Elements of Solar Architecture

8/6/2019 Elements of Solar Architecture

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A project of Volunteers in Asiaof Solar Architecture for Tropical.e mentsReaim HWPSSSKAT Publication No. 10

by: Roland StulzPublished by:Swiss Center for Appropriate TechnologyVarnbuelstrasee 14

CH-9000 St. GallSwitzerlandPaper copies are $ 5 .OO.Available from:Swiss Center for Appropriate TechnologyVarnbuelstrasse 14CH-9000 St. GallSwitzerlandReproduced by permission of the Swiss Center forAppropriate Technology.Reproduction of this microfiche document in anyform is subject to the same restrictions as thoseof the original document.


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FOR TROPICAL REGIONS

Roland 3AtPublication No. 40

St. Gab t980

Varnbbelstr. 14CZII-?OOOSi.Sallen-1 Cr7i I 23 34 81

SKAT SKATSchweizerische Kontaktstelle Swiss Center fortdr AngepassteTechrik Appropriate Technologyam Institut 113 Laleinamerihalor- at the !nstitute for Latin-Americanschung und Entricklungszusammen- Research and lor Developmentarteit Cer ktochsc~hule St.Ga !ien Cooperation, St.Gall Uniborslly

SKATCentre Suisse pour laTechnologie Approprieea Ilnstitut Latino-Am&binet de Cooperation au Developpe-ment, Universitk de St-Gall

SKATCentro Surzo paraTecnologLa Apropiaciaen e! InsKuto Latmwme~:-4uy de Cooperaci6n T&3+2,Universidad de Sarikt-Yzii:2 rb


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Publication No. 40St. Gall 1980

Author:

Published by:

comments,enquiries:

Copyright:

Price:

Roland Stulz, Arch. ETH/Planner BSP, Zurich

SEAT, Swiss Center for Appropriate Technologyat the Institute for Latin-American Researchand for Development Cooperation, St. GallUniversity

All questions and comments concerning thispublication and its contents are welcome atSEAT. Please use the postcard-questionnaireenclosed.

Material of this publication may be freelyquoted, translated or otherwise used.Acknowledgement is requested.

SFr. 7.50, U.S.$ 5.-


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I- __--. -ITABLEOF CONTENTS -1 --- 1

IWTRODKTIONORIENTATIONF THEBUILDINGSABSORPTION,NSULATIOi'l,EAT TORAGESHADING, OLAR ADIATIONONTROLROOF ESIGNVENTILATIONHROUGHALL PENINGSAIR COOLING,UMIDIFICATIONBIBLIOGRAPHY


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c-7 - --~-- ----.-----I - --. ---

In tropical regions where hot climate predominates, man hasmade use of physical laws in building construction for agesto improve living conditions. Many traditional designs andmaterials have evolved in the course of time but have partlydisappeared again with the advent of modern constructiontechnology and industrial production of construction materialsThis publication aims at helping the layman to learn aboutsome simple, inexpensive principles that may be applied inconstruction of new buildings and the improvement of existincl;houses. It may perhaps also serve the professional architectto recall those principles before starting off on a buildingactivity. The brief booklet is by no means complete orexhaustive and concentrates on requirements for hot climateonly, Neither solar heating aspects nor sophisticated techno-logy for cooling or airconditioning are included but simplethings only that can relatively easily be mastered such as:

. orientation of building

. making use of prevallent wind, crossventilation

. reflecting, absorbing and insulating buildingmaterials for roofs and walls

. using trees and obstructions to channel air flowand for shade

. using the evaporation of water for cooling effectsThe field of Solar Architectur is vast and there are manyinteresting approaches and technologies in the state of de-velopment that are beyond the scope of this publication.Persons interested in this field may make use of the enquiryservice of SKAT. We shall deal with all specific questionswithin our capacity.


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1, ORIENTATIONNDPOSITION,OFYE BUILDINGS --I-__ -.i

The appropriate orientation of the buildingin the landscape and in relation to sun andwind is the first main step in the planningprocess. The orientation and position of abuilding are most important for the roomtemperature and the interior climate ofevery building.Orientation is mainly a design problem whichdoesnt create additional building costs,but provides better living comfort.There are often constraints for an optimalselection of a building site and the orientationof the building due to adjacent buildings,roads and land properties.


