Bioclimatic strategies in traditional architecture of dry warm climates, and influences in contemporary architecture.

Juan Izquierdo Cárave

CONTENTS:

Abstract…………………………………..……..1

1. Introduction…………………………………..1

2. Popular architecture in dry warm climates…..2

2.1. The house in Baghdad…………………..3

2.2. A house from Lanzarote…………………4

2.3. The hindu house of Mohenjo-Daro….…..5

2.4. The tower-houses from Yemen….……….6

3. Influences of bioclimatic strategies in the……. analyzed popular architecture over…………… contemporary architecture……………………8

3.1. Glazed openings protection………..……8

3.2. Use of vegetation……………..…………9

3.3. Natural forced ventilation………..…….10

3.4. Thermic inertia…………………..……..11

3.5. Radiant cooling…………………..…….12

4. ‘José Vasconcelos’ library…………………..12

5. Conclusion………………………………….13

6. References……..……………………………14

Bioclimatic strategies in traditional architecture of dry warm climates, and influences in contemporary architecture.

Juan Izquierdo Cárave

Abstract: Bioclimatic architecture seeks for sustainable buildings. Thanks to the study of passive reconditioning strategies developed in popular architecture and its adaptation to nowadays architecture, we can provide a more responsible architecture for the environment. The ‘constants’ we find in popular architecture regarding warm dry climates are, to summarize: protection against sun rays thanks to the use of cantilevers and latticework, providing humidity to the air using vegetation, forced ventilation in order to achieve an air flow that decreases the temperature and renews the air, supplying the buildings with thermic inertia thus reaching more stable temperatures inside it. These strategies have a translation to contemporary architecture of the same climate and others (when the purpose is a derivation of the use of the building and it is similar to the one on a dry warm climate). These strategies allow to minimize the use of active resources for air conditioning and, usually, the reconditioning of livable spaces. This means an energetic and economic saving at the same time that reduces the environmental effect of the building in its surroundings and in the planet as well.

1. INTRODUCTION

During known History, there has always been a very close relationship between climate and architecture. The site has always been crucial when it comes to choose materials, techniques and constructive systems; it has been crucial for the buildings design.

Popular architecture represents the perfect adaption of the climate, the human needs and a sustainable construction among themselves, that’s why it has so much in common with bioclimatic architecture.

A site’s climate is the complex combination of different elements, parameters and decisive factors. Solar radiation is the basic factor. On the one hand, the radiation heats up the air being absorbed by the Earth’s surface and, on the other hand, it evaporates part of the water surfaces when it reaches them, causing diverse humidity, cloudiness and precipitation grades. Also, due to the unbalanced heating of the Earth’s surface, air masses movements are caused, originating winds.

Vernacular town’s architecture has always been conditioned by the climatic factors of their surroundings. The most significants are:

- Latitude on the site: over low latitudes, sun rays hit on a perpendicular and uniform way during the whole year; medium latitudes have very contrasted seasons; and high latitudes are tangentially reached by sun rays, gaining thus a low amount of energy from them.

- Temperature of the sea’s surface: temperature on the surface, either coming from the sea or the earth, has an important impact in the air’s temperature once they get in touch. Certain parts of the Earth have marine masses with quite higher or lower temperatures than the others. This induces particular microclimates in the surroundings. We have one clear example in occidental Europe, where the warm stream coming from the Gulf of Mexico causes a benign climate, at the same time as other areas under the same latitude don’t get any benefit from this, such as the north-American atlantic coast, where the winter temperatures are significantly lower than the ones in Spain. In

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the european coast, the stream coming from its gulf, which ascends until Scandinavia, generates a microclimate in this Norwegian area that allows the appearance of green surfaces when, given the latitude, should be permanently frozen.

- Orographic factor: the existence of natural barriers alters the wind and liquid water masses circulation on the surface and the clouds circulation on the atmosphere. The topography also causes different amounts of sunshine, inducing diverse microclimates in close areas.

- Continental factor: cities or towns located in very continental areas have more extreme climates (warmer during the day and the summer, and colder during the night and the winter), whilst in the ones located near the sea the temperatures are softer and don’t change that much due to the accumulation of solar energy in the water. Also, these will have higher humidities than the ones far from the sea.

