The whole proposal for the eco-boulevard in Vallecas can be defined as an urban recycling operation consisting of the following actions: insertion of an air tree-social dynamizer, over an existing urbanization area, densification of existing alignment trees and reduction and asymmetric arrangement of wheeled traffic circulation. Superficial interventions reconfiguring the existing urbanization (perforations, fillings, paint, etc.) that defaces the executed development.
January 19, 2009
After our installation at the Venice Biennale (“10 things we have learned from the city”) we keep doing some research on anaglyph images. This time we are preparing an exhibition on the Ecoboulevard that will take place in February at the Le Sommer Environnement Gallery in Paris. Here we bring you two examples of the work in process. Try them aout! (f you happen to have a pair of 3D glasses in hand)
September 30, 2008
(click on “more” to see the animation)
November 14, 2016
Evap·o·rate, to pass off in vapor or in minute particles.
All evaporative cooling rely on the energy required for the evaporation of water to absorb heat from the air and lower the temperature. This is due to the very high enthalpy of vaporization of water, the phase transition between the liquid and the gaseous state requires in fact a large amount of energy (which is more properly called enthalpy) that is taken from the air in the form of sensible heat (which is the temperature, something we feel with our skin and determines our comfort) and it is converted into latent heat (which is an energy “hidden” in the vapor component of the air). The result of this adiabatic process is a drop in the temperature of air and an increase in its humidity, therefore it’s clear that this cooling system is particularly effective in dry and hot climate zones where the higher humidity and the lower temperature can be both seen as advantages. Clearly the evaporating process is a key also for some convective cooling processes (that we treated here) but they rely also on the reduced buoyancy of cooler and more humid air to obtain the final effect while evaporative cooling techniques only rely on the evaporation of water.
Although primitive evaporative techniques were used in ancient times (in combination with convective and ventilation devices like windcatchers and qanats in iran) and porous water jars are still used in many hot areas in combination with Mashrabiya other ventilation apertures to naturally cool down the interior of buildings the use of evaporation to cool down outdoor spaces is very recent. Evaporative cooling depends largely on how effective we are able to evaporate water, and a basic physical variable plays a big role in this case: surface-area-to-volume ratio, the more surface area we are able to expose the more energy we are able to exchange. There are basically two ways to proceed nowadays to maximize the surface area, evaporative pads and misting. Evaporative pads are generally used in evaporative cooling machines oriented to indoor cooling, these pads are cheap and effective but they are relatively fragile, require continuous maintenance and are most effective in controlled environments where the airflow can be adjusted and controlled, the “wetpads” are made of porous materials that have to be maintained wet while air passes through. The peculiar structure of these materials offers the largest possible surface area to the passing air which is then humidified and pushed into the building or the room. This technique can’t be used for outdoor cooling clearly because of the required control to the ariflow that is necessary.
Misting is instead widely used nowadays to lower temperatures both in buildings and open spaces. The use of water mist to generate passive cooling in closed buildings is strictly related to passive (or mechanical) evaporation towers and therefore to what we have been explaining in the convective technique post in open spaces the use of water jets and mist is instead very efficient (of course depending on specific climate conditions) and cost effective.
Although it is not strictly designed to be a bioclimatic public space, the Miroir d’eau designed by Michel Corajoud in 2006 in Bordeaux is one of the most successful examples of water evaporation usage in public space design. In this case a large square, just in front of the famouse Place de la Bourse, is designed to be a large water mirror where hundreds of water nozzles spray water from the floor either in the form of a fountain or of a mist cloud. In the first case, where tall gushes are produced, water evaporation is limited and the playful atmosphere dominates the large plaza, but when short mist clouds are produced the evaporation rate of the water is greatly increased and a cooling effect is produced, although in Bordeaux climate conditions are quite mild, and hot days are limited to few occasions during summer the square is very popular.