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3

1,l SITE ORIENTATIOWHART ,IIIn this chart (1) (see bibliography) we list the mainaspects which have to be considered, when you make theselection of a building site:

3BJECTIVES

YDAPTATIONS:POSITION ON SLOPE

DRIENTATION ON SLOPE

RELATION 2'0 WATER

PREFERRED WINDS

CLUSTERING

BUILDING3RIENTATION

TREE FORMS

-HOT HUMIDREGIONSMaximize shadeMaximize wind

High for wind

South

Near any water

Sheltered fromnorthOpen to wind

South, towardprevailingwindHigh canopytrees.Use de-ciduous treesnear building

___.- 1HOT ARIDREGIONSMaximize shade Ilate morning and all afternoon.Maximize humi-dityMaximize airmovement in Isummer.

Low for cool airflowEast-Southeastfor afternoonshadeOn lee side ofwaterExposed to pre-vailing winds -Along E-W axis,for shade andwindSouth

Trees overhangingroof if possible


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r I__--.

12 GENERALULES ORHOTARIDREGIONS II-__-----_ - -A

Fig.3

Fig-s

25" SOUTH ORIENTATION. Exterior wallopenings should face south but shouldbe shaded either by roof overhangs orby deciduous trees in order to limitexcessive solar radiation into thedwelling. The size of the windowson the east and west sides should beminimized in order to reduce heatgains into the house in early morningsand late afternoons.WIND ORIENTATION. Main walls and windowsshould be oriented toward the prevailingwind direction in order to allow max.cross ventilation of the rooms.

SLOPE ORIENTATION: Lower hillsides bene-fit from cooler natural air movementduring early evening and warm air move-ment during early morning.

CLUSTERS. Multiple buildings are bestarranged in clusters for heat absorption,shading opportunities and protection fromeast and west exposures.

TREES. Natural shading by trees offerseffective natural cooling.

RELATION TO WATER. Indoor and outdooractivities should take maximum advantageof cooling breezes by increasing thelocal humidity level and lowering thetemperature. This may be done by locatingthe dwelling on the leeward side of alake or stream.


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5----, AESORPTION,NSULATION, EAT TORAGEFig.8

ABSORPTION/REFLECTION. Heat and lightradiation are either absorbed or reflectedby building materials to a certain degree.In hot areas it is desireable to reflectthe solar heat radiation during the dayas much as possible. On principle thiscan be done by using bright outside wallor roof coatings. (See 2.1 table of solarradiation absorption).

Fig-

INSULATION. The heat flow from outsideinto a room or vice versa can be reducedby insulating a wall or a roof. Theinsulation should be mounted at the "coldside" of the wall. Efficient insulationcan on principle be obtained by porousmaterials, as e.g. wood, panels made ofglassfibres or natural fibres (coca nut),polyurethane foam, bricks, porous concrete,etc. (See 2.2 table of heat insulation).

Fig. 10

HEAT STORAGE. Roof or wall materials storeto a certain degree the heat of solarradiation or transm;;ted by warm air throughwalls and roofs. The stored heat radiatesinto the cool room air after a characteristicstorage time. The heat storage capacitydifferes from one material to the other.It is high e.g. for rocks, water, concrete,etc. (See 2.3 table of heat storage capa-cities).

Fiq 11

ROOM CLIMATE. The comfortable room climatein a house is created by an optimumcombination of air temperature, air humidity,air flow and surface temperature of walls,floor and ceiling. Therefore the ideal roofreflects and insulates well and the idealwalls reflect the solar radiation, theyinsulate the heat peaks during the day,they allow diffusion of humidity and theystore a certain amount of heatwhichtheycan radiate into the room during the night(in hot arid regions). Wall openings allowa cooling air flow. (See 2.4 good examples).


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c

ROOFS white asbestos cement 50%copper sheeting 64%red roofing tile 70%galvanised iron, clean 77%bituminous felt 89%galvanised iron, dirty 89%asphalt 95%aluminium foil, unpolished 39%aluminium foil, polished 15%WALLS

PAINTS

concretefire clay brick (red)white-washbright aluminiumyellowdark aluminiumbright redlight greenblack

SURROUNDING5 grasssand, greyrock

70%70%

21%30%48%63%65%73%97%80%82%84%

Note: The lower the percentage of absorption, thebetter the reflection.