- Altitud over the sea level: the temperature can decrease around half a degree in a saturated air and one degree in dry air every one hundred meters of altitud. Alpine climate is always cold whether its location on the Earth.

- The nature of the earth’s surface: if the surface is inorganic, the heating and cooling will be powerful, the absorption of the water coming from the rain will be slow, and the surface run-off (in the earth) will change slowly and inexorably its constitution. The difference of colors of these surfaces will also take part in its high or low heating.

Regarding the surfaces covered by vegetation, the different temperatures between day and night will be less, on account of the capacity of the vegetation of holding a stable temperature; and the rain water will be properly absorbed for its accumulation in underground aquifers, and an hydrological balance will be permanently established.

2. POPULAR ARCHITECTURE IN DRY WARM CLIMATES

Temperatures reached in these areas are also very high. In low latitudes all around the Earth the sun rays hit it with an almost perpendicular angle during most of the months of the year. This means that it won’t have to through a lot of atmospheric mass, so the irradiance will be significantly high.

In dry warm climates, the atmospheric clarity helps the arrival of solar radiation to the Earth and allows it to take maximum advantage of it if the humidity is also low. This way, at night, that transparency causes cooling due to the night over radiation. This generates a diary high temperature oscillation of temperatures, with very uncomfortable situations during the day and during the night.

Between 0º and 20º latitudes there’s no difference among seasons: the annual oscillation of temperatures will be short.

The ‘constants’ in popular architecture in these areas are based in four main strategies: protection against solar radiation, an important incorporation of thermal mass, evaporative cooling and radiant cooling.

In this climate, the essence is the solar protection in buildings in order for them not to get hot whilst warming the indoor air and open spaces, making possible living in public spaces. Also, vegetation in this climate is lacking and small sized. This stops the possibility of using tress as protective screens for the buildings and open spaces exposed to radiation. Most of these protections will be architectonic.

Some usual strategies on public spaces are:

1 - Courtyards shaded by the building itself.

2 - Narrow streets shaded by the buildings that create them and additional elements which also generate shadows.

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3 - Cantilevers producing shadows over the street.

4 - Streets with an irregular design, avoiding the proper circulation of daily heated air (in most of the occasions higher than 37ºC).

5 - Vegetation that allows evaporative cooling.

The most common strategies regarding buildings are:

1 - Cantilevers which generate shadows on the small openings in the buildings and on the facade.

2 - Thick and heavy walls for achieving an indoor temperature similar to the daily average.

3 - Light colors on the facades in order to reflect the solar radiation.

4 - Inside courtyards with plenty of vegetation and water elements that help the evaporative cooling.

The next examples of popular architecture in dry warm climates are fruit of a synthetic paper written by the professor, doctor of the Technical University of Madrid, Francisco Javier Neila González, about different texts. The authors of these texts will be specified in each of them.

2.1. THE HOUSE IN BAGHDAD

(Carolina del Pozo Cobeña)

Houses in Baghdad try to protect themselves from a warm and dry summer, and from a cold winter with punctual rains, having also frequent dust rains all over the year.

The house in Baghdad, in the same way as most of the popular architecture in islamic towns, opens to itself avoiding big openings communicating to the public space. This way, the house is organized around a courtyard which works as an open-air space with a strictly private nature and protected from the sight of the passers-by, even though it’s always

bound together to the main entrance. The ground floor is the one with the most public character thanks to the diverse disposition of the doors or lobbies separated by opaque surfaces. The private rooms such as the bedrooms are in a gallery on the first floor, facing their openings to the courtyard. This is the most pleasant area of the house in winter because of the fact that the humidity is lower than in the ground floor, but it’s also probably the most warm in summer. These houses are usually equipped with a semi underground room under the living room, where is more pleasant to sleep during the summer.

ILLUSTRATION 1. Section of the House in Baghdad. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila)

The selective use of the rooms allows the adaptation of the necessary comfort in summer and in winter in each of them. Galleries in both floors surrounding the courtyard and cantilevers of 90cm wide in the outside generate a shadow and prevent the spaces with direct radiation to heat up. It is achieved thus a total obstruction from the sun to the house, to the public space and other surrounding houses.

When it comes to the constructive characteristics, it is important to emphasize that the outer walls on the ground floor have a 35cm thickness and are built with clay bricks. The outer walls on the first floor are similar to the ones on the ground floor, although wooden battens are organized every 90cm and, between them, 12cm thickness bricks.

