airwebreathe - The Air We Breathe by Guy Battle 36 “Human...

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Unformatted text preview: The Air We Breathe by Guy Battle 36 “Human history becomes more and more a race between education and cotostrophe.’ H.G, WELLS [lees—1946] Air is an essential resource for Supporting life, a unifging Substance for mankind. Every molecule ofairwe breathe has a 99 percent chance of having been breathed before. Air knows no boundaries or borders. cirCuIating around the Earth in response to temperature and pressure differences and phenomena such as the Coriolis force. created bg the rotation of the Earth. But even so, we do not recog- nize air as a finite resource, and we have not get developed a sense of responsibilitg for it.'At One point our attitude toward water was similar. However, in the latter pa rt of the twentieth centurg. with the drought conditions that plague cities worldwideI we developed a greater sense of responsibilitu for water use. It is now relativelg commonplace for European buildings, at least. to recgcle the water theg use on site. Uurattitude toward air is distinctly different: We fail to recognize our responsibilitg for maintainingair qualitg and cleaningthe air we pollute. And as trees and other plant life—the planet-s natural sgstems for cleaning aire—are destroged, the prob- lem becomes even more acute. The World Wildlife Fund estimates that an area of forest the size of Greece is lost each yea r. and although sustainable timber Supplies are availableI most ofthis tim- beris never replanted.1 The city as Kidney Cities are complex systems ofinputs and outputs. As Herbert Girardet explains in his book Creating Sustainable Cities. "Cities. like otherassemblies oforganisms, have a definable metabolism. con- sisting of flow of resources and products through the urban system forthe benefit of urban populations”? Unce processed by the urban system. these resources form outputs such as airborne emissions, sewage. and industrial and household waste.\Cities are responsible fora vast amount ofwaste. approximately Pf] percent ofwhich is typically returned. untreated, to the bioSphere. The metabolism of our cities is a linear process that has little regard for the destination ofwaste products. The resulting quantity ofemissions puts enor- mous strain on the natural processes in place to deal with them. We now face a situation where the outputs from our species as a whole far exceed the capabilities of our planet's treatment systems. An analysis of our global carbon emissions reveals that between 40 and 50 percent are generated by buildings. 25 percent are from transport. and 25 percent come from industrial sources. This places a heavy responsibility on the shoulders ofthe construction indus- nPPnsnz image of pollution levels mr surface of the Earth 1. 'World. Wildlile Fund Annual Report 2001." httpzi'i’www. world inriiclliteorg:r defaultsection cfm7sectionid—1528cnew spaperid- 158rcontentid=425 2. Herbert Gn'ardet, Crenn'ny Sustainable Dries (Devon: Green Books For the Schumacher Society. 1999]. 32. 37 try. Designers need to address not only the issue of providing clean air forthe occupants of buildings, but also the problem ofmaking sure buildings don't pollute their surrounding environments. This challenge is key to the development of a sustainable future. Rather than exhi biting the attributes of lungs— which merely consume oxygen—our cities should behave as kidneys. cleaning everything that passes through them and generating clean energy. This radical shift in attitude would create cities with a circular metabolism—cities that are able to effectively treat waste products and generate energy as well as consume it. In order to achieve this goal, architects. designers, and engineers need to embrace a combi nation ofnewtechnology and inherited architectural vernacular. The Evolution of the Building Envelope Early architecture existed to create comfortable internal conditions: Roofs. walls. floors, windows, and dgors al_|_ev_olged__tl1roygh_tirn_e__ to fit the climate. This historical evolution has formed a vast lexicon tIfbhiEIo—pertfiologies that designers can now draw upon. In arctic environments, the Eskimo developed a unique strategy for retaining heat usingvery limited natural resources. The semi- spherical nature oftheirstructures maximized floorarea in relation to materials. Once built, the snow construction was completely sealed and then transformed into ice bg repeated meiting from the inside; the snow blocks quicklg congealed into ice in the cold air. Hot air from the stove and the bodies inside the structure rose and was trapped inside the dome, which continued to melt and freeze over, forming a smooth. airtight ice surface. When the igloo was completed, a low wall of snow blocks was built around the outside to create an air space, which was filled with loose snow. The double wall and the snow insulation maintained the interior warmth. [in the other end ofthe spectrum, the humid climate