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I 82 TAELE OF HEAT INSULATIONALUESThis list (2) gives a view over the insulation values ofsome main building materials.Conductivity in W/mK (Xatts(metre thickness, degree centigradedifferential)MATERIAL Conductivityin W/mKAdobe bricksBurnt bricksCement mortarConcreteEarth (humid)Stones, rocks(dense)Sand (dry)lsbestos-cement

0.50.3 - 0.7 -__1.51.8 12.13.5 i0.6 I0.35boardPlywood panelZork granulatedzod (Gry)Sawdust

Insulation panels

0.14 !i0.04 ,0.1 - 0.2 --I0.06

I(expanded poly-urethane)tiood shredded,cemented innetal preformed

0.03 t/I0.12 !

stabs IXass 0.8

Note: The lower the conductivity, the better the in-sulationeffect. E.g. 10 cm of adobe bricks in-sulate as well as 36 cm of concrete,less than1 cm of granulated cork or mineral fibre in-sulation board.To obtain maximum insulation you can combine e.g.a brick or concrete wall with a natural fibre(coca nut) or expanded polyurethane insulationpanel. Roofs can also be insulated directlyunder the roof panels or above the ceiling.


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e. _.

213 TABLE OF HEAT STORAGECAPACITIES -1

The specific heat capacity indicates the amount of heatthat is stored in a cubic foot of a certain material.

,MATERIAL SPEC. HEAT CAPACITY(BTU/CUFT -OF) (Wh/m3, K) tAdobe bricks 25.4 473.6Burnt bricks 24 --447.5Cement mortar 19.2 -----'Concrete 35828 1---- -____ 522.1Sand I18 --,335 6Stone, rocks 19

_ -_-_yLimestone 354.3-----d22.4Asbestos-cement 41L.L.~28 522.1boardPlywood or wood 9.9 184.6panelsWater,Cast IronExpanded poly-Iurethane (in-

62.4 116354 1006.9.57 110.6

sulating panel) i

Note: The higher the heat capacity number the moreheat is stored in the material.An insulatiny board e.g. has a very poor heatcapacity whereas the poorly insulating concretehas a good heat capacity.Adobe is a very good material because it hasquite good insulating and heat capacity qualities.That's the reason why anadobe building usuallyhas a quite comfortable room climate in hot aridregions. In hot humid regions walls and roofsshould have minimum heat capacities. Wood and in-sulating panels are appropriate for those regions.


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/ 2,4 GOODXANPLES (HCT ARID. EGIONS)

. +tii~ckehose Con\ l LA. -

. headman~r

Fit. 12Comfortab le rooi:i cllr;atein small clustereti adoberooms in northern Ghana...

. . . and IT! 5trn solar archirecture withadobe bricks in the united States


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I ,4 GOODEXAVIPLES (HOT-HUI\lIp REGIONS)

These aatak-house: ir. Siz?atra have transparentwood constructed xalls witl-. low heat capacity,good insulation and cross ventilation.The shading is provided by overhanging roofs...

_-_ as uell as balcon;es and rrtes


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Solar radiation control can be obtainedwith shadings like brisesoleils, 'louvres,pergolas, arabian mashrabias and all kindsof curtains made of wood, cement or bamboo.It can be used in any kind of building.Solar radiation control is a simple andeffective way to keep the radiation heatout of the rooms.The shading can be produced with localmaterials and appropriate technologies.Shading devices may in some cases inter-fere with optimal air flow for desiredventilation.


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/i.l . ---lHORIZONTAL SCREENING/ROOF OVERHANG.This is very effective against over-head sun especially on north and southfacades. It can be realized with aroof overhang or with fixed or moveablelouvred windows made of glass, asbestos-cement, cement, wood, etc.All horizontal screening must allow ver-tical air flow.VERTICAL SCREENING. Vertical sreeningelements are best against low sun, i.e.on west and east facades. Maximumefficiency can be obtained with moveableelements. A simple form of verticalscreenings are also window shutters anddoors.These screenings can be made of wood,concrete fins, metal, etc.MASHRABIAS, CURTAINS, SHUTTERS.Arabian mashrabias are traditionalwooden trellis-work which screens againstsun as well as against glare.It's made of wood or bamboo. Curtains ofany flexible material (e.g.linen) can befixed easily in any door or window andcan be wetened to cool the air. Horizontalmoveable shutters can be made of bambooor natural fibre stripes. Screens of pre-formed cement or brick elements can alsogive good protection against solar radiation.PERGOLAS/BALCONIES/LOGGIAS. A pergola canbe made of bamboo or wooden sticks. Thehorizontal screening can be grown in withcreeping vegetation to give better shading.Balconies and loggias as architecturalelements can be helpful to provide shading.VEGETATION. Shading with trees can behelpful as long as it doesn't stopthe cross ventilation. Trees are alsoa source of insects and must therefore beplanted in adequate distance of the building.


