Defining Climatic Zones for Architectural Design in ... Publications/Defining Climatic... · 6 O. O. Ogunsote and B. Prucnal-Ogunsote / Journal of Environ. Tech. 1(2) 2002 1 - 14

Journal of Environmental Technology 1(2) 2002 1 - 14

The Need for Design with ClimateThe need to design with climate has

always been a major considerat ion inarchitecture. Vitruvius, in his Ten Books onArchitecture drew attention to the importanceof climate in architecture and town planning.Fitch (1971) pointed out the extravagantreliance by architects on recent environ-mental technologies and advocates, inconsonance with the Building and RoadResearch Institute, Kumasi, “methods ofbui lding which wi l l enable the bui ldingstructure itself effect the desired environ-mental control” (Essien, 1968).

The search for such methods hasbeen undertaken by several countries, asdocumented by Essien (1968), Fitch (1971),Lacy (1972 and 1977) and Hooper (1975).Contributions have also been made by theUnited Nations Department for Economic andSocial Affairs (1971) and the United NationsCentre for Human Settlements – HABITAT(1984). The importance of f inding suchmethods for Niger ia was st ressed byMadedor (1980) when he expressed the needto provide “guidelines for design for thevarious climatic zones in the country”.

The Need for a Systems ApproachChristopher Alexander (1964), in his

Notes on the Synthesis of Form, pointed out thatthe many variables involved in contemporaryarchitectural decision-making simply outrun thecapacities of even the finest minds. Under suchcircumstances, according to Fitch (1971), “theelectronic computer has inevitably become animportant tool”. This argument is buttressed bythe fact that the very nature of the analysesinvolved in energy-conscious design encouragesthe use of computers (Ogunsote, 1991a). Asystems approach may therefore help solve theproblems faced by architects in developingcountries who have tended to ignore methods ofdesign with climate for various reasons, not leastof which are:• The dynamic nature of the design process.• The considerable time and effort required,

for which the architects receive no obviousextra remuneration.

• The lack of flexibility, the degree ofcomplexity and the arguable ambiguity ofsome of the existing methods (Reynolds,1980).

• Ignorance and lack of training andequipment.

Defining Climatic Zones for Architectural Design in Nigeria:A Systematic Delineation

Dr. Olu Ola Ogunsote and Dr. (Mrs.) Bogda Prucnal-Ogunsote

Department of Architecture, Federal University of Technology, Akure

AbstractThis paper reviews existing definitions of climatic design zones in Nigeria including definitions

based on natural vegetation, the definitions by the National Universities Commission and Nick Hollo,the Koppen system, the Atkinson system, the Martin Evans method, a method based solely on theMahoney tables and the Hosni method based on the concepts of adaptation and set theory. A methodfor the systematic delineation of climatic zones for architectural design is proposed. The method isbasically manual but a computer program, CLIZONE was designed in order to reduce some of itslimitations. The proposed system produced nine different responses for the Nigerian reference stationsused. These responses are used as the basis for proposing six design zones: the Coastal Zone, theForest Zone, the Transitional Zone, the Savannah Zone, the Highland Zone and the Semi-DesertZone. It is concluded that the data available are not sufficient for the accurate determination of theboundaries of these zones and the relativity of all definitions is reiterated. In this respect the open,adaptive and yet stable nature of the proposed system is emphasised.

2 O. O. Ogunsote and B. Prucnal-Ogunsote / Journal of Environ. Tech. 1(2) 2002 1 - 14

Aims and Objectives of the PaperThis paper aims to:

• review the existing definitions of climaticzones in Nigeria as well as somemethods of definition of climatic zonesfor architectural design applicable toNigeria;

• analyse the applicability of the variousmethods to the systematic definition ofclimatic zones for architectural design inNigeria;

• propose a method for the systematicdelineation of climatic zones for archi-tectural design in Nigeria;

• propose the climatic zones for archi-tectural design in Nigeria using theproposed method.

