APR Tropical Architecture Rev1

TROPICAL ARCHITECTURE

Tropical Architecture ARCHITECTURAL BOARD EXAM REVIEWER

PREPARED BY AR. CHRISTIAN CEASAR PINEDA

Contents

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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

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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. 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.

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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

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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

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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.

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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

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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

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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.

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TROPICAL ARCHITECTURE

Human Influence • •

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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.

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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 • •

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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.

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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.

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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

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TROPICAL ARCHITECTURE •

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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.

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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

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TROPICAL ARCHITECTURE

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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.

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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.

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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.

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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.

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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

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TROPICAL ARCHITECTURE Microclimate - local atmospheric zone where the climate differs from the surrounding area • •

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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.

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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

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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

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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

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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 • •

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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).

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These climates usually occur within 5–10° latitude of the equator.

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TROPICAL ARCHITECTURE •

In some eastern-coast areas, they may extend to as much as 25° away from the equator.

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This climate is dominated by the Doldrums Low Pressure System all year round, and therefore has no natural seasons.

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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,

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Results from the monsoon winds which change direction according to the seasons.

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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

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Chittagong, Bangladesh

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Miami, Florida, United States

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Cairns, Australia

Tropical wet and dry or savanna climate (Aw): •

These climates have a pronounced dry season,

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Driest month having precipitation less than 60 mm and also less than (100 − [total annual precipitation {mm}/25]).

Examples:

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TROPICAL ARCHITECTURE •

Mumbai, Maharashtra, India

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Jakarta, Indonesia

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Rio de Janeiro, Rio de Janeiro, Brazil

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Veracruz, Veracruz, Mexico

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Port-au-Prince, Haiti

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Dar es Salaam, Tanzania

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Lagos, Lagos State, Nigeria

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Darwin, Northern Territory, Australia

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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

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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

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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.

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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.

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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

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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

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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)

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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

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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.

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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

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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

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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

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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

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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

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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

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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.

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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.

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TROPICAL ARCHITECTURE

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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.

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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.

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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.

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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

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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

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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

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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

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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.

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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.

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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

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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

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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.

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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.

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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

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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.

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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.

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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

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