of Malagsia averages airtemperatures of between F3°F and 90°E The traditional Malagsian house is designed to encourage ventilation lag means of a number of devices: The building is raised on stilts to catch the strongest winds, and cool air from the shadg ground space under the house is drawn up through the floorboards into the rooms above. The elongated structure with minimal partitions allows easg pasA sage ofair and cross-ventilation. Windg dags are uncommon, but to make the most ofthe occasional winds the roof forms a wind-trap and distribution sgstem. Vents are built into the top of the external walls to allow hot air to be drawn into the roofspace, where it is then vented out. Air circulation through roofjoints ensures effective ventilation oithe roof and dissipates heat gain. In the wide-rangingtemperatures ofthe Middle East, low-energg 38 ventilation sgstems have been part of building design for hundreds of gears. Summer temperatures in Iran mag range From 89°F to 120°F at midday, but fall to 58°F or less at night, and in the winter temperatures range between 68°F and 95°F, dropping down to 48°F at night. These extreme changes are reflected in the wag buildings are designed and used. The badgir, or “wind catcher,“ was developed in Iran and other countries ofthe Persian Gulf. A lixed device capable ofactingas a wind scoop and exhaust, it is open at the top on two or four sides, with a pair of partitions placed diagonallg across each 4 length. The wind towers are nine bg nine feet and up to 21 feet high, with the upper section open to the wind in four directions. The badgir is able to catch breezes from any direction and channel cool air into the room. It also acts as a chimneg. When the winds are low, the towers continue to ventilate the rooms. I In the closelg packed houses of Hgderabad in Pakistan, wind scoops, which catch the wind at the area of greatest pressure and direct it into the building, have been in existence for at least 500 gears. The greatertheir height above the roof, the more effective they are because of increased wind speed and reduced building interference, Wind scoops can also be placed in the ground some distance awag from the building, and the supplg air can be brought in through earth tubes. Though these ingenious cooling devices 39 CPPCSITE ream LEF' igloo, Malagsian house. trough. and wind catcher, with air- :ircull'llnn diagrlms Ltrt Georgianme houses are strikinng different in appearance from those found in Iran. theg are an equallg appropriate solution to the environmental problems faced bgthis region. In the temperate climate ofthe United Kingdom. the Georgian town house was an important development in the design of residen- tial environments. Constructed from materials with good insulation properties and thermal mass credentialsr these buildings maintain a relativelg constant internal temperature. The Georgian sash window is a verg effective wag of introducing natural ventilation: The vertical sashes exploit the differences in air buogancg and wind-generated air movement to allow variable control ofventilation. Earlg skgscrapers such as the Home Insurance Building in Chicago created a new set ofchallenges for engineers. In these buildings, the plan was dictated bg the need to accommodate ventilation sgstems, daglight, and a large number of occupants. While some ofthe earlg skgscrapers contained Iow-energg ventila- tion systems. the introduction offloor-bg-floor air-Conditioning Sgstems Created the kind of controlled environment hitherto never experienced in offices, and led to the gradual acceptance ofthis tech noiogg as the standard. LEF '- HOI'I’IO Insurance Building. things The Impact of Air-Conditioning Air-conditioning, or"rnanufactured air." as it was first described, was originally conceived as a wag to control humiditg. It wasn’t until the beginning of the twentieth centurg that the term “air—conditioning“ was used bg a mill ownerwho combined moisture with ventilation, which actuallg conditioned and changed the air, thus controlling the humiditg so critical in the textile mills. Dne ofthe first examples ofa building air-conditioned for personal comfort was recorded in 1902, when the New York Stock Exchange was equipped with a central cooling and heating system. This system harnessed technologg from the textile mills and adapted it for commercial buildings. It was Willis Carrier, however. who did the most to promote con- trolled air. In 1902, realizingthat air could be dried by saturating it with chilled water to induce condensationI Carrier created the world's first air-conditioning machinerg: Liquid ammonia was pumped through a set ofevaporation coils, and warm air in the room heated the ammonia. which evaporatedI absorbing heat and cooling the air until it reached its dew point. The droplets that formed on the coils drained awag and a fan returned cooler, drger air,3 Not surprisinglgI factories were quick to embrace "controlled air" because it increased productivitg, and office buildings and schools