Definitions of Climatic ZonesClimatic zones are defined for a better

understand-ing of the workings of the globalclimatic system (Markus and Morris 1980). It isnecessary in this respect to differentiate betweenclimatic zones for agricultural purposes andclimatic zones for architectural design. Theformer are usually closely related to vegetationand are not directly linked to human comfortneeds. The definition of the latter stems from thefact that climatic conditions and hence therequirements for thermal comfort are the basisfor the selection of building form and buildingelements such as size of windows, insulationvalue of roofs and walls and orientation. It istherefore possible, in the words of Evans (1980),“to determine the approximate boundaries where

Figure 1: Vegetational types in Nigeria. Source: Iloeje, N. P. (1965). A New Geography of Nigeria.

O. O. Ogunsote and B. Prucnal-Ogunsote / Journal of Environ. Tech. 1(2) 2002 1 - 14 3

a change in the climate and a change in thermalcomfort requirements should be reflected inchanged building form or changed buildingelements”. These boundaries will effectivelydefine the climatic zones for architectural design.

Zones Based on Natural VegetationVegetation is rarely used on its own for

classifying climatic design zones but mostclimatic classifica-tion systems relate to it (Evans,1980). The logic of this is impeccable, since livingvegetation reflects every nuance of climaticconditions throughout the year.

The Times Atlas of the world describesthe characteristics of the main vegetation zones.1There are seventeen different zones and severalsub-zones in the world. The system of classi-fication is generalized and there is considerablevariation within each zone or sub-zone causedby differences in topography, altitude, windpatterns and ocean currents.

There are certain difficulties experiencedwhen defining climatic zones based on vege-tation. One is the difficulty of defining boundaries,since there is usually considerable mixing of flora.Furthermore, the destruction of naturalvegetation leads to a change in climaticconditions.

While the climatic zones for architecturaldesign cannot be established solely on the basis

of vegetation, a knowledge of the distribution offlora can be useful for comparative purposes.The vegeta-tional types in Nigeria are presentedin Figure 1.

The Koppen SystemThe Koppen system of climate classi-

fication is generally accepted for the globalevaluation of climatic zones. This system wasfirst proposed in 1900, but it has been modifiedby several authors since, notable among whichis Trewartha (1943).2 The classification recog-nises seven major zones and several sub-zones(Ogunsote, 1990a). A major shortcoming of thesystem can be traced to its dependence onrainfall and temperature and as such, likeclassifications based solely on vegeta-tionalcover, it does not necessarily relate to buildingdesign for thermal comfort (Evans, 1980). In fact,according to Olgyay (1963), the “classificationsare not directly applicable to housing”. This islinked to the absence of humidity, an importantthermal comfort factor, in the classification.

The Atkinson SystemThis system is commonly used for the

classification of hot climates in relation to buildingneeds and it is discussed in detail by Koenigs-berger et al (1974). It is the basis for the proposalby the United Nations (1971), of house and plan

Table 1: Summary of the characteristics of the Atkinson system of climate classification.

Source: Koenigsberger et al (1974). Manual of Tropical Housing and Building.


Table 3: Summary of the analysis of the validity and logic of the NUC classification of climatic zonesfor architectural design in Nigeria.

Source: National Universities Commission (1977). Standard Guide for Universities.

Table 2: Climatic variation between the two climatic zones identified by the National University Commission.


types for the various climates. This classificationexhibits a bias towards certain climatic types andit is not applicable to cold climates (Evans, 1980).The characteristics of the Atkinson system ofclimate classification are presented in Table 1after Koenigsberger et al (1974).

National Universities Commission MethodThe National Universities Commission

(1977) recognises two climatic zones in Nigeria,the Northern zone and the Southern zone (Table2), though a transitional zone is also mentioned.A closer look at this method however revealedthat the NUC based the division of the countryinto climatic design zones on the Atkinson systemof climate classification. The southern zoneactually corresponds to the warm humid climateand the northern zone to the composite ormonsoon climate. The differences can be foundin the specification of the various seasons andslight adjustments in the temperature andhumidity limits.

