Page E2.2 . 18 February 2004                     
ArchitectureWeek - Environment Department
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Ecohouses in India and Wales


For the more linear houses on the north side, the width of the driveway that separates the two rows of houses is just sufficient to enable winter sunshine to enter the first-floor windows. The sections of these houses are designed with a cutout such that the winter sun is brought into the living/dining space on the ground floor. Terraces on the second floor have skylights that again admit winter sun into the first-floor rooms on the north side of the house.

Wind-Driven Evaporative Cooling

The west house takes advantage of the prevailing northwesterly hot winds that blow during the hot-dry seasons. A vertical screen tower is built on the west wall. This tower houses khus, or evaporative pads, on its outer surface, fed by a water pump. The inner side has adjustable windows opening into the adjacent rooms.

The natural wind pressure drives air through the wet khus and then flows into the adjacent rooms. This vertical arrangement spreads the khus fragrance across the two stories of the house.

In the summer, the combination of ceiling fans and evaporative cooling gives a comfortable environment, except during the pre-monsoon season of very high temperatures (100 degrees Fahrenheit, or 38 Centigrade) and high humidity (65 percent).

Courtyard Roof

The roofed courtyard of the two houses to the south is intended to be the main climate response device. The hipped steel frame roof is clad with a 3/4-inch (20-millimeter) glass sandwich, with a reflective film and frosted underside for the most part, with a panel of transparent glass on the south slope.

This is under-slung by a pair of razais (quilts), which can be pulled across to cover the underside of the roof (for insulation) or allowed to hang down vertically (to allow heat transfer). Above the roof is another frame in bamboo chics, which can similarly be opened to shade the roof or rolled up to catch the sun.

The ridge of the roof is a water channel from which water overflows onto the thin roofing membrane of stone and glass. Some water evaporates and excess water is collected at the foot of the slope and recirculated. This makes the roof a large evaporative cooler over the central space of the house.

All rooms communicate directly with this central space. This method of evaporative cooling supplements a conventional evaporative cooler and is effective even in the most hot-humid period. The operation of the roof component chic, water, razai is adjusted from winter to summer and from day to night.

Thus, the roof provides for, in turn, shading, insulation, evaporative cooling, and direct radiation. The dominant portion of the roofed courtyards with their quilts of mirrors and colorful cloth, the chics, and the possibility of visible monsoon and night sky, becomes a strong aesthetic response to the rhythm of seasonal cycles.

Ecohouse in Wales

Half a world away, in Monouth, Wales, is Tandderwen, home of David Johnson, designed by Andrew Yeats. This house implements a search for an architecture that would be nonpolluting, resource-conserving, and as respectful to the environment and people as possible. The owner wanted to be disconnected from the grid within a year after moving in.

Tandderwen combines wind and solar power to compensate for seasonal variances and to produce a consistent and steady supply of renewable energy. Twenty-eight BP Solarex photovoltaic panels, which provide a 2.1 kiloWatt peak rating, are mounted on a simple wood garden trellis, permitting optimal solar orientation without relying on the house's orientation.

This mounting also prevents excess heat build-up on the panels and allows them to be cleaned without the need for roof ladders. It also allows the system to be upgraded easily in the future.

When the wind is blowing more than the sun is shining, the 2.5 kilowatt Scottish-made Proven wind turbine provides supplemental power. A battery store ensures a backup electrical supply if the sun is not shining and the wind is not blowing.

Both the wind turbine and the photovoltaic array supply the battery, and the power is converted to 230-volt alternating current for running normal domestic appliances. However all appliances have been carefully selected to eliminate unnecessary demand and to optimize the efficiency of essential items. A low-energy cooker, refrigerator, and washing machine have been installed, along with low-energy compact fluorescent lighting throughout the house.

Passive Ventilation and Air Quality

Tandderwen is constructed in such a way that the vapor barrier is eliminated, which ensures that the permeability and density of the layers within the fabric reduce towards the outside. This layering system eliminates condensation.

Natural fabric scatter rugs over waxed reclaimed timber floors, organic paints and stains to walls, avoiding all formaldehyde and equivalents, combined with natural ventilation promise a healthy interior air quality.

These two houses serve as counterexamples to most of today's buildings, which collectively are the earth's most damaging polluters. Unless we stop making buildings that consume over half of all the energy used in developed countries and producing over half of all climate-change gases, we are in danger of destroying the planet.

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Sue Roaf is a professor at the School of Architecture, Oxford Brookes University, United Kingdom. She is known for her approach to design stressing awareness of energy efficiency.

This article is excerpted from Ecohouse2: A Design Guide, copyright 2003, available from Architectural Press and at



ArchWeek Image

West wall of courtyard house in New Delhi, showing "khus," or evaporative pads for cooling.
Photo: Ashok Lall

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Wind-driven evaporative cooling.
Image: A.B. Lall Architects

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Looking up from the court to the multilayered roof.
Photo: Ashok Lall

ArchWeek Image

Sections, New Delhi courtyard houses.
Image: A.B. Lall Architects

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Interactive courtyard roof.
Image: A.B. Lall Architects

ArchWeek Image

Tandderwen, a house in Monouth, Wales, by Andrew Yeats.
Photo: Andrew Yeats, Eco Arc

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Photovoltaic array at Tandderwen.
Photo: Steve Wade, Wind & Sun Ltd. Email:

ArchWeek Image

Ecohouse2: A Design Guide.
Image: Architectural Press


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