were close behind. Between 1911 and 1930. mang movie theaters also adopted air-conditioning, providing moviegoers with a pleasant indoor environment —and an escape From their hot' humid neighborhoods. Air-conditioning as we know it bloomed after World War II, when resources were no longer scarce. The market for personal comfort was growing, and the demand for air—conditioners began to outstrip supplg. Mass-produced machines were marketed as improving personal health, helping people get a better night’s sleep. and keep- ing the interiors of houses clean. Mechanical coolingalso made it possible for architects to design closed spaces with more glass— and to build these glass-walled skgscrapersjust about angwhere. Modern air-conditioning systems are now used globally to control the temperature, moisture content, circulation. and puritg of air. We live in air-conditioned homes. travel to our air-conditioned work places in air-conditioned cars, shop in air-conditioned stores and malls. and enjog sports in airvconditioned arenas. We have gearv round choices offresh or preserved foods kept cool or frozen. and we benefit from advances in medical services made possible bg air-conditioning. Unfortu natelg, these conveniences come at a great cost to the environment. And beyond the environmental implicationsI the human cost of over-conditioned spaces is well documented. In ran LEFT air-conditioning machine l :5 1 diagram of air-candl- tloning agstum 3. 'Greatrlst anlnCCI'mg Minot-enter ms of the lWEI'II:l:"'.l'I Eenturg," National academy oi LI'IEHtE‘E'lng. h'.1p:-'-'www gi'onracinevc:nenis org-grew 15L evemerns‘gu lll ?.htrnl 4O cases ofSick Building syndrome. as it is commonly known, heavily One particularly successful device, the modern wind tower, air-conditioned spaces can actually significantly reduce comfort was adapted from the vernacuiar architecture ofthe Middle East. and productivity. When combined with modern technology, wind towers can be highly effective in poweringventilation systems. Wind towers were Post A'ir- Conditioned Architecture successfully used in the award-winning scheme for the lonica The future ofengineering environments lies in a new generation Headquarters Building in the United Kingdom. Here, Battie McCarthy of buildings that use free energy to drive environmental systems, introduced an interactive facade, a central atrium with wind towers. rather than functioning as hermetically sealed, artificial internal ventilated hollow-core slabs with low-level air suppiy. and an inte- ciimates. By combiningtraditional wind-powered ventilation sys- grated energy strategy with performance-monitoring systems. terns with new building management technologies, it is possible to When they work together, these systems create comfortable office design highly efficient buildings with extremely low emissions. environments without the usual energy expenditure associated These buildings not only have healthier environments—as they with air—conditioned spaces. release less carbon dioxide into the atmosphere—they also cost Ancient wind-scoop principles have also been used to create less to operate than their air-conditioned counterparts. highly efficient windvcapturing devices capable of directing air down The design of natural ventilation systems is now determined and through spaces with great effectiveness. The Bluewater shop- by a detailed analysis ofthe behavior ofair within spaces. ping mail in Kent in the United Kingdom is one successful example: Computational Fluid Dynamics [CFD] analysis is a process of math- Battle McCarthy used wind scoops to ventilate the spaces naturally, ematically modeling the flow ofair relative to temperature and supporting its central concept of the mall as a shopping avenue that pressure. Tools such as CPI] and wind tunnel analysis allow engi- possesses all the benefits of an outdoor street on a sunny day neers to form extremely realistic models of natural ventilation [sunshine. a fresh breeze. the sound of water. calming landscape, systems. This accuracy has led to the development of a number the aroma ofspring flowers, and the enticing lure of freshly ground of different ways of driving natural ventilation systems. coffee], but filters out all ofthe unpleasant aspects ofthe street m o H r Ionlco Headquarters Building. view of ventilators and air-circulation diagram FaR RIGHT Bluewater shopping mall. viewI of ventilator! and air- circulation diagram 41 [cars, noise, pollution, crowded pavements, driving rain, and wind], Wind towers can be augmented with solarenergg to help drive ventilation sgstems. By maximizing solar gain in strategic locations within the extract sgstem and the tower itself, solar energu can make the air rise faster, displacing air from below. This technique requires careful orientation of buildings to maximize solar penetraA tion when needed and to allow iorthe control of excessive solar gain to avoid overheating. The double skin is anotherventilation device that makes use of soiar energy. Research carried out bg Battle McEarthg in association with Franklin Andrews on behalf ofthe United Kingdom Department of Environment, Transport, and Regions. has shown that double—skin buildings can reduce energg consumption and running costs bg 55 percent, and can cut carbon dioxide emissions bg 50 percent in the cold temperate climatic prevalent in the United Kingdom.