The authors tried to use the proposedmethod for a systematic classification and wrotea computer program, NUC, in FORTRAN to dothe necessary calculations. The methodology,analyses and results are discussed by Ogunsote(1990a). The following general observations weremade from the analyses, a summary of which ispresented in Table 3:• There was not even one single case of a

100% concurrence with the zoningcriteria.

• The rainfall limits seem rather arbitraryand contributed much to the low degreeof concurrence with the zoning criteria.

• Even when a high degree of latitude waspermitted, it was not possible to definitelydetermine the zones in which about 30%of the reference stations lie.

From the foregoing it can be argued thatthe NUC definition was not based on an in-depthanalysis. Furthermore, the logical shortcomingsof the method indicate that it may be unsuitablefor the delineation of climatic zones for archi-tectural design in Nigeria.

The Martin Evans MethodThis method was proposed after an

analysis of different existing methods, includingthe Koppen system, the Atkinson system and theMahoney table method (Evans, 1980). Hedefined seven zones in terms of differences in

the air temperatures, the humidity, the rainfall,the sky conditions, the wind and other conditions.He further related these climates to similarclimates and sub-climates and identified thecorresponding Koppen classifications for easycross-referencing.

In proposing the seven climatic types,Evans recognised the need to define zones interms of thermal comfort for building design buthe pointed out the relativity of standards and theimportance of relating to social and economiccontexts especially as regards traditional or

Table 4: The climatic types indicated by programMOTOLA on the basis of the differences indesign recommendations.


Figure 2: Characteristics of the climatic regions in Nigeria according to Nick Hollo / B. J. Garnier.

conventional forms of construction. The method,though based on the Atkinson system proposesmore realistic limiting values of rainfall, tempera-ture and humidity. The descriptive nature of themethod however makes it difficult to systemati-

cally and uniquely identity zones with the aid ofonly very basic climatic data. This does nothowever negate the usefulness of the method inunderstanding the subtleties of the differentclimatic design zones.


The Mahoney Tables MethodA detailed system of classification was

developed by Koenigsberger, Mahoney andEvans and was presented by the UnitedNations (1971) and Koenigsberger et al (1974).The main advantage of this system is thatclimatic zones are defined in terms of buildingneeds such as orientation, spacing, airmovement, openings and construction of wallsand roofs. The method makes use of seventables. The authors wrote a computer program,MOTOLA, to simulate the Mahoney tables

(Prucnal-Ogunsote et al, 1985). A more user-friendly version of the program, Klimax, waswritten in 1989 for the National PrimaryEducation Commission (Ogunsote, 2001). Thisprogram gave a set of recommendations whichindicated 13 different climatic zones. (Table 4).At this stage shortcomings of the Mahoneytables were detected and it became obviousthat they should be revised to incorporate theeffect of the wind and to remove logical errors(Celik, 1973).

Figure 3: The climatic regions for bioclimatic design in Nigeria according to Nick Hollo.


The Nick Hollo ClassificationNick Hollo defined four zones in Nigeria

after Garnier (1967) but he expanded on thisdefinition by identifying sub-regions within thesemajor zones (Figures 2 and 3). The method isappealing and depends heavily on descriptionsand imagery.3 However, when an attempt wasmade to apply the method to locations identifiedonly by the most basic climatic data, its generaland unspecific nature became evident.

The Hosni MethodThis method is based on the concept of

adaptation and set theory. According toSommerhof (1968), adaptive systems aredefined as systems possessing “the ability toreact to their environment in a way that isfavourable, in some sense, to the continuedoperation of the system”. Ashby (1967) defineda behaviour as being adaptive if it maintains theessential variables within limits. Sommerhof(1950 and 1968), saw the notion of adaptationwhen applied to systems as referring to the“appropriate-ness which organic activities showin relation to the needs of the organism, and tothe effectiveness with which organisms meet thedemands made upon them by their environment”.Appropriate response links four spatio-temporallydistinct elements:• events which act as stimuli (S t0)

Figure 4: The essentials of directive correlation after Ashby. Source: Ashby, W. R. (1967). The settheory of mechanism and homeostasis.

