1 BACKGROUNDIn India,33% of the total energy consumption happens in the building sector (1) andprimarily due to the cooling load requirements of summer season which add up toenvironmental pollution, resulting in global warming and ozone depletion.It hasbecome need of the hour to promote passive cooling techniques, to achieve thethermal comfort, thus reducing the air conditioning requirement and for theperiod for which it is generally used.Productivityand satisfaction of indoor building occupants is greatly influenced by thethermal comfort. The interactions between people and thermal environment arestudied through various factors which vary independently of each other.Fanger,P.
O, has developed a concept combining thermal effect of all physicalfactors which create thermal comfort. By means of this comfort equation, it ispossible, for any activity level and any clothing, to calculate airtemperature, air velocity and humidity values which create thermal comfort.(Fanger,P.O, 1970,P 244).Thispaper aims to study the heating and cooling loads of an 80 sqm library space inMumbai, India, known to have a warm and humid climate and work out a designsolution to comparatively a balanced interior solution.To carryout a solution for thermally comfortable indoor space, it is very important tounderstand the climatic conditions of the site and its impact on the any space.This paper analyses the most crucial factor, i.e.
the climatic conditions with respect to thethermal comfort and approaches the space with improvements of an energyconservation design strategy. Mumbai (Latitude: 19.12° N, Longitude:72.
85 ° E, Elevation: 14 MASL) Figure1 India map on Koppen climate classification Image source: Köppen-Geiger,2006 Figure 2 Image source: meteoblu,2017 The climate inMumbai is predominantly warm and humid. Although temperatures are not very highin summer, conditions are uncomfortable due to the high humidity. Mumbai has a tropical climate. When compared with winter, thesummers have much more rainfall. According to Köppen and Geiger, this climateis classified as a tropical savanna climate (Aw) (Figure 1) Figure 3 Image source: meteoblu,2017 It can be best described as moderately hot with high level ofhumidity. The average annual temperature is 26.8 °C in Mumbai.
In a year, theaverage rainfall is 2386 mm.1May is the hottest month with the monthly average daily maximum temperaturereaching as high as 38 °C, coupled with a humidity of about 60% during daytime.(Figure 2,3). Hence, reducing heat gain and promoting heat loss becomesessential to maintain a thermally comfort environment in a space with warm andhumid environment.
Further calculations for heat load are carried out in this paper to analyse therange of heat gain and thus, provide better alternatives for designing anefficient and thermally comfortable space.3. BUILDING AND OCCUPANTS (Base-casemodel)The work inthis essay aims to investigate the energy consumption and thermal comfort in asmall space. It focuses on 80 sq.
mt library room in Mumbai, India, built insidea residential building. (Figure 5). The space dimension is broadly 8m façade by10m depth with a height of 4m.
The density of occupants is 5sq.mt per person(Neufert,2012). The occupants clothing coefficient is 0.6 clo for summer seasonand 1 clo for winter, while their metabolic rate is set to 1.3 met and 1.
4 metfor the summer and winter season respectively (CIBSE 2015; Building Directorate2013).The weather was data was found on the govt officialsites and from the epw file from EnergyPlus.This was later used in the climate consultant.Heat balance equation (Welsh School of Architecture, 2017), is used toinvestigate the energy balance and thermal comfort of the library in steadystate where the thermal mass of the space structure is omitted.The equation states:HEAT BALANCE EQUATION From the calculations it can be noted thatannually there is a heat gain of 242.38KW and thus, cooling is requiredthroughout the year.DISCUSSIONFrom thecalculations above it is safe to infer, annually the worst case of heat gain isthe solar heat gain through single pane reflected coated glass frames (78%) and through ventilation and infiltration(13%) (figure 8).
These are the crucial points which in this paper are furtherworked upon after getting an understanding from the typical practices andtechniques worked in this area to achieve comfort. Figure 8 (From the calculation above) 5. TYPICAL PRACTICES This part will talk about threebuildings. –1.
KohinoorHospital, Mumbai (first LEED Platinum rated project in Asia) (Figure 9)2. ComputerMaintainance Corporation building, Mumbai (Daylight intergration factor)(_)3. Observations forRTI building, Mumbai (with respect to ECBC requirements)(_)5.1. Kohinoor Hospital, MumbaiKohinoor hospitalis 227000 sqft with 150 bed health case facility housing 2 basements,ground +5storey structure. It is amultispeciality hospital implementing a range of energy efficient measures toreduce energy consumption, decreasing green house gas emission and improvingthe quality of patient care.Energy Analysis-· Gross window towall ratio is approx 27% · ConsidersASHRAE/IESNA 90.1(2004) baseline.
