DESIGN GUIDELINES FOR ENERGY EFFICIENT

BUILDINGS

ArchitectJiten Prajapati

Mumbai

September 2006

Contents

Need for energy efficient buildings ?

Design guidelines for two commercial buildings

Warm and humid climateHot and dry climate

Need for Energy Efficient Buildings

User behaviour has changed

Commercial buildings are huge consumers of energyAverage mall - Rs. 25 lakh/ monthMultistoreyed office - Rs. 15 lakh/ month

Large potential for energy conservationCan lead to a thermally comfortable indoor environmentModern science has provided quantitative support

Example - a building without any chajja’s in Mumbai

• No protection from rains and sunshine.

• Has to be air-conditioned and artificially lit

• Manifold increase in consumption of energye.g. Similar building pays Rs. 15 lacs as energy bill per month

What do we mean by energy efficient buildings?

– Buildings that are comfortable for improving the productivity of occupants.

• Understanding climate• Incorporation of passive solar techniques

– Consumption of conventional energy is reduced through appropriate design.

• Understanding thermal performance of building design• Optimising design and operational parameters of the

building

Warm and Humid Zone

Multi-storeyed air conditionedoffice building

Energy Conservation Measures in the Design of

a Commercial Building for Mumbai

J. Prajapati and J. K. NayakEnergy Systems Engineering

IIT Bombay, Powai,Mumbai - 400 076, India

Type of Building Studied

• Fully glazed south facade

• Air-conditioned and artificially lit

• Built-upArea = 7074 sqm

• Conditioned Area = 5400 sqm

• Ground + seven storeyed RCC structure

N

TYPICAL FLOOR PLAN

OFFICE HALL

TOILETS

STAIRCASE

STAIRCASE

PANTRY

TOILETS

CABINS

LOBBYLIFT

L

L

LSTORESTORE

CABINS

BASEMENT

GROUND LEVELGROUND FLOOR

1ST FLOOR

2ND FLOOR

3RD FLOOR

4TH FLOOR

5TH FLOOR

6TH FLOOR

7TH FLOOR

SECTION

NOTE:HATCHED PORTION INDICATESAIR-CONDITIONED AREA

TERR

TERR

FC

GCW

TERR

GCW = GLASS CURTAIN

FC = FALSE CEILING

TERR = TERRACE

LEGEND

WALL

GCW

GCW

GCW

Analysis of climate

Performance of Building

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Ener

gy D

eman

d (G

J/m

onth

)

CoolingHeating

Annual Load = 6384 GJ

Note:

Only cooling load in Mumbai (no heating load)

Component-wise thermal gains

-20%

0%

20%

40%

60%

80%

100%

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

month

Per

cent

age

Surface

InternalConvective

Air exchange

Studies to Improve Building Performance

PARAMETERS INVESTIGATEDGlazing SizeGlazing Type

Orientation (longer axis)Shading

Colour of External SurfacesWall Type

Air Change RateInternal Gain

Scheduling of air changesSetpoint for heating and cooling

Studies to Improve Building Performance

Effect of Glazing Size

4000

4500

5000

5500

6000

6500

BASECASE GLAZINGSIZE

(restrictedto 1.2m

Ann

ual

Loa

d (G

J)

GLAZING SIZE (% saving)BASECASE (Full ht. glass) N.A.(restricted to 1.2m height) 6.5

Effect of Glazing Type

4000

4500

5000

5500

6000

6500

7000

BASE

CAS

E

Sing

le c

lear

Dou

ble

clea

r

Dou

ble

low

-E

Dou

ble

refle

ctiv

eco

ated

Ann

ual

Loa

d (G

J)

Studies to Improve Building Performance

GLAZING TYPE (% saving)BASECASE (single reflective coated) N.A.Single clear -9.3Double clear -6.9Double low-E -0.9Double reflective coated 2.2

Studies to Improve Building PerformanceEffect of Orientation

4000

4500

5000

5500

6000

6500

BASECASE N-S NE-SW E-W

Ann

ual

Loa

d (G

J)

ORIENTATION (longer axis) (% saving)BASECASE (NW-SE) N.A.N-S 6NE-SW 7.7E-W 2.1

Studies to Improve Building PerformanceEffect of Shading

4000

4500

5000

5500

6000

6500

BASECASE 10% 20% 50%

Ann

ual

Loa

d (G

J)

SHADING (% saving)BASECASE (No shading) N.A.

10% 1.720% 3.450% 8.5

Studies to Improve Building PerformanceEffect of Colour

4000

4500

5000

5500

6000

6500

7000

BASECASE dark grey

Ann

ual

Loa

d (G

J)

Effect of Wall type

4000

4500

5000

5500

6000

6500

BASECASE ACCB

Ann

ual

Loa

d (G

J)

COLOUR OF EXT.SURFACE (% saving)BASECASE (White) N.A.dark grey -4WALL TYPE (% saving)BASECASE (Concrete block wall) N.A.ACCB (e.g. Siporex) 2.4

Studies to Improve Building PerformanceEffect of Air changes

40004500500055006000650070007500

BASECASE 0.5 2 4

ACH

Ann

ual

Loa

d (G

J)

AIR CHANGE RATE (% saving)BASECASE (1.0 ach) N.A.

