In India demand of housing particularly in residential sector is growing-up. The policy makers in India have planned to provide shelter to every shelterless people by providing disaster-resistant housing in urban and rural areas. Stress has been given on 'affordable and durable houses' and adoption of 'cost-effective, environment-friendly housing 

construction practices'. In the Union Budget 2009-2010, the honourable Finance Minister has rightly emphasised on low-cost housing and boosted up the
rural housing sector by allocating Rs.8800 crores for Indira Awas Yojna, which is 63% higher than the previous allocation. He has also created a 2000-crore
Rural Housing Fund under the National Housing Bank. The budget also has allocated Rs.3973 crores for housing and provisions for basic amenities for the
urban poor. The sum also includes provisions for a new scheme "Rajiv Awas Yojana (RAY)". At the same time under the National Action Plan on Climate
Change, "Sustainable Habitat" is also a key issue, where stress has been given on energy efficiency in buildings. This paper is an attempt to find out the
best alternative to keep the commitment of the government both in 'housing' and 'climate change' sectors.

Changing Housing Scenario in India - from Kutcha to Pucca

As per the Census reports and other reports by different Government Departments, the house types are gradually transforming to Permanent ("Pucca"
Houses - in which the walls and roof of which are made of permanent material) and Semi Permanent ("Semi Pucca Houses" - in which either the walls or the roof is made of permanent material) types from  Temporary ("Kutcha Houses" - in which both the walls and roof are made of materials that needs to be
replaced frequently) in both rural and urban areas.

In the National Urban Housing and Habitat Policy 2007 of Government of India, current housing shortage in Urban Areas has been estimated as 26.53
million units. Whereas the Working group on Rural Housing for the 11th Five Year Plan - Ministry of Rural Development estimated Housing shortage in
Rural Areas as 47.43 million units. If the trend of conversion into "pucca" houses from "semi-pucca" / "kutcha" continues it is expected that by 2012, about
81% permanent houses in urban areas and about 50% of permanent houses in rural areas will be constructed to fulfil the declaration of "Housing for All" by the Government of India under the National Housing and Habitat Policy 1998. The trend of conversion from Temporary to Permanent or Semi-Permanent structures is likely to continue in view of economic upliftment of common people and different government schemes on providing durable shelters to people
of economically weaker section and lower income group. It has been stated in the Government Policies that about 99% of the housing shortage pertains to
Economically Weaker Sections and Lower Income Group sectors. To provide minimum basic housing need it may be considered that about 45.2 million
housing units with a minimum area of 25 square meter as per the standards of Indira Awaas Yojna scheme will be required, which means a total of 1130
million square meter of built-up space needs to be constructed by 2012.

Common people in India always prefer masonry wall and R.C.C. roof for a building of permanent nature. As per Indian Standards, the peripheral and
main load-bearing masonry walls of any permanent building should be of thickness not less than 230 mm (one brick thickness).

Production and use of Building Materials emits Greenhouse Gases

The process of construction of buildings consumes huge amount of energy and in turn produces large volume of GHG. Among the top seven sectors
contributing to CO2 emission in India, Construction sectors tops the list with about 17% of the total share, when both direct and indirect emission are
considered. This emission comes from production and transportation of building materials like brick, cement, steel, crushed stonechips (coarse aggregate),
sand (fine aggregate) etc.

Brick manufacturing using existing brick kilns in India, which use coal as principal fuel, produces CO2 at the rate of 38 tons per one lakh (0.1 million) of
brick. The above figure was calculated by Global Environment Facility (GEF) in their study on brick production in Bangladesh. Apart from production of
CO2, production of burnt clay bricks also results in serious environmental degradation through exploitation of the top soil mainly from arable lands. production processes of cement and steel are also energyintensive and huge amount of CO2 is emitted during  the process. Emission from crude steel production in sophisticated plants is about 2.75 ton CO2 per ton of crude steel. We may take it as 3.00 ton per ton of processed steel. Sand is another important ingredient of modern building construction and is available from natural sources like riverbeds or queries. But transportation of the same by trucks requires energy.

About 2.62 kg of CO2 is produced per litre of diesel consumption. If it is considered that average transportation distance for sand from the point of collection to point of use is 50 km then the CO2 emission per cu.m of sand will be 3.85 kg or 0.004 ton.

Considering diesel-operated machines at production point and transportation by diesel-run trucks, we can find out that CO2 emission per cu.m. of use of stonechips is about 8.2 kg or 0.008 ton.

"Eco-houses" - a solution to housing shortage and climate change.
There are ample scopes of reduction of emission of GHG from construction activities by reducing use of building materials as far as practicable using innovative  and cost-effective technologies. Cost-effective Construction Technologies and alternate construction materials can bring down the embodied energy level associated with this activity by lowering use of energy-consuming building materials. Since the cost of construction will also be reduced without any change in type of building materials, a strong market force will also be created facilitating use of such technologies. The 'Eco-houses' (Economic and Ecofriendly) would be an ideal and effective solution for the construction sector.

Cost-effective and eco-friendly technologies do not mean low-grade construction with inferior quality materials or compromise with the safety of the buildings and comfort of the inhabitants. Rather the technologies follow the relevant building codes and can also improve the comfort level of the users if designed properly.

