PASSIVE DESIGN STRATEGIES

17TH MAY 2013

ASHOK LALL
CLIMATE : In relation to human comfort

3 DIMENSIONAL SUMMARY BY ECOTECT OF CLIMATE AND COMFORT: CHENNAI

 CLIMATE : In relation to human comfort

3 DIMENSIONAL SUMMARY BY ECOTECT OF CLIMATE AND COMFORT : AHMEDABAD

 TRADITIONAL RESPONSE
PADMANBHAPURAM PALACE
Strategies to minimize energy consumption, particularly for air
conditioning, through the design of the building fabric :

EXPOSURE

INSOLATION / SHADING

HEAT TRANSFER

INFILTRATION

VENTILATION / AIR MOVEMENT

MICROCLIMATE

ILLUMINATION
EXPOSURE

 COMPACT SHAPE
& COMPACT HEIGHT Controlling exposed surface area to floor area ratio.

 ORIENTATION !? Dictated by site and building setback lines.

BUILDING ORIENTATION

SOUTH

WEST

Toilets, staircase lifts and other

services housed on the east
side

Openings on the west façade are

designed to provide natural light
and ventilation and at the same
time cut direct sunlight
EAST

NORTH

The building is oriented to maximize comfort in workplaces. Openings

are mainly restricted to the north and south sides while the west and
east sides are relatively opening free, or with specially designed
openings.
BUILDING ORIENTATION
 INSOLATION
 CONTROL WINDOW AREA - 25% of external
wall is glazed,
rest is opaque
 SHADE GLASS AGAINST SUN
BUILDING SKIN

The fenestration is designed to optimise light, cut

glare. The accessible ‘chhajja’ system with light
timber framework to carry plants and daylight
reflectors forms an outer skin expressing the buildings
response to the external climatic conditions. It also
incorporates a drip irrigation system for planter boxes.
BUILDING SKIN
HEAT TRANSFER
Control heat transfer through roof, walls and
windows.

Heat transfer is a function of the difference

between the internal and external
temperatures, thermal mass and thermal
conductivity.

How much insulation?

Where to place the insulation layer in the

external wall/roof envelope?

INFILTRATION
Tight windows
Air lock lobby at entrance
HEAT TRANSFER
Thermal Bridges!
Heat transfer through window
frame!

External Internal Middle

 MICROCLIMATE
 FOUNTAIN COURT - Evaporative cooling
- Psychological
comfort in seeing
and hearing the play of
water
 Modifying Microclimate
Prioritizing
passive means
for reducing
operational
energy demand.

The intimate scale of

the central court
and presence of
water create a
favorable
microclimate.

Integration of plants and creepers on pergolas

and the building facade provides both a
climatic foil and a heightened experience of
seasonal cycles.
 Systems Integration
Indoor climate control
+
Building fabric
+
Work place

Large mass internal fabric

insulated from outside interacts
with conditioned air flow to act
as thermal fly wheel and store
fan

Day light
reflector

Openable inner
leaf of window
Mud block inner leaf of wall
acts as humidity fly wheel
Daylighting

•Natural light through atrium and skylight

 ENVIRONMENTAL COMFORT

NICOL GRAPH New Delhi

50.0 T min
Tmax (deg
(deg centigrade)
centigrade)

Tmin (deg (deg

centigrade) • Dust and insect free
T max centigrade)
TC (deg centigrade)
fresh air
T Comfort(deg centigrade)
40.0

• Openable
DEG CENTIGRADE

windows, table
fans, lamps to
30.0

enable
individualised
micro environment
20.0

control.
10.0
• Dress code
according to
0.0
season
5

1
Ju -15

1
5

1
5

b 1

5
Ju -30

1
Fe 1-1

M 5-2

M 1-1

A 5-3

A 1-1
M 5-3

Se 1-1

O 5-3

No 1-1

De 5-3

De 1-1

-3
A 5-3
M 1-1

Ju 5-3

A 1-1

Se 5-3
Ja 1-1

Fe 5-3

Ju -1

O 1-1

No 5-3

15
1
01

15
0

0
l0

l1
0

1
0

1
b

p
ar

ar

pr

pr

ug

ug
n

c
ct

ct
ay

ay
Ja

FORTNIGHTS

Acceptance of Nicol adaptive comfort graph

Limits SUMMER- 27 deg C at 60% RH
WINTER- 20 deg C at 60% RH
 INDOOR CLIMATE CONTROL

