the natural passage of air
without the need for high energy consuming equipment
o Wind catchers are able to aid wind driven ventilation by directing air
in and out of buildings.
• Wind driven ventilation depends on
o Wind behavior,
o On the interactions with the building envelope and
51
TROPICAL ARCHITECTURE
o On openings or other air exchange devices such as inlets or
chimneys.
The knowledge of the urban climatology i.e. the wind around the buildings is
crucial when evaluating the air quality and thermal comfort inside buildings as air
and heat exchange depends on the wind pressure on facades.
Air exchange depends linearly on the wind speed in the urban place where the
architectural project will be built.
CFD (Computational Fluid Dynamics) tools and zonal modelings are usually used
to calculate pressure.
• One of these CFD tools, (UrbaWind) makes the link between this
pressure and the real urban climatology
o It computes with a macroscopic method the mass flow rate
incoming the building for each wind characteristic (incidence and
velocity magnitude),
o Give cross ventilation statistics according to the wind statistics of
the considered urban location.
o It helps quantifying the natural cross ventilation induced by the wind
flow crossing the buildings.
Stack driven ventilation
The stack effect used for high-rise natural ventilation
Stack effect is temperature induced.
• When there is a temperature difference between two adjoining volumes of
air the warmer air will have lower density and be more buoyant thus will
rise above the cold air creating an upward air stream.
52
TROPICAL ARCHITECTURE
•
•
Forced stack effect in a building takes place in a traditional fireplace.
Passive stack ventilators are common in most bathrooms and other type
of spaces without direct access to the outdoors.
In order for a building to be ventilated adequately via stack effect the inside and
outside temperatures must be different so that warmer indoor air rises and
escapes the building at higher apertures, while colder, denser air from the
exterior enters the building through lower level openings.
Stack effect increases with greater temperature difference and increased height
between the higher and lower apertures.
The neutral plane in a building occurs at the location between the high and low
openings at which the internal pressure will be the same as the external pressure
(in the absence of wind).
• Above the neutral plane, the air pressure will be positive and air will rise.
• Below the neutral plane the air pressure will be negative and external air
will be drawn into the space.
Stack driven ventilation has several significant benefits:
• Does not rely on wind: can take place on still, hot summer days when it is
most needed.
• Natural occurring force (hot air rises)
• Stable air flow (compared to wind)
• Greater control in choosing areas of air intake
• Sustainable method
Limitations of stack driven ventilation:
• Lower magnitude compared to wind ventilation
• Relies on temperature differences (inside/outside)
• Design restrictions (height, location of apertures) and may incur extra
costs (ventilator stacks, taller spaces)
• The quality of air it introduces in buildings may be polluted for example
due to proximity to an urban or industrial area
Natural ventilation in buildings relies mostly in wind pressure differences but
stack effect can augment this type of ventilation and partly restore air flow rates
during hot, still days.
Stack ventilation can be implemented in ways that air inflow in the building does
not rely solely on wind direction.
In this respect it may provide improved air quality in some types of polluted
environments such as cities.
53
TROPICAL ARCHITECTURE
•
•
•
For example air can be drawn through the backside or courtyards of
buildings avoiding the direct pollution and noise of the street facade.
Wind can augment the stack effect but also reduce its effect depending on
its speed, direction and the design of air inlets and outlets.
Therefore prevailing winds must be taken into account when designing for
stack effect ventilation.
Examples of stack effect ventilation can be seen on aluminum smelters, steel
mills, and glass plants.
Stack effect ventilators have undergone numerous evolutionary steps in recent
years to correspond to new safety standards for protection against weather
penetration, air hygiene for plant workforce and methodology of construction to
reduce total installed costs of greenfield and brownfield projects.
5.1Stack / Chimney Effect
Stack / Chimney effect is the movement of air into and out of buildings,
chimneys, flue gas stacks, or other containers, and is driven by buoyancy.
Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting
from temperature and moisture differences.
• The result is either a positive or negative buoyancy force.
• The greater the thermal difference and the height of the structure, the
greater the buoyancy force, and thus the stack effect.
• The stack effect is also referred to as the "chimney effect", and it helps
drive natural ventilation and infiltration.
• Since buildings are not totally sealed (at the very minimum, there is
always a ground level entrance), the stack effect will cause air infiltration.
o During the heating season, the warmer indoor air rises up through
the building and escapes at the top either through open windows,
ventilation openings, or other forms of leakage.
o The rising warm air reduces the pressure in the base of the
building, drawing cold air in through either open doors, windows, or
other openings and leakage.
o During the cooling season, the stack effect is reversed, but is
typically weaker due to lower temperature differences.
In a modern high-rise building with a well-sealed envelope, the stack effect can
create significant pressure differences that must be given design consideration
and may need to be addressed with mechanical ventilation.
o Stairwells
54
TROPICAL ARCHITECTURE
o Shafts
o Elevators
•
Tend to contribute to the stack effect,
•
Whereas interior partitions, floors, and fire separations can mitigate it.
o Especially in case of fire, the stack effect needs to be controlled to
prevent the spread of smoke.
The stack effect in industrial flue gas stacks is similar to that in buildings, except
that it involves hot flue gases having large temperature differences with the
ambient outside air.
Furthermore, an industrial flue gas stack typically provides little obstruction for
the flue gas along its length and is, in fact, normally optimized to enhance the
stack effect to reduce fan energy requirements.
Large temperature differences between the outside air and the flue gases can
create a strong stack effect in chimneys for buildings using a fireplace for
heating.
Fireplace chimneys can sometimes draw in more cold outside air than can be
heated by the fireplace, resulting in a net heat loss.
5.2 Cross Ventilation
Cross ventilation relies on wind to force cool exterior air into the building
through an inlet (window, door, etc.) and to force warm interior air out of the
building through an outlet (window, door, etc.)
As one would expect, a window's orientation to the direction of wind movement is
critical to the amount of air flowing through an inlet.
55
TROPICAL ARCHITECTURE
Rule-of-thumb
• An inlet is useful for cross ventilation if the direction of wind flow is in the
range of -45 degrees to 45 degrees to the surface normal of the window.
• Energy Scheming operates under this assumption.
• Of course, one can manipulate exterior geometries to redirect air
movement through a window:
Also of importance to cross ventilation is inlet and outlet area. The amount of
heat removed from a building is directly proportional to the inlet and outlet areas.
5.3 Wind Behavior in a room
Theoretically, the global air circulation can be occurred as a result of a heat air
movement in a tropical area go to atmosphere and move up to North Pole and
South Pole.
After reaching at North Pole and South Pole, with the existence of Coriolis
Forces, hence the cool air go down to surface of earth.
Caused by difference of radiation heat and weather change of the mountains and
sea level, hence movement of cool air goes to the tropical area and returning
again.
The air movement occurs because the atmosphere heating is not distributed
evenly.
56
TROPICAL ARCHITECTURE
The quality of not-even heating on the land and sea occurs because the
difference of solar position.
The air moves from the relative chilled and high-pressured area to the relative
warm and low-pressure area.
This air movement makes a system, is a cycle of air circulation movement
applied to the earth surface.
The discussion of surface air movement is necessary known as “gradient wind”.
Gradient wind is the wind at certain high where form of surface coarse can be
neglected.
Air velocity is an amount of vectors following its level or speed and direction. Air
velocity varies from time to time, either its direction or its speed
57