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01 aee1999


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01 aee1999

  1. 1. Bioclimatic Potentialities ofContemporary Housing EstatesArchitecture, Energy and Comfort in AlgeriaKheira Tabet AoulArchitect, PhDUniversity of Science and Technology of Oran, Algeria responsive design a minimum thermal comfort, as well asAbstract an opening to various climatic and cultural contexts.There is a recent but growing interest in developingcountries to integrate environmental aspects in thebuilding sector. This paper stems from former concern Algeria: Background Informationwith thermal comfort and energy efficiency in “modern” Algeria, on the Mediterranean coast is the second largesthousing schemes erected all over Algeria regardless of its country in Africa with 2,382 760 square kilometresclimatic diversity. First, a review of the climatic (Figure1). It stretches from latitude 19o to 36o North, andconditions is presented along the vernacular architectural as such experiences a diversity of topography andsolutions it generated. Then, an investigation is carried climates.out to test the thermal behaviour of self-built houses incontemporary housing estates and investigates theirimprovement by passive means. Simulations, using athermal software (DEROB) were used.IntroductionThe issue of thermal comfort and energy savings in thebuilding sector of Algeria has yet to be properlyaddressed. The initial high needs in terms of housing, asin most developing countries, are still mainly expressedquantitatively, with hardly any consideration of theaftermath on traditional construction methods, culturaland social context, environmental comfort or energyefficiency. The result was the rapid growth ofinternationally styled buildings and infrastructures,reflecting Western technology, introduced into an Figure 1: Location of Algeria in the African continentessentially traditional environment. The consequences ofthis rupture in the housing sector are multiple. In terms of The population, with one of the highest birth rate, isenvironmental comfort, bad design, poor control and a expected to reach 32 millions by the beginning of the newcomplete disregard of the climatic conditions have century. Over 52% of all Algerians are now living inresulted in many substandard houses, where heating and urban settlements and mainly concentrated in its northerncooling are a prerequisite to achieve thermal comfort. coastal part. The desert, which accounts for 4/5 of its totalFurthermore, in the past governmental energy price area, is sparsely inhabited.control has led to unrealistically low energy costs, Petroleum and natural gas on the other hand arediscouraging a rational energy use. This attitude is now principally found in the Sahara. They are Algeria’s mostchanging due to high inflation of energy costs over the important mineral resources, its leading exports and mainlast decade. In this context, urban planners, architects and source of income. The drop in international oil pricesengineers have a key role to play. during the 1980s had a negative impact on the socialist This brief review and investigation undertaken here is a planned economy and contributed partially to its reversalcontribution towards a better understanding of the to an open market one. This meant cuts in all subsidis edclimatic and design requirements to achieve through a sectors and resulted in a high inflation rate. Building and 1–1
  2. 2. Kheira Tabet Aoulenergy sectors were the most affected and as a result their mainly sheep and goat herders, experience equallyprices inflated greatly. rigorous winters and hot summers. Building design In terms of energy use, 35% of all energy is used in strategy has to equally address both heating and coolingbuildings of the residential and tertiary sectors for space requirements, with a high mass and winter sun exposure.heating and cooling, domestic hot water, lighting etc. The The southern slope or the Saharan atlas, a broken seriespotential of energy savings in both sectors (residential and of mountain ranges and massifs is also a semi-arid areatertiary) is estimated up to 10% and 15.6% for and is used chiefly for pasturing livestock. Here, wintersrespectively the year 2000 and 2020 (Guellouz, K. 1992). are short but cold and summers are long, very hot and dry.These savings may only be achieved through the planning Similar design strategies apply here with an emphasis onof efficient saving strategies in general; a sound summer protection.controlled