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ILLUSTRATION 2. Floor plan of the House in Baghdad. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

The most important and particular bioclimatic strategy in houses in Baghdad is the passive cooling. This kind of cooling is achieved thanks to the main piece of the house: the courtyard. The humidity coming from the plants balance the dry in the air and the temperature of the air in the courtyard decreases through evapotranspiration of these. This decreased temperature will influence the rooms directly communicated to the courtyard. Being open on the top causes that the temperature at night, thanks to the higher density of cold air, transforms it in an air bag which accumulates cold air and distribute it around the house during the morning.

The inner walls are cooled during the night and keep this temperature thanks to their inertia and to not receive any solar radiation. This air is distributed through the rooms that need any cooling during the day. It goes until the courtyard whilst pushing the warm air out. The ceilings are usually high in order to let the warm air go up and assemble in the upper space of the room, leaving the cooled air in the habitable space of the room.

ILLUSTRATION 3. Passive cooling and ventilation of the house. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

2.2. A HOUSE FROM LANZAROTE

(Manuel Pérez Romero)

The climate in the Isle of Lanzarote (Spain) is quite similar to the one on the atlantic coast in the african continent with the same latitude. It is called desert climate. The annual thermic oscillation is small and the climate is usually dry with only a few precipitations. In Lanzarote, there’s a lack of water and vegetation due to the fact that most of the earth is sterile because of recent volcanic eruptions.

The houses are normally free-standing, with only one floor, and the rooms are organized surrounding an open courtyard where a special room for collecting and storing water is located.

ILLUSTRATION 4. Section of a house in Lanzarote. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

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This room and the vegetation in the courtyard provide (the same way they did in the House in Baghdad) humidity to the air and manages to decrease the temperature thanks to the evapotranspiration of the green elements. All of the the rooms ventilate through the courtyard. The low and high openings empty the warm inner air and the battens in the doors let the fresh air from the courtyard inside.

The volumes are mostly straight and prismatic with different sizes. The bigger ones are usually located in the north part of the plot, protecting thus the rest of the prisms from the main winds. The courtyard is protected and all of the inner spaces face it, generating blind outer walls.

The small difference between temperatures during the day and the night, and also among the four seasons, makes dispensable additional mechanisms or complementary energies.

It is very interesting how this rural houses protect their plantations from the strong northern winds the same way they protect themselves. The traditional crops of the isle are small conic-shaped excavations, coated with volcanic gravel and protected with low walls that draw semicircular lines on the surface and redirect the winds around the perimeter of the crop field.

This particular concern about the protection against the architecture and plantations comes not only from the direct consequences of it, but from several occasions when the wind comes along with sand particles from the desert causing the ‘calima’.

The house structure is hold by load-bearing walls thicker than 70cm. They support a timber structure over which the roof is sustained. The walls are constituted by basalt blocks masonry, covered by a mortar mix made out of mud and straw over the two faces. The roof surface is also covered with a mud and straw clump. All of the surfaces are whitened with lime in order

to achieve a higher reflexion of the solar radiation.

These houses are buildings with a high thermic inertia: the walls are very thick and there’s an important amount of exterior surfaces in relation to the delimited spaces. This allows the temperature inside the house to be the same all the time.

The materiales used for this construction come right from the isle thanks to the prevailing sand, gravel, stones with a volcanic origin and lime. Nevertheless, wood is not an abundant resource in the isle, so the roof structure is the most critical element in the construction of the house. The span never exceeds 4,5 or 5 meters.

ILLUSTRATION 5. Floor plan of a house in Lanzarote with the crop field craters. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

The reluctant white surfaces over the black, brown and red tones of the earth achieve a perfect integration into the landscape. Also, the crater field caused by the odd way of growing the crop (explained above), together with the white houses make Lanzarote’s landscape unique in the world.

2.3. THE HINDU HOUSE OF MOHENJO-DARO

(Manuel Pérez Romero)

This house is traditional from Pakistan. The tropical-continental air masses cause a climate

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that includes from dry warm to semi-dry warm. The temperature during summer is high and the annual oscillation is moderate.

As well as in the house in Baghdad, the urban tissue is quite dense and disorganized. The air thus can be heated up to 37 ºC and doesn’t move much, making the streets livable in a windy day.

