Sustainable Building Design for Tropical Climates

Niccolò Aste; Federico M. Butera; Rajendra Singh Adhikari; Fabrizio Leonforte

SUSTAINABLE BUILDING DESIGN FOR TROPICAL CLIMATES Principles and Applications for Eastern Africa

Josielyn Arreza

visibility

…

description

303 pages

link

1 file

AI-generated Abstract

This paper discusses sustainable building design principles and their applications in tropical climates, specifically in Eastern Africa. It emphasizes the challenges posed by climate change and resource depletion, detailing the need for significant greenhouse gas emissions reductions to mitigate impacts on ecosystems and resources. The authors highlight the pressing need for strategies that allow economic development without increasing emissions, while also addressing the ecological footprints of countries in this region.

Figures (399)

Adapted from: McKinsey&Company, Resource Revolution: Meeting the world’s energy, materials, food, and water needs, 2011.

Source: Wikipedia - http://en. wikipedia. org/wiki/List_of_countries_by_greenhouse_gas_emissions_per_capita

1.3 INTEGRATED DESIGN FIGURE. 1.3-1 THE PHASES OF THE DESIGN PROCESS IN WHICH CHOICES HAVE AN INFLUENCE ON A BUILDING'S ENERGY PERFORMANCE AND COMFORT The design process, nowadays, is based on a linear path, in three steps: architectural design, followed by design of the mechanical systems (when the building is equipped with an air conditioning system), and then construction (Fig. 1.3-2). The architect — because of his training — usually knows little or nothing about building physics; consequently architectural choices very often have a negative impact on the building’s energy performance, and on the occupants’ comfort. Building envelope design, which aims to achieve the maximum comfort with the minimum primary energy consumption (and thus to minimise GHG emissions), requires that the parameters of comfort and energy be integrated into each of the critical steps of the design process (Fig. 1.3-1). Factors such as climate, master plan, building shape, facade design, the thermo-physical characteristics of the materials, and finally the building plan, must play a role in decisions.

evaluations the energy expert derives recommendations for the architect and the mechanical engineer who, in turn, modify their design choices accordingly, proposing new solutions that have to be re-evaluated. This circular process is repeated until a satisfactory solution is reached, taking into account not only energy, but also aesthetics, functionality and economy (Fig. 1.3-4). The energy expert must have an in-depth knowledge of building physics; he must be able to interact with the architect and with the mechanical engineer; he must not only be capable of managing rules of thumb, but he must also be able to use sophisticated simulation tools for evaluating the energy performance of the building, thermal comfort, daylighting, natural ventilation and all the passive means of reducing energy demands. From these This approach is incompatible with the design of low energy, high comfort buildings. It is necessary to change the design methodology, and make use of an integrated design model that includes, inter alia, the introduction of new professional expertise: the energy expert (Fig. 1-8). To achieve this goal, a high level of integration among the skills called into play in the design process is required.

appropriate control be tackled. Eventually, if the process has been carried out in the best possible way, the amount of primary energy needed will be very small and it will be easily supplied from renewable sources: the higher the energy efficiency of the whole building+HVAC system, the lower the size, and hence the cost, of the renewable energy production system.

It is also essential that these skills are integrated from the earliest stages of the process. Indeed, it is in these phases that most critical decisions are taken, greatly influencing the energy performance of the building, the comfort of the occupants and construction costs (Fig. 1.3-5).

FIGURE. 2.1-1 SOLAR DECLINATION ANGLE. (A) SUMMER SOLSTICE; (B) AUTUMN EQUINOX; (C) WINTER SOLSTICE; (D) SPRING EQUINOX In order to make the study of the solar geometry more intuitive, it is convenient to refer to the apparent movement of the sun, assuming that it moves on the inner surface of a sort of dome (the sky dome), having as its base the horizon line of the site (Fig. 2.1-2). In this way (and it is consistent with our perception), the sun rises in the east, climbs in the sky with a trajectory depending on the hemisphere, the latitude angle © and on the day of the year, and sets in the west. As a consequence of the earth’s movements around the sun, in the course of the year an observer on earth perceives different solar paths, which are characterized by variable heights and lengths, depending on time of year and latitude. The latitude is represented by the angle between the equatorial plane and the radius from the earth’s centre to its surface at the specific location and ranges from 0° at the Equator to 90° (North or South) at the poles. Generally, in the calculations, the northern latitudes are considered positive and the southern ones negative.

Sun path diagrams are a convenient way to represent the annual changes in the sun path through the sky ona single 2D diagram.

FIGURE. 2.1-7 PROJECTION OF SOLAR PATH ON THE POLAR CHART

The attenuation of the radiation is due to the absorption and the scattering caused by the components of the atmosphere (oxygen, ozone, nitrogen and nitrogen oxides, carbon dioxide, water vapour, aerosol, etc.). Both phenomena modify the solar spectrum; absorption because it is selective (i.e. it takes place only for certain wavelengths); scattering because the ratio of the energy scattered in all directions (and thus also back towards space) to that transmitted varies as a function of wavelength and of the characteristics of the medium crossed. The quota of radiation that reaches the earth's surface after the scattering process is called diffuse radiation, while the radiation that comes directly from the sun and penetrates the atmosphere is called direct radiation.

The average power density of solar radiation on a perpendicular surface outside the earth’s atmosphere is about 1370 W/m?. On the earth’s surface, however, the maximum value rarely exceeds 1100 W/m?, because of the filter effect due to the atmospheric components (gas, vapour, dust), which absorb and scatter part of the energy.

FIGURE. 2.1-17. MONTHLY IRRADIATION IN THREE SITES

FIGURE. 2.1-16 NAIROBI, JUNE SOLSTICE IRRADIANCE (ALBEDO = 0.2

FIGURE. 2.1-22 SOIL NATURE AND TEMPERATURE FIGURE. 2.1-21 COLD AIR LAKE STRATIFICATION

FIGURE. 2.1-24 VARIOUS URBAN ENVIRONMENT ALBEDOS (LEFT) AND HEAT TRAP OR URBAN CANYON EFFECT (RIGHT)

Adapted from: T.R. Oke, City size and the urban heat island. Atmospheric Environment 7: 769- 779, 1973

FIGURE. 2.1-25 EFFECT OF URBAN SIZE ON HEAT ISLAND

TABLE 2.1-5 CORRECTION FACTORS AS A FUNCTION OF THE HEIGHT AND ROUGHNESS OF THE GROUND K and a are two coefficients that vary depending on the type of ground, as shown in Table 2.1-5.

A schematic representation of the three parameters is given by the wind rose (Fig. 2.1-27). Presented in a circular format, the wind rose shows the frequency of winds blowing from particular directions. The length of each “spoke” around the circle is related to the frequency with which the wind blows from a particular direction in a given period of time (month, season, year). Each concentric circle represents a different frequency, ranging from zero at the centre to increasing frequencies at the outer circles. A wind rose plot may contain additional information, in that each spoke can be broken down into colour-coded bands that show wind speed ranges. The most useful values are the averages over a long period of time.

FIGURE. 2.1-30 TOPOGRAPHY EFFECTS ON WIND; DEVIATION (LEFT), REINFORCEMENT (RIGHT)

-IGURE. 2.1-31 GROUND-WATER TEMPERATURE DIFFERENCE; SEA (LEFT) AND LAND (RIGHT) BREEZE

IGURE. 2.1-33 BUILDINGS AND ROWS OF TREES EFFECTS ON THE WIND'S CHARACTERISTICS

Another term often used to define passive architecture is “Bioclimatic architecture”, which was introduced for the first time by Olgyay (1963) and later developed by Givoni (1969). More recently the term “green architecture”

FIGURE 3.2-7 HIGH THERMAL MASS AND NIGHT VENTILATION ZONE FOR COOLING

FIGURE 3.2-10 GIVONI BIOCLIMATIC CHART FOR DAR ES SALAAM

FIGURE 3.2-11 GIVONI BIOCLIMATIC CHART FOR LODWAR

FIGURE 3.2-13 GIVONI BIOCLIMATIC CHART FOR KAMPALA

FIGURE 3.2-15 GIVONI BIOCLIMATIC CHART FOR ELDORET

FIGURE 3.2-14 GIVONI BIOCLIMATIC CHART FOR NAIROBI

FIGURE 3.3-5 CFD SIMULATION OF THE AIRFLOW PATTERN IN ROW ARRANGEMENT WITH A RATIO DISTANCE/HEIGHT = 7

Further, it should be taken into account that dispersed buildings with continuous and wide open spaces preserve each building's access to breezes.

