Solar passive features in vernacular architecture of North-East India

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Solar Energy 85 (2011) 2011–2022

Solar passive features in vernacular architecture of North-East India

Manoj Kumar Singh a,⇑, Sadhan Mahapatra b, S.K. Atreya a

a Instrument Design and Development Centre, Indian Institute of Technology Delhi, New Delhi 110 016, Indiab Department of Energy, Tezpur University, Tezpur 784 028, Assam, India

Received 20 July 2010; received in revised form 5 February 2011; accepted 11 May 2011Available online 14 June 2011

Communicated by: Associate Editor Harvey Bryan

Abstract

Energy consumption in the buildings sector is very high and is expected to increase further due to improvements in living standard andincrease in the world’s population. Incorporating appropriate solar passive features in climate responsive buildings are good options forenergy conservation. This kind of building design integrates the micro-climate and architecture with human thermal comfort conditionsand improves the building energy efficiency. From ancient times, people have used solar passive techniques in vernacular architecturesthroughout the world. However, still there is a lack of understanding, both in qualitative and quantitative aspects of solar passive tech-niques in vernacular architectures of North-Eastern India. A field study has been carried out to find out the various solar passive featuresin these naturally ventilated vernacular buildings in different bioclimatic zones of the region. The methodology of this work consists ofsurvey of 150 households (50 houses in each bioclimatic zone) and, interacting with 300 occupants in each zone. The photographic evi-dences of solar passive features in these buildings are also collected. In this paper, the solar passive features related to building form andorientation, envelope design, shading, use of natural ventilation, internal space arrangements and activities of the habitants are explainedfor all the climatic zone of the region.� 2011 Elsevier Ltd. All rights reserved.

Keywords: Solar passive features; Bioclimate; Vernacular architecture; North-East India

1. Introduction

The building sector is one of the biggest economic activ-ities throughout the world. The energy consumption in thebuildings sector is very high and is expected to increase fur-ther because of the improvements of living standards andincrease in the world’s population (BEE, 2010; Singhet al., 2009a). Typically more than 80% of total energy con-sumption in this sector occurs during the operation of thebuildings and around 20% during construction of thebuildings (Liu et al., 2010). Buildings account for 45% ofworldwide energy use and hence significant amount ofgreen house gas emissions to the environment is relatedto this energy use (Singh et al., 2009a). The construction

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doi:10.1016/j.solener.2011.05.009

⇑ Corresponding author. Tel.: +91 11 26591430; fax: +91 11 26582037.E-mail address: [email protected] (M.K. Singh).

industry in India is growing at 9.5% as compared to theworld average of 5.2% (BEE, 2010). Domestic and com-mercial buildings together consume 25% of total energyin 2007–2008. It represents the second major consumer ofenergy after industry in India (BEE, 2010). Building sectorelectricity consumption has increased from 14% in 1970s tonearly 33% in 2004–2005 (BEE, 2010). If energy efficiencymeasures are incorporated in the building judiciously, thenthe potential for energy savings could be 40–50% in thesebuildings (BEE, 2010). To meet the increasing energyneeds, particularly in developing and less-developing coun-tries, the climate responsive buildings or solar passivebuildings with advanced active systems seem to be mostappropriate and efficient solutions to this problem (Kumaret al., 1994). It is also important to mention that reductionin artificial energy (fossil fuel based energy sources) con-sumption directly leads to reduction in CO2 emissions to

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the environment. These all leads us to look again towardsthe vernacular architectures that exist around the worldthrough ages and in particular the North-Eastern regionof India.

The solar passive building design techniques were prac-ticed for thousands of years, by necessity, before the adventof mechanical heating and cooling (Chandel and Aggarwal,2008; Gupta, 1993). It has remained an integral part of ver-nacular architecture in many countries. The scientific basisfor passive solar building design has been developed fromthe combination of local climate, solar heat gain or lossand human thermal comfort (Hastings, 1995; Singh et al.,2009b). Specific attention has been given to the site andlocation of the dwelling, the prevailing climate, designand construction, solar orientation, placement of glazing-and-shading elements and incorporation of thermal mass(Knowles, 2003; Singh et al., 2009b).

Vernacular architecture refers to structures built usinglocally available materials in a functional style devised tomeet the needs of common people in their time and place.Most of the vernacular architecture responds to the regio-nal climate (Albatici, 2009). These kinds of structures gotmodified and evolved over time through feed-back mecha-nisms that already exists in the system, to reflect the envi-ronmental, cultural and historical context in which theyexists (Lau et al., 2007). As different climates require differ-ent architectural responses, in order to satisfy the variousnecessities, vernacular architectures developed throughthe centuries has many original and interesting design prac-tices and technologies (Singh et al., 2009b). The vernacularbuilding construction technique and specifications aremore based on knowledge achieved by trial and errorrather than conventional practices. This art is more oftentransferred by traditions and handed down through thegenerations. It is quite interesting to note that vernaculararchitecture provides a good solution to the climatic con-straints and there is more than one approach to solve thesame climatic constraint (Rakoto-Joseph et al., 2009).These solutions represent the perfect balance between nat-ural built environment and limited technical resources(Zhai and Previtali, 2010). The local builders and residentsalways try to amalgamate the climatic constraints, culture,social, economic and religion, while constructing thesebuilt environment with available resources and affordabletechnology (Dili et al., 2010; Tassiopoulou, 1996). Not onlythese architectures are suitable to the climatic needs of thedifferent areas, but also to the various economic, culturaland social needs.

