A method of forming a vacuum insulated structure includes providing a structural envelope an insulating cavity defined within the structural envelope. An expanding device is attached to opposing outer walls of the structural envelope and the interior cavity is expanded by pulling the opposing outer walls away from one another to define an expanded state. An insulating material is disposed within the insulating cavity to occupy substantially all of the insulating cavity in the expanded state. Gas is expressed from the insulating cavity to collapse the structural envelope to a final state and a final interior volume that is less than the expanded interior volume. The final state of the structural envelope defines a densified state of the insulating material within the insulating cavity. The vacuum port is then closed to hermetically seal the insulating cavity.