Introduction- Energy Eff Biuldings

8/6/2019 Introduction- Energy Eff Biuldings

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Energy efficiency in architecture: An overview ofdesign concepts and architectural interventions

b uildings, as they are designed and used to day, contr ibute to seriousenvironm ental pro blems because of excessive consum ption o f energy andother n atural resources. T he close connection between energy use in bu ild-ings and environm ental dam age arises because energy intensive solutionssought to con stru ct a building & meet its dem and s for heating, cooling,ventilation & lighting cause severe dep letion of invaluable environm entalresources.

H owever, buildings can be d esigned to m eet occupan ts need for therm aland visual comfort at red uced levels energy & resources consum ption. En -ergy resource efficiency in new constr uctions can be effected b y adopting anintegrated app roach to bu ilding design. T he pr imary steps in th is appr oachwould be to:

In corporate solar passive techniques in a building design to min imise load onconventional systems ( heating, cooling, ventilat ion and lighting) Passivesystems provide ther mal and visual comfort by using natu ral energysour ces and sin ks e.g. solar rad iation, ou tside air, sky, wet sur faces, vegeta-tion, inter nal gains etc. Energy flows in th ese systems are b y natural m eanssuch as by radiation, cond uction, convection with m inimal or no u se of mechan ical means. T he solar passive systems t hus, vary from on e climateto th e other e.g. in a cold climate an architects aim would be d esign abuilding in such a way that solar gains are maximised, but in a hot climatehis primar y aim would b e to red uce solar gains, maximise natu ral ventila-tion and so on.

Design energy-efficient lighting and HVAC systems (heating, ventilation and

air-conditioning) On ce the passive solar architectural concepts are ap -plied to a d esign, the load o n con ventional systems (H VAC and lighting)is reduced. F ur ther, energy conservation is possible by jud icious d esign of the artificial lighting an d H VAC system using energy efficient equipm ents,contr ols and o peration strategies.Use renewable energy systems ( solar photovoltaic systems/ solar water heatingsystems) to meet a part of building load T he pressure on the earths non-renewable resources can be alleviated by jud icious u se of earth s renewableresou rces i.e. solar energy. Use solar ener gy for meet ing electrical need sfor a building can furth er reduce consu mp tion of conventional forms of energy.Use low energy materials and methods of construction and reduce transportationenergy An architect also should aim at efficient str uctu ral design, redu c-tion of use of high energy building material (glass, steel etc.) and transp or-tation energy and use of low energy buildings materials.

T hus in brief, an en ergy efficient building balances all aspects of energyuse in a building: lighting, space-cond itioning and ventilation, by providingan op timised m ix of passive solar design strat egies, ener gy-efficientequipm ents an d r enewable sources of energy. Use of m aterials with lowembod ied energy also form a major comp onen t in energy-efficient buildingdesign.


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2 Energy efficiency in architecture: an overview

T he bo ok covers 44 case stu dies on energy and resource efficient arch itec-tural p rojects in Ind ia. Each p roject highlights th e energy efficiency meas-ures, e.g. passive solar interventions, energy-efficient systems, buildingsmater ials with low embodied energy, adop ted b y several architects in theirrespective projects.

T he pr ojects have been classified climate-wise. T he th erm al performan ceof a selected n um ber of buildings have also been p resented. T he incremen talcosts for incorp oration of energy efficiency measures to buildings have beenhighlighted wherever such data was available.

T his chapter br iefly elaborates the passive architectural techniqu es thathave been adop ted b y the architects and draws examples from projects whichhave been covered in th e book.

Architect s can achieve energy efficiency in th e buildings th ey design bystud ying th e macro-an d m icro-climate of the site, applying bioclimaticarchitectural principles to combat th e adverse cond itions, and t aking advan-tage of the d esirable cond itions. Some com mon design element s that d irectlyor indirectly affects therm al comfort cond itions and th ereby the energyconsumption in a building are(a ) landscap ing,

(b) ratio of built form to open spaces,(c) location of water bodies,(d ) or ientat ion ,(e) p lanform, and(f) building envelope and fenestration.