Lakes may also develop similar local wind circulation yatterns.

FIGURE 3.3-6 CFD SIMULATION OF THE AIRFLOW PATTERN IN ROW ARRANGEMENT WITH A RATIO DISTANCE/HEIGHT = 3. AIR FLOW PATTERNS IN ROW ARRANGEMENT (ABOVE) AND STAGGERED (BELOW)

FIGURE. 3.4-1 TOP: VARIATION OF SURFACE TO VOLUME RATIO (SHAPE COEFFICIENT) FOR INCREASING VOLUME OF A CUBE. BOTTOM: EVOLUTION OF THE SHAPE COEFFICIENT FOR DIFFERENT COMBINATIONS OF A 125 M? VOLUME

The shape of the roof should be designed in accordance with precipitation, solar impact and utilisation pattern (pitched, flat, vaulted, etc., figure 3.4-6). To keep roofs cool, they should be sloped towards the prevailing breeze and any obstructions that would prevent the airflow along the roof surfaces should be avoided.

3.4.4 ROOF AND WALL DESIGN FIGURE. 3.4-5 EFFECT OF THERMAL MASS ON THE BEHAVIOUR OF A BUILDING WITHOUT AIR CONDITIONING. THE HIGHER THE MASS, THE SMALLER THE FLUCTUATION AND THE LONGER THE TIME WITHIN THE COMFORT RANGE.

TABLE 3.4-1 ORDER OF MAGNITUDE OF TEMPERATURE DIFFERENCES BETWEEN CEILING UNDERSIDE AND INDOOR AIR FOR DIFFERENT COMBINATIONS OF LIGHT-WEIGHT ROOFS, AT THE TIME OF MAXIMUM SOLAR IRRADIATION ON A CLEAR DAY Source: J. Dreyfus, Le comfort dans I’habitat en pays tropical, Eyrolles, 1960

FIGURE. 3.4-7 ROUNDED ROOFS GENERATE THEIR OWN SHADE THROUGHOUT THE DAY (LEFT) AND RE-EMIT THE HEAT OVERNIGHT (RIGHT)

FIGURE. 3.4-9 VENTILATION OF THE SPACE BETWEEN ROOF AND CEILING A sloping roof with wall shading overhangs and a well-ventilated space between roof and ceiling is also an appropriate solution, provided that the ceiling below the roof is massive (e.g. concrete a minimum of 10-15 cm thick, covered with 5 cm insulation, figure 3.4-13). If, instead of aluminium, galvanised corrugated sheets are used, insulation thickness has to be increased by at least 3 cm. In both cases a reflective surface on the insulation layer or in the lower surface of the roof would improve the performance.

In ventilated roofs like the ones shown in figures 3.4-8 and 3.4-9, the heat between the two skins is removed by the airflow crossing the roof space through openings facing the prevailing winds. The outlet opening should be larger than the opening for the inlet; they should also be placed at different heights in order to obtain air movement by the stack effect when the wind is not blowing. The heat load is reduced by ventilation in the daytime and rapid cooling is allowed at night. In ventilated roofs of the kind shown in figure 3.4-9, roof slopes should be oriented towards the prevailing breeze.

3.4.4.2 WALLS FIGURE. 3.4-14 TOP: FLAT ROOF; BOTTOM: VENTILATED DOUBLE ROOF WITH HEAVY CEILING

3.4.5 OPENINGS IGURE. 3.4-19 FLOORS SHOULD BE DARK-COLOURED IF MASSIVE; LIGHT-WEIGHT FLOORS SHOULD BE LIGHT -OLOURED, TO REFLECT THE SOLAR RADIATION ONTO MASSIVE SURFACES.

Source: Chandra, Subrato, Philip W. Fairey, and Michael M. Houston. 1986. Cooling with ventilation, Solar Energy Research Institute. http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR- 1658-86. pdf

FIGURE. 3.4-22 A KITCHEN-IN-CHIMNEY ONCE USED IN TRADITIONAL HOUSES IN THE ITALIAN ALPS In climates where the cool season is mild, the approach shown in figure 3.4-24, where natural ventilation is enhanced by perforated walls, can be considered.

FIGURE. 3.4-24 A KITCHEN IN PARAGUAY. Source: B. Westhoff, D. Germann, Stove Images, Brandes & Apsel Verlag, 1995

FIGURE. 3.4-23 A WOOD OR CHARCOAL COOKSTOVE AND A HOOD TO EXTRACT SMOKE IN AN OLD TRADITIONAL KITCHEN IN SICILY

FIGURE. 3.5-10 EFFECT OF A HORIZONTAL OVERHANG ABOVE THE OPENING

FIGURE. 3.5-13 VENTILATION, WITH WING WALLS, IN ROOMS WITH ONLY ONE WALL FACING OUTSIDE AND TWO OPENINGS ?1 +N. K. Bansal, G. Hauser, G. Minke, Passive building design: a handbook of natural climatic control, Elsevier science, 1994

Adapted from: N. K. Bansal, G. Hauser, G. Minke, Passive building design: a handbook of natural climatic control, Elsevier science, 1994

Adapted from: N. K. Bansal, G. Hauser, G. Minke, Passive building design: a handbook of natural climatic control, Elsevier science, 1994 Effect of verandas The values of internal air speed deriving from figure 3.5- 16 change if the location of windows is changed, i.e. if they are not centred and opposite. For a given external wind velocity, the value of the average internal air velocity must be corrected according to Table 3.5-1.

Source: N. K. Bansal, G. Hauser, G. Minke, Passive building design: a handbook of natural climatic control, Elsevier science, 1994

Adapted from: O.H. Koenisberger, T.G. Ingersoll, A. Mayhew, S.V. Szoklay, Manual of tropical housing and building, Longman, 1975

Source: G.Z. Brown, M. DeKay, Sun, Wind & Light, Wiley, 2001

Source: G.Z. Brown, M. DeKay, Sun, Wind & Light, Wiley, 2001 FIGURE. 3.5-24 SPINNING WIND CATCHER

Enter the design wind speed on the vertical axis of the graph, move horizontally until the curve for the required ventilation airflow rate is intercepted; then drop to the horizontal axis to read the size of inlet as a percentage of floor area.

FIGURE. 3.5-27 INDUCED VENTILATION: CHANNELLING AIRFLOW

FIGURE. 3.5-26 INDUCED VENTILATION: STACK EFFECT

FIGURE. 3.6-2 IN A HOT-HUMID CLIMATE OVERHANGING ROOFS HELP TO REDUCE THE GLARE FROM

FIGURE. 3.6-1 OPENING TYPES ALLOWING THE REDUCTION OF GLARE IN A HOT-ARID CLIMATE

FIGURE. 3.6-4 EVALUATION OF THE ROOM DEPTH PAST WHICH THERE IS NO DIRECT VIEW OF THE SKY To obtain the total area of the window, including frames and mullions, in a first approximation multiply by 1.20.

The minimum depth of an external light shelf is determined by the shading requirements; the deeper the shelf, the better it shades the window below, preventing the penetration of direct radiation, which causes glare and solar gains. For the interior light shelf, the limiting factor is still the glare; i.e. it is necessary to prevent the penetration of direct radiation.

The depth of the internal light shelf can be extended so as to always intercept the direct radiation through the window above; in the case of east or west-facing windows it may happen that direct radiation is able to penetrate the space between the light shelf and the ceiling, and then it becomes necessary to provide some means of shading. At low latitudes, if the south or north-facing light shelf is tilted upwards (Fig. 3.6-9), the contribution of natural light increases, but the exterior part must be extended to provide satisfactory window shading. The optimum tilt angle, at latitudes near the equator depends on the ratio of X/H, according to figure 3.6-10. The use of a light shelf - if the glass ribbon above it is appropriately sized and the depth of the internal shelf is such that it prevents direct radiation into the space - allows natural lighting to be ensured even when, to avoid glare, the glass area below is protected with a sunscreen. For south-east or south-west (north-west or north-east) facing facades, the resulting depth of the inner shelf may be excessive; in this case a series of smaller shelves, properly spaced, can be used, (Fig. 3.6-11).