This typology of house has a small lobby with a fountain inside and an access to the courtyard. The fountain doesn’t actually have a bioclimatic use as it did in the courtyard from the house in Baghdad, but is used to provide water to the bathrooms (connected to this room).

The most public and noisiest spaces are located in the ground floor. It is interesting how the distribution of the rooms in this kind of house makes it able to participate in the activities coming from the crowded alleys at the same time that hides from the passers-by sight. There is also a particular space in the ground floor which is directly communicated with the street and can be used as a retail store or a stand. The more peaceful rooms are located on the top floor.

It is curious how the spaces can change their function whether is day-time or a different season; specially the open spaces like the courtyard, the gallery surrounding the courtyard, or the rooftop terrace. The purpose of this is to find the most suitable micro-climate.

ILLUSTRATION 6. Floor plan of a house in Mohenjo-Daro. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

It a house that faces into itself, with almost none opening to the outside, and receiving most of the light and air through the openings located in the courtyard. Each house have attached other houses in three of its four faces, leaving only one facade exposed to the street.

The urban tissue is organized hierarchically, having the north-south street as the main one. It is the widest one and it houses the shops. The perpendicular streets (east-west streets) are narrow and give access to alleys where the houses are distributed in small blocks.

The only facade facing the street is under the shadow, consequence of the wideness of these alleys that give access to the houses (1,5 m). This strategy manages to reduce the vertical surface under the solar radiation, and thus a decrease of the heat gain.

The ventilation and lightning of the house, as mentioned, is given through the courtyard, being able to always control the direct solar radiation thanks to a gallery that surrounds it in the top floor. This gallery generates a shadow over the courtyard, transforming it in a transition space between the inner space and the outer space.

The thick outer walls made out of sun-dried brick provide a huge thermal inertia, which is perfect for the inside of the house to reach a comfortable daily average temperature, keeping it like this for most of the year.

2.4. THE TOWER-HOUSES FROM YEMEN

(Gloria Gómez Muñoz)

Yemen has a desert climate, although it is not as hot as the rest of the Arabic Peninsula due to the maritime tropical air masses, dry and stable. The annual oscillation is small.

There are high temperatures, low relative humidity and a few precipitations during the year. Sun protection will be again the main strategy to develop. It is necessary to avoid the

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penetration of the sun into the edification; and also to contribute with vegetation or water elements. The thermic inertia of the walls will be crucial to achieve a stable inner temperature and reach comfort.

ILLUSTRATION 7. Floor plan of a tower-house in Yemen. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

This houses have the peculiarity of being vertical, something very rare in such popular architecture as this. The height can reach eight floors and each of them is rectangular, with 7-10 meters per side. These towers are open to the outside, contrary to other the examples above. The facades are decorated with geometric arabic ornaments made out of gypsum and lime that emphasize the verticality of the building.

The houses are big, the have several square meters among their seven or eight floors. All the member of the family use to live in the same house. The distribution of the different rooms is organized based on age, gender and privacy.

The ground floor has a small lobby, a barn, a storage room and a room for feeding the animals. The second and third floor have more storage rooms and the biggest room in the house, where they celebrate ceremonies and the guests are received (‘diwan’). In the rest of the floors are located the bedrooms, living rooms,

dining rooms, kitchens, bathrooms (separate for women and men). The most important bedroom is the ‘mafraj’, in the top floor, together with the kitchens, located there in order to expel the fumes through the chimneys on the top of the building.

The climate is extremely dry and the precipitations are rare, so the water it is used more than once, ending up watering the vegetation (normally located in the bottom floor) and solid residues such as fertilizer.

Attached to one of the facades there’s the stairs box. They’re built with vaults and are usually very vertical. The size of each stair is 25cmx25cm. These stairs have another function: they are also used as a chimney. The vertical condition allows a proper ventilation of the inner spaces.

One of the main characteristics of bioclimatic architecture is the use of local materials. They are easy to find, avoiding unnecessary transport, pollution and ambiental cost.

These towers are made out of clay (for walls), bricks dried under the sun or cooked and stone. The foundation in the house is usually made with stone (basalt), one meter thick and variable depth. Over the foundation there’s the load-bearing walls created with two shutters and a stuffing material. If it’s constructed with stone, each shutter of the load-bearing wall will be 20-25 cm thick, without any mortar, and with a stuffing made out of rubble and clay. If the material for the load-bearing walls is cooked brick, the stone is replaced by clay blocks (40x25x12 cm) joined thanks to a mud and earth mortar. The inner and the outer faces are then covered with a lime mortar. The one on the outer face is usually decorated.