H owever, in extreme climatic cond itions, one cann ot achieve comfortableindoor cond itions by these design con siderations only. T here are cert aintested an d established concep ts which, if applied t o a design in such climaticcond itions, are able to largely satisfy the t herm al comfort criteria. T hese areclassified as ad vanced passive solar techn iques. T he t wo broad categories of advanced concepts are,

1. Passive heating concepts (direct gain system, indirect gain system,sunsp aces, etc.) and

2. Passive cooling concept s (evaporative cooling, ventilation, wind tower,earth-air tunnel, etc.).

T he com mon ly considered d esign elements for achieving lower energyconsum ption in a bu ilding are as follows.

Landscaping

Land scaping is an impor tant elemen t in altering the microclimate of a place.Prop er landscaping reduces direct sun from striking and heating up of build-

ing surfaces. It pr events reflected light carr ying heat into a b uilding from th egroun d or o ther sur faces. Land scaping creates different airflow pattern s andcan be u sed to direct or d ivert th e wind advantageously by causing a pressuredifference. Additionally, the sh ade created by trees an d t he effect of grass andshru bs reduce air temperatu res adjoining the building and provideevaporative cooling. Prop erly designed r oof gardens h elp to r educe h eatloads in a building. A stud y shows that th e ambient air un der a tree adjacentto the wall is about 2 C to 2.5 C lower than that for unshaded areas, whichredu ces heat gain by cond uction (www.greenbu ilder.com ).


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Trees are the pr imary elements of an energy-conserving landscape. C li-matic requiremen ts govern t he type of trees to be planted. Planting decidu-ous trees on the sou ther n side of a building is beneficial in a comp ositeclimate. D eciduou s plants such as mulberry or C hampa cu t off direct sundu ring summ er, and as these trees shed leaves in winter, they allow the sunto heat t he bu ildings in winter.

T his landscaping strategy has been adopted t o shade the southern side of the RET REAT building of T ERI.

The RETREAT building has deciduous trees on the south side to cut off sum m er gains. These trees shed leaves during winter so that winter solargains are not cut off. W ind breaks are provided in the north and north-east to protect from the winter winds.

Building form /surface-to-volum e ratio

T he volum e of space inside a building that needs to b e heated or cooled an dits relationship with the area of the envelope en closing th e volume affects th ether mal perform ance of the building. T his parameter, known as the S/V(surface-to-volum e) ratio, is deter mined by the bu ilding form. F or any givenbuilding volum e, the m ore com pact t he shap e, the less wasteful it is in gain-ing/losing heat. H ence, in ho t, dr y, regions and cold climates, buildings arecompact in form with a low S/V ratio to redu ce heat gain and losses respec-tively. Also, the b uilding form d eterm ines the airflow patter n a roun d t hebuilding, directly affecting its ventilation. T he d epth of a bu ilding also d eter-mines the r equiremen ts for artificial lighting - greater m ore the d epth, higherthe need for artificial lighting.


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A view of the WALMI building. The flowing form overlooks a water body which has been used toadvantage for modification of the m icro clim ate

Location of w ater bodies

Water is a very good mod ifier of microclimate. It takes up a large amou nt of heat in evaporation an d cau ses significant cooling especially in a hot and dr yclimate. On the oth er hand , in hu mid climates, water shou ld be avoided as itadd s to hum idity.

Water has been used very effectively as a mod ifier of microclimat e in theWALMI building complex at Bhopal.

O rientation

Building orientation is a significant d esign con sideration, mainly with regardto solar radiation and wind.

In p redom inantly cold regions, buildings should be or iented to m aximizesolar gain; th e reverse is advisable for h ot regions. In regions where seasonalchanges are very pronou nced, b oth t he situations m ay arise periodically. Fora cold climate, an orientation slightly east of south is favoured ( especially 15east of south), as this exposes the unit to more m orning than afternoon sunand en ables the house to begin to heat du ring the day.

T his has been amply demonstrated in the ML A hostel building at Shimla.

Similarly, wind can be d esirable or u nd esirable. Quite often, a com prom iseis required between sun and wind orientations. With careful design, shad ingand d eflecting devices can be incorporat ed to exclude the sun or redirect itinto the bu ilding, just as wind can b e diverted or directed to t he extenddesired.