building design and the establishment of Finally, the largest part of the country, the Sahara, hasadequate building regulations (Tabet Aoul, K, 1996). short cold winters, particularly at night and long, very hot and dry summers. Sandstorms are frequent year round and rainfall is scarce. To achieve comfort by passive meansClimate and the Design Comfort only is rather difficult. However, contribution would beRequirements made through high inertia of walls and roof, maximum solar radiation control through shading devices as well asAlgeria falls into two main geographical areas, the the use of night ventilation and evaporative cooling.northern region and the much larger Saharan or southernregion. The northern region is made up of three parallelgeographical zones running east to west, with distinctive Vernacular Architecture; an Adaptation to theclimatic conditions and specific climatic design Contextual Environmentrequirements (Figure 2). Each region developed a characteristic vernacular architecture in harmony with the climate, geography, topography and local building materials. The northern part of the country, with a long colonial influence, and a large industrial and urban expansion after independence, has little authentic vernacular remaining. The Casbah in Algiers, although not well preserved, is certainly the most representative of what is remaining. It is a good example of adaptation to site, and the prevailing warm and humid climate. The urban fabric and the houses naturally follow the topography, hence the slope of the hills so as to take full advantage of the sea breezes (Bensalem, 1997). The villages on the cold mountains of the Aures are clustered in a way that minimises heat losses and their south orientations maximise sun exposure. Loggias areFigure 2: The climatic regions in Algeria: (A): Temperate orientated south and shaded.humid climate; (B). Semi-arid cold climate; (C). Semi-arid hot climate; (D). Hot and arid climate of the desert.The Tell region (A) is a narrow lowland strip,interspersed with mountains, along the country’sMediterranean coastline. It is characterised by a temperateclimate with mild winters and summers. The highhumidity, however is the main source of discomfort inboth seasons. Givoni and Mahoney’s recommendationsfor this climate, emphasise the use of cross ventilationwith protection in summer. The Atlas Mountains (B) with an abundant fertilesoil, have a Mediterranean climate with longer coldwinters and occasional snowfall. Summers arecomfortable and less humid. The emphasis for comfortshould here be put on the winter period, with a prevailingsouth orientation, provision for adequate sunshineexposure and a well-insulated envelope. Further South, the highlands referred to as HighPlateaux (C) maybe looked upon as two sub-climaticzones, the northern and southern slopes of the mountains.The northern semi-arid plateaux, sparsely populated, Figure 3: View of a mountainous village.containing a number of shallow salt lakes and supporting1–2
  3. 3. Bioclimatic potentialities of contemporary housing estates Figure 5: View of Ghardaia’s setting, with compact urban fabric.Figure 4. Village on the highlands The towns are all terraced; streets descend in circles from the high point following the contours of the land. On Under the extreme heat of the Sahara, well illustrated all but the south facing slopes, houses are open at the the M’zab valley towns and the “ksours”, the site was A central courtyard diminishes in area through two orthe first climatic response to the harshness of the climate three stories to a small skylight. On the southern side, theand the sparse arable land. Most of the human settlements rooms, which usually surround the terrace on all fourthere are set on the rocky part of the hills, saving the sides, are left open to the south.fertile land. Actually, the basics of dealing with the extremes ofsummer conditions are similar from Morocco to India,where most of the hot and arid climate zones are found.Houses have developed simple but very efficientstrategies to cope with the climate. However, somearchitectural variations exist. In the M’zab valley, socialand architectural differences are unique, due in part to thepuritanist conduct of the local Islamic indigenouspopulation, the ibadites, who erected five new towns onethousand years ago. Ghardaia, the largest, located at 32-north latitude is in one of the harshest climate. Summertemperature often reach 45°C. The diurnal range is alsovery large, while humidity is very low. Sandstorms