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ILLUSTRATION 8. Section of a tower-house in Yemen. Ventilation diagram. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

3. INFLUENCES OF BIOCLIMATIC STRATEGIES IN THE ANALYZED POPULAR ARCHITECTURE OVER CONTEMPORARY ARCHITECTURE.

3.1. GLAZED OPENINGS PROTECTION.

From an energetic point of view, the most delicate tasks on the construction of the building are the glazed openings. Their heat transmission coefficient is way higher than the one in a wall and also the sun radiation goes through them generating an inner heat that can cause a temperature increase such as a few degrees over the already hot outdoor air.

The opening orientation will play a decisive role when it comes to the amount of energy gained through it. The most advisable orientation for a warm climate would be north (in the north hemisphere) due not receiving much direct radiation expect the first and last hours of a summer day, when this radiation is weak. However, in most of the cases the orientation of the facades and the openings is not a choice because it is conditioned by a

urban tissue and also, the energy reception in winter is usually necessary in warm climates.

On the other hand, orientations east and west are the most unfavorable. In Madrid, under summer conditions, an opening can even gain 488 W/m², whilst an opening oriented to south would only gain 144 W/m². We could assure then that the perfect orientations would be north-south because it would allow the solar gain in winter, the easy protection of the opening during summer and an excellent crossed ventilation due the pressure difference among the spaces linked to each of the facades.

ILLUSTRATION 9. House Balic-Benzing Architekten. Bocksdorf, Burgenland, Austria. 2004-2005.

The south-oriented cantilever in this house allows the big opening in the living room and the dining room to be a non-overheating problem.

In south orientation, the cantilevers must be around 30cm over the opening in the facade y they must exceed the lateral limits. However, the east and west orientation needs the placing of vertical parasols, avoiding the most horizontal sun rays for reaching the window.

In the next example, the whole house is covered with a solar protection made out of bamboo reeds which can be opened when desired. It is the Maison Bessancourt, in France. An interstitial space is created between the inner facade of the building (most of it a glazed surface) and this second bamboo skin which through the air can penetrate in order to ventilate the facade easily and protecting the inner facade from the solar radiation at the same time.

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ILLUSTRATION 10. Maison Bessancourt, Karawitz. Île de France, France.

The roof of this intermediate space is covered with the same kind of lattice as well. This way, if this space heats up, the air goes up and escapes through the upper part, generating a pressure difference and absorbing the fresh air located on the bottom part.

The latticework, as in the popular architecture of dry warm climates, is still used as solar protection for facades. Nowadays there are a lot of them, industrially produced and made in situ, and with materials like ceramics, metal or wood. Probably the best option is to make the lattice with wooden battens because it is a material that doesn’t heat up much due the solar radiation, whilst the ceramics and the metals do, being able to achieve higher temperatures and thus heating up the ventilation air that goes through the lattice.

ILLUSTRATION 11. Metalic lattice in the Casa Bahía, designed by the architect Marcio Kogan.

In Illustration 11, a metallic lattice is shown, used to cover a whole facade with south orientation in the house Bahía, designed by the Brazilian architect Marcio Kogan. As happened in the balconies on the first floor of the house in Baghdad, the lattice allows the ventilation and obtains privacy for the house blurring the sight from the outsiders; and also avoids the sun rays to go right through the glazed surfaces, heating up the inner space, whilst keeping it illuminated.

Even the same architect said: “The house doesn’t use a green software, the calculations are not made with sophisticated equipment. The Bahía constructors knew how to make houses with interior frescos way before the lecorbusian ideas got tropicalised, or even before Sir Norman Foster would have given any scientific, precise and technologic dimension to sustainable architecture. Houses in Bahía have tile roofs, a rustic and banal material, and wooden ceilings. The big wooden screens of lattice that simulate walls, with its arabic origin and brought to Brazil by the Portuguese colonists, have been in our architecture since the beginning of colonization”. Somehow, this is the purpose of this investigation. To simplify bioclimatic strategies of our architecture by just looking what our ancestors did.

