Determination of Overall Coefficient of Heat Transfer of Building Wall Envelopes

Purpose: The purpose of the study was to determine the rate at which heat is transferred through the walls of building envelopes with particular reference to building structures in Ghana. Design/Methodology/Approach: The accidental sampling technique was used to select uncompleted building structures, supported with physical measurements; and interviews were used to gather data in the Kumasi Metropolis. A computer language, C + + for Visual Studios, was employed to design a source code to compute the overall heat transfer coefficient of the walls. Both primary and secondary data were employed in the study. The data obtained using the designed program was analyzed using descriptive analysis in SPSS Statistics 20. Findings: Results indicated a total of sixteen thousand nine hundred and forty (16,940) OCHT values of wall envelopes. Values ranged between 0.09295 W/(m2.K) and 3.4411 W/(m2.K). The walls were categorized and coded concerning the various homogeneous layers making the building envelope. Twelve wall categories in terms of OCHT were obtained. A total number of 4840 concrete walls, 7260 brick walls and 4840 sandcrete walls were identified. Thus, thermal resistances and OCHT values were computed for a total of 16940 building wall envelopes. Research Limitation: The study assumed that contact resistances between wall interfaces were insignificant. Other assumptions include the fact that individual layers were homogeneous; there was equilibrium or steady-state heat transfer; effects of heat storage were disregarded. Secondary data such as thermal resistance, thermal conductance, thermal transmittance and thermal conductivity were largely relied upon even though such data could be fraught with errors which could have a negative rippling effect on the final results. Practical Implication: The values of OCHT computed could be used in the design of air conditioning rooms, cold rooms and warm rooms in temperate regions. The source code could be easily modified to compute OCHT values for more than five layered wall envelopes. Though the source code was specifically designed for walls, it can as well be used to compute OCHT values of any material of multiple layers provided the required secondary data are available. Social Implication: The application of cold rooms in the preservation of fresh meat, cooked food and plant-based crops could reduce food spoilage thus indirectly enhancing the incomes of individuals and households. Originality/Value: The uniqueness of this study lies in the fact that OCHT data on individual walls in Ghana were not available in literature or elsewhere for quick and easy reference. The study has introduced a coding and classification system of wall envelopes in Ghana based on OCHT.