Final answer:
In thermal physics, the spacing between the face of a combustible wall and the box is typically a minimum of 1 inch, in accordance with local building codes to prevent fire spread and allow adequate airflow.
Step-by-step explanation:
The question pertains to the calculation of heat transfer through a wall with specified materials and dimensions. This falls under the topic of thermal physics, which is a branch of physics that deals with the exchange of heat and related phenomena. In typical building practices, the spacing between the face of a combustible wall (such as wood) and the face of a box (such as an electrical box) must comply with local building codes.
These codes can vary, but a common practice is to maintain a minimum gap of 1 inch (2.54 cm) to provide adequate air space and to reduce the risk of fire spread. This spacing allows for airflow that can prevent excessive heat build-up around electrical boxes, especially if they are located near potential heat sources like a wood stove. Proper installation also includes using appropriate insulating and fire-blocking materials to ensure safety and energy efficiency.