Sometimes, it is also found that some of the vernaculararchitectures are not climate responsive. However, in thesearchitectures, cultural and social setup is the decidingparameter and overshadows the climate oriented features(Jeffrey, 1996; Ratti et al., 2003). In the modern buildings,many of the features of vernacular architectures can seemout of date; new materials, new technologies and new con-struction methods are in place. However, in an era whenenergy efficiency is an important area of concern, studying

vernacular architecture has still something new to explore(Al-Azzawi, 1994). Most often the solar passive featuresin the vernacular buildings are very difficult to quantify sci-entifically. However, by carrying out various measurementslike thermal performance study, comfort temperaturesevaluation etc., it is possible to explain the various solarpassive features of the vernacular architecture that persistin different climatic regions. Moreover the building sustain-ability aspects; such as economical, social and environmen-tal, are also truly satisfied in the vernacular architectures.

2. Bioclimatism and vernacular architecture of North-East

India

North-East region lies between 21–30�N latitude and89�400–97�180E longitudes with an approximate area ofabout 254,438 km2 (Singh et al., 2007). The entire North-East region has very uneven topography and the climateof any place is affected by the topography of the particularplace. The major landforms affecting the climate of the siteare mountains, valleys and plains. Above all the wholeregion is heavily vegetated. All these have varying effectson the microclimate of a place. Based on data collectedfrom Regional Meteorological Centre, Guwahati, India,North-East region is classified into three major bioclimaticzones namely: warm and humid, cool and humid and cold and

cloudy (Fig. 1) (Singh et al., 2007). This classification is car-ried out by considering ambient temperature, humidity,rainfall, wind speed, altitude, solar radiation and physicaltopography of the region. Specification of each climaticzone is presented in Table 1.

Indian vernacular architecture is the informal and func-tional structures in rural areas and built with local buildingmaterials to meet the needs of the people. Since it is evidentthat vernacular architecture is greatly influenced by thelocal climate thus the vernacular architectures of the regionacross the different bioclimatic zones are also widely variedin its built forms (Singh et al., 2009b). Vernacular housesconstructed in the region are in direct response to the localclimate, social and cultural setup (Bouillot, 2008; Singhet al., 2009b). This sort of spontaneous process besidesthe other forms leads to a new form of architecture whichthe people of this region commonly call it ‘Assam Type’.This Assam Type architecture form is quite simple, eco-nomical, satisfies the social setup, cultural needs and aboveall, it intelligently meets the climatic requirements (Singhet al., 2009b).

Vernacular buildings of warm and humid climatic zoneuses locally available materials like cane, cane leaves, bam-boo in different forms, wood, mud, lime, and backed bricksin different proportions (Singh et al., 2009b). Surkhi (mix-ture of lime, brick powder, sand and jaggery) is used asbinding material to fix the bricks. Common buildings mate-rials like wood, bamboo, processed mud are used to buildthe houses of the cool and humid region (Singh et al.,2009b). Bamboo is used to make external walls of thehouses. External walls are made of reinforcing woven bam-

Fig. 1. Bioclimatic zones of North-East India (Singh et al., 2007).

Table 1Specifications of bioclimatic zones of North-East India (Singh et al., 2007).

Bio-climatic zones Warm and humid Cool and humid Cold and cloudy

Temperaturerange

Summer Maximum 30–35 �C Maximum 25–30 �C Maximum 20–25 �CMinimum 22–27 �C Minimum 20–24 �C Minimum 14–19 �C

Winter Maximum 25–30 �C Maximum 20–25 �C Maximum 15–20 �CMinimum 10–15 �C Minimum 10–15 �C Minimum 5–10 �C

Humidity (%) 75–90 75–95 80–90Rainfall (mm) 1700–2100 1500–2000 >2000Sky condition Generally clear sky but overcast during

monsoonGenerally clear sky but heavy overcastduring monsoon

Occasionally clear sky but overcastsky rest of the year

Winddirection

Low wind during summer and from SE,N & NE direction

High wind during summer and fromE, SW & W direction

Medium wind from NE, SW & Wdirection

Vegetation Heavy vegetation Heavy vegetation Heavy vegetation

M.K. Singh et al. / Solar Energy 85 (2011) 2011–2022 2013

boo strips between two layers of processed mud. Processingof mud is done by adding beaten straw or chopped jute,cow-dung and lime (Singh et al., 2009b). Baked mud bricksare used in urban houses. These bricks are generally madelocally and backed in small oven made for this purpose.Older houses have thatched roofs (straw/grass) but due

to lack of availability, thatch is being replaced by galva-nized tin sheet nowadays. Building material availablelocally i.e., wood, bamboo, cane, dried cane leaves, stonechips, rock slabs cut in the shape of bricks, surkhi etc.,are used to construct the vernacular houses of the coldand cloudy region (Singh et al., 2009b).


