Final answer:
The question involves reducing the clearance between an appliance and combustible material using a metal sheet, but lacks specific guidelines to provide a precise answer. Safety and manufacturer's instructions must be followed to ensure proper clearance and prevent fire hazards.
Step-by-step explanation:
The question seems to relate to using sheet metal as a heat shield to protect combustible material from the heat of an appliance, possibly a wood stove or similar heating appliance. The use of protective barriers to reduce clearance from combustible materials is a standard practice for safety purposes. However, there is no specific rule or formula provided within the general reference information to directly answer the question regarding how much the side clearance can be reduced by covering a piece of wood with 28-guage sheet metal spaced out 1" (25mm). The safe reduction of clearance would depend on fire safety codes and the appliance manufacturer's instructions.
When it comes to reducing the clearance of an appliance from combustible material, it is crucial to follow the guidelines provided by the manufacturer and any local building codes to ensure safety. In some cases, the use of a heat shield may reduce the required clearance, but the information given does not specify the exact amount by which the clearance can be safely reduced. It is always advised to consult a professional and adhere to safety regulations when dealing with appliances near combustible material to prevent fire hazards.