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__-. -- ^- -.---- ___ __....-__-. ~-._-.-.--_-._..- --'3.2 GOODEXAMPLESOFSHADING ---1, I1.-I_-- -__

Fit. 22Arablac nashrabxa(wooden trel!ls-instead of win63

Fig. 25Pergola withcovering

Fig. 23Fig. 24Mov+ble hcrizontalscreening made ofreed, badoo or woo?

r eed


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14

3.2 GOODXAMPLESF SHADING

Fig. 26Yovable or fixedwindow louvres

Fig. 27Fixed vertical concretefins against morningand evening suii

Fig. 28Wooden shutters which canbe opened according to theposition of the sun

Fig. 29Screen of preformed elements


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15

I3,2 GOODXAMPLESOF SHADING

Fig. 31Overhanginq floor-slabscombined with heat-ab-sorbant glass

Fig. 32Combination of loggia, verricallouvres and horizontal shutters


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r I4, ROOF ESIGN !OOF OVERHANG. In some regions it is

to shade the sun off duringsummer and to use the solar radiationfor room heating through windows duringThis effect can be obtainedwith an appropriate roof overhang.It's dimension depends on the angle ofthe solar radiation. The roofing can bemade of straw (good insulation)

Fig. -34

VENTILATED ROOF. The roof covering shouldbe made of a reflecting material (e.g.asbestos). The room under the roof hasto be ventilated through wall openingsto create a cool buffer zone betweenroof and ceiling. Best results for coolroom are obtained with an insulated-ceiling. Protect roof area againstvermin, bats, etc.ICEHOUSE ROOF. This double roof con-struction includes an outer roof ofshingles and sheathing on wood nailersand an inner roof of roofing felt andand sheathing on rafters (3). This con-skruction has a good insulation effect.

FLAT ROOF. A flat roof should be coveredwith a ventilated roofing because it ab-sorbs during summer the highest solarradiation rate due to the right anglebetween radiation and roof.Heavy rains can damage flat roofsrelatively easily.

Fig.37

ROOF POND. A roof pond, creates a goodroom climate beneath due to heat reflectionand absorption during the day and radiationof stored heat into the room during night.The roof pond may cause serious constructionproblems because the roof has to be 100%water proof and the structure has to resistto the heavy water load. A roof pond re-quires high standard technology.


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r- ~______-..~-. ., 5, VEhTILATIONHROUGHWAL! WEMINGS I

The aim of planning wall openings is to obtain andcontrol a cooling air-flow through the building.Some of the rules for planners and users are:For hot arid regions- Make large openings of roughly equal size so thatinlets face the prevailing nighttime summer breezesand outlets are located on the side of the buildingdirectly opposite the inlets. This allows crossventilation.- Open the windows at night to ventilate the room andcool interior thermal mass.- Close the building up during the daytime to keep theheat out.For hot humid regions- Make the outlet openings larger than the inlets. Thiscreates high velocity of air flow which is necessaryfor effective cooling because hot-humid climates arecharacterized by high daytime and nighttime temperatures.- Open the building up to the prevailing breezes duringthe day and the evening.Openings in roofs- Warm air rises and can get stacked under the roof.To prevent this stack effect, you can arrange outletsin the roof area.


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5.1.1 DESIGN RULES FOR WALLeOPENINGS I._-..-_ iAir-flow in buildings are explained with examplesusing drawings from Robert H. Reed's "Design forNatural Ventilation in Hot Humid Weather". (4)

r1c. 3Kind striking a buildin;creates a region of hiykpressure on the windwardside

Fig. 4cThe wind is deflectedaround the buildingcreating low pressurezones along the sidesand along the entirelee side

Fig. 41Equal pressures on bothsides of symetricallylocated inlet

Fig. 42The air-flow does nottake the shortest route

FlC. 43Unequal pressures on bothside5 of inlet, air-flowdeflected to a differentroute