This study is carried out to find out the different solarpassive features that exist in vernacular architectures ofNorth-East India. Vernacular architectures across theNorth-East India are very popular, widely constructedand naturally ventilated. No serious study has been doneso far related to the existing solar passive features in thevernacular architectures of the region and their role inmodifying the built environment. The study related to ther-mal performance of these vernacular architectures revealsthat these houses are not significantly comfortable in win-ter but fairly comfortable in pre-summer, summer andpre-winter seasons (Singh et al., 2009a). The houses in coldand cloudy climatic zone provide better comfort in com-parison to the vernacular houses in other climatic zones(Singh et al., 2009a). The methodology for this work con-sists of survey of 150 households (50 houses in each biocli-matic zone) and interacting with 300 occupants in eachbioclimatic zone. The photographic evidences of varioussolar passive features of these buildings are also collected.The effectiveness of the existing passive features areexplained on the basis of building form and orientation,envelope design, shading, use of natural ventilation, inter-nal space arrangements and activities of the habitats basedon the survey and information collected during interactionwith the occupants of these houses.

3. Solar passive features in vernacular architecture of North-East India

A solar passive house/structure is designed such that itmakes effective use of solar radiation to warm up indoorsin winter for heating and to block out this radiation in sum-mer for cooling and provides better indoor illuminationthrough natural lighting (Nayak and Prajapati, 2006).The design of solar houses/structures requires a detailedunderstanding of the complex relationship among architec-tural textures, human behaviors, culture and climatic fac-

Table 2Bioclimatic features in vernacular buildings of different climatic zones.

Bioclimatic features Bio-climatic zones

Warm and humid Cool and h

Building area (forsimilar familystructure)

Large with open spaces Less than w

Infiltration High HighEnvelop tightness Low LowShading Present and prominent Not specificWindows to walls

ratio0.22 0.15

Courtyard Present in rural houses but not inurban houses

Present in rurban hous

Orientation ofbuilding plan

Rural houses are E–W direction, southfacing and urban houses are notspecific

Rural housefacing and uspecific

Shape of buildingplan

U-shaped or rectangular (elongatedplan)

Rectangular

tors (Milne and Givoni, 1979; Nahar et al., 2003). Thisstudy is focused on the different solar passive features avail-able in the vernacular buildings in different climatic zonesof the North-Eastern India, based on the survey of vernac-ular architectures at representative locations in different cli-matic zones. The solar passive features reported in thisstudy are related to climatic design, construction materials,activity, topography and built environment. Table 2 pro-vides the various bioclimatic features presents in the ver-nacular buildings of different climatic zones.

In the following sections, the different design aspects ofthe vernacular architectures that exist in the various biocli-matic zones of the region are discussed in details. The mostsignificant solar passive features that are found in thesearchitectures are identified and explained in the subsequentsections.

3.1. Warm and humid climate

3.1.1. Building form and orientation

The building forms of the vernacular architecture ofwarm and humid climate are U shape and elongated plan.Fig. 2 represents the common building plans that persist inthis climate. The shape of the building is in such a way thatit makes most of the surface area exposed to prevailingwind direction. This helps in excess heat loss for thermalcomfort and enhanced natural ventilation to the buildingwhich is one of the essential requirements to overcomethe high humidity of this climatic zone. It is also found thatthe orientations of buildings are East–West direction andsouth facing. This is also the preferred direction becausein this orientation, the courtyard receives maximum sun.Since courtyards lies outside the main building plan andextensively used for post harvesting activities and socialand cultural functions. In the buildings of this climaticzone, it is always made sure that the sources of moisturelike bathroom, toilets etc. are always kept separate from

umid Cold and cloudy

arm and humid Less than warm and humid and cool andhumid

LowMaximumNot present0.11

ural houses but not ines

Not present

s are E–W direction, southrban houses are not

On south slope of mountains to receivemaximum solar radiation and avoidprevailing wind

shape or L-shaped Square plan

Fig. 2. Vernacular architectures and solar passive features in warm and humid climatic zone: (A) approach and open space in front of the building, (B)Chajja and extended roof, (C) window overhang, (D) adobe house construction, (E) structure in veranda to block afternoon sun from entering in therooms, (F) window blind made up of wood and selectively operable, and (G) air gap in ceiling.


the main building plan. Most of the buildings are singlestory and very few are double story.

