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Comfort and Energy Assessment of Low-cost Public Housing Scheme in Ethiopia

Presentation Outline

12/8/2017 International Symposium to Promote Innovation & Research in Energy Efficiency 2017

Belay Zeleke, Dr. E. Rajasekar | Indian Institute of Technology Roorkee

2

IntroductionContextual assessment

Climate characterstics

Discussion & Results

IHDP

Adaptive Comfort Temperature

Sensible Heating and Cooling

Predicted Mean Vote (PMV) & Discomfort Hours

Conclusion & Recommendations

Air Temperature & Mean Radiant Temperature

Alternative Building Materials & Construction Techniques

INTRODUCTION• Ethiopia, located between (3–15° N, and 33–48° E) in

East Africa.

• No existent climate and thermal performance based

building design regulations in Ethiopia.

• Building design and materials specified for

construction in the IHDP are consistent across all

climate zones.

12/8/2017 International Symposium to Promote Innovation & Research in Energy Efficiency 2017 3

Housing Deficit2004

900,000

NOW

Figure 1(Left): Housing demand in Ethiopia. Source; Adopted from Un-Habitat, 2011. Figure 2 (Right-above): Location of Ethiopia. Figure 3 (Right-below): Traditional climate classification of Ethiopia.

Source: Authors

Source: Google Maps

900000

150000

Deficit_2004

IHDP_Supply

Housing Deficit

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.


Contextual AssessmentSelected 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: Michael David Murphy,

Source: A. Davey

Source: de:Benutzer

Source: Oromia Culture And Tourism Bureau

Source: Köppen climate classification scheme

Figure 4: Location of Selected cities & their climate zones.

Context…Cont’d


Location AdaptiveComforthours (hrs)

AdaptiveComforthours (%)

SummerComfort Hours(hrs)/ 2208 hrs

WinterComfort Hours(hrs)/ 2208 hrs

Addis Ababa 1618 18.5 441 294

Dire Dawa 2464 28.1 967 785

Gode 3490 39.8 761 926Gondar 1842 21 736 441Nekemte 1583 18.1 467 388

• 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.

Table 1: EstimatedDiscomfort Hours ofSelected Sites.

Context…Cont’dPUBLIC HOUSING (INTEGRATED HOUSING DEVELOPMENT PROGRAM - IHDP)

• Over 103 project sites in Addis Ababa alone


Selected Building TypologiesSource: Housing Development Program 2006 – 2010 Plan Implementation Report

Figure 6: Sample Picture of IHDP public housing Repi Site, Addis Ababa. Photoby Mekides Worku

Figure 7: Sample layout plans of Studio & 2bed type housing units.

Housing Typology

Building Materials Occupancy Openings Modelling in Design Builder

• Studio type

• One Bed Type

• Two BedType

• 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 2.853 (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 usedfully 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

Modelling & Simulation


Table 2: Considerations taken in to modelling & simulations.

Discussion & Results


Studio Type

One Bed Type

Two Bed Type

Three Bed Type

Addis Ababa

Dire Dawa

Gode

Gondar

Nekemte

Clim

ate

anal

ysis

cond

omin

ium

flat

s in

blo

ck T

ype

A2

adaptive comfort temperature inside air temperature (Ta)

mean radiant temperature (MRT) predicted mean vote (PMV)

total discomfort hours

Variables

Adaptive Comfort Temperature• calculated using the formula

devised in ASHRAE standard 55-2004.

Cont’d


Figure 8 (Upper): Comparison of comforttemperature Tcomf in House 04, Bedroom 01at 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)]

𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 = 0.31𝑇𝑇𝑇𝑇, 𝑇𝑇𝑜𝑜𝑜𝑜 + 17.8

Cont’dSensible 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 SensibleHeating -(KW)

Heating loadvariation (%)

SensibleCooling -(KW)

Cooling loadvariation (%)

Addis Ababa 387 100 878 100Dire Dawa 0 0 12807 1459Gode 164 42 681 78Gondar 0.3 0.1 5803 661Nekemte 387 100 877 100

Figure 10: Comparison of PMV by house type inAddis Ababa

Table 3: Heating & Cooling load comparison.

Cont’d• The number of discomfort hours (time not

comfortable based on simple ASHRAE 55-

2004) also demonstrates the difference in

which these buildings respond at different

environmental conditions.


Figure 11 (Upper): Variations of PMV in housetype 04, Addis AbabaFigure 12 (Lower): PMV of House Type 04 atvarious locations

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.

Cont’d


Figure 13: Air temperature and Mean radianttemperature in House type 04

Table 4: Time Not Comfortable Based on SimpleASHRAE 55-2004 in House Type 04 (Living Room)

Scenario DiscomfortHours (hrs)

DiscomfortHours (%)

Base Case 3932 45Insulated 3718 42Insulated + DoubleGlazing

3473 40

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.


Thank You.


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Comfort and Energy Assessment of Low -cost Public Housing ...inspire.ind.in/presentation/Day3/Spotlight Session/BST_4. belay... · Comfort and Energy Assessment of Low -cost Public