climatic design for energy efficiency

8/12/2019 Climatic Design for Energy Efficiency

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(i) identification of the climate at the buildingsite

(ii) determination of the comfortrequirements of the

relevant climate


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selection of appropriate

architectural features space planning

orientation,

location and size of fenestration shading devices

treatment of buildingenvelope


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CLIMATIC CLASSIFICATION hot-dry

warm-humid

Cold temperate;

composite.


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Inhot-dry climate, emphasis is laid on adopting designtechniques that contribute towards

reduction in indoor air temperature provision of adequate night ventilation.

buildingdesignin warm-humid climate

provision of ample air motion is an important

requirement


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DESIGNCONSIDERATIONS FOR ENERGY

EFFICIENCY IN BUILDINGS

judicious use of electrically operated gadgets;

Development of energy efficient appliances

optimum utilization of non-conventional sources ofenergy

judicious planning and designof buildings


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Passive techniques- Design thermal

environment indoors. cooling of buildings in hot-dry and warm-humid

climates

the mainly aim towards reduction in heat penetrationthrough buildingenvelope

provision of fenestration for inducing desired naturalventilation indoors.


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e uc on n ea ene ra onthrough BuildingEnvelope

Solar radiation incident on buildingenvelope

source of heat responsible for raising the temperature

of exterior surface for creating temperature gradient across the thickness

of the envelope.

- heat is conducted indoors causing a rise in the

interior surface temperature.


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Indoor temperature reduction in the temperature of exterior surface is

necessary for keeping the indoor surface temperatureat a low value

Transparent window facing sun also permits directentry of sun.

-contributes to the rise in the temperature of indoor

- control of direct entry of sun through windows is arequirement for preventing the rise in interior surfacetemperature


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Optimum Orientation amount of daily solar radiation incident per unit area

on N and S facing walls is much less as compared tothat on the walls facing other directions.

for minimum solar heat gain by the buildingenvelope, it is desired that the longer axis of buildingshould lie along East-West direction.


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aspect ratioFor a building glass area equally distributed on all the

four walls

with square plan effect of orientation is nil,With a buildingwith aspect ratio 2:1, the fabric load

is reduced by 30% due to change in orientation fromworst to best


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Shading of Windows Louvers

overhangs

awnings. Optimum dimensions of the louver depend

on the duration of sunshine on the window facade.

Windowsof the same dimensions but oriented

differently should have different dimensions of louversto be effective.


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A simple box type louver- suitable on an eastern faade

Vertical and horizontal louver system- on

the southern faadeAn egg crate type -on the western facade.

Rain shade- northern facade


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overhang with optimum

dimensions cooling load reduction of 12.7% in summer

overshadowing of the windows must be

avoided as it reduces availability of daylight indoors,which in turn results in increased consumption ofenergy for artificial lighting


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Exterior Surface Solar Reflectance Surface colour of the external wall

-the percentage of solar radiation absorbed by the

external surface

-long wave radiation emission.

( a white washed of 0.4 may result in saving of electrical

energy by 40% to 50%.)


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Provision of insulation on walls and roof of a buildingincreases their thermalresistance and curtails conductive heat flow through the buildingenvelope.

Introduction of air cavity in a wall also increases its thermalresistance. Studies on estimation of thermalproperties of such a wall revealed that the overall heat transmission co-efficient U value of a 27.5 cm brick cavity wall (11.25 cm brick + 5.0 cm air gap

+ 11.25 cm brick) is 1.63 W/m2

, K while that of a 22.5 cm solid brick wall with 1.25 cm cement plaster on both the side U value is 2.26 W/m2K. Here, it is worth emphasizing that the thermalperformance of the above cavity wall is slightly better than that of a 35 cm solid brick wall


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Window Optimise the window size and location.

Windows on East and West facades should be

avoided In air conditioned buildings, windows are less

insulating

A single glazed window system the U value is 5.22

W/m2K.A window system of a double glazing with an air gap

of of 12 mm-18 mm - U value 3 W/m2K


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Materia

l

Alumin

um foil

Aluminu

m paint White

wash new

Grey

colour

light

Red brick Grey

colour

dark

Glass

Reflectiv

ity

0.95 0.50 0.88 0.60 0.40 0.30 0.08

Emissivi

ty

0.05 0.50 0.90 0.90 0.90 0.90 0.90

(Long

wave

Radiatio

n)


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AIR

MOTION INDOORS

1. If the prevailing wind is from East or West, buildings canbe oriented at45oto the incident wind.

2. Atleast one window should be provided on windwardwall and the other on leeward wall.

3. Maximum air movement at a particular plane is

achieved by keeping the sill height at 85% of the

height of the plane. 4.the average indoor air speed increases increasing

the width of window up to

about 2/3 of the wall width


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5. The average indoor wind speed in the working zoneis maximum when window height is 1.1 m.