arefrequent and it rarely rains. The clear planning of these towns with fortified outerwalls, the dominant central mosque and the carefullydesigned courtyard house make these communities one ofthe most fascinating in Algeria. Each town has a permanent winter town and a summertown located in the nearby oasis. The winter town is themain residence for mo st of the year. The summer town isused at the hottest time of the year when the population Figure 6: Compact fabric, narrow streets, terrace roofs and two levels courtyards in Ghardaia.migrates to an environment that is cooler and shaded bydate palms. The courtyard house in the M’zab is an overlaying of The overall structure of the main town is compressed two courtyards, as the usual house is three stories high.and condensed. Houses are often part of one another The ground floor is organised around the central physicalwhere walls are shared and boundaries are not easily element of the house and receives light and air from arecognisable. The resulting network of streets is narrow, small opening in the roof called the chebeq (net). The firstenclosed and sometimes entirely covered, easing floor is more open and used mostly in winter times. Themovements between neighbourhoods. second floor is the terrace, which is well protected by a 1–3
  4. 4. Kheira Tabet Aoulhigh parapet and serves as a sleeping area on hot summer result is the standardisation of housing schemes, materialsdays. There is seasonal nomadism between the two floors and construction technologies as well as the reproductionas well as a daily one. The inhabitants move around the of typical plans indefinitely in all parts of the countryhouse to take full advantage of the optimum living with little variation or adaptation to the context.conditions. The most common materials are reinforced concrete, The typical feature in a mozabite dwelling is the prefabricated concrete panels, metal and glass. In these“chebeq” (net), a more or less square hole in the ceiling buildings, high-energy consuming equipment for heatingwhich makes up for almost the total absence of windows. and cooling are necessary to achieve thermal comfort inAn iron grill protects it, and depending on the season and the hot regions.the time of day, may be partially or totally obstructed.The chebeq acts as an air conditioning device too as wellas a source of light. It is worth noting that adaptation to local environment,availability of materials and microclimate has resulted inarchitectural variation or adaptation. For example, ElOued with less palm timber available and frequentsandstorms, has its entire town made on one-storydomed and vaulted houses built around courtyards toprevent accumulating sand. Figure 8: Typical social housing estates built throughout Algeria The second category, which accounts for more than 40% of the actual housing production, is in the form of individual housing estates. Here, the state provides plots of land and one or two individual houses’ plans are proposed. As the owner is the main actor in the construction process, different materials are used. There are also many deviations from the original type plan imposed, as building regulations are rather limited and are not strictly complied with. If building regulations exist at the urban level and in relation to structures and earthquakes, the national building is rather silent on such matters as thermal performance or energy efficiency. Recently, there has been an attempt to develop it at the Maghrebin level (Algeria, Morocco and Tunisia) with an EEC special fund. In this context, climatic data for the three countries was gathered, a climatic classification was carried out, actual and future energy consumption wasFigure 7: The domed and vaulted roofs in El Oued (Southern estimated, regional architecture was identified and details Algeria) for typical building, materials and techniques were drawn. These traditional settlements are a harmonious The next step should include parametric studies oncombination of social, geographical and climatic models as well as building an experimental 50 housingadaptation in a given period of time. The lessons to be units in each country. It is however unfortunate to see thatlearned from vernacular architecture are invaluable in for various reasons the programme is actually at aterms of gaining understanding of the millennium standstill.experiences embodied in design solutions adapted to thelocal environment. However, it should be stressed that The Experimentalliving conditions, contemporary needs