FIGURE. 3.6-14 VENETIANS WITH REFLECTIVE BLADES TO REDIRECT THE LIGHT

FIGURE. 3.6-13 LIGHT SHELF WITH PROFILED SURFACE 3.6.2.2 VENETIAN BLINDS WITH REFLECTIVE SLATS Venetian blinds are a classic system for controlling sunlight, but they can also be used to redirect it. In some cases, the slats have sophisticated shapes and surface finishes.

FIGURE. 3.7-2 PEG'S SHADOW CAST ON A SUNDIAL

There are many methods for evaluating the shadows cast on a surface by projecting elements or by surrounding obstructions, based on the use of diagrams or on analytical tools.

FIGURE. 3.7-5 ANGULAR COORDINATES OF A SHADING OBSTRUCTION

FIGURE. 3.7-4 EVALUATION OF SHADOWS CAST BY OBJECTS USING THE SUNDIAL

In order to use the diagram, the vertical lower semi-axis (from the centre to point B) must be overlaid onto the line perpendicular to the facade drawn in plan at the point being considered. Furthermore, the diameter A-A’ must be aligned with the profile of the facade. In this way it is possible to obtain the so-called shading masks by tracing the profile of the obstructions on the polar diagram. When the solar path falls within the area of the solar obstructions , that is, inside the mask, the observer is shaded (Fig. 3.7-6).

FIGURE. 3.7-9 CONSTRUCTION OF THE SHADING MASK FOR A VERTICAL OVERHANG

The hatched areas of the diagram represent the portions of the sky dome obstructed by the shading elements (the upper semicircle represents the obstruction of the building to which the facade belongs).When the masks obtained on the solar chart of the site are overlaid, the times of day when the observation point is shaded can be found (Fig. 3.7-11). In the previous examples, situations corresponding to facades oriented exactly south were shown. It is, of course, always possible to consider any other orientation by rotating the protractor and aligning the lower vertical semi-axis with the facade. For example, in the next picture (Fig. 3.7-12) a horizontal obstruction on a south-west facade is displayed.

FIGURE. 3.7-11 OVERLAYING THE SHADING MASKS ON THE POLAR DIAGRAM FIGURE. 3.7-12 ORIENTATION OF THE SHADING MASK

FIGURE. 3.7-13 SAMPLE OF SHADING MASK FOR A VERTICAL AND HORIZONTAL OVERHANC

East and west-facing facades are harder to protect than those facing north and south, because of the low position of the sun in the morning and afternoon. Vertical fins, which are usually recommended for east and west orientations at latitudes above 40°, are less suitable in the tropics, because they need to be tilted in order to give effective protection ,and so preclude the exterior view. Solar gains are controlled most effectively with sunshades outside the windows (Fig. 3.7-16 and Table 3.7-1). As the sun is always high in the sky at the equator, horizontal shading devices are the optimal choice for north and south-facing fagades. Horizontal overhangs located above the windows on the north and south-facing fagades are very effective and should extend beyond the width of the window to shade it properly. Horizontal overhangs on the east and west-facing windows need to be very deep for protection in the early morning and in the late afternoon, and are not recommended.

FIGURE. 3.7-15 CALCULATION SCHEME FOR VERTICAL AND HORIZONTAL OVERHANGS

FIGURE. 3.7-18 THE SHADING EFFECT IS A FUNCTION OF THE RATIOS 4/d AND w/d. IT IS NOT A FUNCTION OF THE ACTUAL SIZE

FIGURE. 3.7-17 SINGLE OR MULTIPLE HORIZONTAL SOLAR PROTECTION OF A WINDOW (SECTION). THE SHADING EFFECT IS A FUNCTION OF THE ANGLE a. IT IS NOT A FUNCTION OF THE ACTUAL SIZE

FIGURE. 3.8-1 SOIL TREATMENT WITH WETTED PEBBLES Source: S. Alvarez Dominguez et al., Control climatico en espacios abiertos, Ciemat, 1992 Natural air cooling systems are usually subdivided into wo categories: those based on the adiabatic humidification process and those exploiting the low temperature of the subsoil (which is lower than air temperature in cold and emperate climates in summer). The latter is not suitable for hot-humid climates because the temperature of he subsoil, up to a depth of 3-4 m is very close to air emperature. In hot-arid climates, where the outdoor air emperature during daytime is higher than that of the subsoil, the system would only be effective for one-two weeks, which is the time taken for the soil around the buried pipes to warm up. To avoid this effect it would be necessary for the system to work during nighttime, when cooler outdoor air would cool down the subsoil around the pipes, but the effect would be to warm up the air entering the indoor spaces?’. Alternatively, the evaporative cooling principle can be exploited, as shown in figure 3.8- 1, where the underground soil is cooled by keeping it wet. The evaporation cools down the soil and the gravel or pebble layer protects it from solar radiation.

FIGURE. 3.8-3 EVALUATION OF OUTLET TEMPERATURE IN THE TOWER

Source: http://www.melbourne.vic.gov.au/Sustainability/CH2/DesignDelivery/Documents/CH2_Snapshot6.pd

Source: P. Torcellini, R. Judkoff, and S. Hayter, Zion National Park Visitor Center: Significant Energy Savings Achieved through a Whole- Building Design Process, proc. ACEEE, 2002

FIGURE. 3.8-7 PRINCIPLE OF INDIRECT EVAPORATIVE COOLING; A) OPEN CIRCUIT; B) CLOSED CIRCUIT In an urban environment, due to the noise of the external traffic, it is very often not possible to keep the windows open for natural ventilation. Consequently, even in those periods when the outside air temperature is such that, with adequate ventilation, the air conditioning should not be needed, it becomes necessary to use it. This is the case especially in workplaces where the internal loads due to equipment are significant or where it is not possible to adequately protect the interior space from solar gain.

Recently a Tanzanian brick has been introduced, whose shape lies — in complexity — between the Hydroform and the Bamba bricks (Fig. 3.9-3).

FIGURE. 3.10-4 LIGHTWEIGHT CONSTRUCTION WITH VENTILATED ROOF, OPERABLE WALLS AND SHADED OUTDOOR PORCHES, RAISED ABOVE GROUND These are very good and recommended for dwellings. They are rainproof, allow good ventilation and are secure against thieves. They are not satisfactory in rooms where a high level of daylighting is required, such as classrooms.

FIGURE. 3.10-5 PROVIDE SOLAR ACCESS DURING THE COLD SEASON AND MID-WEIGHT ENVELOPE

FIGURE. 3.10-6 LET THE SUN IN DURING THE COLD SEASON FOR PASSIVE HEATING 3.10.7 PROVISIONS FOR SCHOOLS AND OFFICES BUILDINGS

FIGURE. 3.11-1 HEHE TRADITIONAL HOUSE Source: http://www. flickr.com/search/?q=hehe%20house The roof construction is an interesting compromise between the steeply-pitched, thatched, ridge-pole roofs found in the wet areas of Malawi and the domed, mud covered huts of the dry Masai country. Instead of ridge- poles, these huts have a pair of purlins set on either side of the centre point to allow the rafters to be bent over in a continuous curve, eliminating the ridge. The rafters project to form overhanging eaves, which protect the mud covered vertical walls.

Source: http://en. wikipedia.org/wiki/Chaga_people Houses in Kakamega province, Kenya

Photo credit: courtesy H. Fiebig — 50 treasures of Kenya - http:// thetreasureblog.wordpress.com/2013/05/3 1/kakamega/

Source: May J., Buildings without architects a global guide to everyday architecture, Rizzoli International Publications, New York, 2010

FIGURE. 3.11-4 WOODEN KIKUYU HOUSE Source: http://www. fr.enhols.com/safari-photo-album/view-african- photos.aspx?L=En&aid=25

Huts are built of whatever thorn bushes, brushwood and trees are available in the area. In the plains, huts are usually built using thorn bushes interlaced with leafy vegetation. In the mountains, boughs of trees and thicker foliage are used, while in the relatively arid parts of central Turkana land, it is mainly palm leaves that are collected for construction; these provide shade and at the same time allow ventilation. In the rainy season huts are covered with animal skins, which are fixed with stones or pieces of wood, or fastened with leather thongs; where there is plenty of grass, straw is sometimes used.