0.5 1.72 -3.54 -10.8

Studies to Improve Building Performance

OTHER PARAMETERS (% saving)INTERNAL GAIN BASECASE (100%) N.A.

10% 51.650% 29.1

No internal gain 57.1

SCHEDULING OF AIR CHANGES 1.4SETPOINT (% saving)BASECASE (21 °C - 24 °C) N.A.

( 20 °C - 25 °C) 7.1

Comparison Between Improvedand Basecase Building

0

1000

2000

3000

4000

5000

6000

7000

BASECASE IMPROVED

Ann

ual

Loa

d (G

J)

Annual Load (GJ)

% saving

BASECASE 6384 N.A.IMPROVED 4903 23

• Cooling load predominant in Mumbai

• Internal gains and external surfaces main contributors to heat gain

• Effect of various parameters studied

• Savings of 23% of annual loads can be achieved by optimising building design

Conclusions – Part 1

Acknowledgement:We are grateful to Solar Energy Centre, Ministry of Non-conventional Energy Sourcesfor sponsoring the project

Hot and Dry Zone

Low-rise passive cooledoffice building

Passive Downdraft Evaporative Cooling (PDEC) System

Inspector General of Police (I.G.P.) Complex, Gulbarga

Client:Karnataka State Police Housing Corporation

Architects:

KEMBHAVI ARCHITECTURE FOUNDATION

Identification of Climatic ZoneAnalysis of Climate

Analysis of Building DesignIndoor TemperatureCooling Loads

Passive TechniquePassive Downdraft Evaporative Cooling Tower

Implications of Design

Climatic Zones of India

• HOT & DRY• WARM & HUMID• MODERATE• COMPOSITE• COLD & SUNNY• COLD & CLOUDY Gulbarga

Bio-climatic Chart

COMFORT ZONE

MAR

APR MAY

JAN

Inside Temperature of a Typical Room

comfort fraction

20.00

22.00

24.00

26.00

28.00

30.00

32.00

34.00

36.00

38.00

40.00

8.00

10.0

0

12.0

0

14.0

0

16.0

0

18.0

0

20.0

0

22.0

0

24.0

0

2.00

4.00

6.00

time hrs

tem

pera

ture

deg

C

toa oC tn oCtn +2.2 (upper comfort lim) tn -2.2 (lower comfort lim)tia oC

Cooling Loads - Typical Room

INTERNAL LOADS34%

GLAZING14%

ROOF29%

WALLS4%VENTILATION

19%

WALLS

ROOF

GLAZING

INTERNAL LOADS

VENTILATION LOADS

• Ambient hot-dry air is trapped, cooled by evaporation of water and then introduced in the building.

• Simple system based on shower spray system developed by B. Givoni

• Cost = 17.5 lakhs• Area cooled = 1100sqm.• Estimated Performance in May :

– Outside air temperature = 38 °C

– Temperature of air = 25 °C(at exit of tower)

• About 4 - 10 air changes per hourNote: Approximate cost and area

CROSS BAFFLE WALL TO DIVERT WINDINTO TOWER

INLET OF TOWER

WATER SPRINKLER TO COOL AIR BYEVAPORATION

WOOD CHARCOAL LAYER TO FILTER OUT DUSTAND INSECTS

GROUNDFLOOR

FIRSTFLOOR

TERRACEFLOOR

BAFFLE TO DIVERTAIR FLOW TO DIFFERENT ROOMS

COOL AIR EXITINGFROM PDEC TOWER

WATER COLLECTED INDRAIN FOR RE-CIRCULATION

Design of PDEC System

Estimated performance of PDEC tower in various months

•PDEC system works very well in the summer months

For example,in May, the temperature of cooled air leaving the tower is about 25°C while the corresponding ambient temperature is about 38 °C. Thus, the drop in day-time temperature is significantly high in May, i.e. about 13 °C.

10.0

15.0

20.0

25.0

30.0

35.0

40.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Tem

pera

ture

(°C

)

AmbientPDEC tower

Implicationsof PDEC systemADVANTAGES• Low cost single pass system• Easy to maintain• Entry of birds and pests

prevented• Charcoal tray to filter out dust• Sophisticated water treatment is

not required• Single tower serving multiple

floors• Can be used for pre-cooling the

building at night

DISADVANTAGES• High humidity• Noise due to spraying of water

Energy Savings

Estimated Savings

• Approx. Rs. 3.5 lakhs/ annum

Simple Payback Period

• 5 years

Conclusions – Part 2Passive solar architecture can be used effectively in a non-conditioned building in a hot and dry climate to:

– Provide indoor comfort– Reduce consumption of energy

Acknowledgements:

Kembhavi Architecture Foundation, Hubli and Karnataka State Police Housing Corporation, Bangalore

Thank You