3.2. USE OF THE VEGETATION

The evapotranspiration system of the plants functions this way:

Plants evaporate water in order to decrease its temperature and deal thus with the heat, in this process they cool the environment surrounding them as well. Vegetation have a huge capacity for cooling the air: a grown beech has a cooling capacity of 1000 megajoules per day (each liter of evaporated water through the vegetation produces 2300 Kj (0,64kWh) of cooling). Man’s capacity to take advantage of this energy has been limited because most of the cooling produced by vegetation doesn’t affect the air conditioning of architecture and

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gets loose. There are different systems that allow the canalization of this energy in order to affect the comfort of the users of the building. If we plant vegetation in the courtyards that provide ventilation to the inner rooms of the house, that air will be cooler than the one coming from the street without vegetation and airtight pavement. In contemporary architecture, the vegetation is used with more sophisticated mechanisms, helping to decrease the temperature 3 degrees.

However, the bioclimatic use given to the vegetation nowadays is, most of all, in green roofs and facades. With the roofs, making them ecologic avoids the pavement and the superficial materials to warm and irradiate the heat to the inside of the building. The ecologic roofs, as opposed to garden roofs, don’t have a water tank under them supplying water to the plants if it didn’t rain during a long time. The vegetation of ecologic roofs is only watered with rain water.

ILLUSTRATION 12. House Outrial. Robert Konieczny KWK Promes.

Green facades have always been a decorative element, but recently new patents have been created, achieving to industrialize the system and making them very useful apart from their formal character.

With the purpose of making more efficient the Congress Palace of Vitoria-Gasteiz, a vertical green garden has been designed, occupying

most of the facade and improving its existing insulation to 270%.

ILLUSTRATION 13. New facade of the Congress Palace of Vitoria-Gasteiz.

This vegetal installation on the facade has a total of 1.492 m², being 67% of it a garden with f+p hydroponic system, and the 33% left covered with climbing plants. The f+p system design is composed by airtight boards with a double air chamber that assures the watertightness of the support. A layer of synthetical material is fixed to these. A hydroponic solution flows over this layer, feeding the plants and keeping the necessary pH, conductivity and humidity.

3.3. NATURAL FORCED VENTILATION

Natural ventilation doesn’t always work properly, sometimes because the direction of the wind is not the appropriate, but in most of the cases because the speed of it is not enough to move the needed flow, lead it to every point of the building and cover the energy loss that means to go through all the rooms and devices.

We have then to turn to systems that provoque a forced air renovation. This kind of efforts can be mechanic: ventilators, extractors or boosters that act when the natural ventilation is not enough. These systems can also be combined

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with natural systems in a way that either the impulsion or the extraction is natural and the other is mechanic.

A passive and interesting way to generate ventilation is to instal a solar chimney in the house. If it’s properly located, the warm air from inside the room will go up to the highest point and scape through the chimney. To easy this effect, the chimney has a glazed surface that allows the sun to heat the air inside it making it go up and leave faster. The perfect material for the solar chimneys is the steel because is the one that can get the hottest.

ILLUSTRATION 14. Different designs for solar chimneys. (Arquitectura bioclimática en un entorno sostenible / ‘Bioclimatic architecture in a sustainable environment’. F. Javier Neila).

Another way of forcing the air extraction through a chimney is using the wind. The chimney effect is produced in all the endings exposed to wind, causing then an inner suction. A clear example of this operation are the hop drying places in the south of England. The cone shape of their roofs is finished with a metallic piece with a weathercock and generates the rise of the air inside caused by the Venturi effect previously discussed.

ILLUSTRATION 15. Hop drying place in the city of Kent, England.

3.4. THERMIC INERTIA

In climates with big thermic differences (seasonal and daily), buildings need to store energy in order to keep stable the inner temperature and reduce the consumption. They need thermic inertia. As we have seen in the popular architecture examples before, thermic inertia can be solved with big thicknesses of traditional materials like stone, earth, ceramics or concrete. But nowadays it’s necessary not to lose useful surface so lighter solutions appear, being able to provide that thermic inertia with materials that store energy, not heating or cooling but changing its state.

These are the state change materials or phase change material (PCM). The change is usually solid-liquid and liquid-solid and, during this process, they store or give away the right amount of heat corresponding to the phase change with a constant temperature.

