hotdry_mahendra

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Climatic Zone: Hot and Dry

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Residence for Mahendra Patel, Ahmedabad



Here is one house that depends on solar energy to a great extent. Minimally

relying on the grid for power, the architect has also integrated the house with an

automation system for the purpose of saving energy

Genera l descr ipt ion

The residence of Mahendra Patel (client), located in the hot and dry

climate of Ahmedabad, was required to be fully air-conditioned.

However, the client was extremely concerned about the energy usage

in the building and wanted to achieve an energy-efficient design along

with optimized use of solar energy for meeting a part of its electrical

requirements and water heating needs. The architect has tried to

minimize the air-conditioning load by applying passive solar design

interventions. Judicious use of solar energy systems has been made to

meet a part of the energy demand in the building load.

Ahmedabad is located in the hot dry zone where the summer

temperature goes up to 45 C. Natural comfort conditions can be

achieved by protecting spaces from the heat and glare of the sun. The

site, about 755 m in area, is oriented eastwest with the shorter side

facing the road.

The house is designed in such a way that all the private spaces on the

ground and first floor are connected to the entrance hall through

individual doors. This helps in reducing passage area and loss of air-

conditioning. The double height of the entrance hall gives a grand look.

Though the width of the plot is less, the rooms do not look small

because of bay windows and angled walls. The verandahs play an

important role in the Ahmedabad climate. Hence, the house has been

provided with two big verandahs.


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Design Features:

Enve lope des ign

The building has adequately designed windows with overhangs onthe south wall. Thermally massive stone floors and thick masonry

walls moderate diurnal variations.

East and west walls are protected by a series of extendedterraces developed as building elements to shade walls.

Double glass shutters reduce heat gain.

Energy-e f f i c ient systems

I n s u la t i o n

In this building, an attempt has been made to reduce the annualspace-cooling requirement by nearly 30% with high levels of

insulation. The air-conditioning load was reduced from 36 to 26

tonnes of air-conditioning.

Fly ash bricks were used for masonry work. At every stage of theconstruction, plasticizers were used to decrease voids in the

mortar.

All the terraces and sloping roofs are finished with white Chinamosaic and insulated with 50-mm thick expanded polystyrene

and sand cement plaster.

All the external walls are insulated with 40-mm thick high-density thermocol. These thermocol sheets are stuck to the first

coat of plaster by an adhesive (bitumen). Over these sheets,

galvanized expanded wire mesh was anchored before applying

the second coat of sand-faced plaster.

All the walls are externally finished with white paint, whichreflects most of the sunlight.

Sh a d i n g - c u m - s e r v i c e d u c t s

1.2-m wide projections all around the building also work asservice ducts to carry all utility services such as electricity,

water supply, fan coil units of air-conditioning, etc., in addition

to shading the walls.


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These projections are finished at the top by white China mosaicand covered at the bottom by an aluminium false ceiling, which

can be opened.

B u i l d in g a u t o m a t i o n s y s t e m

A building automation system is integrated with the electrical system

to reduce energy wastage. The system hardware consists of input

sensors such as -

occupancy sensors and temperature sensors for overall utilitymanagement

a lux sensor for measuring ambient light levels water sensors for monitoring and controlling underground and

overhead tank water levels

breakglass, smoke detectors, and magnetic contacts for securityapplications.

The inputs from various sensors are processed by the PLC

(programmable logic controller) and it controls their allied output

systems according to the programme fed into it. The outputs that are

controlled by the PLC are light fixtures, fans, 5-amp plugs, pressure

pumps, softening pumps, air-conditioning, and the security and fire-

alarm system.

The hardware is fully interactive in nature inputs from a particular

sensor will not only activate its directly related output device, but also

other relevant output systems.

A project of this nature not only extends the architects responsibility

to perform as a technocrat, but also supports newly developed

systems. Mahendra Patels house is a good example of a functionalsolar house with automation system.

Renew ab le energy sys tems

So l a r p h o t o v o l t a i c a n d s o l a r w a t e r h e a t i n g s y s t e m s

The solar PV (photovoltaic) system is both technically and economically

suitable for household electrification in the long run. Once the decision

was made to design a house with a PV system, two years of electricity


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bills from the clients existing residence were studied to estimate the

consumption of energy per day.

It was concluded that a connected load of about 18 kW would be

required to fulfill the clients needs.

The installed PV system has a battery bank capacity of 600Ah/120 V nominal. The charging is accomplished during daylight

hours by the 6-kWp solar modules. The charging of the battery

bank is controlled by a power conditioning unit to prevent

excessive discharge or overcharge.

The hot water requirement of the building is met by a 400-litre-per-day solar water heating system.

Indoor a i r qua l i ty

A major issue with a super-insulated, air-tight house is thequality of the internal air. In a poorly designed system, the low

rate of air change can lead to persistent odours, high humidity

levels, and even fungal growth.

Problems of light and air quality are eliminated in this house byproviding north light and a fresh air unit at the top of entrance

hall. This acts as a light shaft, and also aids in the ventilation of

the house.

At a g lance

Pro jec t de ta i l s

B u i l d i n g / p r o j e ct n a m e Residence for Mahendra Patel

S i t e a d d r e s s 15, Kairvi Society, Bodakdev, Ahmedabad

B u i l d i n g t y p e Residential

Cl i m a t i c z o n e Hot and dry

A r c h i t e c t Pravin Patel

A 13 Aditya Complex

Opp. Television Station

Off. Drive in Cinema Road

Ahmedabad 380 054

Yea r o f s t a r t / comp le ti on 1996/97

Cl i en t / o w n e r Mahendra Patel


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B u i l t - u p a r e a 550 m

Co s t o f t h e p r o j e c t Rs 21 million (This includes construction

work, finishes, solar systems, electrical works, security systems,

air-conditioning systems, and interior work)

Design features

o A connected load of 18 kW is used to meet the clients needwithout compromising on any comfort

o Air-conditioning load reduced from 36 to 26 tonnes by passive solarinterventions

o Fly ash bricks are used for masonry worko External walls and roof are insulatedo Windows are with double glass shutterso Walls are finished with white paint, which reflects heato There are 1.2 metre projections all round the building that

work as service ducts to carry all the utility services like

electricity, water supply, fan coil units for air-conditioning, and

also as a shading device

o Problem of air and light quality is eliminated by provision ofnorth light and fresh air unit at the top of the entrance hall

o Solar photovoltaic and solar water heating systems are usedo Building automation system is used to minimize energy wastage

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