and availability ofnew materials have changed, thus care must be taken in Investigationinterpreting the traditional lessons. There are numerous studies about the bioclimatic performance of vernacular architecture in the south ofContemporary Era Algeria. Comparatively, little is known about the thermalThe contemporary housing production might be divided behaviour of the contemporary populace architecturalinto two major categories. The apartment blocks are the production. Especially, that there is a widespread beliefstate response to ever-increasing housing demands. A that all-present buildings under the hot climate aredeficit of 1.5 million units is estimated and it has never thermally inefficient. This is probably the case for thebeen possible to achieve the target of 100 000 dwellings a standardised metal and concrete apartment blocks. It isyear. The bulk of the construction activities in the formal right that one may be tempted to generalise this to allsector are undertaken by state-owned organisations. The types of constructions, as the new forms of buildings are far from traditional designs.1–4
  5. 5. Bioclimatic potentialities of contemporary housing estates In this context, the objective of a research initiated at and Mahoney’s recommendations for building designBiskra university aimed first to evaluate the bioclimatic under such climatic conditions.potentialities of the self-built houses. Then, investigatethe possibilities of improving their performance by minor Design Toolspassive design means. The hypothesis behind this lays in There are a number of methods to evaluate the thermalthe fact that if improvements can be made without a behaviour of a building. In site measurements are acomplete disruption of the construction process then they possibility but they are time consuming, expensive to runmay be readily incorporated. New designs like trombe and require adequate equipment. The other alternative iswalls, solariums, chimneys for ventilation may not be to simulate the real environment. Although, often in thisreadily integrated in the construction process for various case some assumptions are made, they are powerful toolsreasons; inadequate to the context, new, unknown, and rapid to run.expensive etc. There has been an attempt to introducesolar ventilative chimneys by El Minaoui architects in the Traditional Versus Actual Climatic Design Toolsregion of Biskra, but people’s unfamiliarity with the A number of traditional design tools exist, to assist at thedesign blocked them. They argued that they infiltrated early stages of climatic integrated design, such as comfortsand from wind and danger from scorpions. diagrams, solar charts, heat gain or loss calculations etc. Hence a survey was carried out of over 100 individual They provide useful guidelines, based on rules of thumb,houses in Biskra. This included the occupation of the plot on optimum site orientation, type of building componentsof land, orientation, plans, façades, openings, wall properties, sun shading devices and openings as well ascolours, the details of the construction materials as well as indicate the potential requirements for ventilation, heatingadministrating a questionnaire to the inhabitants to or cooling. However, they do lack precise quantitativeexplore the way the spaces are used. assessments. A typological classification was then carried out, first In order to evaluate and compare the thermal impact ofin terms of plot occupancy. Three main types emerged, various building parameters, there is a need for rapidone that fully occupied the land, one that left a garden in evaluations of the building thermal behaviour. Today’sfront and those that left a band in the front and the rear of computer simulation tools present the advantage of rapid,the house. flexible assessments. They allow to integrate most of the The next step was to verify the thermal behaviour of elements involved in the building heat exchange.the most representative types of houses. If these are to be On the other hand, they do require precise data, whichfound thermally uncomfortable then the next stage aims may only be available at the latest design stages as well asto test possible improvements gained through first the requiring a lengthy input process. Further, the non-correct application of passive climatic design principles in integration of these assessments on Cad tools so far,accordance with the user habits, preferences and ways of hinder their extensive use by (Sriti & Tabet Aoul, 1999). DEROB-LTH (Dynamic Energy Response