In winter, during the morning of a cold day, the PCM is solid. The energy source is the sun; then, it is necessary to capture the solar energy with the design of the house through glazed openings. Once the storage of the solar radiation has been completed (with constant temperature and liquefying the PCM), the constructive system achieves a temperature close to the one necessary for the state change and absorbes energy. In the evening, the temperature of the system starts to decrease until it’s lower than the one necessary for the phase change of the PCM. In this moment, the

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cycle is reversed and, as the substance solidifies, gives away the stored energy in a constant temperature process.

The most suitable phase change temperatures are those lightly over the comfort temperature, between 21 and 25ºC. If the temperature is very high, the substance could not be able to start the liquefaction process due to not receiving enough energy, and if it’s very low, it will give away the energy at an excessive cold temperature.

If the purpose of this integration is to regulate the temperature in summer or the one on a warm climate as the ones studied here, it is necessary to choose a substance that has higher change temperature. Since the source of the energy is night ventilation, the change temperature should not be lower than the air temperature so, if the night temperature aren’t lower than 20ºC, the solidification temperature will have to be higher but never exceed the inner comfort temperature. That’s why the most recommended are the ones varying from 20ºC to 24ºC.

3.5. RADIANT COOLING

The radiant cooling consists in the existence of a cold focus that acts as a heat sewer. This will be the sky. Every body with a different temperature exchange heat trying to equal their temperatures. The sky has a very low temperature; the emitting body is the building and the earth. In order to achieve effective radiation phenomenons, the atmosphere must be clean, with any excess of humidity pollution or other particles in the air. Desert climates named before are the most ideal for this strategy.

‘Cold ceiling’ are used in order to develop this operation. The most suitable surface for irradiating to the sky is a horizontal roof. The surfaces that irradiate the most in the infrared will be the best. The outer surface of the roof will irradiate to the sky cooling itself (mostly during the night). If air circulates through it we

will have then a useful fluid for reconditioning. In order to achieve a more efficiency, water can also circulate through a device similar to a flat sun collector and store it like cold water in a tank. This water can later go through a ceiling, a radiant wall or even through the battery of a ventilator.

ILLUSTRATION 16. The rooftop cools through re-irradiation during the night. The air in contact with this surface cools as well and is used for the reconditioning of the room.

4. ‘JOSÉ VASCONCELOS’ LIBRARY

This project, located in Mexico City and designed by the architect Alberto Kalach, integrates a public library with a botanical garden. This long-shaped building is 250 meters extended, divided in three big bodies. It has a steel structure, combined with concrete and glass, surrounded by green spaces an water.

Mexico City is one of the biggest, polluted and aggressive urban areas on the world. The building is designed inside a big botanical garden and has a close relationship with it. The reading areas offer the users the chance of experimenting a direct contact with nature. All the spaces benefit with natural light and ventilation.

We can see in this project almost all the strategies mentioned before, taken from examples that belong to popular architecture in dry warm climates.

The great facades, which are oriented to east and west because of its long and narrow nature, have deep sun protectors made out of concrete with that form an outer skin, avoiding the direct sun radiation except when the inclination

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angle of those is very low. The inner skin of these facades is completely glazed, allowing a blurred natural lightning and very efficient in almost every lecture spot. The use of artificial lightning is not necessary during day hours in almost every corner of the library.

On the other hand, the use of vegetation is decisive in this project. The building is lost in a botanical garden with several endogenous species from the region and water layers. This environment is large enough to provide humidity and cleaning to this atmosphere, usually polluted in Mexico City. The volumes attached to the main body, with only one storey, are covered with an ecologic green roof.

ILLUSTRATION 17. Inner spaces of ‘José Vasconcelos’ Library. (Photographer: Íñigo Bujedo Aguirre. Source: ’Plataforma Arquitectura’).

Ventilation is not a main problem in this building. The long east and west facades have windows that can be opened in the inner glazed skin, making easy to achieve crossed natural ventilation. The air used to ventilate wouldn’t normally need any kind of conditioning in this city during most of the months; however, in this library is a wet and clean air thanks to the outer vegetation.

ILLUSTRATION 18. Outer spaces of ‘José Vasconcelos’ Library. (Photographer: Íñigo Bujedo Aguirre. Source: ’Plataforma Arquitectura’).

