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