Fig. 44Inlet altered by a sall onone side, an open door orshading device. The airflows diagonally throughthe room compelled by thepressure forces along thefacade


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5J.2 DESIGN ULES FOR WALL OPENING

ig 46 The \'eIocit..- OF a:r-flows is 15~:~cased lithe 1r.7et 1: s-?z?lerthan the outlet

Fig. 47 The size of the outletcompared to the inletis declslve. The airspeed outsrde thebuiidlng is taken as100, the Inside valuesare expressed as a per-centage of thrs

Fig. Good cross ventilatrorrequires that the windapproaches the buildlncfrom the most favourabledirectron. Frgs. 48 and49 show that improvemenrcan be made by landscaplnfor by takrng suitablebuilding measures. Thesechanges too, are alsobased on the distributionof the pressure andsuction on the facades andaround the building.


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6,1,1 AIR COOLING,UMIDIFICA?ION ---IIn hot arid regions the air can be cooled by humidifyingit. Mainly in North Africa traditional methods of crossventilation and air humidification show very good results

(5) l

Flq. 50 A traditional system ofcross ventilation thr;)u:hair captors 0~ roofs or Iterraces Flq. 51

pression -

*/I winddirectionpression +

Fig. 53

Fir;. 52By hcmidifyinq the airwith water filled jarsin the air inlets theeffect of cooling can beimproved


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21--. --- ------j6,1,2 AIR COOLING,URIDIFI~ATION

air

Fig. 54 Ar, ex:;l;ilc, how t !I


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22

I7, BIBLIOGRAPHYND ABLE FPICTURESBibliography(1) Partially from "Solar Dwelling Design Concepts"by U.S. Dept. of Housing and Urban Development,May 1976 U.S. Government Printing Office, Washington,D.C. 20402.(2) From "The Passive Solar Energy Book" by E. MazriaRodale Press, Emmaus, Pa., USA, 197913) See "The Passive Solar Energy Book"(4) From "Building in the Tropics" by G. Lippsmeier1969 by Verlag Georg D.W. Callwey, Miinchen(5) From "Sahel et technologies alternatives"by CINAM (Republique francaise, Ministgre de lacooperation). Collection Technologies et DeveloppmentNo 3. August 1977

Table of PicturesThe pictures in this manual are made by the author orthey are copied from:- "African traditional architecture" (S. Denyer): Fig. 12by Heinemann, London, 1978- "Building in the tropics" (G. Lippsmeier): Fig. 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32 See (4) above- "Sahel et technologies alternatives: Fig. 50, 51, 52, 54,

55, 56 See (5) above- "Mazingira" No. 12/1980: Fig. 53


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SKAT Publications

1. Jean-Max Baumer: S.zhweizerische Kontaktstelle fiir Ange-passte Technologie (SKAT), St. Gallen 1977, 39 Seiten2. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungs-lander, Literaturstudie, St. Gallen 1977, 132 Seiten,vergriffen3. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungs-lander, Bibliographie, St. Gallen 1977, 307 Seiten,vergriffen4. Jiirg Nipkow: Angepasste Technologien fiir EntwicklungslZn-der, Sonnenenergie-Gerate fiir Haushalte, St. Gallen

1977, 62 Seiten, Fr. 8.505. Sabine Huber: Probleme des Technologie-Transfers von Indu-strielandern in Entwicklungslander, St. Gallen 1978,43 Seiten, vergriffen6. Gerhard Schwarz: Hemmnisse und Hindernisse bei der Ver-wirklichung des Konzepts der Angepassten Technologiein Entwicklungslandern, St. Gallen 1978, 53 Seiten,

Fr. 14.--7. Otto Langenegger: Einsatz von Bohrmaschinen fiir die Wasser-beschaffung in Aethiopien, St. Gallen 1979, 43 Seiten,Fr. 14.--8. Helvetas: Manual for Rural Water Supply, SL. Gall 1980,

175 pages, 10 scale drawings, Fr. 34.--9. Felix Sigrist (editor): Desecador solar simple, St. Gall1980, 25 pages, Fr. 7.--

10. Roland Stulz: Elements of Solar Architecture, St. Gall 1980,24 pages, Fr. 9.--Forthcoming:

. Roland Stulz: Appropriate Building Materials

. Ueli Meier: Harnessing Water Power on a Small Scale

Documents

Elements of Solar Architecture