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Table 1 The energy contents of com m only used building m aterials are as follows

Building Elem ents/m aterials KW h/cum (in situ)

Cem ent concrete 1:5:10 402Lim e concrete with brick ballast 1:4:8 1522 (80% in brick)Brick m asonry 1:5 676

Brick m asonry 1:4 709Random rubble m asonry 1:4 267Stabilized m ud with 6% lim e 197Stabilized m ud with 10% lim e 320RCC roof (10 cm ) 174/m 2Stone slabs in RCC joists 132/m 2Cem ent plaster 1:4 20.65/m 2Cem ent plaster 1:6 15.09/m 2Lim e surkhi 1:4 11.05/m 2

Source Energy contents of building m aterials for India: paper by Dr C L Gupta. Green Architecturefestival, Nasik, February 19 94; data Courtesy Sanjay P, Rakesh Ahuja. Geeta V

Sectional details showing useof alternative construction

techniques. Ferrocem ent solarchim ney and ventilation duct in

corbelled arch dem onstratesuse of passive solar ventilation

techniques.

T hermal insulationInsu lation is of great value when a bu ilding requ ires mechanical heating orcooling and helps redu ce the space-cond itioning loads. Location of insula-tion and its optimum thickness are very impor tant . In hot climates, insula-tion is placed on the ou ter face (facing exterior) of the wall so that th erm almass of the wall is weakly coupled with t he extern al source and stronglycoupled with the interior.

U se of 40 m m t hick expand ed polystyrene insulation on walls andverm iculite concrete insulation on th e roof has brought d own space-condi-tioning loads of the RET REAT building by about 15% .


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Roof The roof receives significant solarradiation and plays an impor tant r ole inheat gain/losses, daylighting, andventilation.

Depend ing on the climatic needsprop er roof treatm ent is very essential.In a ho t region, the roof should haveenou gh insulating proper ties to

Terrace detail

Parapet detail

air flow cooling

Earthen pots for

15% heat radiati

100% 85%

Lime concrete gola

Bitumen felt waterpro

earthen pots for insu

terracotta tiles ove

Roof details showing use of earthern potsfor roof insulation

Broken China m osaic can be used as topm ost layer in roof for reflection of incidentradiation

minimize heat gains. Some r oof protec-tion m ethod s are as follows

A cover of deciduou s plants or creep-

ers can be provided. Evaporationfrom leaf surfaces will keep th erooms cool.T he entire roof surface can be cov-ered with inverted ear then pot s. It isalso an in sulatin g cover of still airover th e roof.A rem ovable cover is an effectiveroof-shading device. T his can bemoun ted close to th e roof in th e dayand can be rolled up to p ermitradiative cooling at night.T he up per surface of the canvasshould b e painted white to minimizethe rad iation absorbed by the canvasand con sequent con du ctive heat gainthrough it.Effective roof insulation can beprovided by u sing verm iculite con -crete. T his has been used in theRET REAT building at Gual Pahari(near N ew Delhi) and has reducedroof conduction by 60%.

The skylight on the roof of West BengalRenewable Energy Developm ent Agencyoffice building provides natural light for inneroffice spaces and is connected to the officespaces for inducing ventilation by stack effect


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T he ro of can also be used advantageously for effective ventilation an ddaylighting by incorpor ating vents an d skylights. T his has been dem onstratedeffectively in th e recent ly con stru cted office bu ilding of the WBRE DA (WestBengal Renewable Energy Developmen t Agency) at C alcutta.

WallsWalls are a m ajor part of the bu ilding envelope an d r eceive large amoun ts of

solar radiation. T he heat storage capacity and h eat cond uction p roper ty of walls are key to meeting desired t herm al comfort cond itions. T he wall thick-ness, material, and finishes can be chosen b ased on th e heating and coolingneeds of the bu ilding.

Appropr iate therm al insulation an d air cavities in walls reduce heat t rans-mission int o the bu ilding, which is the p rimar y aim in a h ot region.

A ir cav itiesAir cavities within walls or an attic space in th e roof ceiling com bina tionredu ce the solar heat gain factor, thereb y reducing space-conditioning loads.T he perform ance improves if the void is ventilated. Heat is transmittedthrou gh the air cavity by convection and radiation. A cavity represent a

resistance that is not pro por tional to its thickness. For a thickness >2 0 mm ,the resistance to h eat flow remains nearly constant . Ventilated air d oes notredu ce radiative heat tran sfer from roof to ceiling. T he radiative compo nentof heat tr ansfer m ay be redu ced b y using low emissivity or high reflectivecoating (e.g. alum inium foil) on either su rface facing t he cavity. With alu-minium foil attached t o the t op of ceiling, the resistance for downward heatflow increase to abou t 0.7 m 2k/w, compared t o 0.21m 2/k in th e absence of th e foil.