FIGURE. 3.11-6 ROUND HUTS AT LAKE VICTORIA 3.11.1.4 HOT SEMI-ARID/SAVANNAH CLIMATE ZONE

Photo credits: the apostrophe, http://www. flickr.com/photos/ dirty_dan/4312427571/

Source: Mwakyusa A.T.H., Traditional and contemporary building styles used in Tanzania and to develop models for current needs, A dissertation submitted in partial fulfillment of the requirements for the award of the degree doctor of philosophy, St. Clements University British West Indies, 2006

FIGURE. 3.11-10 NYAKYUSA TRADITIONAL HOUSE: MAIN RECTANGULAR HOUSE AND ROUND HOUSE (WIFE'S HOUSE) Source: Mwakyusa A.T.H., Traditional and contemporary building styles used in Tanzania and to develop models for current needs, A dissertation submitted in partial fulfillment of the requirements for the award of the degree doctor of philosophy, St. Clements University British West Indies, 2006

FIGURE. 3.11-9 MASAI, KENYA: THE ENVELOPE IS MADE WITH COW DUNG AND ASH OVER A STRUCTURE IN WOOD AND THATCH The Nyakyusa house of Southern Tanzania, found in Mbeya Region, uses bamboo in all its elements ( walls, roof and ceiling), is rectangular in shape and has a pitched and gable roof (Fig. 3.11-10).

Photo credit: Graham‘n‘Judy, http://www. flickr.com/photos/ grahamcole1/5401688845/lightbox/

FIGURE. 3.11-15 MUD BONDED WITH STICKS AND REEDS APPLIED TO A FRAME MADE OF WOOD

Source of Burundi hut: http://www.skyscrapercity.com/showthread. php?t=978522

FIGURE. 3.11-16 RECTANGULAR SHAPED HOUSES: THATCHED AND IRON ROOFS Mud bricks, made trom a mixture mix of clay, water and straw and dried in the sun, are also used. Mud bricks are cheap and keep warm in winter and cool in summer as hey provide thermal mass. Houses built of mud or with mud bricks are vulnerable to heavy rains and flooding. The overhang of the thatch roof is used to shade and protect he walls from rainfall and the house is constructed on stilts, which prevents it from being flooded during the wet season. Houses are not equipped with windows. The hatched roof is about 25-30 cm thick and is made of palm eaves and grass. It helps to mitigate thermal conditions, providing good insulation and maintaining warmth during he cool nights. The houses show adequate strategies to ace the climatic conditions, such as sun protection due to he roof and thermal mass due to the walls being made of clay and straw. More recently, ventilation has been improved by the addition of some openings; however, iron sheets are less suitable for roofing because they make the house uninhabitable when the sun shines and are noisy when it rains.

Photo credit: Maria Chiara Pastori FIGURE. 3.11-17 SWAHILI TRADITIONAL HOUSE IN KIGAMBONI (DAR ES SALAAM, TANZANIA)

FIGURE. 3.11-18 ORIGINAL TOWN PLAN OF NAIROBI, 1900, SHOWING THE RAILWAY LINE/STATION AND PRESENT MAP OF THE CITY Source: (top) Hake A., African Metropolis, Sussex University Press, 1977; (bottom) http://nairobiarch638.wordpress.com/

FIGURE. 3.11-19 PLAN OF THE COLONIAL AREA OF DAR ES SALAAM IN THE MID 19'¥ CENTURY (TOP) AND TODAY (BOTTOM)

Source: Mweu M., Colonial public architecture in Nairobi, Kenya: an environmental analysis, M.Phil.Essay 01, Architecture and History of Art Library (The Martin Centre), 2001

FIGURE. 3.11-22 RAILWAYS BUILDING WITH DEEP ROOF OVERHANGS AND EARTH COLOURED FINISHES

The City Hall building (Fig. 3.11-24), with its elongated plan shape and the south facing main facade, exploits the street layout to the best advantage. Heavy masonry walls (60 cm thick) built with hand hewn blocks of trachyte tuff were invariably used, with several advantages:

FIGURE. 3.11-27 THE HIGH COURT OF TANZANIA, DAR ES SALAAM: VIEW FROM THE STREET, PORTICO AND GALLERY SHADED TO REDUCE SOLAR GAINS The building has two storeys and the load-bearing walls are made of coral stones set in lime mortar.

FIGURE. 3.11-26 LARGE OPENINGS AND VERANDAS FOR NATURAL VENTILATION In the High Court Building in Dar Es Salaam (Fig. 3.11- 27), the ground floor is higher than the other floors for representative purposes. This feature turns into an advantage for the ventilation of the indoor spaces through the elongated windows, which are composed of different operable portions and wooden blinds to allow ventilation as well as preserving privacy and protecting from solar radiation.

Source: Anthony B. Almeida, Tanzania Revenue Authority building, in Kakuru Linda, Mosha Comfort, Nestory Rose, Theme:Mapping the Stars of Dar, Star Buildings, Star Places, 2011

Legend: NFRC = National Fenestration Rating Council; SHGC = Solar Heat Gain Coefficient; VT = Visual Transmittanc FIGURE. 4.1-1 SOLAR RADIATION TRANSMITTANCE THROUGH DIFFERENT TYPES OF GLASS.

Long-wave radiant heat has considerable weight in the overall energy balance of glass, thus reducing it dramatically improves the performance of glass in cold climates. For this reason low-emissivity films are used. Standard glass has an emissivity equal to 0.84 in the far infrared, which means that it emits 84% of all the energy that can theoretically be emitted by radiation; since the value of the emissivity coincides with that of absorption it also means that when a flow of radiant energy in the far infrared strikes the glass, it absorbs 84% of radiant energy and reflects 16%. Glass protected by a low-emissivity film, however, has an emissivity of about 0.04, so this glass emits only 4% of the radiant energy that it can theoretically emit, and reflects 94% of the radiation in the far infrared that strikes it; the radiation that comes from the inside is therefore almost totally returned, greatly reducing the losses. This property, which is extremely positive in cold climates and seasons, makes the low-e glass unsuitable or even useless in hot climates and seasons and constitutes an unjustifiable cost, as shown in figure 4.1-2. Since the solar radiation spectrum extends from ultraviolet to the near infrared, while objects at room temperature emit radiation in the far infrared, the ideal glass should be capable of transmitting the radiation in the visible range leaving the spectral distribution unchanged, so as to ensure the same colour perception that would occur in the absence of glass. It should also be capable of meeting other different (and contradictory) needs in the cold and the hot seasons. In the cold season, the ideal glass should be able to transmit the near infrared fraction of solar radiation indoors, to contribute to space heating, and it should be able to block the far infrared radiation emitted by heated rooms (Fig. 4.1-3, line 1); in the hot season, by contrast, the ideal glass should be able to block the near infrared component of solar radiation, to reduce the heat gain, and transmit the far infrared radiation emitted by the interior space (Fig. 4.1-3, line 2).

reduces the amount of solar energy passing through it, since the transmission of the radiation is lower over the whole spectrum, than that of clear glass. Grey and bronze glass, on the other hand, attenuates the radiation (low transmission), but does not alter the spectrum in any appreciable way. In order to meet the ideal requirements, glazing has evolved a great deal in recent years, but still has limitations, which must always be taken into account.

TABLE 4.1-1 INDICATIVE VALUES OF THE CHARACTERISTIC PARAMETERS OF SOME TYPES OF GLASS

Sloped surfaces help to soften glare. These surfaces should be light-coloured and provide an intermediate brightness between window and room surfaces, making an easier transition for the eye and thus reducing eye fatigue due to the contrast of luminance (Fig. 4.1-6). To maximize lighting and HVAC energy benefits, < whole building simulation should be conducted in order tc avaluate the total glazing area used for daylighting before a daylight scheme is finalised.

* J. O'Connor, Tips for Daylighting with Windows — The Integrated Approach, Berkeley, Ernest Orlando Lawrence Berkeley National Laboratory 1997. http://windows. IbI.gov/daylighting/designguide/designguide. html

Use separate apertures for view and daylight. A good approach for excellent daylighting and glare control is the separation of view and light windows. Use high transmission, clearer glazing in clerestory windows, and lower transmission glazing in view windows to control glare (Fig. 4.1-7). The daylight windows should be sized to provide the illumination required in the space when the view windows’ curtains are drawn. Large windows require better and more expensive glazing. The larger the window, the lower the solar factor and visible transmittance must be. The larger the window, the greater the need for high performance glass.

