This work investigates the thermal properties of Polyvinyl Chloride (PVC), Plaster of Paris (POP), asbestos, and cardboard commonly used as ceiling materials. The steady state method for Lee’s disc apparatus was employed to determine these thermal properties which include, thermal conductivity, thermal resistivity, thermal diffusivity, thermal absorptivity and density. The obtained results of thermal conductivity showed that, POP ceiling has the highest value of 0.1314 while card board has the least value of 0.0851 where as PVC (0.1083) and asbestos (0.1068) fall in between them. Also the results of thermal conductivity of this research ranged from (0.08510.1314w) which corresponds to the previous work of the researchers. Hence all these materials are good insulators. The thermal resistivity of these ceiling samples showed that, the card board ceiling has highest value of 11.7509, while POP has the least value of 7.6103, the asbestos value (9.3633) and PVC value (9.2336) fall in between them. The results of the ceiling samples for thermal diffusivity showed that PVC ceiling has the highest value of) while asbestos ceiling has the least value of 6.0 x), where the POP value of 1.20 x) and card board value of 8.0) fall in between them. Also results of thermal absorptivity of these ceiling materials showed that, the card board ceiling has the highest thermal absorptivity of 21.319 while PVC has the least thermal absorptivity of 7.573, where the POP (17.407) and asbestos ( 15.070) fall in between them. The density results of these ceiling materials were showed that, the POP has the highest density value of 979.84 kg/m3 while the P V C has the least density value of 203.59 kg/m3, where the asbestos ( 824.13kg/m3) and card board (645.81 kg/m3) densities value fall in between them. The results obtained showed based on comparison that, PVC and asbestos may be better materials for building insulation since they have better thermal efficiency. Card board among the samples used was found to have the least thermal efficiency base on the comparison where as POP falls in between them. Thus, this research may provide guide for many users of the materials.
1.1 BACKGROUND OF THE STUDY
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.
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 etal., 2007). One way to reduce the thermal discomfort is by the use of radiant barrier (i.e. ceilingboard) 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 the thermal properties of the materials use in the building (Etuk et al., 2007).
The study of the thermal properties of materials will help us to know whether materials are suitable to use as Ceiling materials in our houses, school and industries.
Heat propagated in the interior spaces in buildings through roofs and walls and partly through Ceiling panels by the process of conduction and radiation (George et al., 2010). This is because the common materials used as roofing sheets are materials like zinc and aluminum which have high thermal conductivities (Michael et al,2012).
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.
Insulator is a material or devised used to inhibit or prevent the conduction of heat or electricity (Gesa et al., 2014). Proper selection of insulating materials is based on their thermal properties whichinclude: the thermal conductivity, thermal absorptivity, thermal diffusivity, specific heat capacity (Gesa et al 2014). The primarily function of insulator in buildings are: To conserve energy, to reduce heat loss or heat gain, to maintain a temperature condition, to maintain the effective operation of equipment or chemical reaction, to assist in maintaining product at constant temperature, to prevent condensation, to create comfortable environmental condition and protect personnel. Insulation reduces heat transfer through the envelope in building. Whenever there is a temperature difference, heat flows naturally from a warmer space to a cooler space. To maintain comfort in winter (the coldest season of the year), the heat lost must be replaced by the heating system; and in summer (the warmest season of the year), the heat gained must be removed by the cooling system. Therefore, it makes sense to study the thermal properties of insulator in order to reduce gains or loss of energy in buildings and to increase comfortable condition in houses, schools and industries.