ofThe Context; the City of Biskra Buildings)Biskra, at the foot of the Aures Mountains is a DEROB-LTH, a powerful program for assessment of thecommercial centre for the nomads of the surrounding thermal behaviour in multizone buildings, was used inregion. It is located in the northern part of the desert at this investigation. It was first developed at the Numerical34.8o North latitude, 5.73 longitude East and at the altitude Simulation Laboratory, University of Texas, Austin,of 87m. USA. This latest version has been successively updatedIt falls under the third climatic zone, the hot and dry and developed at the Department of Building Science atclimate. Thus, in winter it experiences mild days (average Lund Institute of Technology, Sweden. (Kvist Hasse,16 to 22o C) but cold night temperatures (average 7-9o C). 1999).The diurnal range is often greater than 10o C. Summer on The program consists of 8 modules. Six of thethe other hand is very hot, the temperature can easily modules are used to calculate values for temperatures,reach 40o C, and the diurnal range for the hottest month heating and cooling loads. It can take account of 8reaches 13 o C. Humidity varies between 40 to 70% in volumes and simulate buildings of arbitrary geometries.winter but may drop to 15% during the hottest part of thesummer. Rain is rare and generally comes in the form of Base Case Model Used in DEROBstorms. The dominant wind direction is from Northwest to The base case model tested is the most recurrent type ofsouth east with 6 to 12m/s velocity (Atlas climatologique individual houses surveyed in terms of land occupation,national, 1998; Capderou, 1985). morphology and architectural details. It consists of and L- According to Givoni’s bioclimatic diagram, Biskra’s shaped building occupying over half of the rectangularclimatic data fall beyond the comfort zone for winter and plot of land with partial front garden and a backyard.summer. High inertia of the envelope, provision of night It is 15m wide along the main façade, divided into 5mventilation and evaporative cooling should improve structural spans, and 10m along the contiguous walls withsummer conditions. The winter season would require bordering houses. Except for one span that goes to 15mheating and that is despite the provision of internal gains. and encloses the partial front garden. The north, southAppendices A and B present respectively the climatic orientation was considered for the base case, although thedata of Biskra along with its corresponding comfort chart survey highlighted random orientations according to the 1–5
  6. 6. Kheira Tabet Aoulsite and the existing street constraints. The impact of an Parametric Studyoptimum orientation i.e southnorth was tested. The initial objective being to test gradually the least disruptive changes in the building so as to be realistically possible to incorporate them in the construction process. Four main categories were considered. • First the effect of the variation of the orientation from north to south was tested for both summer and winter (2 cases). • Then the impact of various external wall properties was tested. It included a self bearing wall (300 mm) made of a locally produced material; the sand lime brick which has the advantage of replacing the expensive concrete and steel structure and requires no surface treatment (mortar or plaster). An infill with this type of brick within the traditional structure was also tested (150mm of sand lime bricks insteadFigure 9: View of the model as simulated in DEROB of the hollow concrete blocks). The double hollow Internal load was evaluated according to the variation brick (100 and 150mm bricks) partition wall with aof occupancy of the house (6 persons in total) and the use 50mm air space is also a commonly usedof its appliances and summed up to 23Wh/m². construction practice and was also tested. The last Four windows of 1.5m width and 1.2m of height were type though hardly used was tested to evaluate theused. One was on the south façade and the three others on impact of a highly insulated wall. Here, an insulatingthe north façade. The recessed window frame within the material (polystyrene 50mm) replaced the air space.wall thickness was simulated as a shading device on all These options were also tested for the summer andwindows. Closed window shutters at night and between winter period (8 cases).11 am and 17 pm in summer were also taken into • The third category tested the impact of modifyingconsideration. some roof properties, mainly to accommodate