The most popular and time-tested cost-effective and eco-friendly technologies (CEEFT) for construction of permanent buildings in India are Rat-trap bond wall, Brick Arches and Filler Slab roof. There are some more available technologies like Compressed Earth Block (CEB) wall, Bamboo Reinforced Cement Concrete (BRCC) panels in walls and roof, Ferroconcrete tiles in roof, Composite Brick Panel roof etc., which require specialised manpower and machinery and also involves production of building components separately. But Rat-trap Bond wall, Brick Arches and Filler Slab Roof uses the familiar building materials like ordinary brick, cement, sand, steel and clay tiles. They do not require any specialisation or special equipment for production. Any ordinary
mason with some initial guidance can build Eco-houses.

Rat-trap Bond Wall

Rat-trap bond is laid by placing the bricks on their sides having a cavity of 4" (100mm) with alternate course of stretcher and headers. The headers and stretchers are staggered in subsequent layers to give more strength to the walls. The main advantage of this bond is economy in use of bricks, giving a wall of one brick thickness with fewer bricks than a solid bond. The main features of Rat-trap bond wall are:

• Strength is equal to standard 10" (250mm) brick wall, but consumes 20% less bricks.
• The overall saving on cost materials used for construction compared to the traditional 10" wall is about 26%.
• The air medium created in between the bricklayers helps in maintaining a good thermal comfort inside the building. This phenomenon is particularly
  helpful for tropical climate of South Asian and other countries.
• As the construction is done by aligning the bricks from both sides with the plain surfaces facing outwards, plastering is not necessary except in a
  few places. The finished surface is appealing to the eye from both internally & externally,
• Buildings up to two stories can easily be constructed with this technique. Mr. Laurie Baker has pioneered this type of construction and had built
  such houses more than 40 years ago without having any signs of distress till now.
• In R.C.C. framed structures, the filler walls can latease be made of rat-trap bond.
• Due to lesser load on the base of the walls, the width of foundation is also decreased, resulting in a saving of about 8% on use of bricks, cement and
  sand in foundation and plinth.

Brick Arches

The traditional R.C.C. lintels can be replaced by brick arches for small spans and save construction cost upto 30% by way of reducing use of cement and steel. Arches of different shapes combined with brick corbelling also produces excellent architectural appearance to the external brick masonry wall surfaces.

Filler Slab

This is normal R.C.C. slab where in the bottom half portions, between two reinforcement bars, concrete is replaced by filler materials such as bricks,
tiles etc., These filler materials are so placed as not  to compromise with structural strength and also becomes lighter than normal slabs. As use of steel,
cement and other aggregates are less the filler slab becomes less costly. These are safe in terms of load bearing capacity also.

The main features of Filler Slab are:

• Consumes less concrete and steel due to the reduced weight of the slab by the introduction of a lighter, low-cost filler material like burnt clay tiles.
  Reinforcement bars are placed in between the filler materials.
• Enhances the thermal comfort inside the building due to heat retardant quality of the filler materials and the air gap between two burnt clay tiles.
• Make saving on cost of this slab compared to the traditional slab by about 23%.
• Reduces use of concrete and saves cement, sand & stonechips by about 49%.
• Reduces use of steel by about 13%
• Plastering of the ceiling is optional. It produces a good look if plastering is done only on concrete surface of the ceiling.

By adopting the techniques mentioned above a straightaway reduction of 17% to 20% can be achieved in cost of construction of the basic structure without compromising with the safety, durability and aesthetic aspect of the buildings and for a 25 sq.m. single-storied residential house for Low Income Group or Economically Weaker Section, the saving will be to the tune of Rs.26000/- i.e. about Rs.97/- per sq.ft.

And in terms of reduction of Green House Gas emission by lowering quantities of building materials, reduction in CO2 emission for construction of
basic foundation and superstructure of a 25 square meter single-storied residential building is about 2.13 MT.

If we consider that about 50% of 1130 million square meters i.e. 565 million square meter of builtup area that has to be constructed in India to meet the housing shortage would be of permanent nature, we can reduce Green House Gas emission by 48 million tons by constructing Eco-houses.

As 17% saving is a sizeable amount also for people from Economically Weaker Section, Lower and Middle CO2 emission from building materials used for basic structural work in foundation, superstructure and roof for a single-storied residential building of 25 sq.m. built- up area income groups, the 'Eco-houses' (Economic and Ecofriendly) will be a natural choice for people of India and it will, in turn, be beneficial to the environment also.

Need of the Hour …….Till now most of the Government bodies and Municipalities of India are reluctant to accept this technology and give permission to people to build their house with Cost-effective Technologies. The market force of cost reduction will definitely play a major role in acceptance of Cost-effective Technologies if Governments / Municipal Bodies acknowledge these technologies and direct their concerned departments to adopt them. Promotion of cost effective technologies through institutes like the HUDCO sponsored Building Centres has to be rejuvenated. Effective steps like training and skill upgradation of masons, Sensitisation of architects, engineers, technicians and common people through awareness generation programmes are of utmost importance to promote and  popularise Eco-houses.

Acknowledgement:

• Laurence Wilfred "Laurie" Baker (1917-2007) - the British-born Indian Architect who pioneered costeffective energy efficient construction technology
  in India.
• Ar. Anadi Sankar Bose, Er. Gopinath Chatterjee, Er. Sudin Nandi of Forum of Scientists, Engineers & Technologists (FOSET).
• All those who are relentlessly working to popularise the cost-effective technologies in our country.
• Science & Society Division, Dept. of Science & Technology, Govt. of India.
• Housing and Urban Development Corporation of India (HUDCO)

Nilanjan Sengupta,Secretariat Member,Forum of Scientists,Engineers & Technologists (FOSET)