Fenestration and shadingOf all the elements in the b uilding envelope, windows and other glazed areasare most vulnerable to heat gain or losses. Prop er location, sizing, and detail-ing of wind ows and shading form an imp ort ant par t of bioclimatic design asthey help to keep the sun an d wind ou t of a building or allow them whenneeded.

T he location of openings for ventilation is determ ined by prevalent winddirection. O penings at higher levels naturally aid in venting out hot air. Size,shape and orientat ion of openings mod erate air velocity and flow in t heroom ; a small inlet and large outlet increase velocity and distribut ion of airflow thro ugh th e room. When possible, the ho use should be so positionedon the site t hat takes it advantage of prevailing winds. T he p revailing winddirection is from t he south/ south-east dur ing summer. T he recommend a-tions in IS:3362-1 977 C ode of practices for natu ral ventilation of residentialbuildings (first revision) shou ld b e satisfied in the design of windows forlighting and ventilation. T here shou ld be sufficient air motion in h ot hu midand warm hu mid climate. In such areas, fans are essential to provide com -fortable air motion indo ors. Fenestrations having 15 to 2 0% of floor area arefound ad equat e for both ventilation and d aylighting in hot and d ry, and h otand h umid regions.

N atural light is also adm itted into a b uilding throu gh glazed openings.T hu s, fenestration d esign is primarily governed by requirem ents of heat gainand loss, ventilation and d aylighting. T he impor tant comp onen ts of a win-dow that govern these are t he glazing systems an d sh ading devices.


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Glazing systemsBefore recent innovations in glass, films, and coatings, a typical residentialwind ow with one or t wo layers of glazing allowed roughly 75-85 % of thesolar energy to ent er a building. Intern al shading devices such as cur tains orblinds could reflect back some of that energy outside the b uilding. M ost of the energy, primar ily heat-remained inside, which affected th e ther malcomfort. T he weak therm al characteristics of windows became a p rime tar getfor research and development in an attempt to control the indoor tempera-ture of buildings.

A detailed write-u p on en ergy efficient glazing system is provided inApp en dix ???.

Windows adm it direct solar radiation and hence pro mot e heat gain. T his isdesirable in cold climates, but is critical in overheated climates. T he windowsize should b e kept minimu m in h ot and dr y regions. For example, inAhmedab ad, if glazing is taken as 10% instead of 20% of the floor area, thennum ber of uncomfortable hours in a year can be redu ced by as much as 35%(J K N ayak, et al).

Shading devices

H eat gain thr ough wind ows is deter mined by the overall heat loss coefficientU-value (W/m2K ) and the solar energy gain factor, and is much higher ascompar ed to that t hrou gh solid wall. Shading d evices for windows and wallsthu s mod erate heat gains into the bu ilding. In a low-rise residen tial buildingin Ahm edabad (hot an d dr y climat e), shading a window by a hor izont al 0.76-m deep chhaja can reduce the maximum room temperature by up to 4.6 C(from 47.7 to 43.1 C ). Moreover, the number of uncomfortable hours in ayear with tem peratures exceeding 30 C can be reduced b y 14% (J K N ayak,et al).

Shading devices are of various types:1. Moveable opaque (roller blind, cur tains, etc): T hese can b e highly effec-

tive in redu cing solar gains but eliminate view and imp ede air movement.

2. Lou vres: M ay be adjustable or fixed. T hese affect view and air movementto some degree.

3. Fixed overhangs.

Relative advantages an d disadvantages of these shad ing devices have beenenum erated as follows.

M oveable blinds or curtainsBlock the transm ission of solar radiation th rough glazed wind ows, espe-cially on th e east and west wallsIn ho t and d ry climates, when ambient air is hott er than ro om air, theyhelp to reduce con vective heat gain.In warm, h um id climates, where airflow is desirable, they impede ventila-tion.For air-con ditioned b uildings, where the flow of outside air is to beblocked, they can redu ce cooling load.

Overhangs and louvresBlock that p art of the sky thro ugh which the sun passes.Overhangs on south -oriented wind ows provide effective shading from t hehigh-altitude sun.An extended roof shades the entire nort h or south wall from t he noon sun.


