A cold-storage building 16 × 35 m is built on a concrete slab having a thickness of 15 cm, which is placed on a suitable insulating material in contact with the ground. During the start-up period the interior of the building is exposed to convection air with h = 20 W/m2 · ºC and T = −15ºC. The ground temperature may be taken as +15ºC. The design objective is to achieve a steady-state temperature of 0ºC at the inside surface of the concrete floor. Consider different insulating materials and thicknesses and recommend a selection that will achieve a cooldown within a reasonable period of time. For the design, take into account only the floor slab of the building.