3.1.2. Envelope design

The vernacular building envelops of this climatic zoneare massive in construction. Massive walls are either madeup of mud or backed bricks, but all have light weight roofs.Most often galvanized tin sheets are used for roofing. How-ever, thatched roofs also exist in this climatic zone. Massivewall has the property of storing and radiating heat (capac-itive effect) (Kruger and Givoni, 2008). By providingproper thickness and tightness, these walls can be effec-tively used to modulate the indoor temperature.

Fig. 2D represents of an adobe house construction.Adobe is prepared with a mixture of soil containing clay,water and lime. Addition of lime protects walls frommoulds and fungus formation. It is interesting to note thatbeaten straw, chopped jute, sand and gravel etc. are notadded to mud for processing. The mud-blocks are preparedon site and placed one above the other to erect the walls.Thickness of this type of wall is around 0.51 m. Since thisregion receives heavy rainfall the entrances of the housesare pulled inside. To minimize the damages due to rainfall,the walls of the mud houses are made on the raised plat-form so that the drained water from the roof cannot crum-ble the side walls. In most of the houses in this climaticzone, the inter-room partition walls are made by reinforc-ing woven bamboo between layers of mud. Some pukkavernacular houses, more than 70 years old are still in use.These houses are constructed using bricks and surkhi (usedas mortar to bind the bricks and for plastering the walls).Studies show that a wall of 0.38 m to 0.51 m thickness,made up of surkhi and backed mud brick give a time lagof 10–15 h (Singh et al., 2009b).

From the Table 1, it is evident that warm and humid cli-mate zone receives heavy rainfall. To overcome this cli-matic constraint, all the vernacular houses have slantingroofs facing two or four directions. In most of the cases,roofs are extended to act as an overhang to protect the wallfrom rainfall and also from direct solar radiation (Fig. 2B).It is also found the chimneys and vents arrangements existin the roofs. This feature allows warm air of attic space toescape, leading to the formation of natural draft andenhanced natural ventilation (Fig. 3).

3.1.3. Shading, openings and use of natural ventilation

Windows, doors and ventilators play an important rolein modifying the indoor environment in vernacular archi-tecture of this region. In this climatic zone, the windowto wall ratio is about 0.216, which results in large numberof openings (Fig. 2A and B). The windows and ventilatorsare about 50% of the total floor area, which in turn help inachieving the enhanced ventilation. It is found from thefield measurements that the interior natural illuminationlevel is 15–22 lux, which is far below the standards (50lux for family living rooms) (Singh et al., 2009b). This isbecause the windows and ventilators of most of the housesdo not have glazing. It is also observed that wooden blindshave been attached to the doors and windows of the oldvernacular houses from outside (Fig. 2F). These blindshave the provision of selective opening (Fig. 4). This fea-ture provides enhanced control to the occupants to letthe desired daylight to come indoors. It can also be keptin such a way that it allows only the diffused solar radiationto enter indoors. Doors have also the same provision andcan be operated in same manner to modify the indoor envi-ronment to retain the comfort conditions. Movable woo-den blinds on doors and windows can be opened

Fig. 3. Warm air escapes through the vents and chimneys on the roof in warm and humid climate.

Fig. 4. Window construction techniques in warm and humid climate.


outwards and the internal doors and windows to interiors(Fig. 4). In this kind of doors and windows interior win-dows and doors are fitted with glazing (Fig. 4). Naturalventilation and air exchange are used to regulate the indoortemperature in these houses. To achieve this, local winddirections and position of windows, doors and ventilatorsplay a major role. The high level of humidity in this cli-matic zone throughout the year constraints the design touse the natural ventilation and air exchange effectively.Vernacular houses of this zone are porous in constructionand infiltration is very high.

Fig. 5. Shading (Chajja) and blinds at veranda to block a

Shading plays an important role in modulating heat gainof the building. Vernacular houses of this zone have over-hangs (Chajja) on windows and also roofs are extendedoutward to act as overhang (Figs. 2C and 5). Extendedroofs and overhang on windows not only protect the wallfrom crumbling due to rainwater but also provides shad-ing. Fig. 2E shows a veranda on the East–West side run-ning along north to south of a school building. A verticalwooden structure is provided on the west side veranda toblock the afternoon sun from entering the classrooms(Fig. 5). It is also observed that the vegetation is effectivelyused for shading.

fternoon solar radiation in warm and humid climate.