The thermic inertia in this building is negligible. Even though the building looks massive due to the deep and shaded openings between the concrete battens, the only thing really standing between the outside and the inside is the glazed skin. Thermic inertia is more useless in a building that is only used during daytime. It is usually more important in a building occupied constantly like a house.

5. CONCLUSION

Bioclimatic architecture is not a complex field or that requires high technology. The key to supply an space with proper conditions in order to make it livable are in our ancestor’s architecture. Tradition and experience got to perfection simple techniques and also easy to develop for adapting to the climate where the construction takes place.

With the modern movement, in many cases, architecture was tried to separate from its surroundings, depriving architecture of its local character. This caused the series production of systems that were developed the same way in places with totally different climates.

Fortunately, collective conscience of our society embraces (more and more each day), the need of respecting the environment, avoiding the waste of naturales sources, and decreasing the toxic and greenhouse gases

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release to the atmosphere. This way, bioclimatic architecture tries to minimize the energetic need of the building through passive strategies, using the technology near us in order to achieve: to produce enough energy to supply the energetic needs of the buildings; to use sustainable materials (keeping in mind its absorbed energy, its recycling and origin); to reach a proper relationship with the environment; to deal with the remains in a way that cause the less impact possible to the earth; and to achieve the most use of potable water possible.

The designer has to keep in mind, more urgent each day, the need of saving energy and minimize the environmental impact produced by the constructions. It doesn’t make sense to turn the back to the bioclimatic strategies, like the ones mentioned in this text, in order to reach formal or fancy standards. Active ways of reconditioning should only be used in totally necessary cases and not as a pretext with the purpose to design the kind of architecture the architect wants to in a particular place. This strategies are not, in any case, opposed to beauty or good appearance of architecture. It’s totally the opposite. The functionality of the architectural sources makes the project more intelligent and gives interest to it, further than just attractive shapes and materials.

Architects should go back to build with common sense and to achieve this there is no better reference than to look back to popular architecture in towns around the world, whose experience has reached to build in a sustainable and easy way, without any important technologic requirements.

6. REFERENCES

[1] Neila González, F. Javier. Arquitectura bioclimática en un entorno sostenible. Madrid: Munilla-Lería, 2004.

[2] Neila González, F. Javier. Acondicionamiento ambiental y habitabilidad del espacio arquitectónico. Madrid: Munilla-Lería, 2013.

[3] Neila González, F. Javier. El clima y los invariantes bioclimáticos en la arquitectura popular. Madrid: Instituto Juan de Herrera, 2003

[4] Beatriz Garzón. Arquitectura bioclimática. Nobuko

[5] Helena Granados Menéndez. Rehabilitación energética de edificio. Tornapunta Ediciones.

[6] Gracia Cardona. Casa bahía de Marcio Kogan. Ecologismo a la brasileña. 21 abril 2010. <http://diariodesign.com/2010/04/casa-bahia-de-marcio- kogan-ecologismo-a-la-brasilena/>

[7] Laura Huertas. Casa Balic-Benzing. 2 febrero 2012. <https://proyectos4etsa.wordpress.com/category/0>

[8] Mercedes Penichet Castillejo. El potencial de la refrigeración evaporativa como estrategia bioclimática pasiva. Universidad Internacional de Andalucía. 2011. <http://dspace.unia.es/bitstream/handle/10334/1688/0235 _Penichet.pdf?sequence=1http://www.plataformaarquitect ura.cl/cl/02-361726/casa-outrial-robert-konieczny-kwk- promes>

[9] Adfer Dazne. Jardín vertical en el Palacio de Congresos de Vitoria. 19 enero 2014. <http://blog.isarquitectura.es/2014/01/19/fachada-vegetal- en-el-palacio-de-congresos-de-vitoria-gasteiz/>

[10] F. Javier Neila González, C. Acha Román, E. Higueras García y C. Bedoya Frutos. Los Materiales de Cambio de Fase (MCF) empleados para la acumulación de energía en la arquitectura. Su aplicación en el prototipo Magic Box. Materiales de Construcción. Vol. 58, 291, 119-126. julio-septiembre 2008

[11] "Biblioteca Jose Vasconcelos / Alberto Kalach" 28 enero 2011. Plataforma Arquitectura. <http://www.plataformaarquitectura.cl/cl/02- 67254/biblioteca-jose-vasconcelos-alberto-kalach>

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