Vaporizing water coming from the floor is a quite common and effective mean to condition large open spaces, the effect that everybody has noticed of a slight refreshment when passing by a fountain in a square or, even more, while staying close to a waterfall is due to the very same thermodynamic principle, the small drops of water that the are created when water breaks while falling to the ground or splashing into more water dramatically increase the surface-area-to-volume ratio favoring a faster evaporation, the nebulized microscopic drops evaporate instantly causing a sudden temperature drop that can be magnified by the wind or other design inventions. In the Sevilla 1992 EXPO this effect was widely used, large fountains and water basins were placed all around the EXPO along all the main paths and squares to increment climatic comfort, in some areas even vertical walls of water were designed to expose the visitors to an even more effective cooling device, but the most common strategy was the use of conventional fountains and mist nozzles integrated in the many green shading roofs.
The design of these spaces has to be developed with special care, the effectiveness of the strategies used in Seville for example varied much depending on the surrounding conditions, evaporative cooling could be very effective if combined with the right design of protective and shading elements, with a correct sun and wind exposure and material use but could be also nullified simply by not considering the wind variation. Even if water vaporization is widely used in many terraces, bars, public venues, etc. because of its low cost, obtaining an effective bioclimatic effect is harder to achieve. Ecosistema Urbano employs evaporative cooling in one of their seminal project, in the Vallecas ecoboulevard, the Ludic and the Media Tree are not equipped with evaporative towers but with water spraying nozzles that are oriented towards the circular public space beneath them.
The main innovation in the use of evaporation in this case is due to the form of the designed public space, because, as we already said, there is not much to innovate about the nozzles technology itself. Actually the most important issue is the control of the water flow and pressure as it has to be correctly regulated depending on the actual dry-bulb and wet-bulb temperature, relative humidity etc. in the case that those variables are considered, evaporation should be instantaneous without any dripping nor condensation. In the case of the Media Tree temperature and humidity sensors regulate the flow and the pressure of the water flowing to the spraying nozzles constantly adapting it to the weather conditions. In this case the design is particularly effective not only because of the cooling technology but mostly because of the shadow provided by the “trees” themselves and the protective design of the ground section that allow the cooled air to linger in the “inhabited” space and not being immediately dispersed.
But misting has a close bound with atmosphere and space, being one of the few atmospheric phenomena that we can directly observe fog and mist have been used also to define spaces, these new approaches, even though not directly related with bioclimatic architecture, open the door for future developments. In one of their most famous, and paradoxically iconic, works Diller+Scofidio designed a “formless, massless, colorless, weightless, odorless, scaleless, featureless, meaningless” that was basically made of mist and nothing else. Their explication for the work was open-ended, blur-building was not only the name they gave to it but also a factual assertion: the definition of it was also blurry. This event contributed to redefine, or to destroy, the meaning of building and the separation between what is a building and what is environment, up to even questioning what is architecture, for the first time the space was not defined by walls or windows or any stable solid material but was only an undefined mutating cloud made of vaporized water.
But this wasn’t in fact the first building that used mist water to blur its edges (although that they are all curiously related to universal expositions, more about expos here), the Pepsi pavilion in Osaka was the result of the fructuous cooperation between engineers and artists within the Experiments in Art and Technology group and it was constantly covered with a thick layer of fog that partially hid it. In this case the building was still present and firm, a concrete entity with an interior and exterior form and a “conventional” space inside but the fog sculpture, designed by the japanese artist Fujiko Nakaya who spent her life working with fog, contributed to the creation of a memorable innovative pavilion.
At the Seville EXPO in 1992 the so called “bioclimatic sphere” was also one of the main attractions of the whole exhibition and surely one of the most iconic ones. A tubular sphere was placed in the middle of one of the most important boulevards of the exhibition rounded by fountains and water basins as a part of the bioclimatic design of the open space of the exhibition. Although being highly symbolic and recognizable this sphere as reported in the follow-up publications about the Expo was not really contributing to any bioclimatic effect on the square or the boulevard, this depended basically on the fact that the device was placed in an open space and the diffusion of mist was not controlled in any way (a very interesting publication about the follow up of the climate conditioning in the EXPO 92 has been published by the same engineers that contributed to the design of the project and a short extract can be found here).
In 2016 also the famous artist Olafur Eliasson started working with fog and misting, naturally he is not concerned with the bioclimatic function of fog but more about the terms of landscape and vision and interaction between the user and the fog itself. Placed in the Versailles garden, “fog assembly”, is a ring emitting a swirling mist that involves the objects around and changes appearance depending on the site conditions. The user is invited to interact with the installation, crossing it and begin part of the fog it is producing, in this sense, this artwork can be easily assimilated to a public space generating a connection with the theme of this research.