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The office building for the W estBengal Pollution Control Board isa land m ark of energy andresource conscious architecturein this region. Efficient planningand carefully designed shading

devices, fenestration design andefficient lighting design hasbrought about 40% energysavings over a conventionalbuilding of sim ilar size andfunction. This picture shows theeast facade with inclined louversto cut off solar gains.

East and west open ings need mu ch bigger overhan gs, which may not bepossible and can be achieved by por ticos, or verand as, on th ese sides or b yspecially designed louvres to suit th e bu ilding requ irements.

T he scientific d esign of fenestration an d shading d evices in th e WestBengal Pollution C ont rol Board building has brought down t he projectedenergy consumption substantially (TERI. 1996).

FinishesT he external finish of a surface determ ines the amoun t of heat absorbed orrelected by it. For example, a smooth and light colour su rface reflects morelight and heat in com parison to a dark colour surface. Lighter colour su rfaceshave higher emissivity and should be ideally used for warm climate.

Advanced p assive heating techn iques are used b y architects in b uildingdesign to achieve therm al comfort con ditions in cold climate.

Passive solar heat ing system s can be b road ly classified as:1. Direct gain systems2. Indirect gain systems

Direct gain

D irect gain is the m ost comm on p assive solar system. In this system, sun lightenters ro oms th rough windows, warm ing the interior space. T he glazingsystem is generally located on the sou ther n side to receive maximum sunlightdu ring winter ( in the nor ther n hem isphere). T he glazing system is usuallydou ble-glazed, with insulating curtains to red uce heat loss during night.South -facing glass admits solar energy into th e bu ilding, where it str ikesther mal storage mater ials such as floors or walls mad e of adobe, br ick, con-crete, stone, or water. T he direct gain system uses 60-75 % of the su ns energystriking the windows. T he interior th erm al mass temper s the intensity of heatdu ring the d ay by absorbing heat. At night, the ther mal mass radiates heatinto th e living space, thu s warming the sp aces.

Advanced passiveheating techniques


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D irect gain can be achieved by various forms of openings such asclerestories, skylight wind ows, etc. designed for th e requ ired h eating.

D irect gain systems have been used for day-use room s by architect SanjayPrakash in th e residen ce for M ohini M ullick at Bhowali. T he user is ex-tremely satisfied with t he th erm al performan ce of the d irect gain system in

Indirect gain system

In an ind irect gain system, therm al mass is located between the sun an d th eliving space. T he ther mal mass absorbs th e sunlight that str ikes it and tran s-fers it t o th e living space. T he ind irect gain system u ses 30-45% of the su nsenergy striking the glass adjoining the th ermal m ass. Some com mon ly usedind irect gain system s are as follows.

Trombe wallA tromb e wall is a therm ally massive wall with vents p rovided at th e top andbott om. It m ay be made of concrete, masonr y, adobe, and is usually locatedon the south ern side (in the nort hern h emisphere) of a building in order tomaximize solar gains. T he ou ter su rface of the wall is usually painted black for maximizing absorp tion an d t he wall is directly placed b ehind glazing withan air gap in between.

Solar radiation is absorbed by the wall du ring the day and st ored as sensi-ble heat. T he air in th e space between th e glazing and the wall gets heated upand enters th e living spaces by convection th rough t he vents. Cool air fromthe room s replaces this air, thu s setting up a convection cu rren t. T he ventsare closed du ring night, and heat stored in th e wall during th e day heats upthe living space by cond uction an d rad iation.

Trom be walls have been extensively used in the cold regions of Leh.Various form s of Tro mb e walls have been t ried and tested in t he Led eg hostelat Leh (refer to th e chapter on the Ledeg Trainees H ostel for their advan-tages).

It is noteworth y that in buildings with th ermal storage walls, indoor t em-perature can be maintained at about 1 5 oC when the outside temperature isas low as -11 oC (M azria E. 1979) .

Gen erally, thickness of the storage wall is between 200 mm and 450 m m,the air gap between the wall and glazing is 50-150m m, and the tot al area of each row of vent is abou t 1% of the storage wall area (Levy M E, Evans D,and G ardstein C . 1983).

T he trom be wall should be adeq uately shaded for redu cing summ er gains.