3.1.4. Internal space arrangements

Ceilings of the vernacular houses play an importantrole. Different types of materials like plywood, asbestossheet, wooden planks and woven bamboo mat etc., areused to make ceilings. Ceiling separates the living volumefrom the attic. It also minimizes the heat gain during sum-mer and heat loss in winters. In these architectures theheight of the ceilings are about 4.57 m to 5.49 m and havean opening in the extreme end. The height of the ceilingand the openings help in the formation of natural draft.The warm air escapes through the opening and finallythrough chimneys and vents provided on rooftops(Fig. 6). In some of the houses, multilayered ceilings andair gap between the false ceilings are also found(Fig. 2G). These features provide the enhanced insulationto the ceiling. There is a provision to regulate the openingsprovided in the ceiling. In summer it is kept opened so thatthe warm air can escape and leads to the formation of nat-ural draft. However in winter, it is kept closed to trap thewarm air in indoors.

Vernacular architectures of warm and humid climatehas minimum of 3–4 rooms excluding veranda, kitchenand bathrooms, in some of the houses, the number ofrooms goes up to 7–8. Basically numbers of rooms dependon the number of family members and socio-culturalrequirements. General dimensions of rooms are about3.05 m by 4.27 m to 4.27 m by 4.27 m. Building plan isdone in such a way that each family member gets adequateprivacy and comfortable space in the buildings.

3.1.5. Activities areas

Vernacular architecture is a good example that explainsthe balance that exists between local climate, available localmaterial, affordable technology, design techniques, living

Fig. 6. Air movements in the room and escape thro

style, traditions and socio-economic conditions of theregion. While constructing a house the residents alwaystry to address the climatic constraints, culture, social, eco-nomic and religion. The requirements of the people putforth a form of architecture called ‘Assam Type’. Itsuniqueness lays in its simple form, easy to built, economic,light structure, maximum use of locally available material,slanting roof and proper ventilation. Above all, the func-tionality of this assam type house meets the socio-culturalrequirements. These features make this architecture verypopular in North-East and still it is being widely con-structed. It is also found that rural houses are differentfrom urban houses. Courtyard is common and integral partof these kinds of residential architectures. Courtyard actsas an activity centre by supporting social gathering duringfestivals and celebrations. It also acts as a climate modifierby collecting cool air in night time and a source of shade inday time. It also plays important role in natural ventilationand enhanced air circulation. Since the region is an agricul-tural driven economy, so courtyard is also very often usedfor post harvesting activity, like drying and winnowing.Transition spaces like veranda, corridors etc. are very com-mon and act as buffer space in these buildings. This spacehas got added advantages as this can be modified accordingto the needs in summer and winter months to maintain theindoor comfortable conditions.

3.2. Cool and humid climate


The common layout (Fig. 7) of the vernacular architec-tures of this climate is L shaped or rectangular shaped(elongated plan). The orientations of the houses areEast–West and south facing to receive maximum solar

ugh vent on roof in warm and humid climate.

Fig. 7. Vernacular architecture and solar passive features in cool and humid climatic zone: (A) wooden framed two story house and courtyard, (B)thatched roof house, (C) extended roofs, openings in the form windows and doors, (D) internal wall construction on which processed mud will apply, (E)wall with thick layer of processed mud, and (F) floor is elevated from the ground.


radiation. L shape house plan provides a large veranda.People of this region use the veranda for installing tradi-tional weaving equipment. It also acts as a buffer spaceand is easily modified according to requirements in the dif-ferent seasons of the year. This shape also provides an openspace in front of the house. Every house in this region hasan open shaded structure which acts as a store for agricul-tural equipments and extensively used for social meetingsand festivals (Fig. 7A). The open space also guides theair movement and act as a climate modifier.


Vernacular house of this zone generally have lightweightstructures. Rural houses are based on wooden frame struc-ture but urban houses are brick structures. The thickness ofexternal wall in urban house is around 0.20 m to 0.38 m butin rural houses the external wall thickness is 0.07 m to0.13 m. In both the cases inter room partition walls are0.07 m to 0.13 m thick. Vernacular houses in urban setupuses surkhi as plaster and binding agent to fix the bricks.A typical rural house in this climate zone is a low energystructure. These houses use locally available building mate-rials. The walls of vernacular houses are made by reinforc-ing a particular species of bamboo (locally called sigmit)between the two layers of processed mud (Fig. 7A). Mudis processed by adding cow dung, lime and beaten strawor chopped jute. It is interesting to find that processingof the mud is not done in the other climates. Processingof the mud enhances the binding properties and increasesthe porosity of mud. Increased porosity actually increasesthe water retention property of the mud and which internprovides resistance to temperature change and helps toretain comfort conditions at indoors. The houses are con-structed on raised platform. Floor height is around 0.4 mto 0.5 m from the ground (Fig. 7B). This protects the walls

from the drained water in rainy season. During the interac-tion with local people, it is also found that they favor theuse of this particular bamboo in wall construction becauseit shrinks very less when dried in comparison to other avail-able bamboo species. However, less shrinking does notdeteriorate the strengths of wall too much (Fig. 7D). Formtheir uses across the years they also come to know that it isalso less attacked by termites.

