THERMAL PERFORMANCE OF ROOF MATERIALS AND CONFIGURATIONS SUITABLE FOR RESIDENTIAL BUILDINGS IN IBADAN, NIGERI

Abstract

Heat influx through roofs is the leading cause of internal temperature imbalance problems in buildings. Roofing materials and configurations are key in regulating heat infiltration into buildings. There is a dearth of information on their synergistic contribution to the control of internal temperature imbalance. This study was designed to investigate the thermal performance of selected roofing sheets and underlays, under different configurations in residential buildings in Ibadan. Plywood-Lined Aluminium Roof (PLAR) and Selected Roofing Materials (SRM) [Stone Coated Sheets (SCS) and Aluminium Roofing Sheets (ARS)], were tested using ice and steam apparatus for 5 and 7 minutes, based on UNE EN standard. These and Selected Ceiling Materials (SCM) [Polyvinyl Chloride Ceiling (PVC), Asbestos (ASB), Plaster of Paris (POP), Gypsum (GYP) and Plywood Ceiling Board (PCB)], were tested using fabricated conductivity apparatus, for Thermal Conductivity (TC) (W/mK), Thermal Resistivity (TR) (mk/w), Thermal Diffusivity (TD) (m2/s), Specific Heat Capacity (SHC) (J/kgK), and Thermal Absorptivity (TA) (J), based on ASTM standards. Forty-five prototype buildings were constructed using a factorial combination of three roofing sheets, five ceiling underlays, and three angular configurations. Optimum Comfortability Roof (OCR) for the buildings were obtained using multichannel data logger between 9 am to 10 pm at 30 minutes interval for six months. Data were analysed using descriptive statistics and ANOVA at α0.05. The TC; 135.60-150.62 (TCPLAR), 83.680-97.069 (TCSCS), and 76.149-123.43 (TCARS); indicated PLAR was a suitable heat conductor. The TR; 0.0066-0.0074 (TRPLAR), 0.0103-0.0119 (TRSCS), and 0.0081-0.0131 (TRARS), implied PLAR has poor heat resistance. The SHC; 3.726-4.739 (SHCPLAR), 3.164-8.887 (SHCSCS), and 2.180-7.082 x 103 (SHCARS), indicated the heat storage potential of PLAR. The TD; 1.066-1.507 (TDPLAR), 1.390-3.095 (TDSCS), and 1.021-2.643 x 10-7 (TDARS); implied heat diffuses slowly through PLAR. The TA; 392.66-398.09 (TAPLAR), 425.18-491.07 (TASCS), and 327.73-380.55 (TAARS), indicated that PLAR possessed good heat absorption. Similarly, TC for underlays; 0.191 (TCPVC), 0.125 (TCASB), 0.184 (TCPOP), 0.228 (TCGYP), and 0.283 (TCPCB), indicated that PCB was an insulator. The SHC; 1.654 (SHCPVC), 2.050 (SHCASB), 1.596 (SHCPOP), 2.070 (SHCGYP), and 2.850 x 103 (SHCPCB), showing that PCB had a better storage capacity. The TD; 1.360 (TDPVC), 0.399 (TDASB), 1.266 (TDPOP), 1.410 (TDGYP) and 0.456 x 10-7 (TDPCB), showed that PCB diffused heat slowly. Also, TA; 319.00 (TAPVC), 338.24 (TAASB), 336.93 (TAPOP), 334.24 (TAGYP), and 353.43 (TAPCB), suggested higher TA in PCB. The temperature of the SCM decreased with increase in the angle of configuration. The average temperature at 30, 45, and 60°, for 6 pm and 10 pm were; PLAR (37.04-29.74, 35.5-28.66, 31.02-28.64°), SCS (37.14-26.28, 35.18-26.38, 37.28-28.06°), and ARS (36.97-29.7, 38.72-30.16, 37.82-29.58°), respectively, implied that between 45° and 60° gave OCR ranged 22 - 29°, with the highest coefficient of correlation (R2 = 0.95, 0.70, 0.90) obtained. A significant difference between the OCR of SRM and SCM was observed. Plywood-lined Aluminium, stone-coated and Aluminium roofs configured between angles 45° and 60° offered acceptable thermal performance with the plaster of paris or polyvinyl chloride as roof configurations in Ibadan.