FIGURE. 4.1-10 FOR THE PURPOSES OF GLARE CONTROL AT EQUAL SUN PROTECTION CAPABILITY, HORIZONTAL BLADES RESULT IN A MORE UNIFORM ILLUMINATION Before selecting the external sunscreen to use, it is advisable to:

FIGURE. 4.2-2 GENERAL ARCHITECTURE OF AN HVAC PLANT

FIGURE. 4.2-1 EXAMPLE OF A THERMAL ZONES DIVISION IN A LARGE OFFICE BUILDING The functions of an HVAC plant can be accomplished by means of different configurations and components, which can be generally organized in five main subsystems:

FIGURE. 4.2-3 SCHEMATIC DIAGRAM OF ALL-AIR, ALL-WATER AND AIR-WATER SYSTEMS

FIGURE. 4.2-6 FOUR DIFFERENT FAN-COIL USES Induction Units The specific room spaces for fan-coils must be carefully considered as noise due to their fan may be a concern for occupants. Otherwise, these units are very flexible and a variety of products is available on the market, providing several aesthetic and technical solutions (Fig. 4.2-6), which are easily adaptable to heterogeneous contexts.

Chilled beams Another type of chilled beam is “active” (Fig. 4.2- 8, right); while the passive type relies solely on natural convection, the active type works as the induction unit. Active chilled beams are more effective for cooling than passive beams, because of the increased convection and air circulation within the building zone, and because they are coupled with the ventilation system, providing at the same time temperature and humidity control (ventilation air properties are first managed in an air handling unit and then channelled to the beam), but they consume more energy to operate.

FIGURE. 4.2-8 CHILLED BEAMS WORKING PRINCIPLE. PASSIVE (LEFT); ACTIVE (RIGHT)

FIGURE. 4.2-10 RADIANT CEILING AND PRIMARY AIR

Radiant ceilings consist of panels with embedded pipes (Fig. 4.2-9). Pipes can be either embedded in customized construction elements or in pre-cast construction components, such as false ceilings. disadvantage is that accurate humidity control is required to avoid condensation. Since these systems have no condensation drain, when the water circulated in the pipes is too cold and internal humidity is not controlled, serious condensation problems may occur, especially in hot humid environmental conditions. For this reason, such water terminal units must necessarily be combined with a good air handling system (Fig. 4.2-10). This type of cooling system is virtually maintenance-free and allows energy saving as long as water temperature is higher than in fan-coil systems, with reduced losses in the distribution subsystem and higher efficiency in generating chilled water. Radiant ceilings, by performing the cooling effect primarily through radiation, can provide a comparable comfort level at higher internal air temperatures, lowering the mean radiant temperature, thus enabling a more efficient operation. However, a

4.2.1.4 ENERGY RECOVERY FIGURE. 4.2-15 SCHEMATIC OF AN AHU (WHEN USED FOR SPACES WITH HIGH INTERNAL LATENT LOAD (THEATRES, CONFERENCE ROOMS, BALL-ROOM, ETC.) A REHEAT COIL MAY BE NECESSARY AFTER THE COOLING COIL)

In principle, a dual duct system has the same advantages and disadvantages as a multi-zone system, but it can be considered more flexible to changes in zoning requirements.

FIGURE. 4.2-17 CROSS FLOW HEAT EXCHANGER An enthalpy wheel consists of a rotating cylinder filled with an air permeable material with a large surface area, which is the medium for the sensible energy transfer. As the wheel rotates between the ventilation and exhaust air streams it picks up heat and releases it into the colder air stream. At the same time, the use of desiccant materials inside the wheel, such as silica gel, allows the transfer of moisture through the process of adsorption, which is predominately driven by the difference in the partial pressure of vapour within the opposing air-streams. Enthalpy wheels are the most effective devices for energy recovery but accurate system design and careful selection of appropriate components are needed in order to guarantee the wheel's durability.

FIGURE. 4.2-18 ENTHALPY WHEEL HEAT RECOVERY SYSTEM

In commercial buildings in tropical and subtropical regions, air-conditioning may be necessary throughout the year, and the latent cooling load is a large part of the total. For this reason, in order to increase energy efficiency, the recovery of the enthalpy (both sensible and latent energy) of the exhaust air is essential and can usually be performed by using a fixed plate energy exchanger (Fig. 4.2-17) or an enthalpy wheel (Fig. 4.2-18). In the first, two air-streams (inlet and outlet) flow in adjacent but separated ducts and exchange sensible and latent heat by using special materials which transfer sensible heat and are water vapour-permeable.

Several types of air terminal devices are available (Fig. 4.2- 21). The most common are:

FIGURE. 4.2-21 DIFFUSER AND REGISTER TYPES

Evaporative cooling can be used to enhance heat recovery; in evaporative cooling the heat exchanger’s exhaust air is cooled by spraying water on it before it enters the heat exchanger (Fig. 4.2-19).

hydronic terminal units) and transfers it to the external environment by means of a water cooled condenser; In the absorber, the concentrated liquid solution absorbs the vaporized refrigerant and the cooling water removes the vapour absorption heat. As the refrigerant vapour is absorbed the concentrated solution returns to a diluted state and is pumped to the generator, completing the refrigerant cycle.

FIGURE 4.2-28 OPEN COOLING TOWER (LEFT); CLOSED COOLING TOWER (RIGHT)

FIGURE. 4.2-30 DIRECT EVAPORATIVE COOLING.

FIGURE. 4.2-29 SCHEME OF EVAPORATIVE CONDENSER

FIGURE. 4.2-32 TWO-STAGE EVAPORATIVE COOLER

FIGURE. 4.2-33 INDIRECT EVAPORATIVE COOLING COUPLED WITH DIRECT-EXPANSION (DX) COOLING SYSTEM Since the systems use 100% outside air for cooling, they can also be paired with heat recovery to capture some of the energy that is lost in the exhaust air stream and reduce the ventilation cooling load.

The incandescent lamp exploits this principle; it comprises, apart from the filament, a transparent or translucent glass container that protects it, the filarnent supports and the screw base. The container is filled with an inert gas, typically a mixture of nitrogen and argon, which reduces the oxidation of tungsten, which must be avoided for two reasons: firstly, the erosion of the filament results in its cracking (this influences the life of the lamp); secondly vapours tend to be deposited on the inner wall, reducing its transparency (which translates into a reduction in the luminous efficacy). For this reason, the temperature is kept far below melting point, and this has a negative effect on the optical efficiency of the lamp, and thus on the luminous efficacy. Their operation range lies between 2700 and 3000 K and, since their spectrum is practically coincident with the black body spectrum, their colour temperature coincides with their operation temperature.

TABLE 4.2-3 COLOUR TEMPERATURE AND CLASS Metal halide lamps are high intensity discharge lamps, which are very efficient light sources that are more like incandescent than fluorescent lamps in size and shape. Like all discharge lamps they need a blast to work. The light is emitted from a small arc tube located inside a protective outer bulb. The relatively small size of this arc tube permits some optical control similar to that possible with a point source. When increased colour rendering is desired, metal halides are added to the mercury in the arc tube. The white light emitted by metal halide lamps is moderately cool, but there is enough energy in each part of the spectrum to provide very good colour rendering. Metal halide lamps are some of the best sources of light because they combine many desirable characteristics in one lamp: high efficacy (68-120 Im/W), long life (10000- 20000 hours), very good colour rendering, and small size for optical control. However, they are not generally suitable for interior lighting because their minimum power is rather high. Metal halide lamps

FIGURE. 4.2-39 LIGHT SPECTRUM AND EMITTED ENERGY OF INCANDESCENT AND FLUORESCENT LAMPS 8 The correlated colour temperature is the absolute temperature of a black body whose chromaticity most nearly resembles that of the light source.

