Abstract: Insulator influences performance efficiency of the solar heater. In order to reduce the cost of solar device, it is advisable to use as local insulating material. Some agricultural wastes are abundant and causing environmental nuisance in Nigeria. This research focussed on use of some agricultural waste as insulator in box-type solar device. A box-type solar heater was developed. Dried insulating materials (maize cob, air, maize husk, coconut coir and polyurethane foam) were used to fill the space between the inner and outer boxes in such a way that there was an 80 mm thickness of insulating materials all around between the inner box and the outer box. The space housing the insulating materials was sealed with four pieces of plywood noggins. Heat retention and water abilities of the solar device were tested for period of 3 years. Peak stagnation temperatures for 1st to 3rd year were 159, 140 and 138°C, respectively. These were obtained using coconut coir (1st and 2nd year) and polyurethane foam (3rd year). During the dry season, shortest duration taken to heat 1 and 1.5 L of water was 50 and 65 min, respectively in coconut coir insulated device. Time required to boil 1 L of water in wet season ranged from 120-170 min. Comparatively the orders of performance were coconut coir, polyurethane foam, maize cob, maize husk and air. The evidence from performance evaluation indicates that agricultural by-products like maize husk, maize cob and coconut coir can perform as solar device insulator.