the The ventilation rate was differently set for winter and summer extreme heat. First, an insulated roof wassummer. It was assumed to be 1ach/hr in winter except considered with a 50mm cork block (conductivityfor one hour of the morning were it was set to 5ach/hr 0.043 and specific heat 0.42). Then, the colour wascorresponding to the common practice of opening changed from a dark sandy one , 60% absorptance towindows during house cleaning. Summer night a white one (25%). The second case tested theventilation was assumed to be equivalent to 20ach/hr for impact of shading the terrace with a 2m highpart of the night (1am to 7am) and 1ach/hr for the rest of parapet. This has the advantage of improving visualthe day. privacy for a space commonly used for sleeping in The building components and the materials commonly summer. The impact of these options was tested forused on the base case are listed with their thermal the hottest and coldest months of the year (6 cases)properties in table 1. • Finally, an increase of window size from 8% to 15%Table1: Building elements of the base case with their of glazing to wall ratio was tested for both seasons (2 corresponding material characteristics cases). Thickness Conductivity Specific heat Density Results and Discussion (mm) (W/mK) (Wh/kgK) kg/m3 Since the initial objective is to assess the thermal behaviour through the passive climatic features of the existing houses, the results are presented in terms ofExternal wall operative temperatures. This is the most relevant Cement 15 0.93 0.29 1800 mortar parameter for thermal comfort. Hollow concrete 150 1.1 0.3 1300 Block The Thermal Behaviour of the Base Case Cement 15 0.93 0.29 1800 mortar In the original house modelled (base Case), the operativeRoof temperatures in winter are constantly below comfort Cement 70 0.93 0.29 1800 level. They range from 11.7°C to 13.6°C, while the Ribbed slab 200 1.15 0.3 2100 comfort zone, according to Mahoney’s tables is at least Plaster 15 0.35 0.26 800 between 17 and 23°C at night. During morning in summer, the temperatures are within the upper limit of theFloor comfort zone, but they do go beyond the comfort zone, Earth 500 1.4 0.22 1300 particularly at night. The upper nights limit for comfort Concrete 150 1.7 0.24 2300 being 25°C, while temperatures rise to 35°C. Tiles 15 0.8 0.24 800Window 40U value=5.0 W/m2K)1–6
  7. 7. Bioclimatic potentialities of contemporary housing estatesImpact of Orientation 14 18 16 17 13 15 14 Temperatures Temperatures 13 12 12 11 9 10 7 11 8 5 1 3 5 7 9 11 13 15 17 19 21 23 10 6 Hours of the Day 1 3 5 7 9 11 13 15 17 19 21 23 South Orientation Winter North Orientation Winter Hours of the Day Outdoor Temperature Winter Hollow Concrete Block Brick silico calcair 150mm Brick silico calcair 300mm External wall air space External Wall polystyrene Outdoor TemperatureFigure 10: Impact of north / south orientation in winter. Figure 12: Impact of various types of external walls in winter.There is little heat gain from changing orientation fromnorth to south in both seasons. 0.4°C is gained in winter 39 39during midday and respectively 0.6°C in summer. 37 37However, it should be noted that the limited glazing to Temperatures 35 35wall ratio (8% and 2.5% in each façade) explains thislimited influence. An increase in window size is certainly 33 33required before any noticeable difference might be 31 31pereceived. 29 29Impact of Window Size 27 27 25 25 17 1 3 5 7 9 11 13 15 17 19 21 23 15 Hours of the Day 13 Hollow Concrete Block Brick silico calcair 150mm Temperatures 11 Brick silico calcair 300mm External wall air space External Wall polystyrene Outdoor Temperature 9 7 5 Figure 13: Impact of various types of external walls in summer 1 3 5 7 9 11 13 15 17 19 21 23 Hours of the Day Impact of Roof Properties South Orientation [8%] South Orientation [15%] The most interesting result lies on the impact of roof Outdoor Temperature winter colour on the operative temperature during summer. It decreases the operative temperature up to 1.8°C, which isFigure 11: Impact of increased window size, south a substantial result due to the simple addition of whiteorientation (winter) colour to the roof. Comparatively, the roof insulation and the high parapets are less significant. The combination of An increase of glazing from 8% to 15% ratio to the three parameters should be an interesting case andwindow wall was tested for the south orientation only, would be taken for optimising the initial model.where heat can be gained, for both summer and