November 7, 2016
Con·vec·tion. Convection results from the tendency of most fluids to expand when heated.
The use of convective air flows with the purpose of cooling traditional houses was not alien to traditional Persian and middle eastern architecture. Joining the “simple” badgir ventilation system with more refined and complex cooling technologies was one of the most advanced points reached by Persian/Iranian building knowledge. Passive cooling systems in the Yazd desert were so advanced that iced formed (and accumulated) during the cold winters could be conserved frozen until the height of the long, hot, desertic summer.
In addition to sensible cooling, the cooling caused by a change of air temperature but not its humidity, badgir combined with a savvy use of water can provide also evaporative cooling which is generally more effective than sensible cooling alone.
In order to do so, windcatchers have to work together with a water source that supplies water which is then evaporated cooling down the flowing air, this can be achieved in many ways. The first one is taking advantage of the of the basement damp walls of the windcacher itself, if there is enough humidity in the underground the basement walls will be constantly wet and when the wind tower is working as an air intake the evaporation of the thin superficial layer of water will cool down the downward incoming stream of air. The second solution is to put a water source, if available, right under the shaft of the tower, a fountain or a small pool is used in this case, sensibly and evaporatively cooling down the entering wind. A great example, found in Yazd, combines and refines even more these two methods placing the tower further than usual from the house (50 m) and then using an underground tunnel to connect the tower with the house. The tunnel, being underground benefits both from the earth thermal inertia and from the humidity of the soil and at the end of the tunnel a fountain is placed to cool down even more the air. The third, and more advanced, passive cooling system based on windcatchers benefits from an underground water stream to cool down the water.
The use of convection with the purpose of cooling public space is mostly centered on evaporative towers, in a normal evaporative (cooling) tower hot water is distributed in the upper part of the tower, the sprayed hot water release heat in the atmosphere condensing and flowing down to the bottom of the tower where it is collected and recirculated if it’s the case. In evaporative towers designed to cool the surrounding space the process is inverted, cool water is sprayed with nozzles at the top of the tower and rapidly evaporating absorbs energy from the air coming in from the top of the tower, the cooler and more humid air being denser descends to the bottom and causing the area above it to cool down. The design of an evaporative tower able to work properly is challenging, a single design flaw or dysfunction can cause the sprayed water to condensate an drip.
During the 1992 Seville Expo the white towers of the Avenida de Europa were originally designed just to be architectural objects landscaping one of the main avenues of the exhibition but considering a wider plan to improve public space comfort in the whole exhibition area, technically developed with the help of the “termotecnica” group of the university of Seville, were converted into evaporative towers to improve the environmental conditions in the area.
The design, obviously not conceived thinking about the cooling effectiveness, had to be converted a posteriori into a cooling machine. Two main modifications were made: a wind collecting cap was added to the top of the tower and nozzles were installed inside it. For six months the exhibition remained open and the engineers responsible for the bioclimatic design of the event collected data about the functioning and the performances of the design (the report can be found in this book). The added wind-collecting cap proved to be too small for the purpose it was installed and was not sufficient to “catch” enough wind during an average summer day. The second flaw was caused by the structural design of the tower itself, the internal part of the chimney wasn’t smooth and wasn’t totally free either, the secondary steel structure that stiffened the tower was in fact a lattice continuously crossing the chimney section, water nozzles were installed in circles on the inner perimeter of the membrane and functioned properly but the vaporized water copiously condensed on the lattice structure causing continuous dripping under the tower itself. This was obviously a major flaw and the towers functioned only partially, also due to the difficult maintenance of the water nozzles.
In 2004 Ecosistema Urbano realized one of its most iconic designs, the eco bulevard in Vallecas, Madrid. Each one of the three trees has different characteristics and each one is focused on a different aspect of public space, but in this case the most interesting is the northernmost one that was designed as a rack of twelve evaporative cooling towers grouped to form a semi-enclosed public space shaded and cooled by the bioclimatic tree. Each one of the cylinders is made of two textile tubes, the exterior and reflexive one creates a protective layer for the inner cooling mechanism, the interior tube is the evaporative tower itself. A cap, provided with three openings to collect winds from all directions, is placed on the top of the inner cylinder, right under the cap there is a fan that starts spinning when temperatures rise above 28ºC to increment the existing breeze or to move the air if there is no breeze at all. About at the height of the fan water is sprayed creating a fine mist and its evaporation greatly increases the cooling effect on the air descending in the inner tube and then exiting in the semi-enclosed public space, delimited by the crown of the cooling towers.