FIGURE. 4.2-40 COMMON SHAPES OF FLUORESCENT

The Lighting Handbook, Tenth edition-Reference and Application, Illuminating Engineering Society, 2011

TABLE 4.2-4 LAMP PERFORMANCE AND OPERATING CHARACTERISTICS*

Luminaires are divided into five groups, in relation to the distribution of the luminous flux in the space above and below the horizontal plane passing through the centre of the unit (Fig. 4.2-42). Photometric curves

FIGURE. 4.2-46 MAINTAINING DESIGN ILLUMINANCE WITH ELECTRIC LIGHT SWITCHING IN LAYERED ZONES Artificial lighting can be controlled by a photosensitive cell so that it is automatically switched on or off when daylighting reaches a certain level or continuously dimmed so that electric lighting supplies just the supplemental light necessary to meet the illumination requirements. The use of automated daylight control can save 30-50% of the electric lighting energy in office buildings, often during a building's peak load times (Fig. 4.2-47).

Most timers are centrally located to turn lights on and off at a pre-set cycles. These are excellent whenever there is a regular schedule of activities.

Properly designed artificial lighting control can yield functional, aesthetic, psychological, economic and environmental benefits. Lighting control allows for the flexible use of spaces, as well as the creation of an interesting and varying lighting environment. Lighting control is also is one of the best ways to save large amounts of energy simply by allowing unneeded lights to be turned off. Lighting control generally requires the use of automatic devices, such as occupancy sensors, photo- sensors, timers, and remote switching equipment.

Evaluation of the depreciation factor is, therefore, quite complex, and should be performed only if it is possible to make reasonable predictions about the frequency of maintenance. In general, in a first approximation, the following values can be used, when other conditions are same: The illumination produced by a luminaire on the working plane is never uniform, unless it is indirect ighting; uniformity increases, however, with the increase of the distance between the work plan and the luminaire and with the increase in the number of devices. One can, herefore, identify an optimal ratio between the spacing D between the luminaires and the useful height h: D/h<7.5 and considering D’ < D/2, the distance between the extreme uminaires and the wall in case of direct illumination. In he case of linear luminaires, such as those with tubular luorescent lamps, the minimum spacing between the two contiguous extremes of the lamps in line, should be equal o at least half of the length of the luminaire.

TABLE 4.2-7 UTILISATION FACTOR OF TYPICAL LUMINAIRES (CONTINUED) * Note: Due to the wide variation in design and arrangement of prisms in optical controllers, the Utilization Factors shown for prismatic materials can only provide a general guide. Reference should be made to the manufacturers concerned for authoritative information.

*Mixture: value of lifetime depending on the specific composition TABLE 4.2-8 GWP AND LIFETIME OF DIFFERENT REFRIGERANTS

TABLE 4.2-10 ENERGY SAVING, COST SAVING AND CONSTRUCTION INDICATORS FOR THE DIFFERENT TYPES OF HVAC SYSTEMS

TABLE 4.2-9 BUILDING SERVICES, THERMAL COMFORT, INTERNAL AIR QUALITY AND ACOUSTIC INDICATORS FOR THE DIFFERENT TYPES OF HVAC SYSTEMS

TABLE 4.2-11 ENERGY CONVERSION TECHNOLOGIES

Source: Sustainable Architecture in Japan — The continuing challenge 1900-2010 & beyond, Nikken Sekkei, 201(

TABLE 4.4-1 APPROXIMATE Ro VALUES OF AIR CONDITIONED BUILDINGS IN HUMID TROPICAL CLIMATE Retrofit strategies to improve the energy and environmental performance of the building envelope are based on passive design (e.g. improvement of thermal quality of opaque envelope, control of solar radiation, etc.): this topic is treated in Chapter 4.

4.4.1.3 FENESTRATION When renovating existing buildings, it may be cost effective to install external sunscreens to reduce the effects o solar radiation on windows facing east or west. Internal blinds, even if they are opaque, have solar factors that are to high; these types of devices are not effective in preventing overheating due to solar radiation and are normally used fo protection from glare. There are several solutions for effective solar control, as shown in Table 4.4-6.

*Guidelines on energy audit, Energy Efficiency Office, The Government of the Hong Kong, 2007 - http://www.emsd.gov.hk/emsd/e_download/ pee/Guidelines_on_Energy_Audit_2007.pdf

4.4.2.3 IMPROVEMENT OF AIR HANDLING AND VENTILATION PERFORMANCE Table 4.4-9 shows how energy consumption due to the Air Handling Units (AHU) can be reduced.

Installation of zone control systems Control of the thermal energy output of the HVAC system is one of the most cost-effective measures for the reduction of energy consumption and the improvement of the thermal comfort of the occupants.

1.4.5 EVALUATION OF ENERGY SAVING POTENTIAL

FIGURE. 4.5-2 LUMINANCE DISTRIBUTION IN A WALL WITH A WINDOW (LEFT) AND RENDERING OF THE WALL AS IT APPEARS TO THE EYE (RIGHT)

FIGURE. 4.5-1 ILLUMINANCE DISTRIBUTION (ISOLUX CURVES), LEFT, AND RENDERING OF THE ROOM AS IT APPEARS TO THE EYE, RIGHT

1.6 ENERGY PERFORMANCE CERTIFICATES AND GREEN BUILDING RATING SYSTEMS

FIGURE. 4.5-3 SHADOWS ANALYSIS WITH ECOTECT

The biggest advantage of using this approach is that tt enables the design and construction teams to make comparisons between different design options to identify the most cost-effective and energy-efficient design solution. The energy performance evaluation method can be carried out either by simple calculations or by means of a dynamic simulation model (Fig. 4.6-3). Computer simulation of energy use can be accomplished with a variety of computer software tools and in many cases may be the best guide for making a building project energy- efficient. However, this approach does require considerable knowledge of building simulation tools and very close communication between members of the design team. FIGURE. 4.6-1 THE INGREDIENTS FOR ENERGY EFFICIENT BUILDINGS

FIGURE. 4.6-5 CLIMATIC ZONES IN BRAZIL There are five possible levels of energy performance of buildings: E is the lowest and A is the highest (Fig. 4.6- 6). The EPC does not define the upper limit of level A, since higher efficiency can always be pursued. In this respect, the demand for higher levels of efficiency includes commissioning. Commissioning is planning and executing projects to ensure that they effectively achieve the expected performance, correcting defects or adjusting equipment if necessary to achieve the proposed objectives. In Brazil 8 Bioclimatic zones were defined (Fig. 4.6-5), according to climatic data.

A rating for a specific building is typically valid for 10 years, unless there are major changes in that building, e.g. construction and alteration. This timeframe also takes into account the pace of technological innovation.

FIGURE. 4.6-7 EXAMPLE OF EPC LABEL INDIA”?

FIGURE. 4.6-9 INTERACTIONS TABLE [CIBLE = TARGET]. Source: CERTIVEA, Référentiel pour la qualité environnementale des batiments — Batiments tertiaires, 2012 - http://www.certivea. fr/assets/ documentations/9be0d-Guide_Generique_20-01-2012.pdf

Source: http://www.usgbc.org/leed/rating-systems Name of the Rating Scheme under LEED _—Applicatic

Once a project is registered, the applicant will have access to the USGBC’s LEED Online system. This system provides online templates that must be completed for each prerequisite and credit, and is used to upload supporting documentation. As the project progresses it is important to document necessary data. The LEED Online system also has credit interpretation rulings that provide technical answers to the questions officially submitted by other users. It is important to note that achieving some credits requires that the building be occupied for a certain period of time after construction. Once all of the documentation is assembled and the construction is finished, the documentation is submitted to the GBC! for review and certification. The entire LEED process typically takes anywhere from one to five years, depending on the type and requirements of the desired certification.

FIGURE. 4.6-10 LEED CERTIFICATION SCORECARD BREAKDOWN The number of credits available and the number of credits needed for each rating level varies with each rating scheme. When evaluating the credits, the cost of achieving each credit must be considered. The certification levels and the associated credit percentages achieved are shown in Table 4.6-5.

(Source: UN-Habitat - State of the World's Cities 2008/2009 - Harmonious Cities, Earthscan, 2008)

TABLE 5.1-1 ENERGY STORAGE TRANSFER LOSSES [%] Wastewater and solid wastes Recycling wastewater and solid wastes and using them as energy sources, is essential in an energy efficient city.