The direct gain system of theBhowali house.The picture highlights the fullyglazed walls for the dayuse room sfrom inside.

this residence.D irect gain systems h ave some limita-

tions. T hey cause large temperatu re savings(typically 10 C ) b ecause of large variationsin inpu t of solar energy. Strong su nlight,glare, and ultraviolet degrad ation of thehou se material are some disadvantages of direct gain systems. However, being rela-tively simple to con stru ct an d inexpensive,they are by far the most com mon systemsused world wide.


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Water wallWater walls are based on the sam e pr inciple as that for trom be walls, exceptthat they emp loy water as the t herm al storage material. A water wall is ather mal storage wall made u p of dru ms of water stacked up behind glazing. Itis usually painted black to increase heat ab sorption . It is mor e effective inredu cing temperat ure swings, but the t ime lag is less.

H eat transfer throu gh water walls is mu ch faster than th at for trombewalls. T herefore, distribution of heat n eeds to b e contr olled if it is not im me-diately required for heating the bu ilding. Buildings that work dur ing thedaytime, such as schools and offices, benefit from the rap id heat t ransfer inth e water wall.

Overheating dur ing summer m ay be prevented by using suitable shadingdevices.

Roof-based air heating system

In th is technique, incident solar radiation is trapped b y the roof and is usedfor heating interior spaces.

In th e Nor ther n H emisphere, the system usu ally consists of an inclinedsouth -facing glazing and a nor th-sloping insulated surface on th e roof.Between th e roof and the insulation, an air po cket is form ed, which is heatedby solar radiation. A moveable insulation can b e used t o redu ce heat lossthrou gh glazed panes du ring nights. T here can be variations in the detailingof the roof air heating systems. In th e H imachal Prad esh State C ooperativeBank bu ilding, th e south glazing is in the form of solar collectors warm ingthe air and a blower fan circulating the air to th e interior spaces.

Office

Return Air

supplyduct

Skylight

Heated Air

Meeting Room.

PART SECTION

A.H.U.

Roof based air heating system forwinter heating in Him achalPradesh State Cooperative BankBuilding.


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Sun spaces

A sun space or solarium is the comb ination of direct and ind irect gain sys-tems. T he solar radiation heats up t he sun sp ace directly, which in tur n heatsup the living space (separated from th e sun space by a m ass wall) by convec-tion and cond uction through the m ass wall. In the n orthern hemisphere, thebasic requirement s of buildings heated by sun space are (a) a glazed sout h-facing collector space attach ed yet separated from the bu ilding and (b) living

space separated from th e sun space by a therm al storage wall. Sun spaces maybe used as winter gardens ad jacent t o the living space. T he H imurja buildingin Shimla has well desgined solariam as integral part of south wall to maxim-ise solar gain.

Advanced passivecooling techniques

Before the t ur n of the cent ur y, buildings were designed to take ad vantage of daily temperature variations, convective breeze, shading, evaporative cooling,and radiation cooling. However, with a thou ghtless imitation of the west,these con cepts too k a back seat an d buildings became energy guzzlers. Today,with h igh energy costs and growing environm ental concer ns, many of thesesimpler techn iques are once again becoming attractive. Passive coolingsystems rely on natu ral heat-sinks to remove heat from th e building. T heyderive cooling directly from evaporation, con vection an d r adiation withou tusing an y int erm ediate electr ical devices. All passive cooling strategies relyon d aily changes in tem peratu re and relative hu midity. T he app licability of each system dep ends on the climatic cond itions.

T he relatively simple techniques that can b e adopt ed to provide natu ralcooling in t he bu ilding have been elaborated earlier. T hese are

Redu ction of solar and con nective heat impor t byorientation of buildingshading by adjoining buildinglandscapingwind ow shad ing devices

surface finishes

Redu ction of heat transmission in the building bythermal insulationair cavities

T hese design strat egies redu ce heat gains to inter nal spaces. T his sectionbriefly elaborates th e passive techniqu es that aid h eat loss from the b uildingby convection, rad iation, evaporation , or b y using storage capacity of sur-roun ding spaces, e.g. earth b erm ing.