Fig. 7B and C shows the vernacular houses havethatched and tin roofs. Vernacular houses of these climaticzones have slanting roofs to overcome the heavy rainfalls.Earlier thatch (dried grass or straw that are tied togetherand are lied in layers on top of wooden or bamboo frame)roofs were quite common (Fig. 7B). Thatched roofs aregenerally made slanting on four sides due to ease in con-struction (Fig. 7B). Thatch is an excellent insulator andminimizes both heat gain or heat loss. One of the greatestdisadvantages with the thatched roof is that it needs tobe replaced after every 1 or 2 years. This leads to extra costin maintenance. Nowadays grasses are not readily availableso people started using galvanized tin sheets for roofing.Use of tin sheet increases the initial cost but has other ben-efits like long life, minimum maintenance.

3.2.3. Shading, openings and use of natural ventilationSize of windows and doors in the vernacular architec-

ture of this region are small. Ventilators are not presentin the houses of this region (Fig. 7C). In this climatic zone,windows and doors are about 30–40% of the total floorarea. Window to wall ratio is about 0.15. Very few houseshave glazing in the windows. Often windows and doors arecompletely made up of wood. This considerably reducesthe natural indoor illumination level. In our field experi-ments, it has been found that the natural illumination levellies in between 15 and 22 Lux. This natural illumination

Fig. 8. Vernacular houses on elevated platform and extended roof and gap between base of the wall and floor enhancing the air movement in cool andhumid climate.


value is very low as compared to the standard that lies at 50Lux in family living rooms.

Vernacular houses of this climate are porous in con-struction. In the study, it has been found that almost inall the vernacular houses, the external walls of the houseshave openings by about 5–8 cm from the floor (Fig. 8).This feature lowers the insulation level and increases theinfiltration. This gap usually increases discomfort in winterbut is good in summer as it helps in the formation of draftto enhance natural ventilation. In winter occupants of thehouses close these openings with the help of jute sacks.There is also a gap of 15–20 cm between the external walland roof. This feature also leads to the increase ininfiltration.

In this study, any specific feature in the vernacularhouses that may be related to shading has not found. Allthe vernacular architectures are built in such a way thatthey receive maximum solar radiation. Though in our ther-mal performance study, it has been found that due tounavailability of ceilings there is a discomfort period inpeak winter and peak summer months due to quick heatloss and heat gain. Roofs of the houses are extended towork as overhang (Fig. 7). However, these extended roofsare primarily constructed to protect the wall from heavyrainfall rather than for shading.


From the Table 1 and building bioclimatic charts, it isfound that most of the time of the year the outdoor condi-tions lies in the comfort zone (Singh et al., 2007). So build-ings of this region should not be tight on infiltration andnatural ventilation. Rather high infiltration and naturalventilation makes the indoor environment more comfort-able. The same phenomenon observed in the vernacular

houses of this region. In urban vernacular houses use ofceiling is common but not present in every house. Ceilingsare porous in nature and provide greater infiltration andenhanced natural ventilation. In rural houses false ceilingsare seldom found. Absence of false ceiling exposes theentire living volume of the room in direct contact to roof.So, there is sudden increase (heat gained by the roof radi-ated to indoors) and drop (heat loss) in temperatures of liv-ing volume. This leads to discomfort in peak winter andpeak summer months.

Vernacular architecture of cool and humid climate hasminimum 3–4 rooms excluding veranda, kitchen and bath-rooms. In case of joint family the number of rooms goes upto 6–8. Bed rooms are basically small in size i.e. 3.05 m by3.05 m. In all the houses one room is made relatively large.The size of this room is almost double the size of bedrooms. This space is often used as visitor’s/guest roomand for other social occasions. Rural houses have mudfloors plastered with a mixture of clay and cow-dung.Rooms are configured in such a way that each memberof the family gets adequate privacy and comfortable spaceas per social practice.

3.2.5. Activities areasThis study shows that vernacular houses of this climate

provides the adequate comfort space to its occupants aswell as met their social and cultural requirements. The ver-nacular houses are constructed using locally availablebuilding materials leading to economical structure. Useof locally available building materials provides maximumflexibility and adaptability to the local environmental con-ditions. Rooms of the house are configured depending onthe usability and also to meet the privacy requirements.As a tradition, a central room larger than other rooms is


must also be in the structure to meet the social and culturalrequirement. Veranda is generally made larger in size toaccommodate other house hold activities. There is alsoprovision in the houses for grain storage and other socialand cultural activities during family/festival celebrations.The courtyard is common in all the houses of the regionand has multiple uses like drying of crops, winnowing,cloth weaving and children playing space etc.

