ADAMAWA STATE LIBRARY:A STUDY OF PASSIVE CONTROL SYSTEMS FOR THERMAL COMFORT IN A HOT AND DRY TROPICAL ENVIRONMENT

ABSTRACT

One  of the  main  goals  of this  study  is  to  provide   a  comfortable   study environment.  The quest for comfortable useable  and livable space is the reason for the creation of a new field in science called “Thermal Comfort”.

The global problems of Architectural models of Hot and Dry tropical environment can best be addressed by the introduction of passive control systems for thermal comfort.  The  question  becomes:  how  much  comfort  up to  date  could do this scientific responsibility?

This research seeks to define the comfort zone for studying in hot and dry tropical environment, establish climatic design advices/criteria  and investigating whether thermal comfort  in the Adamawa  state library can be achieved through passive control systems only.

Results obtained  from thermal  study in the Adamawa  state library under  study show that when investigated using the ASHRAE thermal sensation scale,  74.9% of the  respondents   found  the  thermal  indoor  conditions  of the  state  library uncomfortable,  76.0% during the summer period  and 72.8%  during the winter period.  On the whole,  only 25.1 % of the respondents  were comfortable  (within comfort zone),  finding the thermal indoor  conditions acceptable,  hence the need for thermal control systems in the Adamawa state library and for the purpose  of this study, passive control systems is the interest. In an attempt  for this study to improve  the indoor thermal condition of buildings in  the  tropics,  with  the  interest  to  reduce  energy  consumption  in  buildings  by passively achieving thermal comfort, it is proven that humans can and do live in a range  of climates  from  the  tropics  to  high  latitudes, just  as  in  the  case  of this study,  the respondents  are able to adapt to the hot-dry  tropical  environment  that they are used to.  So the term  ‘thermal  comfort’ does simply describe  a person’s psychological  state of mind.

1.0       INTRODUCTION

Buildings  are meant  to  provide  a safe  and  comfortable  internal  environment despite variations in external conditions. Experience has shown that, to the occupants, the most important consideration  is the thermal comfort. This is the condition   of  thermal   balance   between   man   and  the   indoor  under   given conditions.   Architect   and  environmental   engineers   always  aim  at  creating comfort in buildings, thereby designing control systems with a view to creating thermal  comfort  and  improve  the  performance  of the  people  when  at  work (Building Science Corporation, 2003).

Buildings are designed to meet our basic need for, which are, Shelter (protection from the  elements  of weather),  Security  and  Thermal  Comfort  (warmth  and light).

Many  of these  basic  needs  were  originally  met by  a cave with  a fire at the entrance to provide both  security and comfort. Nowadays,  although we might expect  more  sophistication  in  delivery,  and  more  facilities,  the  fundamental needs remain the same.

Once the needs for shelter and security are met, the remaining main requirement is for a ‘comfortable’ internal environment. Whilst this may seem a simple task to achieve,  in practice there  are many  factors to be considered  in the aim to provide comfortable conditions for the building occupants.  (Bensalem,  1995)

Thermal  Comfort  has been  defined  as  ‘the  condition  of mind  which  expresses satisfaction with the environment’.  The indoor  environment  should be designed and  controlled  so  that  occupants’  comfort  and  health  are  assured.  (American Society of Heating,  Refrigerating  and Air-Conditioning  Engineers,  1985,  cited in Chartered Institution of Building Services Engineers,  Guide A,  1999)

Researches  were  initiated  because  standards  that  are  currently  used  in  these regions  to  achieve  thermal  comfort  in  buildings  are  those  from  the  northern latitudes.  As a result,  many believe that mechanical air-conditioning  systems are the ways to achieve thermal comfort  in buildings  (American National  Standards Institute/ American  Society of Heating, Refrigerating  and Air-Conditioning Engineers  55-1992), this example,  is used  worldwide,  despite  the  fact that this standard  is based  on data  from climate  chamber  experiments  performed  in mid latitude climates. Thus, this has presented  a question as to whether it is true that people living in the tropics have the same levels of comfort as those in the mid or northern latitudes.

People spend most of their time in buildings  or urban spaces.  Although  comfort models  mostly  talk  about  indoor  climate  but  both  indoor  and  outdoor  climate should be taken into consideration not only in urban design but also in buildings. So both indoor and outdoor comfort is a matter of attention.

1.1       BACKGROUND OF STUDY

The first major  issue of most discussions about climate is the thermal comfort level (Salleh, 2004).  Thermal  comfort  is  defined  as ‘the  state of mind,  which expresses satisfaction with the thermal environment’  (ASHRAE, 1985), the definition  quickly  perceived,  but  hard  to  exploit  in physical  parameters.  Air temperature,  air movement,  radiation  and  humidity  are not  the  only  climatic characteristics  that  affect  human  comfort  but  they  are  the  dominant  ones. Thermal-comfort  problems  are varied and as they may be caused by different factors  such as conversion  of building  operational  and physical  characteristics and occupant  behavior  and  interference,  they  can be difficult  to  identify and solve (Van Hoof, 2007).

