Presentation Outline. Comfort and Energy Assessment of Low-cost Public Housing Scheme in Ethiopia. Contextual assessment. Discussion & Results

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2 Comfort and Energy Assessment of Low-cost Public Housing Scheme in Ethiopia Belay Zeleke, Dr. E. Rajasekar Indian Institute of Technology Roorkee Presentation Outline Introduction Contextual assessment Discussion & Results Conclusion & Recommendations Climate characterstics Adaptive Comfort Temperature IHDP Sensible Heating and Cooling Predicted Mean Vote (PMV) & Discomfort Hours Air Temperature & Mean Radiant Temperature Alternative Building Materials & Construction Techniques 2

3 INTRODUCTION Ethiopia, located between (3 15 N, and E) in East Africa. No existent climate and thermal performance based building design regulations in Ethiopia. Building design and materials specified for Housing Deficit construction in the IHDP are consistent across all climate zones. Source: Google Maps IHDP_Supply Deficit_ , Housing Deficit NOW Figure 1(Left): Housing demand in Ethiopia. Source; Adopted from Un-Habitat, Figure 2 (Right-above): Location of Ethiopia. Figure 3 (Right-below): Traditional climate classification of Ethiopia. Source: Authors 3

4 Intro (cont d) Design & construction irrespective to climatic conditions means either to create uncomfortable indoor environments or to increase the need for maintaining thermal comfort through artificial means (Bodach, Lang and Hamhaber, 2014). The IHDP does not include thermal performance assessment of the public housing. Aim: to investigate the thermal comfort and energy performance variations of these buildings across the five major climate zones of Ethiopia. 4

5 Contextual Assessment Selected Cities and Their Climate Five cities are selected for the study, one from each major climate zone according to Koppen Geiger classification. Addis Ababa, Dire Dawa, Gode, Gondar & Nekemte. Source: de:benutzer Source: Oromia Culture And Tourism Bureau Source: Köppen climate classification scheme Source: Michael David Murphy, Source: A. Davey Figure 4: Location of Selected cities & their climate zones. 5

6 Context Cont d A simple adaptive comfort hour comparison done using climate consultant reveals all the selected sites are only comfortable for less than 40% of the time (Table 1). Figure 5 (Upper): Climate conditions. Location Adaptive Comfort hours (hrs) Adaptive Comfort hours (%) Summer Comfort Hours (hrs)/ 2208 hrs Addis Ababa Dire Dawa Winter Comfort Hours (hrs)/ 2208 hrs Table 1: Estimated Discomfort Hours of Selected Sites. Gode Gondar Nekemte

7 Context Cont d PUBLIC HOUSING (INTEGRATED HOUSING DEVELOPMENT PROGRAM - IHDP) Over 103 project sites in Addis Ababa alone Selected Building Typologies Source: Housing Development Program Plan Implementation Report Figure 6: Sample Picture of IHDP public housing Repi Site, Addis Ababa. Photo by Mekides Worku Figure 7: Sample layout plans of Studio & 2 bed type housing units. 7

8 Modelling & Simulation Housing Typology Building Materials Occupancy Openings Modelling in Design Builder Studio type One Bed Type Two Bed Type Three Bed Type Floor: ground floor is composed of 20 cm thick class C-25 Reinforced concrete, upper floors is made of suspended ribbed slab External walls: are made of Class 'C' HCB wall with approximate U-value of (w/m2-k). Pitched roof is used in all condominium projects made of EGA 500 openings are decorated with 4mm thick single layer clear glass joined to frames with putty. 3.8 people/ Urban House (CSA, 2011) Year round 24 hours occupancy 10-15% window to wall ratio used fully operable and all doors have a fixed rectangular top window Envelope properties and building materials are defined based on the actual building specification. Bathrooms and circulation areas are considered as unoccupied space, effect of neighbouring buildings is not considered Table 2: Considerations taken in to modelling & simulations. 8