winter.Up to 1.1°C is gained in winter when it is most needed,while only 0.6°C is gained in summer. This is the result of 39the high sunrays in summer as well as the effect of 37closing the external shutters for most of the day. This 35 35result is a positive passive design feature and further test Temperaturesshould be carried out to investigate the optimum glazing 33to wall ratio for optimising winter heat gain. 30 31 29Impact of wall properties 27The test on the various types of walls shows little 25 25variation for both summer and winter. However, the more 1 3 5 7 9 11 13 15 17 19 21 23stable thermal behaviour of the sand lime brick wall Hours of the Day(300mm) has to be noted, as by its thickness it increases Roof non- insulated Roof insulated roof colourwall’s inertia. Further, if the comparison is done on a cost roof parapet Outdoor Temperaturebasis too, then the latter would be more advantageous,being a bearing wall. This reduces greatly the high cost of Figure 14: Impact of various roof types in summerthe traditional structure of concrete beam and columns. 1–7
  8. 8. Kheira Tabet Aoul Optimum Case etc... These aspects however fall beyond the scope of this Finally, a test was run with the optimum parameters for study and should be the target of future work. each category considered. The main glazed façade was orientated south. The external walls were made of 300mm Conclusions sand lime bricks. An insulated roof with a white colour The most important benefit gained through this and 2m high parapets was adopted. 15% glazing to wall investigation lies beyond the specific results obtained. A ratio was considered for the opening. better understanding of climatic design generates the impetus to integrate it into any future design. 17 Solar energy applications to architecture hold a lot of promise for developing countries because in addition toTemperatures 14 being environmentally expedient they are also technologically less sophisticated and may lead to 11 substantial energy savings in the building industry. It 8 must be stressed that when the recommendations are achieved to a reasonable extent, the greatest impetus to 5 the development of passive solar architecture would be 1 3 5 7 9 11 13 15 17 19 21 23 25 outright statutory support in the form of regulation and Hours of the Day incentives as well as the proper training of building professionals, Out Temp BaseCase Optimum Finally, it is hoped that this study is a modest contribution towards a better understanding of thermal comfort and housing design by passive means. Figure 15: Effect of optimising all parameters in winter References Atlas Climatologique National. (1998) Office National de Meteorologie, ONM, Algiers, ONM Biskra. 40 Bensalem, R., (1995), “climate responsive architecture”, 35 Arhitecture, energy and environment, Tools for climatic Design, Lund Centre for Habitat Studies, Temperatures 30 Lund University. Sweden. 25 Capderou, M., (1985) Atlas solaire de l’Algerie Tome 2,OPU, Algiers, Algeria. 20 1 3 5 7 9 11 13 15 17 19 21 23 25 Givoni , B., (1998) , Climate considerations in Building Hours of the Day and urban design, Van Nostrand reinhold, new Outdoor Temperature Base Case Summer optimum Summer york. Figure 16: Effect of optimising all parameters in summer Guellouz. K., (1992), Seminar: Reglementation thermique des batiments dans les pays du Maghreb, Tunis, Although, temperatures remained outside the comfort p.5. zone for winter, it should be stressed that a 2.5°C increase compared to the base case is a positive result, taking into Kvist Hasse (1999) DEROB-LTH for windows. User consideration the minor changes tested. Similarly, in Manual. Department of Building Science. Lund summer the reduction of up to 1.7°C during the evening is Institute of Technology, Lund University. Report a positive trend. Summer temperatures are within the limit TABK-99/7019. of the comfort zone during the day but not during the night, when stored heat is transmitted indoors. However, Sriti, L ; Tabet Aoul, K., (1999), Etude et optimisation de due to the traditional lifestyle of the inhabitants of Biskra, la performance thermique de l’habitation where people sleep outdoors in summer, this might be a individuelle contemporaine, cas d’etude Biskra, minor effect. Seminar on renewable energy , 11-12 November, As a mean of summing up, one might say that given Algiers, Algeria the conflicting requirements for equal consideration of both seasons (cold winters, hot summers), the exercise of Tabet Aoul, K., (1996), Housing design, energy optimisation will be limited to a certain extent. Favouring, conservation and building regulation: the case of for example summer protection hinders winter benefits. Algeria, the 4th European Conference on Further, there is probably a limit to the impact of Architecture, Berlin, Germany, 26-29March; pp. passive design means on thermal comfort, if they are solely related to the sole features of the building. Extra benefits will be gained through the sound site layout, street height to width ratio, including vegetation, water 1–8