Studies have shown that there is no absolute standard of thermal comfort. This is not surprising,  as humans can and do live in a range of climates from the tropics to   high   latitudes.   So   the   term   ‘thermal   comfort’   describes   a   person’s psychological  state of mind and is usually referred to in terms of whether one feels too hot or too cold.

Thermal comfort is very difficult to define because you need to take into account a range of environmental  and personal  factors when deciding what  will make people  feel comfortable.  These factors make up what is known  as the ‘human

thermal  environment’.  The  best  that  you  can realistically  hope  to  achieve  is a thermal environment that satisfies the majority of people in the workplace,  or put more simply,  ‘reasonable  comfort’.

Health   and   Safety   Environment   (HSE)   considers   80%   of  occupants   as   a reasonable  limit  for the  minimum  number  of people  who  should be  thermally comfortable in an environment. Therefore thermal comfort is not measured by air temperature  alone  but  by  the  number  of library  users  complaining  of thermal discomfort in the context of this study.

Adamawa  state  is  located  at the Northeastern  region  of Nigeria,  lying  between latitude 9°N and longitude  12°E  of the equator. The state falls within the tropical climatic  zone,  characterized  by  relatively  hot  and  dry  climate  with  an  annual average temperature  of 39°c and an average relative humidity of 40.9%.  The sky is mostly  clear  in  day  and this permits  longer  hours  of sunshine.  The  average duration of sunshine varies from 5.5 hours per day in August  and 9.7 hours per day in December.  Hence,  there is an Average of 2954 hours of sunlight per year with an average of8.1  hours of sunlight per day.

Adamawa  state  experiences  low  atmosphere  moisture  content,  a  large  diurnal range  of temperature   and  an  absence  of convective  type  of cloud,  hence  the indoor thermal discomfort experienced.

Because thermal comfort is psychological, it may affect our overall morale. User complaints  may  increase,  productivity  may  fall and  in  some  cases people  may refuse   to   work   in   a  particular   environment.   Some  aspects   of  the  thermal environment,  such as air temperature,  radiant heat,  humidity  and air movement, may also contribute to the symptoms of sick building syndrome.

People  employ  adaptive  strategies  to  cope  with their  thermal  environment,  for example,  donning or removing  clothing,  unconscious  changes in posture,  choice of heating,  moving to cooler locations  away from heat sources.

The problems arise when this choice (to remove jacket, or move away from heat source) is removed, and people are no longer able to adapt. In many instances the environment  within which people  work  is  a product  of the processes  of the job they are doing, so they are unable to adapt to their environment.

Perceptions   of  this   environment   are   affected   by   air   temperature,   radiant temperature, relative humidity, air velocity, human activities and clothing. More general  definitions  of comfort  include  a sense  of relaxation  and  freedom  from worry or pam.

Several  thermal  comfort  studies  in  hot-dry  climates  have  been  conducted  to develop a data base of the thermal environment  and subjective  responses  of the people  living  in  these  climates.   These  studies  were  initiated  mainly  because ANSI/ASHRAE   55-1992  thermal  Environmental  Conditions  for Human Occupancy  is based  on  data  from  climate  chamber  experiments  performed  in mid-latitude  climates (ASHRAE  1992). In 1991, de Dear et al (1991a) conducted some field experiments on thermal comfort in Singapore. Busch (1990, 1992) conducted  a similar  study  in  Bangkok.  Results  from these  studies  showed  that people  in  tropical  regions  can  tolerate  warmer  temperature  than  predicted  by comfort  models and ASHRAE  55-1992  standards.  Later  de Dear et al.  (1991b) also performed  climate  chamber  experiments  on thermal  comfort  of 32 college students in Singapore. The result showed that the sample’s mean temperature preference  was 25.4°C  (77.7°F).  More  thorough  studies were  performed  by  de Dear and Fountain (1994) in Townsville, at latitude 19°s on the northeast coast of Australia.  The study sample sizes were 628 and 606 respectively  for the dry and wet seasons. The studies were performed  in a controlled office setting. A mobile measurement  system was used, recording the air temperature, dew-point temperature,   radiant  asymm etry,   air  velocity,   and  luminance.   Questionnaires were also used to assess the subjects’ thermal acceptability, preferences and sensations  clothing  and activities,  and other  subjects’ background.  Results  from this study  showed that thermal neutrality, based  on ASHRAE  scale occurred  at about 24.4°C (76°F),  with preferred temperature  of 23S°C (74.3°F).  The subjects could tolerate excessive air movement but were less tolerable to air that was too still. These findings showed the importance  of extending thermal comfort studies in climates other than mid-latitude climates.

1.2      STATEMENT OF ARCHITECTURAL PROBLEM

Comfort has been defined as “the condition of mind which expresses satisfaction with  the  environment”.   The  indoor  environment   should  be  designed   and controlled so that occupants comfort and health are assured. CIBSE, Guide A, (1999)

Thermal  comfort  is today  a major  problem  faced by designers  in the tropics especially  in  a  country  like  ours,  where  one  cannot  rely  on national  power generation  rather   must  source  for  alternative   sources   if  comfort   must  be achieved.

The  question  remains:  what  level  of indoor thermal  comfort  is  adequate  for adaptability in buildings in the Hot and Dry tropical environment?