9 Discussion & Results condominium flats in block Type A2 Studio Type One Bed Type Two Bed Type Three Bed Type Addis Ababa Dire Dawa Gode Gondar Nekemte Climate analysis Variables adaptive comfort temperature inside air temperature (Ta) total discomfort hours mean radiant temperature (MRT) predicted mean vote (PMV) 9

10 Cont d Adaptive Comfort Temperature calculated using the formula devised in ASHRAE standard TTTTTTTTTT = 0.31TTTT, oooooo Figure 8 (Upper): Comparison of comfort temperature Tcomf in House 04, Bedroom 01 at different locations in summer. Figure 9 (Lower): Temperature difference b/n comfort temperature & outdoor temperature (Tcomf - Tout, c) [Ideal difference should not exceed 2 3 c (Nicol, 2004)] 10

11 Cont d Sensible Heating and Cooling Annual heating and cooling demand is compared across different climates. Predicted Mean Vote (PMV) & Discomfort Hours Simulation results of the PMV assessment reflect the ineffectiveness of the building materials and design elements used in this public housing scheme in enhancing thermal comfort for the occupants. City Sensible Heating - (KW) Heating load variation (%) Sensible Cooling - (KW) Addis Ababa Dire Dawa Gode Gondar Nekemte Table 3: Heating & Cooling load comparison. Cooling load variation (%) Figure 10: Comparison of PMV by house type in Addis Ababa 11

12 Cont d The number of discomfort hours (time not comfortable based on simple ASHRAE ) also demonstrates the difference in which these buildings respond at different environmental conditions. Figure 11 (Upper): Variations of PMV in house type 04, Addis Ababa Figure 12 (Lower): PMV of House Type 04 at various locations 12

13 Cont d Air Temperature & Mean Radiant Temperature studies by show (Walikewitz et al., 2015) that the differences between air temperature (Ta) and mean radiant temperature (Tmrt) are negligible during most periods. Current study shows similar results. Use of Alternative Building Materials & Construction Techniques used a fiberglass insulation board for both external and internal walls and also changed the window glazing to double. The results show a 5% increase in comfort. Figure 13: Air temperature and Mean radiant temperature in House type 04 Scenario Discomfort Hours (hrs) Base Case Insulated Insulated + Double Glazing Discomfort Hours (%) Table 4: Time Not Comfortable Based on Simple ASHRAE in House Type 04 (Living Room) 13

14 Conclusion Climate variations were not taken in to account in the Integrated Housing Development Program (IHDP) of Ethiopia. The similarity between the outdoor temperature differences between the cities and the pattern of differences on the simulated comfort indexes of PMV show the ineffectiveness of the building envelop and natural ventilation in achieving comfortable indoor environment in the condominium houses. During the summer in Addis Ababa 441 hours or 20%, Dire Dawa 967 hours or 43.8%, Gode 761 hours or 35.2%, Gondar 736 hours or 34.5% & Nekemte 467 hours or 21.2% of the times the buildings could be made comfortable using adaptive measures. The current trend of same standard building envelops across all the climate regions leads to such variations in indoor thermal comfort. There is a potential to carefully assess this and define it for specific climate zones. this study highlights the need of introducing building thermal performance regulations in Ethiopia and subsequently the Integrated Housing Development Program. 14

