Heat transfer through a square cavity enclosing a thin hollow-cylinder is theoretically investigated in the present work. The coupled continuity, momentum and energy equations governing the fluids contained in the present system are solved numerically. High accurate finite volume method utilizing well-known CFD software is implemented. Good agreement was obtained between the numerical and published results under special constraints. It is found that a significant improvement in the insulating property of the present system as compared to that of pure square cavity is attainable when the hollow-cylinder is placed very close to the middle of the isothermal boundaries. Moreover, larger hollow cylinder diameters and smaller Grashof numbers are found to produce further improvement in the insulating property of the present system. In addition, the maximum reported enhancement in the insulating property of the present system is 1.96 times that of the pure closed square cavity, The reported optimum management is equivalent to having a square cavity filled with a number of solid rods equals to 4.0 times that producing the same insulating property of the pure square cavity. Accordingly, a building envelope made of at least bricks with horizontal square perforations assembled through an at least single layered network of horizontal hollow-pipes placed close to the middle of hot/cold boundaries is recommended. (C) 2012 Elsevier B.V. All rights reserved.