THERMAL PROPERTIES OF SOME SELECTED MATERIALS USED AS CEILING IN BUILDING

1.1 Introduction

A ceiling is an overhead interior surface that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings can be decorated to taste, and there are many fine examples of frescoes and artwork on ceilings especially in religious buildings. The most common type of ceiling is the dropped ceiling, which is suspended from structural elements above. Panels of drywall are fastened either directly to the ceiling joists or to a few layers of moisture-proof plywood which are then attached to the joists. Pipe work or ducts can be run in the gap above the ceiling, and insulation and fireproofing material can be placed here.

As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.

1.2 Background of Study

A ceiling board is a horizontal slab covering the upper section of a room or internal space. A ceiling board is generally not structural but is a shell concealing the details of the structure above. However, the ceiling might be holding up building materials such as heat or sound insulation. In modern buildings, electric lights, smoke detector, security cameras and signage are commonly attached to ceilings.

In Nigeria, the use of zinc made roofs without ceilings are very common, thus there is intense heat transfer to the internal environment, which may cause thermal discomfort to the inhabitants (Etuk et al., 2007). One way to reduce thermal discomfort is by the use of radiant barrier (i.e. ceiling board) which reduce the heat flux. However, the knowledge of thermal properties of different materials is very important in the choice of the types of materials to be used as a radiant barrier since the heat flow through any building depends on thermal properties of the materials use in the building (Etuk et al., 2007).

George et al., (2010) carried out a research on comparison of thermal properties of some selected materials used as ceiling in building design. The research was executed using five samples of ceiling materials i.e. P V C, POP, cardboard, asbestos, suspended. During their research thermal conductivity, thermal absorptivity, thermal diffusivity, thermal resistivity, specific heat capacity and density were determine for each sample. The result showed that, P V C and card board have higher thermal absorptivity’s value, where the POP, asbestos and suspended have lower thermal absorptivity’s value. Based on the molecular point of view of thermal absorptivity, POP, asbestos and suspended are best materials with high thermal insulation efficiency.

Ceiling materials are overhead interior surfaces that can cover the upper limits of the room. They are not generally considered as structural element but finished surfaces concealing the underside of room structure or the floor of store above. To reduce the intensity of this heat, there is need to use materials of tolerable thermal responses as ceiling materials in buildings. Good insulating materials will have high value of thermal resistivity. This implies that, different type of ceiling materials will have different thermal behaviors.

This research however, is based on the production of ceiling board from local raw materials. These local raw materials include cement, fibre cellulose, fibre obtained from ground paper, mainly waste paper, water and some other additives.

There are different types of ceiling boards. These include; Gypsum ceiling boards; Acoustical ceiling boards; Gypsum fibre ceiling boards; and Cement fibre-ceiling boards. These types of ceiling boards are grouped in accordance to the raw materials used for the production. Gypsum ceiling boards are produced from gypsum, Acoustical ceiling boards are obtained from mineral wool, gypsum and small amount of paper and starch. Gypsum fibre ceiling boards are produced from gypsum and fibre to reinforce the ceiling board.

This study however will be based mainly on the production of fibre cement ceiling boards. This consist essentially of an inorganic binder usually calcium silicate formed by the chemical reaction of a siliceous material and a calcareous material. This is reinforced by organic fibres, fillers and pigment compatible with the fibre reinforced cement to form a ceiling board.

In the past, ceiling boards were produced using Asbestos a fibre present naturally in rocks. It was used because of its high tensile strength, poor heat conductivity and high fire resistance. However, asbestos causes asbestosis, which leads to cancer. As a result of this problem, manufacturers of ceiling boards went into research to find out substitutes that can be used in the production of ceiling boards. This substitute includes shredded wood, cellulose fibre agricultural waste etc. Rather than industrial products (glass-fibre, iron fillings) and man-madematerials, the fibres best suited to the socio-economic circumstances of developing countries are natural fibres.

Ceiling boards are required in houses to reduce sound and heat and they give additional aesthetics. A ceiling with its upper surface highly reflective, having a good heat insulation and low thermal capacity is recommended in hot climates. As a performance standard, it is recommended that thermal conductivity of ceiling boards should be within 0.50-0.15 W/mK. All types of asbestos fibers are known to cause serious health hazards to humans. Amosite and crocidolite are considered the most hazardous asbestos fiber types; however, chrysotile asbestos has also produced tumors in animals and is a recognized cause of asbestosis and malignant mesothelioma in humans, and mesothelioma has been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines. Asbestos ceiling boards are fragile, pose health risks and relatively costly. Therefore, there is a compelling need to produce alternative products that are cheap, using local organic materials that could pose little or no health hazards.

Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Thermal Properties of Some Selected Materials Used as Ceiling in Building.

1.3 Statement of Problems

Investigation revealed the challenge of the existing research which entails that there is health threat of the existing production material, which is asbestos that is known to be cancerous. This research intends to see if local materials (Rice husk, cassava starch, epoxy resin and hardener) are effective additives for ceiling board.

1.4 Aim and Objectives of Study

The aim of the study is to investigate the Thermal Properties of Some Selected Materials Used as Ceiling in Building. In achieving this aim, the following specific objectives were laid out as follows:

1. To study the possibility of making use of local raw materials for the production of ceiling board;
2. To produce a ceiling board with good acoustic and thermal insulating properties;
3. To compare the values of each thermal properties for thermal efficiency;
4. To produce a board with reduced cost to discourage importation thereby saving Nigeria her foreign exchange and booting her economic status; and
5. To determine thermal resistivity and measure thermal conductivity, absorptivity and diffusivities of the ceiling.

1.5 Research Questions

The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:

• Are there significant differences on flexural strength between the waste paper ceiling board among without and with Rice husk, cassava starch, epoxy resin and hardener?
• How can thermal conductivity, absorptivity and diffusivities of the ceiling be measured and calculated?

1.6 Significance of Study

The present study will be beneficial to the following:

To the Environment: This study will lessen the amount of trees being cut for the production of wood ceiling board. It will offer a viable solution to problems caused by waste water lilies and paper.

To the Community: It will offer potential income to people who will venture out making ceiling boards.

To the Students: This study will increase the knowledge of students regarding on practicing the 3R’s namely reduce, reuse, and recycle. It will likewise increase their scientific skills.

The study will also be important to create awareness to the general public, on which of the materials to go for, while constructing buildings in order to get maximum thermal comfort.

1.7 Scope of Study

The scope of the research is focused on the Thermal Properties of Some Selected Materials Used as Ceiling in Building. The materials in consideration include P V C, POP, asbestos and cardboard. The thermal properties of interest include thermal conductivity, thermal resistivity, thermal radiation, thermal absorptivity, thermal diffusivity, specific heat capacity and density.

1.8 Limitations of the Study

During the course of this study, many things militated against its completion, some of which are:

1. Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
2. Research material: availability of research material is a major setback to the scope of the study.
3. Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
4. Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).

1.9 Organization of the study

The study is organized into five chapters; Chapter one deals with the study’s introduction and gives a background to the study. Chapter two reviews related and relevant literature. The chapter three gives the research methodology while the chapter four gives the study’s analysis and interpretation of data. The study concludes with chapter five which deals on the summary, conclusion and recommendation.