A blueprint shows ductwork labeled as 20" x 12" and has 1" acoustical lining. How big should you fabricate the duct?

To determine the correct size for fabricating the duct, it is essential to consider the dimensions shown on the blueprint and account for the acoustical lining, which will add to the overall dimensions of the duct. The blueprint specifies that the duct should be 20 inches by 12 inches.

When an acoustical lining that is 1 inch thick is applied to the interior surfaces of the duct, it effectively increases the overall dimensions by 2 inches in each direction (1 inch for each side of the duct). Therefore, you add an inch to both sides of the width and an inch to both sides of the height.

Starting with the original dimensions:

• Width = 20 inches + 1 inch (left side) + 1 inch (right side) = 22 inches

• Height = 12 inches + 1 inch (top) + 1 inch (bottom) = 14 inches

Thus, the fabricated duct dimensions become 22 inches by 14 inches to accommodate the thickness of the acoustical lining while maintaining the required internal dimensions for airflow and insulation properties. This reasoning justifies why the answer indicating a fabricated size of 22" x 14" is correct.