How thick is the concrete envelope that typically surrounds an encased duct?

The typical thickness of the concrete envelope that surrounds an encased duct is generally standardized at 3 inches. This thickness provides adequate protection and insulation for the ductwork, ensuring both structural integrity and efficiency in thermal regulation. Concrete serves as a durable barrier, preventing damage from external forces while also minimizing heat loss or gain, which can be crucial in various applications. Choosing this thickness also balances considerations such as material cost, weight, and the necessary physical space in construction while fulfilling safety and performance requirements in most building codes and engineering practices.