“1 Double skins can operate in mang seasonal modes. In winter, the cavitg acts as a thermal bufferzone between inside and out. This reduces space-heating requirements, as both conduction and infiltration gains are limited. Good solar penetration is achieved and acoustic protection is offered. This warm blanket of air around the building can be used to preheat the fresh supplg air, saving energy expenditure and the emissions associated with it. nnpnsnr i.ri=' air-circulation diagram of Tramba Iwall erratum-r His—n diagramof labgrlhth at o H T view of Commarzhank Head- quarters with air cireutation dia gram 3.. Bottle McCurthg and Michael W-gginton wrth l'ranklmrtmclrews, "Environntr.-ntal Second Skin Sgstems,"schedu|eo‘ For publication EDUZ. 42 During mid-season, the skins can be opened, allowing natural ventilation. Fresh air is taken in without energy expenditure in heat- ing or cooling, and blinds can be adjusted to let in or shut out light. Good daglight penetration is achieved and services can be relocated to the perimeter ofthe building, increasing net rentable space. Acoustic insulation is also reduced. During summer. the skin is sealed, and blinds within the cavitg provide solar control. Space- cooling loads are reduced, increasing net rentable areas and reducingcapital expenditure. Exhaust air is extracted through the cavitg to remove heat gains. One example ofthe use ofthis technique is the Commerzbank headquarters in Frankfurt bg Foster and Partners. Here, a double skin was installed on each side ofthe triangular building. The dou- ble-facade cavity creates a sheltered zone with controlled infiltration, so the inner-skin, doubleAglazed tilt windows can be opened at all levels, despite external air pressure. The skg gardens, which occur everg 10 stories, are ventilated at high levels, and oxggenated air is fed to the atriums to ventilate the internal atrium offices naturally. These two sgstems allow natural ventilation through both sides ofthe floor plate at all levels. The Trombe wall, one of the earliest forms of double skin, was developed bg the English horticulturist Edward Morse. Morse, who observed that dark curtains drawn behind a window become warm and create warm aircurrents. built the first soiar wall in 1881[now known as the Trom be wall]. Modern Trombe-wall techniques use high thermal mass concrete skins to maximize solar-energy absorp- tion. The warm air currents inside the building can be used to assist natural ventilation, and-the radiative heat from the thermai mass can be used forspace heating.S Another element frequently used in treating air is the Earth itself. which has a natural geothermal temperature that can be used to heat or cool air. Thermal Iabyrinths draw air through a complex of underground corridors to preheat or precool it. Typically constructed out of concrete to maximize thermal mass and notched to increase surface area. labyrinths can significantly'reduce the energy require- ments ofbuildings. The new National Museum ofWorld Cultures in Gothenburg. Sweden. will use a thermal labyrinth to heat air during the winter and cool it duringthe summer. The air will be drawn down into the labyrinth through a remote wind scoop in an ecologically rich area. Water can aiso be used to treat air in buildings. Introducing water features in and around buildings not only increases our sense ofwell-being and harmonyI but can clean the air itself. {When air passes over water, its humidity rises. and microscopic droplets I[$93fl“939mflflflflfltlflflflflflflflflflfl’g ‘ In“ E on 3‘"- I. S y-I "a: a E E 2' .- I. H “ .l' p. S 5. Trornbe walls invented rn lBEl [H.S. Patent No. 246.625] by Edward Horse of Salem. Massachusetts. 43 clingto dust particles carried in the air. Theirweight increases and they become too heavy forthe air to carry—thus the air becames cleaner} In hotter climates. water can cool air as it evaporates. By directing airthrough the path of evaporating water. the air temperature is reduced significantly at the cost ofa slight rise in humidity, This technique can be used to cool air in atrium and circulation spaces. where temperature is more important to comfort than lower humidity. Air can be treated and conditioned. distributed and extracted in numerous ways that are both very low energy and produce zero emissions. But the story doeSn't end there. We need to go further than simply reducing energy consumption and emissions. For some time, the environmental community has promoted the three R's: Reduce. Recycle. and Reuse. Recently it has been sug- gested that we add a fourth R: Recover. The reme...
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