3.3. Cold and cloudy climate


Layout of vernacular architectures (Fig. 9) of this cli-mate is rectangular shaped and very few houses are L

shaped. There is no distinction in the plan of rural andurban houses. Orientations of the houses are major con-cern in this climatic zone. Almost all the houses are con-structed on south slope of the mountains. This is done toreceive the maximum available solar radiation. It is alsofound that the proper care has taken to obstruct the winddirections. Houses are constructed in such a manner thatthey do not fall in the path of prevailing winds. Verandasare not extensively used in this climatic zone as it is in othertwo climatic zones.


The external walls of this climatic zone buildings aremade up of rock slabs (cut in the shape of bricks). Thick-ness of the external walls is 0.25 m to 0.30 m. The vernac-ular house that are more than 70 years old, surkhi is usedas binding material and for plastering. However, in modernhouses surkhi is being replaced by sand and cement. Theinterior room partition walls are 0.03 m to 0.08 m thickand are made up of reinforced woven bamboo in the twolayers of mixture of sand and cement. Envelope is tightlyconstructed to minimize the infiltration. Houses are con-

Fig. 9. Vernacular architecture and solar passive features in cold and cloudy cslopes, receiving the maximum solar radiation and openings are smaller in sbamboo and wood and floor is elevated from the ground, (D) low energy dwellthe ground, and (F) arrangement of chimney to let the smoke out from the k

structed in such a manner that it surface to volume ratiosalways be less. The site planning of these buildings are alsovery important so that minimum area of building envelopeis exposed to the prevailing wind and total structure as ahole receives maximum solar radiation throughout theday (Fig. 9B). Floor of these houses are built at around1 m height from the ground. The space available underthe floor is used to store fire wood or keeping pets like pigsand poultry birds (Fig. 9E). In this climatic zone lowenergy houses are made up of bamboo and wood(Fig. 9C and D). These houses are generally constructedon raised platform of wood. Wooden planks are also usedfor flooring in these houses. To minimize the infiltrationfrom floors, entire floor is covered with cane mat. Driedcane leaves are used for roofing. Walls are made up ofmulti-layered (2–3 layers) woven bamboo tied together.To minimize the infiltration cane leaves are inserted inbetween the multiple layers of woven bamboo. The floorof this low energy architecture is generally elevated (0.50–1 m) from the ground (Fig. 9E). Vernacular houses of thisclimatic zone have also slanting roofs in two directions toovercome the heavy rainfalls like other climatic zones(Fig. 9B). Different types of materials like plywood, asbes-tos sheet, wooden plank, woven bamboo and cane etc. areused to make ceilings in this climatic zone. Ceiling sepa-rates the living volume from the attic and minimizes theheat loss in winter. In these traditional architectures theheight of the ceilings are about 2.45–2.75 m.

3.3.3. Shading, openings and use of natural ventilation

The size of windows and doors in the vernacular archi-tecture of this region are small in comparison to other twoclimatic zones (Fig. 9B). Ventilators are present in thehouses but are fixed permanently (Fig. 9B). The windowsand doors are about 30% of the total floor area. Windowto wall ratio is about 0.108. Windows and doors are

limatic zone: (A) thick wall made up of stone blocks, (B) building in southize, (C) low energy dwellings made up of locally available materials likeings on south slopes to receive maximum radiation, (E) floor is raised fromitchen and space heating arrangement.


completely made up of wooden frame. Almost all thehouses have got glazing in the windows and ventilators(Fig. 9A and B). Since room height is less so natural illumi-nation level is better in these houses in comparison to otherclimatic zones. The houses are compact, having minimumsurface to volume ratio. In other climatic zones, there isa gap between external wall and roof base (eaves) but thisis completely shielded in this climatic zone. This helps totrap the heat in the attic. There is also no provision to enterthe heat to the interiors through the ceiling. Shading tech-niques are not used in the houses of this climatic zone asthere is always a concern to receive maximum solar radia-tion available. The roofs are seen extended in all the sidesof the house only to protect the wall from the rain water.


Vernacular architecture of this zone has minimum 2–3rooms excluding veranda, kitchen and bathrooms. In caseof joint family the number of rooms goes up to 4–5. Bedrooms are basically small in size and are on the south side.This is done to keep the room warm using solar heat gain.Generally floors of bedrooms and guest rooms are woodenbut floors of veranda, kitchen and bathrooms are cemen-ted. One difference in the plan of the houses of this zoneis that the bathrooms are constructed in interiors. But toi-lets are still constructed separately from the main buildingplan. One prominent structure in the kitchen is the cookingplace. Cooking is generally done in open air, by burningfirewood. Cooking place in the kitchen is located in sucha way that heat generated by its radiation can enter tothe leaving area. There is chimney arrangement in everyhouse to carry the smoke out (Fig. 9F). Other than this,there is always a provision of fire place in almost all thevernacular houses. These are generally used in winter daysand wood charcoals are used as fuel.