15 Thank You. 15

16 References AIA Research Corporation (1979). Climate and Architecture, II. Ansi/Ashrae (2004) ANSI/ASHRAE 55:2004 Thermal Environmental Conditions for Human Occupancy, Ashrae, 2004, p. 30. doi: /s Bodach, S., Lang, W. and Hamhaber, J. (2014) Climate responsive building design strategies of vernacular architecture in Nepal, Energy and Buildings. Elsevier B.V., 81, pp doi: /j.enbuild Dear, R. De, Brager, G., Berkeley, U. C., De Dear, R., Brager, G., Dear, R. De and Brager, G. (1998) Developing an adaptive model of thermal comfort and preference, ASHRAE Transactions, 104(Part 1), pp Available at: /ieq/dedear1998_thermcompref. Dili, A. S., Naseer, M. A. and Varghese, T. Z. (2010) Passive environment control system of Kerala vernacular residential architecture for a comfortable indoor environment: A qualitative and quantitative analyses, Energy and Buildings. Elsevier B.V., 42(6), pp doi: /j.enbuild Etzion, Y., Pearlmutter, D., Erell, E. and Meir, I. A. (1997) Adaptive architecture: integrating low-energy technologies for climate control in the desert, Automation in Construction, 6(5 6), pp doi: /S (97) Givoni, B. (1992) Comfort, climate analysis and building design guidelines, Energy and Buildings, 18(1), pp doi: / (92)90047-K. Haase, M. and Amato, A. (2009) An investigation of the potential for natural ventilation and building orientation to achieve thermal comfort in warm and humid climates, Solar Energy. Elsevier Ltd, 83(3), pp doi: /j.solener Krü, E. L. and Zannin, P. H. T. (2004) Acoustic, thermal and luminous comfort in classrooms, Building and Environment, 39(9), pp doi: /j.buildenv Kuchen, E. and Fisch, M. N. (2009) Spot Monitoring: Thermal comfort evaluation in 25 office buildings in winter, Building and Environment. Elsevier Ltd, 44(4), pp doi: /j.buildenv Labaki, L. C. and Kowaltowski, D. C. C. K. (1998) Bioclimatic and vernacular design in urban settlements of Brazil, Building and Environment, 33(1), pp doi: /S (97) Hyde, R. (2000). Climate Responsive Design: A study of buildings in moderate and hot humid climates. E & FN Spon, USA. 16

17 Cont d Lin, Z. and Deng, S. (2008) A study on the thermal comfort in sleeping environments in the subtropics-developing a thermal comfort model for sleeping environments, Building and Environment, 43(1), pp doi: /j.buildenv Ministry of Works and Urban Development (2010) Housing Development Program Plan Implementation Report, (July), p. 50. Available at: Nicol, F. (2004) Adaptive thermal comfort standards in the hot-humid tropics, Energy and Buildings, 36(7), pp doi: /j.enbuild Nicol, J. F. and Humphreys, M. A. (2002) Adaptive thermal comfort and sustainable thermal standards for buildings, 34, pp Oktay, D. (2002) Design with the climate in housing environments: An analysis in Northern Cyprus, Building and Environment, 37(10), pp doi: /S (01) Rajasekar, E. and Ramachandraiah, A. (2010) Adaptive comfort and thermal expectations a subjective evaluation in hot humid climate, Adapting to Change: New Thinking on Comfort, (April), p. 18. Available at: Rajasekar, E., Udaykumar, A., Soumya, R. and Venkateswaran, R. (2015) Towards dynamic thermal performance benchmarks for naturally ventilated buildings in a hot-dry climate, Building and Environment. Elsevier Ltd, 88, pp doi: /j.buildenv Un-Habitat (2011) Condominium Housing in Ethiopia: The Integrated Housing Development Programme. Available at: and figures/africa/ethiopia_condominiumhousingun-habitat2011.pdf. Vijayalaxmi, J. (2010) Concept of Overall Thermal Transfer Value (OTTV) in Design of Building Envelope to Achieve Energy Efficiency, International Journal of Thermal and Environmental Engineering, 1(2), pp doi: /ijtee Walikewitz, N., Jänicke, B., Langner, M., Meier, F. and Endlicher, W. (2015) The difference between the mean radiant temperature and the air temperature within indoor environments: A case study during summer conditions, Building and Environment, 84, pp doi: /j.buildenv Bureau of Indian Standards. (1987) Handbook on Functional Requirements of Buildings (Other than Industrial Buildings), Kapoor Art Press. Peel MC, Finlayson BL & McMahon TA (2007), Updated world map of the Köppen-Geiger climate classification, Hydrol. Earth Syst. Sci., 11, Givoni, B. (1976) Man, Climate & Architecture, Applied Science Publishers LTD 17