Ventilation

Outd oor breezes create air m ovement t hrough th e house interior by thepush -pull effect of po sitive air pr essure on the wind ward side an d negativepressure (suction) on th e leeward side. Good natu ral ventilation req uireslocating op enings in op posite pressure zon es. Also, designers often choose toenhan ce natu ral ventilation u sing tall spaces called stacks in bu ildings. Withopenings near t he top of stacks, warm air can escape whereas cooler airenters t he bu ilding from op enings near th e groun d. Ventilation b y creatingstacks has been effectively used in the WBREDA office bu ilding in C alcutta.Located in a warm hu mid climate, ind uced ventilation was a primar y designstrategy for this bu ilding.


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Inn ovative ventilation strategies by use of bu ilding integrated solar chim-neys have been used in Sud ha and Atam Ku mar's residence in the com positeclimate of N ew Delhi.

T he windows, as discussed earlier, play a dominan t role in indu cing in-door ventilation du e to wind forces. Other p assive cooling techniques th atindu ce indoor n atural ventilation and are used by architects to achieve pas-sive co oling ar e as follows.

Section of the W BREDA officebuilding showing ventilationstrategies

Air conditioned area

North light

South breeze

Hollow roof withconcrete precastsection (proposed butnot implemented)

High level window

to allow morenorth light& betterventilation

Horizontal breakerto reduce directsun & light shelvefor better daylightdistribution

2 4 0 0

Cash Accounts

Drive Way

Water body

Green surface

Conference

Insulated false ceiling

3 6 0 0

3 6 0 0

8 5 0 1 2 5 0

Exhibition

Operable glasslouvers

Low-E InsulatedGlass

Proposed administrative cumoffice building for WestBengal Renewable EnergyDevelopment Agency. However in thdesign, two more floors were addethe first floor

(proposed butnot implemented)

Picture showing buildingintegrated solar chim ney inSudha and Atam Kum ar'sresidence at New Delhi foreffective ventilation especiallyduring hum id season. The insetshows a closer view of thechim ney top

AirventA typical vent is a cut-o ut in the apex of a dom ed or cylindrical roof. T heopenings in t he pr otective cap over the vent d irect wind loss across it. Whenair flows over a cur ved surface, its velocity incr eases, resultin g in lowering of the pressure at t he apex of the curved roof. T he hot air un der th e roof flows


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out throu gh th e vent. Air vents ar e usu ally placed over living room s, oftenwith a pool of water directly un der t he vent, to cool t he air which is movingup b y evaporation.

T he special form of domes restr icts use to th e top floor only. Acousticconcent ration often occu rs in th is type of ceiling.

W ind tower in Jodhpur Hostel tocatch favourable cool wind fromsouth-west for passive cooling

Wind tower

In a wind tower, the hot am bient air enters th e towerthro ugh the op enings in the tower, gets cooled, and t husbecomes heavier and sinks down. T he inlet and ou tlet of room s ind uce cool air movement. In th e presence of wind, air is cooled mo re effectively and flows fasterdown t he tower an d int o th e living area. After a wholeday of air exchanges, the tower becomes warm in t heevenings. Dur ing the night, cooler amb ient air comes incontact with th e bottom of the tower through theroom s. T he tower walls absorb heat du ring the d aytimeand release it at night,warming the cool night air in thetower. Warm air moves up, creating an up ward d raft,

and draws cool night air throu gh the door s and win-dows into th e buildin g. T he system works effectively inhot an d dr y climates where diur nal variations are high.T he Jodhpu r hostel designed by Dr Vinod G upta useswind tower for sum mer cooling.

A wind tower works well for ind ividu al un its not formulti-storeyed apart ments. In dense urban areas, thewind tower has to be long enough to b e able to catchenou gh air. Also protection from d riving rain is diffi-cult.

Courtyard effects

D ue to incident solar radiation in a cour tyard, the air gets warmer and rises.C ool air from t he groun d level flows throu gh the louvred op enings of roomssurrou nd ing a cour tyard, thus prod ucing air flow.

At night, the warm roof surfaces get cooled by convection an d rad iation. If this heat exchange reduces roof surfaces temperatur e to WBT of air, conden -sation of atmospheric moisture occurs on the roof and the gain d ue to con-densation limits fur ther cooling.

If the roof surfaces are sloped towards the inter nal cour tyard, the cooledair sinks into t he cour t an d en ters the living space thr ough low-level open-ings, gets warmed up, an d leaves throu gh higher-level openings.

H owever, care should be taken th at the cou rtyard d oes not receive intense

solar radiation, which would lead to con du ction and radiation heat gains intothe bu ilding. Intensve solar radiation in the cour tyard also prod uces im-men se glare.