3.3.5. Activities areas

Vernacular architecture of cold and cloudy climate isgreatly influenced by the prevailing climatic conditions.Main concern of the vernacular building design is maximiz-ing solar heat gain and minimizing heat loss. The housesare made compact with small number of rooms of lesserarea. This is also made easy because family size is small.From the interaction with the occupants, it is found thatthe vernacular houses fairly satisfy the social and culturalneeds of the occupants in these buildings. The people ofthis climatic zone together make a community centre whichis being used by the people at the time of festivals andsocio-cultural events.

4. Conclusions

Vernacular architecture of North-East India serves agood example towards the bioclimatic building design. Itis quite interesting to note that this vernacular architectureprovides a good solution to the climatic constraints of theregion. The existing vernacular buildings represents an

excellent balance between local climatic constraints, useof locally available building materials, design techniqueslearnt through ages, supporting existing living style andtraditions and socio-economic conditions. Use of locallyavailable building materials has certain advantages forexample since the material is from same climatic condi-tions, it shows more adaptability, longer lifespan and bettereconomic. From environmental point of view this hasadded advantages such as: (a) low environmental impactin production, renewability and even natural dissolution(b) significant reduction in energy involved in processingand transport and (c) make the structure light, flexibleand with good anti-seismic.

The local builders learnt the techniques from formergenerations and always try to explore better solutionswithin the existing resources. This sort of spontaneous pro-cess leads to a new form of architecture which is called as‘Assam Type’. This assam type houses are semi-pukkaand pukka forms of buildings. The unique features ofassam type house are (a) wooden framed walls for anti seis-mic (b) roof arrangements (c) false ceilings (d) proper ven-tilation and (e) using locally available building materials.This type of architecture form is quite simple, economical,satisfies the social setup, cultural needs and above all, itintelligently meets the climatic requirements. The buildingplans of the commonly available houses of climatic zonesare presented and corresponding functional building dia-gram has been developed based on these common buildingplans that meet the socio-cultural requirements. It has alsobeen found that some solar passive techniques are used inthese houses to control the indoor environment andaddress the existing climatic constraints.

In this study on vernacular architecture of warm andhumid zone, it has been found that these kind of architec-tures are quite different from the modern times rural orurban houses. Rural and urban houses, those are con-structed around 70 years back are of similar architecture.Envelopes of these houses are constructed massive usingthe locally available material to use its capacitive effect tominimize the indoor temperature fluctuations. Over allstructure of the buildings are made porous and orientedin such a way that most of their surface area is exposedto the prevailing wind directions which enhances the natu-ral ventilation. This also helps to overcome the discomfortcaused by the high humidity present in the air. Slantingroofs are extended to act as overhang. The extended por-tion of the roof, shades the considerable portion of wallto minimize the heat gain and also protect the walls fromgetting in contact with the draining rain water from theroof. Ceiling in the vernacular architecture is constructedusing different materials to separate attic space from theroom volume. The height of the rooms, vents and chimneyspresent on the roof tops are used intelligently. In thesearchitecture the doors and windows are about half of thefloor area. Movable ventilators are provided above thedoors and windows. Large numbers of windows and venti-lators provides the needed natural ventilation. However,


lack of glazing in the windows leads to low level of indoornatural illumination. Examples of different shading tech-niques are also observed. Overhang over the windows arevery common features in the houses. Courtyard plays vitalrole in the vernacular building plan of this climatic zone. Itserves multiple purposes starting from climate modifier tomeeting day to day requirements and social-cultural needs.It is also found that toilets and bathrooms are kept sepa-rate from main building plan because of religious beliefsand to avoid excess moisture and to maintain the highhygiene level.

Vernacular architecture of cool and humid climate islight structures. Concern for prevailing climates like highhumidity, heavy rainfall and wind is found in the existingarchitecture. Lot of openings leads to high infiltration.Doors and windows are small in size and small in numbersleads to low illumination level. Size and configuration ofrooms depend on the functionality. Seldom use of ceilingis found in vernacular houses of rural area. However, over-all layout and building plan satisfies the occupant’s require-ments and socio-cultural setup. In rural houses courtyardalso plays a vital role and function as activity centre.

In cold and cloudy climate, concern for prevailing cli-matic conditions can be easily observed in the design ofthe houses. These houses use locally available materials.Houses are compact and show acceptable thermal perfor-mance. These houses provide better comfortable time incomparison to the houses in other climatic zones. Sincethe functionality of the houses is in accordance to the needsof the occupants and have enhanced control over indoorenvironments. It is also necessary to mention that in thesehouses, habitants have the flexibility to control their per-sonal privacy and environmental conditions in the formof different adaptive actions (Singh et al., 2011). It alsocan be justified form the long term monitoring study ofthe houses, that the existence of solar passive features inthe vernacular houses of the region make the houses com-fortable to live in. This study also found that the architec-ture of cold and cloudy zone has shown better thermalbehavior in maintaining comfortable indoor environment.This study satisfies us to enlist the existing features andtheir usefulness.

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Solar passive features in vernacular architecture of North-East India

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