  9. 9. Bioclimatic potentialities of contemporary housing estatesAppendix B Location Biskra Longitude 5.73 ° Latitude 34.8 ° Altitude 87 m Air temperature °C Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec High AMT Monthly mean max. 16.8 18.6 21.9 25.5 30 36.3 39.3 38.5 33.6 27.1 20.8 17.5 39.3 23.15 Monthly mean min. 7 8.9 11 14.2 18.5 23.6 26.8 26.4 22.7 16.9 11.4 8 7 32.3 Monthly mean range 9.8 9.7 10.9 11.3 11.5 12.7 12.5 12.1 10.9 10.2 9.4 9.5 Low AMR Relative humidity % Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monthly mean max am 69.9 70.6 60.3 57.3 53.2 45.9 39.4 45.3 57.4 64.3 71.5 72.2 1 <30% Monthly mean min pm 35.3 32.7 25.2 22.7 20.2 16.5 14.8 18 25.9 31.6 37.2 38.9 2 30–50% Average 52.6 51.65 42.75 40 36.7 31.2 27.1 31.65 41.65 47.95 54.35 55.55 3 50–70% Humidity group 3 3 2 2 2 2 1 2 2 2 3 3 4 > 70% Rain and wind Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Rainfall mm 13.3 12.9 7 12.7 13.5 5.1 3.5 8.5 10.5 12.2 21.4 3.5 124.1 Wind, prevailing NW NW NW NW NW N, NE, E, SE, Wind, secondary N N NW S, SW, W, NW Diagnosis °C Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec AMT Monthly mean max 16.8 18.6 21.9 25.5 30 36.3 39.3 38.5 33.6 27.1 20.8 17.5 23.15 Day comfort, upper 29 29 31 31 31 31 34 31 31 31 29 29 Day comfort, lower 23 23 25 25 25 25 26 25 25 25 23 23 Thermal stress, day C C C O O H H H H O C C Monthly mean min 7 8.9 11 14.2 18.5 23.6 26.8 26.4 22.7 16.9 11.4 8 H=Hot Night comfort, upper 23 23 24 24 24 24 25 24 24 24 23 23 O=Comfort Night comfort, lower 17 17 17 17 17 17 17 17 17 17 17 17 C=Cold Thermal stress, night C C C C O O H H C O C C AMT >20°C AMT 15–20°C AMT <15°C Comfort limits Day Night Day Night Day Night Humidity group Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper 1 26 34 17 25 23 32 14 23 21 30 12 21 2 25 31 17 24 22 30 14 22 20 27 12 20 3 23 29 17 23 21 28 14 21 19 26 12 19 4 22 27 17 21 20 25 14 20 18 24 12 18 Meaning Indi- Thermal stress Rainfall Humidity group Monthly mean range cator Day Night Air movement essential H1 H 4 H 2–3 <10°C Air movement desirable H2 O 4 Rain protection necessary H3 >200mm Thermal capacity necessary A1 123 >10°C Outdoor sleeping desirable A2 H 12 H O 12 >10°C Protection from cold A3 C Indicators Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total H1 H2 H3 A1 1 1 1 1 1 1 1 1 8 A2 1 1 1 3 A3 1 1 1 1 1 5 1–9
  10. 10. Kheira Tabet Aoul Indicator totals from data sheet H1 H2 H3 A1 A2 A3 8 3 5 Low High Low High Low High Low High Low High Low High Layout 0 10 1 Orientation north and south (long axis east–west) 5 12 11 12 0 4 Compact courtyard planning Spacing 11 12 Open spacing for breeze penetration 2 10 As above, but protection from hot and cold wind 0 1 1 Compact layout of estates Air movement 3 12 Rooms single banked, permanent provision for air 0 5 movement 1 2 6 12 Rooms double banked, temporary provision for air 2 12 movement 0 0 0 1 1 No air movement requirement Openings 0 1 0 0 Large openings, 40–80% 11 12 0 1 Very small openings, 10–20% Any other conditions 1 Medium openings, 20–40% Walls 0 2 Light walls, short time-lag 3 12 1 Heavy external and internal walls Roofs 0 5 Light, insulatted roofs 6 12 1 Heavy roofs, over 8h time-lag Outdoor sleeping 2 12 1 Space for outdoor sleeping required Rain protection 3 12 Protection from heavy rain necessary Size of opening 0 0 Large openings, 40–80% 0 1 1 12 Medium openings, 25–40% 2 5 6 10 1 Small openings, 15–25% 0 3 Very small openings, 10–20% 11 12 4 12 Medium openings, 25–40% Position of openings 3 12 In north and south walls at body height on windward 0 5 side 1 2 6 12 1 As above, openings also in internal walls 0 0 2 12 Protection of openings 0 2 1 Exclude direct sunlight 2 12 Provide protection from rain Walls and floors 0 2 Light, low thermal capacity 3 12 1 Heavy, over 8h time-lag Roofs 0 2 Light, reflective surface, cavity 10 12 3 12 Light, well insulated 0 5 0 9 6 12 1 Heavy, over 8h time-lag External features 1 12 1 Space for outdoor sleeping 1 12 Adequate rainwater drainage1–10