Adapted from: S. A. Alvarez et al., Control Climatico en Espacios Abiertos — Projecto EXPO ‘92, Secretaria General Tecnica del

FIGURE. 5.1-2. ENERGY CONSUMPTION BY SECTOR IN HOT/WARM CLIMATE Source: UN-Habitat - State of the World's Cities 2008/2009 - Harmonious Cities, Earthscan, 2008

5.2.5.1 SIZING THE RAINWATER STORAGE TANK

FIGURE. 5.2-4 BIOGAS PRODUCTION FROM SEWAGE WATER AT NEIGHBOURHOOD LEVEI When biogas is upgraded, bio-methane can be obtained. The possible uses of bio-methane into a network are equivalent to those of natural gas and can be summarized as follows: Before the final disposal, sludge has to be treated. Also in this case, treatments can be bio-chemical or thermal and the most common are anaerobic digestion and gasification.

Sources: http://www.ashden.org/winners/kistO5 and G. RNembrini, A. Kimaro, Using Biogas Plants for Treatment of Urban Community Wastes to Supply Energy and Improve Sanitation, presented at the Expert Group Meeting on “Energy Access for the Urban Poor”, December 2006, Nairobi

FIGURE. 5.2-6 FUNCTIONAL SCHEME OF THE PLANT

Adapted from: UN- Habitat, State of the World's Cities 2008/2009 - Harmonious Cities, Earthscan, 2008

FIGURE. 5.3-2 ORGANIC PERCENTAGE IN URBAN WASTE IN A SAMPLE OF CITIES, UN-HABITAT, 2008 5.3.4 WASTE TO MATTER AND WASTE TO ENERGY Apart from rational and general schemes of management, site specific factors should also be taken into consideration. These are as follows:

Photo credit (top): USFWS Pacific Southwest Region -http://www. flickr.com/ FIGURE. 6.1-3 PV ON PITCHED ROOF

crystalline silicon cells is rated between 180 and 260 W, (according to the quality of the cells).

Photo credit Laurent Lacombe - http://upload. wikimedia.org/wikipedia/commons/c/cf/Projet_BIPV_-_Gare_TGV_de_Perpignan.jpg; right: California Academy of Science, San Francisco, USA, Architecture: Renzo Piano Workshop

The flat solar collectors are a very simple concept: an absorbing plate, integrated with the pipes for the heat ransfer fluid, is placed into a box insulated at the back and along the sides. The absorber plate surface exposed o solar radiation is normally black, painted or “selective” a treatment that allows the performance to be improved hanks to the low emissivity in the far infrared). A ransparent cover, located in front of the plate, reduces he convective losses and, mainly, the radiative ones in the ar infrared (greenhouse effect). aN

FIGURE. 6.2-2 EVACUATED SOLAR COLLECTOR (MODEL SYDNEY)

FIGURE. 6.2-3 UNGLAZED SOLAR COLLECTOR The evacuated collectors consist of a series of evacuated glass tubes, each of which contains an absorber and pipes through which a heat transfer fluid flows. The vacuum reduces convection heat loss between the absorber and the glass, increasing efficiency and allowing temperatures in excess of 100 °C to be achieved. To increase the amount of solar radiation on the absorbing plate, some models of evacuated collectors are provided with a reflector foil, often appropriately shaped.

FIGURE. 6.2-6 PUMPED SOLAR WATER HEATING SYSTEMS (A) WITH SINGLE STORAGE VESSEL (B) WITH SEPARATE PRE-HEAT VESSEL

In cold and temperate climates, because of the low air temperature, in the absence of sun the water in the absorber can freeze, damaging it. To avoid this, the water circulating in the collectors is mixed with an anti-freeze liquid and goes to a heat exchanger situated in the storage tank, in a closed circuit (Fig. 6.2-6). Thus, the water coming from the mains is heated in the storage tank, from which it is delivered to the users according to their needs.

Usually, solar thermal systems are designed to provide about 70% of the hot water demand and the auxiliary heater provides the rest. To provide more than 70% would not be economically profitable. For this purpose, the size of the storage tank is about 50-70 liters per square meter of collector area. For a first estimate of the collector area needed in EAC climates, the graph in figure 6.2-8 can be used.

FIGURE. 6.2-7 SINGLE FAMILY, INTEGRATED STORAGE SOLAR DHW SYSTEM The graph gives the collector area needed to produce 100 litres/day of hot water at 40 °C, with an annual solar fraction76 of 0.7, as a function of the annual solar radiation incident on horizontal surface (see Appendix 4 for data). The area needed for production of different amounts of hot water is linearly proportional.

FIGURE. 6.2-10 MAIN COMPONENTS OF A SOLAR-POWERED DESICCANT COOLING SYSTEM

In the former, the most common, the rotation axis is horizontal and, therefore, the blades rotate in a vertical plane. A typical horizontal axis wind turbine generally has three blades (there are cases of two-bladed and single blade models). A rudder keeps the blades’ plane always facing the wind direction. A control system slows down or blocks the rotation speed when there is high wind. The COP (Coefficient of Performance, see chapter 4) of this system is about 0.5-0.6, i. e. very close to that of a solar system with absorption cooling. Therefore, for solar desiccant cooling also, the ratio of the surface of the solar collectors to that of the space to be conditioned ranges between 0.1 and 0.3.

In general, for installations on the roof, a few kW vertical axis turbines are recommended due to their low noise level. Because of the shape of the rotor these turbines have a very limited visual impact. The only downside is the higher than the average cost. Vertical axis wind turbines do not need a system to follow the variable wind direction, and for this reason they are generally very robust and durable, since they are mechanically simpler.

Since the power is a function of the cube of wind speed, it is not possible to evaluate the mean power obtainable by a given device simply by using the mean wind speed. Energy production depends on the wind speed distribution (wind duration curve, figure 6.3-4). An example can better highlight the importance of the wind duration curve. Let's take two extremes for a wind turbine whose diameter is 5m: In both cases the average wind speed in the period is 8 m/s. From the graph of fig. 3 it can be derived that in case a) the mean power produced is 2 kW and in case b) is 15.5/2 = 7.75 kW.

Adapted from: J. P Holdren, K. R. Smith, Energy, the environment, and health; in: UNDP. World Energy Assessment — Energy and the Challenge of Sustainability, 2000

Adapted from: B. Westhoff, D. Germann, Stove Images, Brandes & Apsel Verlag, 1995

Source: B. Westhoff, D. Germann, Stove Images, Brandes & Apsel Verlag, 1995 it rises up out of the top of the chamber directly onto the pot. If a “pot skirt” is used, the heat can be made to also go up the sides of the pot, further increasing the rate of heat transferral. The woodfuel is placed on a shelf at the base of the stove, using only the ends of the wood making fuel consumption more economical. This principle is applied in various different models; fuel saving is above 50% compared to a three stone fire. A type of fixed rocket stove is shown in figure 6.4-6. More advanced designs employ metal, bricks and cement and are generally used for fixed stoves. The most popular type of fixed and movable stove is the “rocket stove”. It is scalable and comes in a multitude of forms, all using the same principle and adapting it to the capacity requirements and purpose of the stove. The principle of the rocket stove, as shown in figure 6.4-5, is a narrow combustion chamber in the form of an elbow which sucks in air at the bottom, heats it, and as it is heated,

FIGURE. 6.4-6 BRICK ROCKET STOVE 6.4.1.2 KITCHEN STOVES The Rocket Lorena is a domestic clay-based, wood-fired stove which can be made to take more than one pot (Fig. 6.4-7). The benefits of the model are that all smoke is expelled out of the indoor area through the chimney; it also cooks efficiently, cutting down fuel consumption. The Rocket Lorena can also be fuelled using briquettes made from animal dung. The Jiko Janja is similarly designed but constructed using brick and cement.

A fireplace heating system consists of a high-efficiency fireplace (whose combustion temperature is increased with the use of a glass shield closing the firebox), equipped with fans to circulate heated air and an air-to-water heat exchanger usually placed in the upper part of the combustion chamber (Fig. 6.4-9). Moreover, in some products, an additional fraction of energy can be recovered thanks to the water circuit, by which cold water is circulated by a pump in the heat exchanger and used for heating purposes or to produce DHW.

FIGURE. 6.4-10 HEATING WOOD STOVE WITH AUTOMATIC FUEL AND COMBUSTION CONTROL Problems related to environmental pollution due to the smoke produced by fireplaces and wood burning heating stoves must be given careful consideration. If automatic fuel and combustion control systems can assure optimal burning in all operating conditions, this will significantly reduce airborne particulate.