• the response ( Rt1)• the environmental circumstances (Et1)• the goal (Gt2).

Sommerhof used this model to defineeffective response, appropriate response andadaptation (Sommerhof, 1968). Adaptation isdefined as “a form of non-accidentalappropriateness” and adaptive behaviour aspossessing the “typical character of involving anobjectively biased and non-accidental occurrenceof appropriateness and success”. Everyadaptation is therefore an instance of directivecorrelation as shown in Figure 4 (Ashby, 1967).

Hosni (1978) used this definition topropose a method of defining the relation fromthe set of climates of selected locations in Egyptto the set of possible alternative architecturalresponses such that given “any element in thefirst set, one and only one element in the secondset results”. After considering the procedures ofOlgyay (1963), Givoni (1969) and Mahoney, hedecided upon the Mahoney method and wrote aFORTRAN program, SPECOO, to do thenecessary calcula-tions.

The Proposed MethodThe general inconsistency of the zones

obtained when using different methods of climateclassifica-tion is obvious and disconcerting.Schiller however pointed out that the essence

I

H

P Set Z of

outcomes

Set R of alternative responses

Set CV of initial environmental circumstances

H ⊂ ( I-1(G)) ° P

t0 t1 t2

G

Set E of environmental circumstances


Table 5: The set E’ of environmental circumstances. Table 7: The relation from the set of climates to theset of possible alternative architectural responses.

The proposed system was developedalong lines similar to those followed by Hosni(1978) and it uses the Sommerhof definition ofadaptation to establish the relation from the setof climates to the set of possible alternativearchitectural responses such that given anyelement in the first set, one and only one elementin the second set results.

A revised version of the Mahoney tableswas used for the definition. When this revisedversion was compared with the logic of the Hosnicomputer program SPECOO, it was found thatthe revised elements were very similar, though

which every definition tries to state is simply thepoint which it is for the time being important toelucidate. “It follows that the essences anddefinitions of things are necessa-rily plural,variable, relative, and never absolute”.4 Evans(1980), also pointed out the complexity of therelation between climate and building designwhich is further compounded by the fact that cost,technology and social custom will affect almostall design decisions. The need to define zonesand regions despite these difficulties is howevergenerally accepted (Chapman, 1977; Learmonthet al, 1971).


not identical. The climatic data used are the sameas those required for the Mahoney tables, exceptfor the wind data, which were omitted. Theclimatic data for the reference stations gave theset of initial environmental circumstances, CV.The Mahoney tables 1 to 4 were used todetermine the humid and arid indicator totals withthe aid of the table for the determination of thecomfort limits as well as the table for thedetermination of the humid and arid indicators.The humid and arid indicator totals obtained gavethe set E’ of environmental circumstances (Table5).

Table 8: Table of possible alternative architectural responses.

Table 6: The set E of environmental circumstances.


The revised Mahoney table 5 whichreplaces the former Mahoney tables 5 and6, was used to ana lyze the set E ’ o fenvironmental circumstances. This gave theset E of environmental circumstances (Table6), such that each and every member of theset E’ of environmental c i rcumstancescorresponds to one and only one memberof the set E of environmental circumstances.Next, the relation P from CV, the set of initialenvironmental circumstances to E, the set

o f env i ronmenta l c i rcumstances wasdefined. Finally, the relation H from CV, theset of initial environmental circumstances,to the se t o f poss ib le a l te rna t ivearchitectural responses was determined(Table 7).

This is basically the proposed systemwith the computerization option left out.Thus when basic climatic data is given forany location in Nigeria the proposed systemcan be used to determine the climatic design

Figure 5: The proposed climatic zones for architectural design in Nigeria.


zone in which the location lies by taking thefollowing steps:• Use the Mahoney tables 1 to 4 to manually

determine the humid and arid indicatortotals.