The ecobulevar, being a fully designed public space, can count on many other design characteristics that improve the overall functioning of the cooling towers, their efficiency and the energetic behavior. The design of the public space under the “tree” is very important, the enclosing section, creates a favorable space for artificial climate conditioning, though it is an open space the “habitable” part (the first 2m from the ground) are somehow closed by the design of the pavement itself, this design contributes to the refrigeration of the central area reducing the hot breeze influence at the ground level and avoiding the direct escape of cooled air. Solar panels contribute to the over sustainability of the artifact generating enough energy to power the fans and the pump for the water. Extensive studies on the ecobulevar, demonstrated that air temperature at the ground level can be up to 9ºC cooler than the air at the top of the tree and that the average temperature difference is around 6,5ºC.
The last two examples are practically based on the same design principle but there are huge differences concerning both the size and the technological character of the project.
The first one is the wind tower that the British architects Foster+Partners designed for the Masdar Institute in the planned city of Masdar, Abhu Dhabi (which they also planned). The Masdar institute is, as of 2016, one of the few built parts of the city, which, in turn, is facing serious development and financial problems with only the 5% of the planned area being completed. The core plaza of the institute hosts a 45m tall windtower that contributes to the climatic comfort of the plaza channeling down the breezes that often spire in the desert, it is important to notice that the tower is not the only element designed to improve the ambient conditions of the plaza but all the strategies are focused on the sustainability and the comfort of both the buildings and the public spaces, in this case the dense urban form is supposed to reproduce the one of the traditional local architecture and buildings façades are self shadowing reducing the reflected sun radiation in the square, streets are narrow, etc.
This tower is a hi-tech interpretation of traditional ones, its size is greatly increased (the highest windtower in Iran is 33m high) and many design details are engineered improvements of the original windwoter concepts. The 45m teflon sleek tube is naturally designed to offer the smallest possible resistance to the passage of the wind and to reduce the possibility of condensation to the nebulized water used for passive cooling. Computer controlled louvers opens and close according the direction and the speed of the incoming wind and reduces the suction caused by negative pressure on the downwind side of the tower, with this refined mechanism, and the triangular design, the tower is always exploiting the precious wind. To increase even more the cooling potential a ring of water nozzles, also computer controlled, is placed right at the top of the shaft transforming this tower in a evaporative cooling device.
A low-tech version, though very similar in the functioning is the windtower built at the Nitzana Educational Village, in the Negev desert at the border between Israel and Egypt. This design is constituted only by a vertical metal chimney topped by a fixed wind catcher oriented towards the prevailing wind. The playful design is enhanced by a clever usage of the bottom part of the tower, a perforated ceramic brickwork is used to enclose a relatively generous meeting place that can host dozens of people from the local community, to reduce solar gain on the habitable part of the tower a sun protection is installed around it permanently shadowing the ventilating part.
The cooling process is based on a combination of wind-catching, mechanical ventilation, and evaporative cooling. In the upper part of the shaft a large fan is installed to generate an artificial windflow (power is apparently generated by solar panels placed on the south side of the tower) and under the fan two rings of nozzles are placed to implement passive evaporative cooling. Though being quite a raw design, this cooling tower uses all the technical mechanisms to achieve a cost effective cooling for the small public it has to refrigerate. Compared to the Masdar windtower this one might have a major flaw, in both the Ecobulevar and Masdar the proper cooling shaft is always protected from the direct sunlight, in this case instead the shaft is thermally conductive and prone to overheating,
But the most advanced look at what convection means for the perception and comfort of the human body in the space has to be find in Rahm’s “Digestible Gulf Stream”. In this project, two white sleek metal boards are placed at different heights in a room, one of the boards, placed on the floor, is constantly heated to 28º C, the second one, hanging at a higher point is cooled down to 12ºC. The temperature difference between the two panels creates a convective flow, the air heated on the lower plan becomes less dense and lighter and tends to float towards the second object that gradually cools it down causing it to descend until reaching again the warm plate. This constant air flow is invisible but certainly perceivable by the human body, for the purpose of the exhibition in fact, actors with different clothing (from naked to well dressed) were standing on the plates showing various levels of comfort and doing various activities that had a different impact on the heat production.