Fenestration· Fenestration detail Capacity to retain and reflectheat· Double glazedunits with high performance reflective glass of 1.2U value.Envelope· WALL : Externalbrickwall 230mmAirgap: 650mmExtruded Polystyrene: 75mmBrickwall:100mm· Roof: 200mm thkRCC with 75mm extruded insulation entirely above deckLighting · Double glazed window Efficient and intelligentlighting system with LED/CFL combination· LED for covelighting· Activitywisedistribution to achieve optimum lux level· Occupany sensorsin public toilets· Carefulcircuiting for efficient lighting stategyAchieved overallLPD of 0.54W/sqft.5.2 ComputerMaintainance Corporation building, MumbaiIt is a cubicalform office complex of 25mx25m with height of 30m.This building is a goodexample for integration of day lighting system.
· Windows onperiphery are unable to transmit day light into the working areas.· To introducedaylight on all floors, a central atrium with circulation routes around theatrium is designed.· Double glazedperipheral windows are split in two parts to serve different purposes : upper half for day lighting and lower half forview.· Upper windowincorporates light shelves which respond which repond to the angle of incidenceof sunlight on different faces of the building.
· Motorized louversautomatically adjust to reflect sunlight on white ceiling.The net effect ofthis daylight integration factor succeeds in achieving dayligh without anyartificial lighting during day light hours. 5.3 Observationsfor RTI building, MumbaiThe RTI building,Mumbai is a air conditioned building in an area of 4972sqm. The observation for this building with respect to ECBC is carried out by Teri,The energy and resource insitute for the PWD(public work department) .The table (9) shows energy consumption by a running building while followingthe ECBC requirements. 6.BEST PRACTICEIndia’sEnergy Conservation Building Code(ECBC) currently provides guidance which has potentialto reduce energy loads in a convention building by 40% to 60%, as stated by theMinistry of Power, Govt of India,2007.
But this guidance isn’t compulsory tofollow as of yet.Bioclimatic chart of Mumbai shows May to be the hottest month withaverage daily maximum temperature as high as 32? with a humidity of 60% during daytime. Thereby suggesting mechanicalair conditioning from April to October during these days. The months ofJanuary, February, November and December are comparatively comfortable.Due to highRelative humidity, cross ventilation is bothdesirable and essential to protect the building envelope from direct solarradiation through shading.In order toproduce an efficient design, it is important to resist heat gain by decreasingexposed surface area, increasing thermal resistance, increasing buffer spaceand increasing shading; and to promote heat losses through ventilation ofappliances, increase air exchange rate throughout the day and decreasinghumidity levels. Recommended design parameters for the basecase: 1.
Glazing TypeDoubleglazing with reflective coated glass has higher performance in contrast to the single panereflective coated glass (base case). This is because single pane clear glassincreases the load by 9.3%, whereas the double glazing with reflective coatingdecreases the load by 2.
2%. (Handbook ofenergy conscious design,2006 pg. 239)2.
WindowSizeThe base case of window size 2.8X2.8 mintakes huge amount of solar gain. Reduction of glazing size to 1.
2m height haspotential to reduce the annual load by 6.5% (Handbook of energy consciousdesign,2006 pg. 397) 3. ShadingAnother way of reducing the solar gain Isto provide windows with external shading by means of external shading by meansof external shading by means of external projections like chajjas. If 50% ofwindow areas are shaded, then annually there can be a load reduction of 8.5%(base case: no shades)4. WallType Having an autoclaved cellular concreteblock over concrete wall (base case) can reduce the heating load by 2.
4%,because of its lower U value.5. Colourof external wallDark colour over white colour for theexternal surfaces can increase the load by 4% annually. Hence, is avoided.6. AirExchangesLowering the air exchange rate to 0.
5achfrom 5ach(base case) reduces the annual load by 1.7%. 7. CONCLUSIONThe combination of all design parameters istaken into account will reduce 25.
3% of the heating load. Hence, succeeding in optimisingthe energy balance/comfort for the library of 80sqm in Mumbai,India.