• Use these indicator totals and the set ofenvironmental circumstances (Table 6) todetermine the corresponding member ofthis set.

• Determine the adapted response with theaid of Table 8.

• If required, obtain the design reco-mmendations manually from the revisedMahoney table 5 using the humid and aridindicator totals.The indicated response will uniquely

identify a climatic zone containing only locationsgiving the same response. A computerisation ofthis method, CLIZONE, effectively reduced thelimitations:• of climatic data (Ogunsote, 1990b;

1991b);• imposed by the method used to determine

the relationship between climatic cond-itions and building requirements;

• of the number of possible responses;• imposed by the tendency to enforce rigid

geographical boundaries of design zones.The proposed method of systematic

delineation of climatic zones for architecturaldesign in Nigeria thus has the following form froma practical viewpoint.• Inform CLIZONE of the station you want

to analyze, stated as the name of thelocation and the period over which thedata were recorded. If the data are notavailable, enter them using one of thesubroutines named CLIDATA (Ogunsote,1991b).

• CLIZONE does all the necessary compu-tations and comparisons and interactivelypresents, among others, the indicatortotals, the response and the designrecommendations. A printed report of theanalysis is automatically produced.

The Proposed Climatic ZonesThe computer program, CLIZONE, was

written in FORTRAN by the authors for thedetermination of the response adapted to givenenvironmental circumstances. The program wasimplemented on the CDC Cyber 72 under the

NOS operating system at the Iya AbubakarComputer Centre, Ahmadu Bello University,Zaria, Nigeria. The climatic data used - long-termaverages of usually over 20 years - werepresented by Prucnal-Ogunsote et al (1985). Theresponses obtained are presented in Tables 7and 8. The nine responses obtained were usedto propose six zones (Figure 5):

Coastal Zone: response 1Forest Zone: response 2Transitional zone subzone a: response 3

subzone b: response 4Savannah Zone subzone a: response 5

subzone b: response 6Highland Zone: response 7Semi-Desert Zonesubzone a response 8

subzone b: response 9

The Semi-Desert Zone was establishedmainly for convenience since only two stationsfall within the zone and the design recommenda-tions for each are different. In the Transitionaland Savannah Zones, the far-reaching simi-larities between responses 3 and 4 as well as 5and 6 respectively were used as the basis fordefinition (Ogunsote, 1993).

ConclusionThe definition of climatic zones for

architectural design in Nigeria is misleadinglyapparent. Divisions of the country into southernand northern regions are obviously simplistic andlacking in scientific conviction. More elaboratemethods are capable of forging scientific relationsbetween the climate and building design but thisenvironmental determinism is achieved throughever-increasing complexity. In the final analysis,it is realised that it is impossible to absolutelydelineate climatic design zones, since alldefinitions are necessarily plural and relative. Theproposed system is open and adaptive, yetstable. The locations lying in the different climaticdesign zones have been identified (Figure 5) butthe limited data available do not allow for theestablishment of boundaries.

Notes1. See Table 5.1 in Evans (1980) showing

Plate 5 of the Times Atlas of the World,Comprehensive Edition, London 1968.

2. Trewartha “offered modifications of thesedivisions based on isotherms of thecoldest months” and established zerodegree Celsius as the limit below which


special building requirements maybecome necessary.

3. All the information presented on the NickHollo method of climate classification wasobtained from the handouts he preparedfor students while he was a lecturer in theDepartment of Architecture, AhmaduBello University, Zaria, in the late 1970’s.Mr. Nick Hollo had remarkable talents ofgraphic expression and much of theinformation in the handouts was containedmore in the form of presentation than thecontent.

4. This quotation, after F. C. Schiller, wasobtained from Ackoff, R. L. (1962).Scientific Method. John Wiley and Sons,New York. p 147.

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Defining Climatic Zones for Architectural Design in ... Publications/Defining Climatic... · 6 O. O. Ogunsote and B. Prucnal-Ogunsote / Journal of Environ. Tech. 1(2) 2002 1 - 14