Rahm’s pioneering work in “climatic architecture” is extremely interesting, in this case the space is defined only by its temperature which is something we are not really used to, our normal physical division of space (walls, windows, curtains…) is totally visual but then our comfort is determined by variables like air temperature, this is particularly true in public space, where usually there are no “rooms” and the use (or the avoidance) of space is more often determined by factors like shadow, noise, comfort, etc.
December 11, 2014
This week we come with some good news in a row! Some days ago, we were notified that our project dreamhamar has been awarded as BEST PRACTICE by the UN at the Dubai 2014 International Award for Best Practices to Improve the Living Environment.
The Spanish submissions to this award have been highly appreciated: 62 of them were labelled as GOOD practices, 17 as BEST practices and 2 selected for the international AWARD.
From now on, the project will be part of the UN-HABITAT Best Practice Database. It’s our third project to join that list, together with the previously selected Plaza Ecópolis and the Ecoboulevard. The project will also be showcased in the Décimo Catálogo español de Buenas Prácticas and added to the “Ciudades para un Futuro más Sosteniblelibrary, CF+S” online library.
Here is a short video about the methodology (Dream Your City) we used in the dreamhamar project in Norway:
You can find more about the project on the www.dreamhamar.org website and on the recently published book “Dreamhamar: A network design process for collectively redesigning public space”, which explains the project’s actions and methods in great detail.
See the previous posts about dreamhamar.
March 23, 2011
Ecosistema urbano is always searching for talented people, but many times it works the other way around and we feel very lucky to be directly contacted by them. Today I want to introduce you to four different people who have recently joined us at ecosistema urbano. We are very pleased with their contribution and their unique backgrounds, which bring a fresh approach to our work.
February 18, 2011
In a recent coffee-break in Ecosistema Urbano we have been discussing the project for City of Culture of Galicia by Eisenman Architects and one of us used the expression “Bilbao effect”. Inevitably, this reminded me of a post I had written some time ago for the blog complexitys (HDA | Hugh Dutton Associés) and I would like to share my ideas with our readers:
A recent article on ArchDaily talked about our ‘in progress’ footbridge at La Roche sur Yon.
We’re pleased to be a subject of interest for a such an important architecture website, and what we appreciate even more is the public feedback and the list of comments left, which have inspired some interesting reflections about our work here at HDA.
I would particularly like to share some thoughts on the idea (or even obsession) of “being original” in architecture, the meaning of copying someone or something, and what this could imply nowadays, in a time when everybody is talking about copyright and how it’s changing with new communication technologies.
December 7, 2010
We have inaugurated the exhibition at DAZ, and now we can show you a bit of how it looks, as well as how it has been produced.
The whole exhibition comes inside a suitcase and a bag (that you can take with you as hand luggage on the plane).
The big pictures on the wall are made of A4 self-adhesive papers, stuck one next to each other.
The drawings are made directly on the walls of the exhibition room with markers in two colours (COPIC markers: tahitian blue + salmon red). These colours are compatible with cyan-red 3d glasses, and allow us to have two different points of view depending on the eye we are blinking.
Finally, we have made a photosynth with all the pictures of the finished exhibition, as the best way to have an idea of how it looks, especially for those who won’t have the opportunity to see it.
(to view this photosynth you will need to download and install Silverlight, it’s fast and easy!)
March 11, 2010
Inauguramos con este post un nueva sección: #followcreative. En ella, de manera similar a la de #followarch (donde presentamos estudios de arquitectura), iremos presentando a profesionales de otras disciplinas creativas.
Hoy os queremos hablar de Emilio P. Doiztúa, fotógrafo que nos acompaña en nuestro trabajo, ofreciéndonos siempre nuevos puntos de vista sobre nuestros proyectos.