Protection of openings from heavy rainfall in Akure

Transcription

1 A term paper on Protection of openings from heavy rainfall in Akure Compiled by UMELE P.J.OGA ARC/05/5646 ARC 810: APPLIED CLIMATOLOGY Submitted to The department of architecture, School of post graduate studies Federal university of technology, Akure Nigeria In partial fulfillment for the award of masters of technology (M.TECH) Degree in architecture. Course mentor: Prof. O.O Ogunsote August 2011

2 ABSTRACT. Akure falls within the tropical climate zone and as thus exhibit hot and humid weather conditions. There is abundant rainfall due to the active vertical uplift or convection of air that takes place there, and during certain periods, thunderstorms can occur every day. Nevertheless, this belt still receives considerable sunshine. Due to the excessive rainfall that occurs at some instances, design consideration must be taken to protect buildings especially the openings against such rain. The protection of rain from openings in building is discussed with special reference to Akure, Ondo state. 1.0 INTRODUCTION One of the major functions of a building is to provide for protection against inclement weather and maintain a comfortable thermal limit. Nature in its disposition has been able to provide for distinct weather conditions across the major regions of the world and of course, the ability to survive in this various weathers has been built on along the timeline of history. Contemporarily, Nigeria falls within the tropical climatic region of the world and as thus exhibit distinct weather conditions within the north and south regions. In the south, users have to contend with variables such as warm temperatures, high humidity and precipitation among others, though this varies a little from individual zones within the region i.e. Southern region while the northern region has to contend with hot and dry conditions. A knowledge of the weather condition in this area is very important as it relates to other very important sectors such as agriculture, meteorological services, tourism etc.(oluwagbemi 2007.p1).Ogunsote and Prucnal-Ogunsote, 2002b, 2002c identified six major design zones namely coastal zone, forest zone, transitional zone, savannah zone, high climate and semi desert zone respectively. Akure

3 falls within the coastal climatic zone; the implication being that any architectural design scheme must align with the climatic need of the zone. This write up in its limit delineates the prevention of openings from rain in Akure. 2.0 STUDY AREA The study area is limited to the confines of Akure, Ondo state, south western Nigeria. Ondo state contains eighteen Local Government Areas, the major ones being Akoko, Akure, Okitipupa, Ondo and Owo. The majority of the state's citizens live in urban centers. The ethnic composition of Ondo State is largely from the Yoruba subgroups of Akoko, Akure, Ikare, Ilaje, Ondo city and Owo.While the1991 census put the population of Akure at 324,000, the current population of the city is put at 495,000 people. It is projected that by 2015, Akure will be inhabited by about 1.8 million people. The projected figure is expected to result from the impact of industrial growth. The state has recently been classified as an oil-producing state while Akure has been classified as a Millennium Development City. All these factors are expected to greatly influence the population growth of the city. (Igbekele, 2002) Akure is a traditional Nigerian city and like other traditional Yoruba towns in the country, it existed long before the advert of British colonial rule in Nigeria. It lies approximately on latitude North of the Equator and longitude East of the Greenwich Meridian and is situated 250m above sea level.

4 Location of Ondo state Source;department of urban and regional planning, federal university of technology,akure Nigeria Plate 1: Map of Nigeria showing Ondo state. Plate 2: Map of Ondo state showing Akure Plate 3: Map of Akure. Source: department of urban and regional planning, federal university of technology, Akure Nigeria

5 3.0 CLIMATIC CONDITIONS The south has four seasons: (i) The long wet season that starts in mid-march and lasts till July is a season of heavy rains and high humidity... The short dry season. This is the August break and it starts from July August and lasts for about one month. (iii) The short wet season. It follows the August break and lasts from September to October. During this period rainfall is not usually heavy compared to the first wet season and the total amount of rainfall is less. (iv) The long dry or harmattan season which continues from November to mid-march. Harmattan mornings are usually cool and misty, however the mist disappears after sunrise. The afternoons are full of haze due to dust in the air brought by winds from the north. ( Oyenuga, 1967; Ileoje, 2001). The altitude and proximity to the seas determine to a large extent the distribution of temperature in Nigeria. Generally, temperatures are high throughout the year because Nigeria lies within the tropics and the mean monthly figure could go above 27 0 C, while daily maximum temperatures can go between beyond 35 0 C 38 0 C depending on the location (Iloeje, 2001). Temperatures in the Akure rarely exceed 35 C; a daytime maximum of 32 C is more common. At night, the abundant cloud cover restricts heat loss, and minimum temperatures fall no lower than about 22 C. This is because a substantial part of the Sun s heat is used up in evaporation and rain formation, This high level of temperature is maintained with little variation throughout the year. The seasons, so far as they do exist, are distinguished not as warm and cold periods but by

