Method of forming large diameter duct with liner and the product formed thereby

A method of forming a tubular duct lined with a duct insulation board, comprising:

• providing a tubular metal duct having a diameter of at least thirty inches;
• providing a duct insulation board having a first major surface, a second major surface with a facing sheet adhered thereto, and a thickness;
• cutting a plurality of parallel grooves in said first major surface of said duct insulation board which are spaced on 3.14 inch centers across said first major surface, have sidewalls extending perpendicular to said first major surface, and have a depth from 70% to 90% of the thickness of said duct insulation board;
• forming said duct insulation board into a tubular configuration with said grooves extending parallel to a longitudinal axis of said tubular configuration;
• and placing said duct insulation board within said tubular metal duct with said grooves extending parallel to a longitudinal centerline of said tubular metal duct and said facing of said second major surface conforming to an interior surface of said tubular metal duct.

A method of forming a tubular duct lined with a duct insulation board, comprising:

• providing a tubular metal duct having a diameter no greater than thirty inches;
• providing a duct insulation board having a first major surface, a second major surface with a facing sheet adhered thereto, and a thickness:
• cutting a plurality of parallel grooves in said first major surface of said duct insulation board which are spaced on 1.57 inch centers across said first major surface, have sidewalls extending perpendicular to said first major surface, and have a depth from 70% to 90% of the thickness of said duct insulation board;
• forming said duct insulation parallel board into a tubular configuration with said grooves extending parallel to a longitudinal axis of said tubular configuration;
• and placing said fibrous duct board within said tubular metal duct with said grooves extending parallel to a longitudinal centerline of said tubular metal duct and said facing of said second major surface conforming to an interior surface of said tubular metal duct.