Earth air tunnels

D aily and ann ual temp erature fluctuations d ecrease with the increase indepth b elow the ground surface. At a d epth of about 4 m below ground, thetemperature inside the earth remains nearly constant roun d th e year and isnearly equal to the an nu al average temperatu re of the place. A tunn el in t heform of a pipe or otherwise emb edded at a depth of abou t 4 m below the


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ground, will acquire the same temp erature as the surroun ding earth at itssurface and th erefore the ambient air ventilated th ough th is tunn el will getcooled in summ er and warm ed in winter an d this air can be used for coolingin summ er and heating in winter.

Earth air tunnel has been used in the composite climate of Gurgaon in theRET REAT building. T he living quarters (th e south block of the RET REAT )are maintained at com fortable temperat ures (appr oximately between 20 Cand 30 C) rou nd the year by the earth air tun nel system, supplemented,whenever required, with a system of absorp tion chillers powered by LP Gdur ing monsoons and with an air washer during dr y summer. However, thecooler air un dergrou nd needs to b e circulated in th e living space. Each roomin the Sout h Block has a solar chimney; warm air rises and escapes throu ghthe chimn ey, which creates an air current for the cooler air from the u nd er-groun d tu nn els to replace the warm air. Two blowers installed in the t un nelsspeed up t he process. T he same mechan ism supplies warm air from thetun nel dur ing winter ( for details please refer to chapt er on RET REAT )

Evaporative cooling

Evaporative cooling lowers indo or air tem peratu re by evaporating water. It iseffective in h ot-d ry climate where th e atm ospheric h um idity is low. Inevaporative cooling, th e sensible heat of air is used to evaporate water,thereby cooling the air, which in tur n cools th e living space of the b uilding.Increase in cont act between water and air increases rate of evaporation.

T he presence of a water bod y such as a pon d, lake, sea etc. near the build-ing or a fountain in a cour tyard can p rovide a cooling effect. T he m ost com-mon ly used system is a d esert coo ler, which com prises of water, evaporativepads, a fan, and p ump.

Evaporative cooling has been tried as a roof-top installation solar energycentre, Gu rgaon. H owever, the system has now become d efunct du e to poorwater supply in th e area.

Passive downdraught coolingIt is a evaporative cooling that h as been u sed for many centu ries in p arts of the M iddle East, not ably Iran and Turky. In t his system, wind catchers guideoutside air over water-filled pot s, inducing evaporation and causing a signifi-cant dr op in temp eratur e before the air enters the interior. Such wind catch -ers becom e primar y elemen ts of the architectu ral form also. Passivedownd raught evaporative cooling is par ticularly effective in hot dr y climates.It h as been u sed to effectively cool the Torren t Research C entre inAhmedabad.

Passive downdraught cooling hasbeen successfully used at TorrentResearch Centre, Ahm edabad.The wind catchers for the systemare the predom inant architecturalelem ents in this building


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T his books contains 44 case studies of energy and resource efficientarchitecture which have used on e or a comb ination of the above concepts an dtechniqu es. In ad dition to th e above many of the projects have adopt edinn ovative daylight ing strat egies. use of ener gy efficient lightin g and space-cond itioning strategies are primar y strengths of some buildings.

In th e present era of growing environm ental concern s, these case stud ieswould inspire an architect to design and create a better to mm orrow.

References Uses of land scaping for energy conservationGiani, Florida: Depar tmen t of Physical Sciences, Florida Intern ational Un iversity

Man ual on solar passive architecture: energy systems engineering IIT D elhi andSolar Energy C entre, Ministry of N on-conventional Energy Sources, Governm ent of India, New D elhi)

Bansal N K, H auser G , Minke G. Passive building design: A handb ook of Natura lclimatic con trol.

Nayak J K, H azra R. Development of design gu idelines by laws.

T homas A Fisher. 1992AIA, November 199 2www.??????

T ERI report 96RT__ Window design op timisation

Mazria E. 1979T he Pa ssive Solar Energy book, Rod ale Press, Pennsylvania

Levy M. E ., Evans D., and Gardstein C ., T he Passive Solar Construction H andbook,Rodale P ress, Pennsylvania, 1983 ).

Documents

Introduction- Energy Eff Biuldings