How long does it take for heat to transfer through a wall?

Say there is a 10 x10 x10 air tight box with no openings of any kind. All six surfaces are insulated with a wall thickness of 5 inches and the overall R value of the walls is R20. The starting ambient temperature inside the box is 70 degrees. The box is place inside a large kiln with a constant temp of 120... show more Say there is a 10 x10 x10 air tight box with no openings of any kind. All six surfaces are insulated with a wall thickness of 5 inches and the overall R value of the walls is R20. The starting ambient temperature inside the box is 70 degrees. The box is place inside a large kiln with a constant temp of 120 degrees. How long before the temperature begins to rise inside the box?
Update: There is no thermal bridging other than the insulation itself.
Update 2: The dimensions of the box are in Feet and the specific heat would be 1 degree to confirm the change and also calculate how long until the temperature inside the box is equal with the kiln temperature.
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