TABLE 6.4-1 BIOMASS CLASSIFICATION ACCORDING TO THE SUPPLY SECTOR Source: European Biomass Industry Association - http://www.eubia.org/index.php/about-biomass/biomass-characteristics

Adapted from: P. Caputo, Impianti a biomassa. Dal riscaldamento alla trigenerazione. Edizioni Ambiente, Milano, 2011

Source: European Biomass Industry Association - http://www.eubia.org/index. php/about-biomass/biomass-characteristic. TABLE 6.4-3 SOME CHARACTERISTICS OF BIOMASS FUELS COMPARED TO OIL AND COAL

Source: European Biomass Industry Association - http://www.eubia. org/index.php/about-biomass/biomass-characteristics) 6.4.2.2 AVAILABLE AND APPLICABLE TECHNOLOGIES FOR TRANSFORMING BIOMASS INTO ENERGY

FIGURE. 6.4-13 SKETCH OF DOWNDRAFT (A) AND UPDRAFT (B) GASIFIERS

Adapted from: C. Roth, Micro Gasification: Cooking with gas from biomass, GIZ HERA, 2011

FIGURE. 6.4-15 SCHEME OF A BIOGAS DIGESTER.

Adapted from: F. Cotana and D. Giraldi, Renewable energy for agricultural companies: a biogas micro-chp project - http://www. ciriaf. it/ft/File/Pubblicazioni/pdf/1447. pdf

The Turgo turbine (Fig. 6.5-2) is similar to the Pelton but he jet strikes the plane of the runner at an angle (typically 20°) so that the water enters the runner on one side and exits on the other. Therefore the flow rate is not limited by he discharged fluid interfering with the incoming jet (as is he case with Pelton turbines). As a consequence, a Turgo urbine can have a smaller diameter runner than a Pelton or an equivalent power.

Reaction turbines exploit the oncoming flow of water to generate hydrodynamic lift forces to propel the runner blades. They are distinguished from the impulse type by having a runner that always functions within a completely water-filled casing. All reaction turbines have a diffuser known as a ‘draft tube’ below the runner through which the water discharges. The draft tube slows the discharged water and reduces the static pressure below the runner and thereby increases the effective head.

FIGURE. 6.5-5 KAPLAN TURBINE The Francis turbine (Fig. 6.5-6) is essentially a modified form of propeller turbine in which water flows radially inwards into runner and is turned to emerge axially. For medium-head schemes, runner is most commonly mounted in a spiral casing with internal adjustable guide vanes.

Adapted from: S. Sangal, A. Garg, D. Kumar, Review of Optimal Selection of Turbines for Hydroelectric Projects, International Journal of Emerging Technology and Advanced Engineering, Volume 3, Issue 3, March 2013

FIGURE. 7.1- 2 GRAPH REPRESENTING THE NET ZEB BALANCE CONCEPT Adapted from: K. Voss, |. Sartori, E. Lollini, Nearly-zero, Net zero and Plus Energy Buildings — How definitions & regulations affect the solutions, REHVA Journal — December 2012

TABLE 7.1-1 GIVES AN OVERVIEW OF RELEVANT TERMINOLOGY ADDRESSING ENERGY USE IN BUILDINGS AND THE CONNECTION BETWEEN BUILDINGS AND ENERGY GRIDS. Adapted from: K. Voss, |. Sartori, E. Lollini, Nearly-zero, Net zero and Plus Energy Buildings — How definitions & regulations affect the solutions, REHVA Journal — December 2012 In a ZEB some form of electricity storage (physical or virtual) has to be provided. Physical storage could be thermal , which is already used for both heating and cooling. Or it could be the storage of the energy that can be obtained by the integration of non-predictable energy production systems, like solar and wind, with systems that Virtual storage is that obtainable by means of sophisticated control systems, enabling the operation (or/off) of the electrical appliances and of the HVAC system, according to the weather, the needs of the grid, instantaneous kWh cost, etc., minimising the supply- demand mismatch as much as possible. a fuel mix that — at that moment — is generating more CO, per kWh than the average). The ideal is that a ZEB should not only minimise the load match index, but should also supply energy to or absorb it from the grid at the time that is most convenient (economically or environmentally). can be modulated according to the needs, such as gas or biomass CHP. In the case of gas, the fossil primary energy consumed can be balanced with the surplus production from the renewable energy system.

97 ttp://www2.aiatopten.org/hpb/searchby.cfm?search=Location

If the design and construction of a zero energy residential building is a challenge, requiring high level integrated design, the challenge with commercial buildings is even bigger, due to the greater complexity of their architecture and mechanical systems. For this reason the number The Hawaii Gateway Energy Centre (HGEC)®” complex is situated on the south coast of Kona on the Big Island of Hawaii (lat. 20° N, tropical climate). It serves the Natural Energy Laboratory of Hawaii (Fig. 7.1-3). The complex houses administrative office space, rest rooms, support areas, and a large multi-purpose space used for displays, outreach, conferencing, and education. It has a total floor area of about 335 m2.

FIGURE. 7.1-4 HAWAII GATEWAY ENERGY CENTER ENERGY BALANCE; 2007 DATA Locally manufactured construction materials used for HGEC include lava rock, concrete, and concrete masonry units. Although these materials did not meet LEED credit criteria for local materials, the production plants are located within 25 miles of the project, significantly reducing the energy embedded in their transportation. These materials are also inherently durable and should require no regular maintenance. Construction materials with post-industrial or post-consumer recycled content include steel, thermoplastic olefin (TPO) roofing, copper roofing, thermal and acoustic insulation, gypsum board, carpet, resilient flooring, and counter tops. Indoor finishes emit low or no volatile organic compounds (VOCs). Carpet tile was used in lieu of glue-down carpet in the multi- purpose space, and gravity-laid resilient flooring was used in the administrative areas.

Picture credits: Jerome Balleydier FIGURE. 7.1-8 NATURALLY VENTILATED CLASSROOM IN ENERPOS. THE CROSS-VENTILATION IS ADJUSTABLE, THANKS TO MANUALLY OPERATED LOUVRES ON BOTH SIDE OF THE CLASSROOM. EFFICIENT CEILING FANS PROVIDE THE REQUIRED AIR VELOCITY OF 1M/S TO ENSURE THERMAL COMFORT DURING WINDLESS DAYS The main feature of the building is the use of passive means and natural resources such as sun and wind to achieve thermal and visual comfort. Active energy consuming systems such as air-conditioning and artificial lighting should be used as a last resort.

FIGURE. 7.1-7 VIEW OF THE GREEN PATIO COMPOSED WITH NATIVE AND EXOTIC SPECIES Picture credits: Aurélie Lenoir

The building integrated photovoltaic roof covers an area of 350 m? and enabled, in the same period the production of 104 kWh of electricity per square meter of the building’s floor area, with a net surplus of 90 kWh/m?. The building thus produces about seven times more electricity than its own consumption.

The ZEO building uses integrated design concepts where active energy and passive energy systems are interwover into the office building. Several building elements alsc serve as the energy systems of the building. These methods help to mitigate the extra costs of construction (its cos’ was 20% to 30% more than conventional Malaysiar office buildings).

The Malaysia Energy Centre (Pusat Tenaga Malaysia) was established to fulfil the need for a national energy research centre that can co-ordinate various activities, specifically energy planning and research, energy efficiency, and technological research, development and demonstration.

Source: Courtesy Bill Dunster Architects

Key takeaways

Knowledge of solar geometry is very important for architectural design and energy efficiency strategies, since solar energy greatly influences the energy performance of buildings.
Low energy urban design means that shading and illumination of surfaces as well as wind must be analysed so that shape, orientation and distances between buildings can be optimised in order to control solar radiation and ventilation, with the aim of reducing the energy demands of individual buildings.
The temperature inside the buildings is almost constant throughout the 24 hours and thermal comfort is entirely dependent on solar protection and natural ventilation.
In air systems, air is ducted into the different thermal zones of the building to transfer thermal energy and/or to provide ventilation.
"Energy performance" is defined as the calculated or measured amount of energy needed to meet the energy demands associated with a typical use of the building, which includes, inter alia, energy used for heating, cooling, ventilation, hot water and lighting.

Log In

SUSTAINABLE BUILDING DESIGN FOR TROPICAL CLIMATES Principles and Applications for Eastern Africa

Sign up for access to the world's latest research

AI-generated Abstract

Figures (399)

Key takeaways

Related papers

Related papers