SUSTAINABLE COMFORT

Sustainable spatial comfort-case study of naturally ventilated buildings in Olubadan estate Ibadan

By

Adewale Adunola and Kolawole Ajibola

Dept of Architecture O.A.U.Ile-Ife

There is constant exposure of buildings to solar radiation in the tropics and this leads to overheating of interiors. This makes indoor comfort a challenge to architects in this region.  Most of the countries in this part of the world are not as rich as the developed countries.  Air-conditioning of building spaces in these countries would render the buildings unsustainable. This paper examines the sustainability of thermal comfort within the living spaces of naturally ventilated residential buildings in the warm-humid climate of Ibadan, Nigeria.   

 The concept of comfort provision through natural means needs to be assessed to determine the viability of residential buildings constructed to be naturally ventilated in the warm humid climate. It seems as if people living in the warm-humid climate may be finding the endoclimate endurable with the general building tradition of free-running buildings.  There is however a need to examine the extent to which these buildings are thermally comfortable.  The measure of the comfort experience of the occupants would indicate the acceptability or non-acceptability of the buildings with reference to sustainability. 

            Unfavourable environmental conditions reduce the level of human performance. A comfortable indoor environment must be created for human activities. Residential buildings which are occupied for the most part of the day need to provide adequate comfort for the occupants. However, in Nigeria, buildings can be thermally uncomfortable for considerable periods. This may be due to poor design standards. Costa (1989) observed that traditional buildings in Nigeria have laid too much emphasis on socio-cultural and economic factors to the neglect of environmental factors. Ajibola (1997, 2001) highlighted the problems of adopted European building design and repetition of buildings in locations of different climatic conditions. Also highlighted are problems of improper orientation, sizing of windows, building shapes and forms that are non-functional. Barozzi et al (1992) stated that there are constraints of extreme environmental conditions, poor building technology and limited financial resources manifesting in low standards of thermal comfort of buildings in developing countries.

            There is need for concerted effort to formulate new passive building technologies for the developing countries in the warm humid climate.  The incessant electric power outages in Nigeria for example, point to the fact that active air-conditioning systems can not be relied upon for the provision of indoor comfort.  Studies focusing on the attainment of thermal comfort in naturally ventilated residential building spaces are desirable.  Provision of adequate cross-ventilation is considered by Szokolay (1992) as “the only passive control method with some promise of success in tropical warm-humid climates” after the application of the Control Potential Zone (CPZ) technique.  There should be thorough understanding of the practicality of attaining this theoretical deduction.

            This study is focused on users experience of thermal comfort using a survey of human responses. It is based on the explanation given by Webb (1959) on the appropriateness of field study for thermal comfort evaluation. According to Webb (1959) physiological measurements cannot be made on people to determine their level of thermal comfort. The opinion of a number of subjects should be obtained independent of bias and analysed statistically to determine the level of comfort.

             Thermal Comfort and Sustainability

 Thermal Comfort is generally defined as that condition of mind which expresses satisfaction with the thermal environment. (I.S.O.1984). It is a state of well-being with respect to temperature depending on achieving a balance between the heat being produced by the body and the loss of heat to the surroundings. Building spaces are to provide the occupants desirable environmental conditions. The level of thermal comfort within a building space determines to a large extent the level of functionality of the space. This is because human activities within such spaces can only be satisfying when the thermal environment is conducive to the users. It is necessary therefore to have sustainable spatial comfort. The attainment of this objective should be highly emphasized in schools of architecture and in professional practice.

To have sustainable thermal comfort there must be the capability of maintenance. The building configuration must be capable of maintaining an acceptable range of comfort level at minimal or no extra cost to the users. As stated by Edwards (1999), building design is appropriate when minimum energy input and the lowest level of technology achieve effective, efficient and healthy conditions. According to Szokolay (1992), provision of adequate air movement is a very viable passive control method in tropical warm-humid climate. In line with this, air movement within a space should  be examined to determine how to make the space comfortable.