6 variation of rainfall and cloudiness. Greatest rainfall occurs when the Sun at midday is overhead on the equator.this occurs twice a year in March and September and consequently there are two wet and two dry seasons. Further away from the equator, the two rainy seasons merge into one, and the climate becomes more monsoonal, with one wet season and one dry season. In the Northern Hemisphere, the wet season occurs from May to July, in the Southern Hemisphere from November to February 4.0 RAINFALL IN AKURE Rainfall is a form of precipitation; other forms include snowfall, hail, dew, frost and fog. From the data available, there is one general cause of rain that is cooling of air saturated with water vapour. Thus when air which is saturated with water is cooled (either by forcing it to rise or by any other means) condensation takes place followed by rainfall. The cooling process may however be due to various causes and this has led to the classification of rainfall into conventional, orographic and cyclonic rainfall. Akure enjoys a moderate tropical climate with maximum temperatures rarely rising above 33 C and minimum temperatures rarely falling below 20 C. Relative humidity is also moderate with maximum relative humidity rarely rising above 86% and minimum relative humidity rarely falling below 40%. There is some form of precipitation throughout the year, even though there are distinct wet and dry seasons. There is usually more than six hours of sunshine, even during the rainy season. Table 1: Average Climatic Conditions in Akure ( ).

7 Akure Jan Feb Mar Apr May June July Au Sept Oct Nov dec 2004 Mean monthly maximum temperature ( C) Mean minimum monthly temperature ( C) Mean Daily Maximum Relative Humidity (%) Mean Daily minimum Relative Humidity (%) Precipitation(mm ) Hours of sunshine Mean Wind Velocity (m/s) Source: Analysis of data collected from weather stations in Akure by Federal University of Technology, Akure (FUTA) students. (Adedeji Y.M.D, Aluko O.O and Ogunsote O.O) 5.0 PROTECTION OF OPENINGS Ogunsote 1991, identified rainfall as a major problem which must be solved. The situation is more exaggerated especially with the issue of climate change and global warming that has in some cases gone a little extreme. There are no particular templates for solving problems but solutions are consequently a product of the problem at hand. As a result of this, it is impertinent

8 to identify the problem(s) at hand and localize the solutions therein. The major openings in buildings in Akure include windows, doors, impluviums, and permanent openings such as inlets and outlets. These openings of course are needed to maintain internal comfort temperatures and as thus should be protect from rain. The following is therefore envisaged. 1. RECESSED OPENINGS. Placement of openings in recessed position will reduce the likelihood of rains to penetrate openings. Plate 4: Use of recesses in preventing rainfall through openings. Source: researcher s achieve. 2. LONG ROOF OVERHANGS:

9 Long overhangs accompanied by high pitched roofs will allow easy flow of rain and reduce the likelihood of rain penetration as a result of higher vertical angles. 3. Openings should be oriented away from the major wind directions. 4. EXTERNAL SHADING DEVICES. External shading devices such as horizontal, vertical and egg Crete shading devices and hoods can be effectively used towards preventing rains from openings especially windows. 5. WIND BREAKERS : Rains are mainly influenced by wind and as such wind deflectors such as trees or other mechanism can be used to deflect the winds and consequently rains. Plate 5: Use of wind barriers in preventing rainfall through openings. Source: researcher s achieve. 6 OUTDOOR SPACES

10 Verandas and balconies should be provided. For openings such as impluviums, allowance should be made for water collection and drainage between the building and the site in view. These suggestions as outlined above are not exhaustive of the vast pool of possibilities that exist as regards the subject matter. 6.0 CONCLUSION AND RECOMMENDATION Rainfall continues to be a problem that has to be resolved in the forest climatic zone. The situation is more aggravated in this era of climate change and global warming. The recent manifestations of rainfall in Lagos and Ibadan with similar climatic conditions will continue to redefine the approaches to protecting buildings against this natural phenomenon and might definitely require more advanced seismic solutions. While heavy rainfall becomes a problem in some instances, it also presents opportunities which can be maximized for the benefit of mankind. It is natural that these rains come, effort must be geared to protect against rain using methodologies that best fit into our climate end economy. REFERENCE: Adedeji, Y. M. D, Aluko, O. O. and Ogunsote, O.O (2010) sustainable landscaping and green housing in tropical climates: a case study of Akure, Nigeria. Fagbemi K.B and Oke O.E (2007) Recommendations for design with

11 climate in Akure. Being an unpublished B.tech term paper submitted to the Department of Architecture, Federal University of Technology, Akure Nigeria. Igbekele A. (2009). Akure city profile. Retrieved from Akure city profile. PDF on the 24th july, 2011 Iloeje, N.P. (2001). A new geography of Nigeria. New Revised Edition. Longman Nigeria PLC. 200 p. Oludare J.O (2007) The climatic data and the implications for architectural design in Akure. Being an unpublished M.tech term paper submitted to the Department of Architecture, Federal University of Technology,Akure Nigeria. Ogunsote, O. O. (1991). Introduction to building climatology: A basic course for architecture students. Ahmadu Bello University Press, Zaria. Pruncnal Ogunsote, B. (2006) Reflection of Culture and Climate in the Vernacular and Modern Architecture of Akure. Department of Architecture, Federal University of Technology,Akure Nigeria.