In answering this question, passive means of achieving thermal comfort would be studied and adopted in solving the thermal comfort situations in the Hot and dry tropical environments.

1.3       AIM OF STUDY

This study is aimed at defining the comfort  zone for studying  in hot and dry tropical  environment,  establishing  climatic  design  advices/criteria  and investigating  whether  thermal  comfort  in  the  Adamawa  state  library  can  be achieved through passive control systems only.

1.4      OBJECTIVES OF STUDY

The following objectives are necessary to achieve the study aim.

1.         To understand  and  optimize the  various  factors that  influence thermal comfort,

2.         To establish the level of discomfort and the percentage  of users that are uncomfortable within the library hall,

3.          To understand the users perception of the environment and their level of adaptation,

4.         To establish climatic design advices for hot and dry tropical environment,

5.          To establish various systems of passive thermal control and their degree of efficiency.

1.5       RE SEARCH QUESTIONS

The  primary  policy  challenges  involve  improving  thermal  conditions  so  that basic physiological needs are met. However,  issues’ relating to what is perceived as  comfort  (as  distinct  from  what  a  doctor  or  engineer  might  prescribe  as comfort), lie beyond these basic needs and are important when considering the prospects for a low-carbon society. At what temperatures are people comfortable enough? Do their perceptions  of a comfortable temperature  range change with time and, if so, what happens to change those perceptions?

1.6      SIGNIFICANCE OF STUDY

Today,  both  indoors  (homes,  offices,  learning  and  study  environment)   and outdoor environment have become uncomfortable  useable spaces because of the climatic challenges poised to us.  Therefore, this study is a timely one,  at a period where global warming and thermal comfort issues are most pressing, a priority to architects and designers around the world.

A  library  is  a  citadel  of learning  which  collects,  orgamzes,  preserves  and provides  access  to  knowledge  and  information.  In  our  contemporary  world, libraries have been digitalized by the introduction of the internet. Yet libraries are not patronized and this is not due to insufficient study materials or facilities but because of the indoor thermal conditions we face.

This research  seeks to proffer  design advice to the indoor thermal comfort in hot and dry tropical environment  and for the purpose  of this study,  this advice shall be adopted for the Adamawa state library.

1. 7      SCOPE AND LIMITATION OF STUDY

There  is no  absolute  standard  of thermal  comfort.  This  is not  surpnsmg,  as humans can and do live in a range of climates from the tropics to high latitudes. An internationally-accepted definition of thermal comfort,  used by ASHRAE,  is

‘that   condition   of  mind   which   expresses   satisfaction   with   the   thermal environment’  (ISO 7330).  Perceptions  of this environment  are affected  by air temperature  of the  interior, radiant  temperature,  external pressure,  velocity  of airflow, human activity and clothing. More general definitions of comfort include a sense ofrelaxation and freedom from worry or pain.

The  study  focuses  on  establishing  vanous  design  advice  of thermal  control systems for thermal comfort in its hot and dry tropical environment which shall be adopted as a recommendation for Adamawa State library.

Considering the period of time in which this research was carried out, data was collected  from  established  sources  and  references  drawn  from  related  case studies.  However,  questionnaire and oral interviews were administered and used

to generate successive information and data to draw further references and conclusions for this research study.

1.8      RESEARCH METHODOLOGY

This is a corpus based research on thermal comfort and the passive systems for its  control  in a hot and dry tropical  environment.  This study adopts primarily descriptive  survey  and  correlated  case study research  and  designs  of passive control systems for thermal comfort in the hot-dry tropics.

Descriptive   in  the  sense  that  it  will  partly  be  concerned  with  identifying, interpreting and describing existing conditions,  from a design point of view, with special emphasis on the Adamawa state library and analyzing the life situation as to what improvement the study would impact on it.

The correlated case study research is to focus on studying and understanding past studies of related  interest  and evaluation  the present  situation and advices  for design of passive  control systems for thermal comfort  in the hot-dry tropics to create reliable considerations for the design proposals.

1.8.1    STUDY ARE A AND POPULATION

Adamawa  state is  located  at the Northeastern  region of Nigeria,  lying between latitude 9″N and longitude  12″E  of the equator.  Jimeta is the metropolis of Yola, the capital city and administrative center of Adamawa State, Nigeria.  Located on the Benue River,  it has a population  size of over 276,075 according to National census 2006.

Established in 1841,  Yola was the capital of a Fulani state until it was taken by the British in 1901. Daytime temperatures  can easily exceed 40°C during the dry season (April/May).

Yola is split into two parts. The old town of Yola where the Lamido resides is the traditional city but the new city of Jimeta (about 5 km NW) is the administrative and commercial centre. Generally the term Yola is now used to mean both.

This study would be carried out in Adamawa state Library, Yola. Considering the peculiarity of the climatic conditions of Yola,  a hot and dry tropical region with long hours of sunshine and relatively  low humidity,  the Adamawa  state library would serve as a good model for this study.  Thermal comfort is a global issue and a study  of this  area,  would  add to the knowledge  of design  criteria  for thermal control system for hot and dry tropical environment.

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