            Study Context

The study area  was the Olubadan Housing Estate in Ibadan, the capital city of Oyo State in Nigeria.  The estate is located along New Ife Road opposite the New Gbagi Market.  The construction of the estate was started in 1979.  There are three categories of housing in the estate: (1) Low Cost Housing consisting of three typologies (2 bedroom, 3 bedroom and 4 bedroom apartments).  (2) Medium Cost Housing consisting of two typologies (3 bedroom and 4 bedroom apartments) and (3) High cost housing consisting of one typology (4 bedroom apartments).  The Olubadan Estate also has a number of educational, commercial and industrial units.  Although the roads are untarred they are motorable.  Essential services like water, electricity and telephone are available in the estate. The population of the estate was estimated to be over seven hundred.

There were a number of reasons for the choice of Olubadan Estate for this study. Since the study is focused particularly on thermal comfort in naturally ventilated residential buildings the buildings in the estate were found appropriate. The architectural designs for all the typologies incorporated naturally ventilated spaces. The design was by Nigerian architects utilising a variety of designs categorised as low, medium and high class residential housing. Their work reflected the general house types typical for designed bungalow, residential building estates in Nigeria. The construction materials for the buildings in the estate were those commonly used for residential buildings in the country. The Olubadan Estate housing units were therefore appropriate for the study.

The estate was chosen because of the opportunity of having a number of typologies of housing units which were repetitive.  This helped in making the results of the field surveys valid since errors of subjectivity were minimised through the assessment of responses from people living in similar typologies. The variety of design of the buildings were also representative of contemporary residential buildings of the three categories of housing.

Ibadan is located on longitude 7⁰22’N and latitude 3⁰58’E in the South-Western part of Nigeria.  The city is in the warm-humid climatic zone.  This is the climatic context for this study. According to Hyde (2000) the warm-humid climate is found close to the Equator and extends to 15⁰ latitude, North and South. The dominant feature is lack of seasonal variations in temperature.  It is characterized by high humidity and high temperatures (Hyde, 2000).   The seasonal pattern is dominated by periods of high rainfall, fairly evenly distributed.  There is small diurnal and annual variations of temperature and little seasonal variations.  There are light winds and long periods of still air. According to Ojo (1977) Ibadan is seasonally humid because of its inland location.

        

References  

Ajibola K. (1997). Ventilation of spaces in a warm-humid climate-case study of some housing types.Journal of Renewable Energy.Vol 10,No 1 pp 61-70.

Ajibola K. (2001). Design for comfort in Nigeria-a bioclimatic approach. Journal of Renewable Energy. Vol 23 pp 57-76

Barozzi G.,Imbabi M.,Nobile E.and Sousa A. (1992). Physical and numerical modeling of solar chimney-based ventilation system for buildings. Building and Environment. Vol 27 No 4 pp 433-445

Costa R. (1989). Architecture in black Africa-between development and tradition.J.Solar Wind Energy. Vol 6 No 4 pp383-387.

Dante E. (1960). Periodic heat flow characteristic of simple walls and roofs.JIHVE, Vol  28.

Edwards B. (1999). Sustainable Architecture- European directives and building design. Architectural Press, Oxford,U.K.                                                                        

Egan D.M.(1975). Concepts in thermal comfort. Prentice-Hall Inc. Englewood ,New Jersey , U.S.A.

Hyde R. (2000). Climate Responsive Design. E and F.N. Spon.London U.K.

I.S.O. (1984). Moderate thermal environments:determination of the PMV and PPD indices and specification of the conditions for thermal comfort. Int.Std. ISO 7730. International Organization for Standardization. 

Koenigsberger O.H.,Ingersoll T.G.,Mayhew A.and Szokolay S.V. (1973). Manual of  Tropical Housing and Building, Part 1 Climatic Design. Longman Inc. London U.K. 

Ojo O. (1977). The Climates of West Africa. Heinemann Educational Books Ltd. London U.K.

Szokolay S.V., (1992). Design and research issues-passive control in the tropics In: Proceedings of the 1^st World Renewable Energy Congress Vol 4, Sayigh A.A.M. ed. Solar and low-energy architecture. Pergamon Press,Oxford U.K.  

Webb C.G., (1959). An analysis of some observations of thermal comfort in an equatorial climate. Brit. Journal of Ind. MedicineVol 16 No 3 pp 297-310