GRADED CLIMATE CONTROL BRIEF

1. Work spaces – Good
2. Connecting passage – Moderate
3. Ancilary spaces – Exhaust vent

AHU
Conditioned air discharge
near floor level at columns
SOLAR ENERGY
Photovoltaic panels
and solar water
heating panels are
integrated with the
building design,
facing south. These
are supplementary
energy sources for
building operation.
SOLAR ENERGY
Assessing the potential of passive / low energy strategies
First – Assuming a high mass building envelop Second – The temperature of evaporatively
insulated from the outside, the indoor dry bulb cooled air (Tev) which would be flushed through
temperature (or theoretical internal radiant the building is plotted assuming an efficiency of
temperature) resulting from the decrement factor 70% with respect to wet bulb temperature.
and the thermal time lag (Tmass), is plotted.

DBT (Dry bulb

31st May temperature)

Tmass (inside temp. due to

44 insulated/mass building
42 envelope)
40 Tev (Temp. of
evaporatively cooled air)
38
36 WBT (Wet bulb
Temperature

34 temperature)
32 Tba (Predicted temp. for
30 'basic' comfort)
28
Tgo (predicted temp. for
26
'good' comfort)
24
22 ET (Effective
20 temp.combining Tmass +
0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Tev)
CET (Corrected effective
Time temp taking fanned air
speed of 2m/s)

A case of New Delhi

Third – The effective temperature that would
be felt on combining the effect of radiant Fourth – A circulating fan is introduced and a
temperature modified by evaporatively corrected effective temperature (CET) for a wind
cooled air (ET) is plotted assuming that it speed of 2 metres per second, applied to the
would lie half way between Tev and Tmass. effective temperature of the Third step, is plotted
Effectiveness of the passive/ low energy strategies is assessed by the cooling degree hour method.

Cooling degree hours (cdh)

Cooling degree hours not met by passive low energy means

 Chennai
Results and Findings New Delhi

6000 4000
3500

Cooling degree hours

Cooling degree hours

5000
3000
4000 Cooling degree hrs 2500
(cdh) Cooling deg

3000 2000
cdh not met by passive low cdh not met
1500
2000 Bangalore energy means energy mea
1000
1000
500
0 0
May June July August May June July August
Months
Legend Months

Cooling degree hrs (cdh)

Ahmedabad cdh not met by passive low energy

means Bangalore
4000
3500 1600
Cooling degree hours

3000 1400

Cooling degree hours

2500 Cooling degree hrs (cdh)1200
1000 Co
June
2000 July August cdh not met by passive low
800
1500 energy means cdh
Months 600 me
1000
400
500
200
0
0
May June July August
May June July August
Months Months
Building Envelope and Optimized Space Conditioning
Simulation Study for Delhi

Another energy simulation* was carried out with TRNSYS energy and systems simulation software on an existing
7-storey building in New Delhi.

The parametric study aimed at assessing the Energy Saving Potential of different design strategies including Passive
Design Strategies and Alternative Active Cooling Systems, as well as a combination of both passive and active
strategies.

This May be considered an idealized design .

The Passive Design Strategies included:

• Solar Protection in the way of Exterior Blinds and Overhangs
• Natural Ventilation
• 10 cm Outside Insulation (Expanded Polystyrene)
• Double Glazing with low Solar Heat Gain Coefficient
• White finishes on Exterior Walls

Alternative Active Cooling Systems included :

• Indirect adiabatic cooling and, for the remaining cooling load, a new generation high-performance air conditioner with
an evaporative condenser.
• The optimal solution combines both passive design and active cooling solutions, achieving more than
85% savings in the cooling load.

Simulation Studies indicate a potential of 40 – 80 % saving in operational energy compared

to BUA
Integrating Thermal Mass and Air Movement

COOLED FRESH AIR DUCTS (19 C – 22 C

SLAB TEMPERATURE : 26 C(SUMMER)

TO 20 C(WINTER)

CEILING FANS(UPTO 2 C
ADDITIONAL COOLING

RADIANT PIPING CEILING FANS & COOLED FRESH AIR

Integrating Thermal Mass and Air Movement
Integrating Thermal Mass and Air Movement
Pre cast hollow blocks forming cooling ducts