6. For a total fenestration area (inlet plus outlet) of20% to 30% of floor area, the average indoor windvelocity is around 27% of outdoor velocity. % of theoutdoor velocity (


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15. A partition placed parallel to the incident wind, has little influence on the pattern of air flow but when located perpendicular to the main flow, the same partition creates a wind shadow. Provision of a partition with spacing of 0.3 m underneath, helps augmenting air motion near floor level in the leeward compartment of wide span buildings. 16. Air motion in a buildingunit having windows tangential to the incident wind is accelerated when

another unit is located at end-on position on downstream side (Figures 5(a) and 5(b)). 17. Air motion in two wings oriented parallel to the prevailing breeze is promoted by connecting them with a block on the downstream side


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7. In regions having fairly constant wind direction, thesize of the inlet should be kept within 30% to 50% ofthe total area of fenestration and buildingshould

beoriented perpendicular to the incident wind.Since,inlets smaller than outlets are more sensitive to

change in wind direction, openings of equal sizes arepreferred in the regions having frequent changes in

wind direction. 8. In case of room with only one wall exposed to outside,provision of two windows is preferred to that of asingle window


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9. Windows located diagonally opposite to each other,with the windward window near the upstreamcorner, give better performance than other window

arrangements for most of the buildingorientations. 10. Horizontal louver, ie, a sunshade, atop a windowdeflects the incident wind upward and reduces airmotion in the zone of occupancy. A horizontal slotbetween the wall and horizontal louver prevents

upward def lection of air in the interior of rooms. Provision of L type louver increases the air motion inthe room provided that the vertical projection doesnot obstruct the incident wind (Figures 3(a) and 3(


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11. Provision of horizontal sashes inclined at an angle ofin the appropriate direction helps to promote the air motion

inside rooms. Sashes projecting outward are more effective than those

projecting inwards. 12. Air movement at working plane 0.4 m above the floorcan be enhanced by 30% using a pelmet type wind deflector

13. Roof overhangs help air motion in the working zone inside buildings. 14. Verandah open on three sides is preferable since it

causes an increase in the room air motion for most ofthe orientations of buildingwith respect to theincident wind


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Any thing to do with vastu ?

Dr.L.S.Jayagopal


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Open spaces


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Slope of roof


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doorsDoors should open towards North or East side.Main Gate should be on the North East direction.For the house facing a road on the South side the

Main Gate should be on the South or South-Eastand not on the South-West.For the house facing a road on the West side the

Main Gate should be on the West or North-West

and not on the South-West.


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Gates and doors


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The Master Bedroom should occupy the South-West portion of the plot.

Kitchen should be placed on the South East.

Puja should be placed on the North East.

Bathroom should come on the Eastern side of theplot, if that is not possible South-East or North-

West should be the preferred Side forBathrooms.


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. Verandahs should come on the East and North and

not on the West or South. Overhead tank should be either in South or West.


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Out houses should be in South East or NorthWest but they should not touch the North andEast walls of the main of the main house.

Septic tank should be placed in North West orSouth West part of the Plot.


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VastuWhere ?

When?

By whom?Why ?


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Indo Gangetic Plain

Early settlement

Indian

civilization


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Vedic periodAtharvana veda

Stapata veda


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South east-Soorya


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North east-Easanya


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North east- JalaJala moola


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North west-Vayu


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Niruthi-South west

Corner with nospecific attributes


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Other directional Gods


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Solar Architecture South East

N

S

WWE

Agni

Vayu Easa/jala

Niruthi

Sun rises in south of EastMorning sunCool in evening


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Solar Architecture North East

N

S

WWE

Agni

Vayu Easa/jala

Niruthi

Shade throughout theday/year


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Solar Architecture North West

N

S

WWE

Agni

Vayu Easa/jala

Niruthi

Mansoon crosses thecornerHeat in evening


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Solar Architecture South West

N

S

WWE

Agni

Vayu Easa/jala

Niruthi

No shadowthroughout day/yearCools late in night


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Soft-Medim-Harsheast

south

pudan sukkiran chandran

angagaragansuriyanguru

sani kethuragu

north

west


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suriya

yama

pudan sukkiran chandran

angagaragansuriyanguru

sani kethuragu

guberan

varuna


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Open space

Central bramastanam

Outer open space

Inner verandah


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Room andveedhies


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Room andveedhies


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Fibonacci Numbers Fibonacci Numbers: 1,2,3,5,8,13,21,34,55,89

Golden ratio=1/2, 2/3,

3/5, 5/8, 8/13, 13/21 =21/13=1.615.


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Fibonacci Numbers Number of spirals=21,34


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Golden sections


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Human scale


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Golden ratio


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Preferred room dimensions Basic 8 steps

Basic+ 1+1

Pushantramarhram basic + 3

10 ,11

Golden ratio for 10- 16, 17

Square 20 22


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foundationsLayers

sandJamum size atones+sand

Monkey head

Size stones+

sand

Coconut sizeStones +sand

Pumkin sizeStones +sand

1/8 of room width

Each layer 1 6

climatic design for energy efficiency

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